[Openvpn-devel,05/12] openvpnmsica: Revise MSI custom actions interop

Message ID 20200309131728.380-5-simon@rozman.si
State Accepted
Headers show
Series
  • [Openvpn-devel,01/12] openvpnmsica: Remove required Windows driver certification detection
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Commit Message

Simon Rozman March 9, 2020, 1:17 p.m.
Sequence scripts in temporary files has been discontinued in favor of
much simpler sequence strings passed to individual custom actions.

Pros: no temporary files; less code
Cons: the evaluation phase must make a complete plan what to perform in
each deferred custom action

Signed-off-by: Simon Rozman <simon@rozman.si>
---
 src/openvpnmsica/Makefile.am                  |    4 +-
 src/openvpnmsica/msica_arg.c                  |  139 +++
 src/openvpnmsica/msica_arg.h                  |  112 ++
 src/openvpnmsica/msica_op.c                   | 1043 -----------------
 src/openvpnmsica/msica_op.h                   |  430 -------
 src/openvpnmsica/openvpnmsica.c               |  713 ++++++-----
 src/openvpnmsica/openvpnmsica.vcxproj         |    4 +-
 src/openvpnmsica/openvpnmsica.vcxproj.filters |    4 +-
 src/tapctl/basic.h                            |   19 +-
 src/tapctl/tap.c                              |    1 +
 10 files changed, 678 insertions(+), 1791 deletions(-)
 create mode 100644 src/openvpnmsica/msica_arg.c
 create mode 100644 src/openvpnmsica/msica_arg.h
 delete mode 100644 src/openvpnmsica/msica_op.c
 delete mode 100644 src/openvpnmsica/msica_op.h

Comments

Lev Stipakov March 23, 2020, 1:58 p.m. | #1
Hi,

I must say I am not super familiar with this component nor MSI in general.

Stared at the code, compiled with MSVC and tested some exported
functions with rundll32.

This has removed lots of code, so it makes sense, assuming that all
required functionality is still in place.

It would be nice to have unit tests for msica_arg_* functions -
they're doing dangerous low-level stuff.

Acked-by: Lev Stipakov <lstipakov@gmail.com>
Gert Doering March 24, 2020, 2:26 p.m. | #2
Your patch has been applied to the master branch.

Very cursory review only.  Test compiled on MinGW.

commit e24049d55644f698a8f1ddc199ba39944394edfa
Author: Simon Rozman
Date:   Mon Mar 9 14:17:21 2020 +0100

     openvpnmsica: Revise MSI custom actions interop

     Signed-off-by: Simon Rozman <simon@rozman.si>
     Acked-by: Lev Stipakov <lstipakov@gmail.com>
     Message-Id: <20200309131728.380-5-simon@rozman.si>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg19523.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering

Patch

diff --git a/src/openvpnmsica/Makefile.am b/src/openvpnmsica/Makefile.am
index db8502b8..9d18854a 100644
--- a/src/openvpnmsica/Makefile.am
+++ b/src/openvpnmsica/Makefile.am
@@ -2,7 +2,7 @@ 
 #  openvpnmsica -- Custom Action DLL to provide OpenVPN-specific support to MSI packages
 #
 #  Copyright (C) 2002-2018 OpenVPN Inc <sales@openvpn.net>
-#  Copyright (C) 2018-2019 Simon Rozman <simon@rozman.si>
+#  Copyright (C) 2018-2020 Simon Rozman <simon@rozman.si>
 #
 #  This program is free software; you can redistribute it and/or modify
 #  it under the terms of the GNU General Public License version 2
@@ -48,7 +48,7 @@  endif
 libopenvpnmsica_la_SOURCES = \
 	dllmain.c \
 	msiex.c msiex.h \
-	msica_op.c msica_op.h \
+	msica_arg.c msica_arg.h \
 	openvpnmsica.c openvpnmsica.h \
 	$(top_srcdir)/src/tapctl/basic.h \
 	$(top_srcdir)/src/tapctl/error.c $(top_srcdir)/src/tapctl/error.h \
diff --git a/src/openvpnmsica/msica_arg.c b/src/openvpnmsica/msica_arg.c
new file mode 100644
index 00000000..0014537a
--- /dev/null
+++ b/src/openvpnmsica/msica_arg.c
@@ -0,0 +1,139 @@ 
+/*
+ *  openvpnmsica -- Custom Action DLL to provide OpenVPN-specific support to MSI packages
+ *                  https://community.openvpn.net/openvpn/wiki/OpenVPNMSICA
+ *
+ *  Copyright (C) 2018-2020 Simon Rozman <simon@rozman.si>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#elif defined(_MSC_VER)
+#include <config-msvc.h>
+#endif
+
+#include "msica_arg.h"
+#include "../tapctl/error.h"
+#include "../tapctl/tap.h"
+
+#include <windows.h>
+#include <malloc.h>
+
+
+void
+msica_arg_seq_init(_Inout_ struct msica_arg_seq *seq)
+{
+    seq->head = NULL;
+    seq->tail = NULL;
+}
+
+
+void
+msica_arg_seq_free(_Inout_ struct msica_arg_seq *seq)
+{
+    while (seq->head)
+    {
+        struct msica_arg *p = seq->head;
+        seq->head = seq->head->next;
+        free(p);
+    }
+    seq->tail = NULL;
+}
+
+
+void
+msica_arg_seq_add_head(
+    _Inout_ struct msica_arg_seq *seq,
+    _In_z_ LPCTSTR argument)
+{
+    size_t argument_size = (_tcslen(argument) + 1) * sizeof(TCHAR);
+    struct msica_arg *p = malloc(sizeof(struct msica_arg) + argument_size);
+    if (p == NULL)
+    {
+        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_arg) + argument_size);
+    }
+    memcpy(p->val, argument, argument_size);
+    p->next = seq->head;
+    seq->head = p;
+    if (seq->tail == NULL)
+    {
+        seq->tail = p;
+    }
+}
+
+
+void
+msica_arg_seq_add_tail(
+    _Inout_ struct msica_arg_seq *seq,
+    _Inout_ LPCTSTR argument)
+{
+    size_t argument_size = (_tcslen(argument) + 1) * sizeof(TCHAR);
+    struct msica_arg *p = malloc(sizeof(struct msica_arg) + argument_size);
+    if (p == NULL)
+    {
+        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_arg) + argument_size);
+    }
+    memcpy(p->val, argument, argument_size);
+    p->next = NULL;
+    *(seq->tail ? &seq->tail->next : &seq->head) = p;
+    seq->tail = p;
+}
+
+
+LPTSTR
+msica_arg_seq_join(_In_ const struct msica_arg_seq *seq)
+{
+    /* Count required space. */
+    size_t size = 2 /*x + zero-terminator*/;
+    for (struct msica_arg *p = seq->head; p != NULL; p = p->next)
+    {
+        size += _tcslen(p->val) + 1 /*space delimiter|zero-terminator*/;
+    }
+    size *= sizeof(TCHAR);
+
+    /* Allocate. */
+    LPTSTR str = malloc(size);
+    if (str == NULL)
+    {
+        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, size);
+        return NULL;
+    }
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable: 4996) /* Using unsafe string functions: The space in s and termination of p->val has been implicitly verified at the beginning of this function. */
+#endif
+
+    /* Dummy argv[0] (i.e. executable name), for CommandLineToArgvW to work correctly when parsing this string. */
+    _tcscpy(str, TEXT("x"));
+
+    /* Join. */
+    LPTSTR s = str + 1 /*x*/;
+    for (struct msica_arg *p = seq->head; p != NULL; p = p->next)
+    {
+        /* Convert zero-terminator into space delimiter. */
+        s[0] = TEXT(' ');
+        s++;
+        /* Append argument. */
+        _tcscpy(s, p->val);
+        s += _tcslen(p->val);
+    }
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+    return str;
+}
diff --git a/src/openvpnmsica/msica_arg.h b/src/openvpnmsica/msica_arg.h
new file mode 100644
index 00000000..d2158e0f
--- /dev/null
+++ b/src/openvpnmsica/msica_arg.h
@@ -0,0 +1,112 @@ 
+/*
+ *  openvpnmsica -- Custom Action DLL to provide OpenVPN-specific support to MSI packages
+ *                  https://community.openvpn.net/openvpn/wiki/OpenVPNMSICA
+ *
+ *  Copyright (C) 2018-2020 Simon Rozman <simon@rozman.si>
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License along
+ *  with this program; if not, write to the Free Software Foundation, Inc.,
+ *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+
+#ifndef MSICA_ARG_H
+#define MSICA_ARG_H
+
+#include <windows.h>
+#include <tchar.h>
+#include "../tapctl/basic.h"
+
+
+#ifdef _MSC_VER
+#pragma warning(push)
+#pragma warning(disable: 4200) /* Using zero-sized arrays in struct/union. */
+#endif
+
+
+/**
+ * Argument list
+ */
+struct msica_arg
+{
+    struct msica_arg *next; /** Pointer to the next argument in the sequence */
+    TCHAR val[];            /** Zero terminated argument string */
+};
+
+
+/**
+ * Argument sequence
+ */
+struct msica_arg_seq
+{
+    struct msica_arg *head; /** Pointer to the first argument in the sequence */
+    struct msica_arg *tail; /** Pointer to the last argument in the sequence */
+};
+
+
+/**
+ * Initializes argument sequence
+ *
+ * @param seq           Pointer to uninitialized argument sequence
+ */
+void
+msica_arg_seq_init(_Inout_ struct msica_arg_seq *seq);
+
+
+/**
+ * Frees argument sequence
+ *
+ * @param seq           Pointer to the argument sequence
+ */
+void
+msica_arg_seq_free(_Inout_ struct msica_arg_seq *seq);
+
+
+/**
+ * Inserts argument to the beginning of the argument sequence
+ *
+ * @param seq           Pointer to the argument sequence
+ *
+ * @param argument      Zero-terminated argument string to insert.
+ */
+void
+msica_arg_seq_add_head(
+    _Inout_ struct msica_arg_seq *seq,
+    _In_z_ LPCTSTR argument);
+
+
+/**
+ * Appends argument to the end of the argument sequence
+ *
+ * @param seq           Pointer to the argument sequence
+ *
+ * @param argument      Zero-terminated argument string to append.
+ */
+void
+msica_arg_seq_add_tail(
+    _Inout_ struct msica_arg_seq *seq,
+    _Inout_ LPCTSTR argument);
+
+/**
+ * Join arguments of the argument sequence into a space delimited string
+ *
+ * @param seq           Pointer to the argument sequence
+ *
+ * @return Joined argument string. Must be released with free() after use.
+ */
+LPTSTR
+msica_arg_seq_join(_In_ const struct msica_arg_seq *seq);
+
+#ifdef _MSC_VER
+#pragma warning(pop)
+#endif
+
+#endif /* ifndef MSICA_ARG_H */
diff --git a/src/openvpnmsica/msica_op.c b/src/openvpnmsica/msica_op.c
deleted file mode 100644
index 63aa6c83..00000000
--- a/src/openvpnmsica/msica_op.c
+++ /dev/null
@@ -1,1043 +0,0 @@ 
-/*
- *  openvpnmsica -- Custom Action DLL to provide OpenVPN-specific support to MSI packages
- *                  https://community.openvpn.net/openvpn/wiki/OpenVPNMSICA
- *
- *  Copyright (C) 2018 Simon Rozman <simon@rozman.si>
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License version 2
- *  as published by the Free Software Foundation.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-#ifdef HAVE_CONFIG_H
-#include <config.h>
-#elif defined(_MSC_VER)
-#include <config-msvc.h>
-#endif
-
-#include "msica_op.h"
-#include "../tapctl/error.h"
-#include "../tapctl/tap.h"
-
-#include <windows.h>
-#include <malloc.h>
-#include <msiquery.h>
-#include <objbase.h>
-
-#ifdef _MSC_VER
-#pragma comment(lib, "msi.lib")
-#pragma comment(lib, "ole32.lib")
-#endif
-
-
-/**
- * Operation data persist header
- */
-struct msica_op_hdr
-{
-    enum msica_op_type type;  /** Action type */
-    int ticks;                /** Number of ticks on the progress indicator this operation represents */
-    DWORD size_data;          /** Size of the operation data (DWORD to better align with Win32 API) */
-};
-
-
-void
-msica_op_seq_init(_Inout_ struct msica_op_seq *seq)
-{
-    seq->head = NULL;
-    seq->tail = NULL;
-}
-
-
-void
-msica_op_seq_free(_Inout_ struct msica_op_seq *seq)
-{
-    while (seq->head)
-    {
-        struct msica_op *op = seq->head;
-        seq->head = seq->head->next;
-        free(op);
-    }
-    seq->tail = NULL;
-}
-
-
-struct msica_op *
-msica_op_create_bool(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ bool value)
-{
-    if (MSICA_OP_TYPE_DATA(type) != 0x1)
-    {
-        msg(M_NONFATAL, "%s: Operation data type not bool (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(type));
-        return NULL;
-    }
-
-    /* Create and fill operation struct. */
-    struct msica_op_bool *op = (struct msica_op_bool *)malloc(sizeof(struct msica_op_bool));
-    if (op == NULL)
-    {
-        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op_bool));
-        return NULL;
-    }
-
-    op->base.type  = type;
-    op->base.ticks = ticks;
-    op->base.next  = next;
-    op->value      = value;
-
-    return &op->base;
-}
-
-
-struct msica_op *
-msica_op_create_string(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_z_ LPCTSTR value)
-{
-    if (MSICA_OP_TYPE_DATA(type) != 0x2)
-    {
-        msg(M_NONFATAL, "%s: Operation data type not string (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(type));
-        return NULL;
-    }
-
-    /* Create and fill operation struct. */
-    size_t value_size = (_tcslen(value) + 1) * sizeof(TCHAR);
-    struct msica_op_string *op = (struct msica_op_string *)malloc(sizeof(struct msica_op_string) + value_size);
-    if (op == NULL)
-    {
-        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op_string) + value_size);
-        return NULL;
-    }
-
-    op->base.type  = type;
-    op->base.ticks = ticks;
-    op->base.next  = next;
-    memcpy(op->value, value, value_size);
-
-    return &op->base;
-}
-
-
-struct msica_op *
-msica_op_create_multistring_va(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ va_list arglist)
-{
-    if (MSICA_OP_TYPE_DATA(type) != 0x3)
-    {
-        msg(M_NONFATAL, "%s: Operation data type not multi-string (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(type));
-        return NULL;
-    }
-
-    /* Calculate required space first. */
-    LPCTSTR str;
-    size_t value_size = 1;
-    for (va_list a = arglist; (str = va_arg(a, LPCTSTR)) != NULL; value_size += _tcslen(str) + 1)
-    {
-    }
-    value_size *= sizeof(TCHAR);
-
-    /* Create and fill operation struct. */
-    struct msica_op_multistring *op = (struct msica_op_multistring *)malloc(sizeof(struct msica_op_multistring) + value_size);
-    if (op == NULL)
-    {
-        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op_multistring) + value_size);
-        return NULL;
-    }
-
-    op->base.type  = type;
-    op->base.ticks = ticks;
-    op->base.next  = next;
-    LPTSTR value = op->value;
-    for (va_list a = arglist; (str = va_arg(a, LPCTSTR)) != NULL;)
-    {
-        size_t size = _tcslen(str) + 1;
-        memcpy(value, str, size*sizeof(TCHAR));
-        value += size;
-    }
-    value[0] = 0;
-
-    return &op->base;
-}
-
-
-struct msica_op *
-msica_op_create_guid(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ const GUID *value)
-{
-    if (MSICA_OP_TYPE_DATA(type) != 0x4)
-    {
-        msg(M_NONFATAL, "%s: Operation data type not GUID (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(type));
-        return NULL;
-    }
-
-    /* Create and fill operation struct. */
-    struct msica_op_guid *op = (struct msica_op_guid *)malloc(sizeof(struct msica_op_guid));
-    if (op == NULL)
-    {
-        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op_guid));
-        return NULL;
-    }
-
-    op->base.type  = type;
-    op->base.ticks = ticks;
-    op->base.next  = next;
-    memcpy(&op->value, value, sizeof(GUID));
-
-    return &op->base;
-}
-
-
-struct msica_op *
-msica_op_create_guid_string(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ const GUID *value_guid,
-    _In_z_ LPCTSTR value_str)
-{
-    if (MSICA_OP_TYPE_DATA(type) != 0x5)
-    {
-        msg(M_NONFATAL, "%s: Operation data type not GUID-string (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(type));
-        return NULL;
-    }
-
-    /* Create and fill operation struct. */
-    size_t value_str_size = (_tcslen(value_str) + 1) * sizeof(TCHAR);
-    struct msica_op_guid_string *op = (struct msica_op_guid_string *)malloc(sizeof(struct msica_op_guid_string) + value_str_size);
-    if (op == NULL)
-    {
-        msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op_guid_string) + value_str_size);
-        return NULL;
-    }
-
-    op->base.type  = type;
-    op->base.ticks = ticks;
-    op->base.next  = next;
-    memcpy(&op->value_guid, value_guid, sizeof(GUID));
-    memcpy(op->value_str, value_str, value_str_size);
-
-    return &op->base;
-}
-
-
-void
-msica_op_seq_add_head(
-    _Inout_ struct msica_op_seq *seq,
-    _Inout_ struct msica_op *operation)
-{
-    if (seq == NULL || operation == NULL)
-    {
-        return;
-    }
-
-    /* Insert list in the head. */
-    struct msica_op *op;
-    for (op = operation; op->next; op = op->next)
-    {
-    }
-    op->next = seq->head;
-
-    /* Update head (and tail). */
-    seq->head = operation;
-    if (seq->tail == NULL)
-    {
-        seq->tail = op;
-    }
-}
-
-
-void
-msica_op_seq_add_tail(
-    _Inout_ struct msica_op_seq *seq,
-    _Inout_ struct msica_op *operation)
-{
-    if (seq == NULL || operation == NULL)
-    {
-        return;
-    }
-
-    /* Append list to the tail. */
-    struct msica_op *op;
-    for (op = operation; op->next; op = op->next)
-    {
-    }
-    if (seq->tail)
-    {
-        seq->tail->next = operation;
-    }
-    else
-    {
-        seq->head = operation;
-    }
-    seq->tail = op;
-}
-
-
-DWORD
-msica_op_seq_save(
-    _In_ const struct msica_op_seq *seq,
-    _In_ HANDLE hFile)
-{
-    DWORD dwWritten;
-    for (const struct msica_op *op = seq->head; op; op = op->next)
-    {
-        struct msica_op_hdr hdr;
-        hdr.type  = op->type;
-        hdr.ticks = op->ticks;
-
-        /* Calculate size of data. */
-        switch (MSICA_OP_TYPE_DATA(op->type))
-        {
-            case 0x1: /* msica_op_bool */
-                hdr.size_data = sizeof(struct msica_op_bool) - sizeof(struct msica_op);
-                break;
-
-            case 0x2: /* msica_op_string */
-                hdr.size_data =
-                    sizeof(struct msica_op_string) - sizeof(struct msica_op)
-                    +(DWORD)(_tcslen(((struct msica_op_string *)op)->value) + 1) * sizeof(TCHAR);
-                break;
-
-            case 0x3: /* msica_op_multistring */
-            {
-                LPCTSTR str;
-                for (str = ((struct msica_op_multistring *)op)->value; str[0]; str += _tcslen(str) + 1)
-                {
-                }
-                hdr.size_data =
-                    sizeof(struct msica_op_multistring) - sizeof(struct msica_op)
-                    +(DWORD)(str + 1 - ((struct msica_op_multistring *)op)->value) * sizeof(TCHAR);
-                break;
-            }
-
-            case 0x4: /* msica_op_guid */
-                hdr.size_data = sizeof(struct msica_op_guid) - sizeof(struct msica_op);
-                break;
-
-            case 0x5: /* msica_op_guid_string */
-                hdr.size_data =
-                    sizeof(struct msica_op_guid_string) - sizeof(struct msica_op)
-                    +(DWORD)(_tcslen(((struct msica_op_guid_string *)op)->value_str) + 1) * sizeof(TCHAR);
-                break;
-
-            default:
-                msg(M_NONFATAL, "%s: Unknown operation data type (%x)", __FUNCTION__, MSICA_OP_TYPE_DATA(op->type));
-                return ERROR_BAD_ARGUMENTS;
-        }
-
-        if (!WriteFile(hFile, &hdr, sizeof(struct msica_op_hdr), &dwWritten, NULL)
-            || !WriteFile(hFile, op + 1, hdr.size_data, &dwWritten, NULL))
-        {
-            DWORD dwResult = GetLastError();
-            msg(M_NONFATAL | M_ERRNO, "%s: WriteFile failed", __FUNCTION__);
-            return dwResult;
-        }
-    }
-
-    return ERROR_SUCCESS;
-}
-
-
-DWORD
-msica_op_seq_load(
-    _Inout_ struct msica_op_seq *seq,
-    _In_ HANDLE hFile)
-{
-    DWORD dwRead;
-
-    if (seq == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    seq->head = seq->tail = NULL;
-
-    for (;;)
-    {
-        struct msica_op_hdr hdr;
-        if (!ReadFile(hFile, &hdr, sizeof(struct msica_op_hdr), &dwRead, NULL))
-        {
-            DWORD dwResult = GetLastError();
-            msg(M_NONFATAL | M_ERRNO, "%s: ReadFile failed", __FUNCTION__);
-            return dwResult;
-        }
-        else if (dwRead == 0)
-        {
-            /* EOF */
-            return ERROR_SUCCESS;
-        }
-        else if (dwRead < sizeof(struct msica_op_hdr))
-        {
-            msg(M_NONFATAL, "%s: Incomplete ReadFile", __FUNCTION__);
-            return ERROR_INVALID_DATA;
-        }
-
-        struct msica_op *op = (struct msica_op *)malloc(sizeof(struct msica_op) + hdr.size_data);
-        if (op == NULL)
-        {
-            msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeof(struct msica_op) + hdr.size_data);
-            return ERROR_OUTOFMEMORY;
-        }
-
-        op->type  = hdr.type;
-        op->ticks = hdr.ticks;
-        op->next  = NULL;
-
-        if (!ReadFile(hFile, op + 1, hdr.size_data, &dwRead, NULL))
-        {
-            DWORD dwResult = GetLastError();
-            msg(M_NONFATAL | M_ERRNO, "%s: ReadFile failed", __FUNCTION__);
-            free(op);
-            return dwResult;
-        }
-        else if (dwRead < hdr.size_data)
-        {
-            msg(M_NONFATAL, "%s: Incomplete ReadFile", __FUNCTION__);
-            return ERROR_INVALID_DATA;
-        }
-
-        msica_op_seq_add_tail(seq, op);
-    }
-}
-
-
-static DWORD
-msica_op_tap_interface_create_exec(
-    _Inout_ const struct msica_op_string *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the name of the interface to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        MsiRecordSetString(hRecord, 1, TEXT("Creating TAP interface"));
-        MsiRecordSetString(hRecord, 2, op->value);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    /* Get all available network interfaces. */
-    struct tap_interface_node *pInterfaceList = NULL;
-    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, TRUE);
-    if (dwResult == ERROR_SUCCESS)
-    {
-        /* Does interface exist? */
-        for (struct tap_interface_node *pInterfaceOther = pInterfaceList;; pInterfaceOther = pInterfaceOther->pNext)
-        {
-            if (pInterfaceOther == NULL)
-            {
-                /* No interface with a same name found. Create one. */
-                BOOL bRebootRequired = FALSE;
-                GUID guidInterface;
-                dwResult = tap_create_interface(NULL, NULL, NULL, &bRebootRequired, &guidInterface);
-                if (dwResult == ERROR_SUCCESS)
-                {
-                    /* Set interface name. */
-                    dwResult = tap_set_interface_name(&guidInterface, op->value);
-                    if (dwResult == ERROR_SUCCESS)
-                    {
-                        if (session->rollback_enabled)
-                        {
-                            /* Order rollback action to delete it. */
-                            msica_op_seq_add_head(
-                                &session->seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK],
-                                msica_op_create_guid(
-                                    msica_op_tap_interface_delete_by_guid,
-                                    0,
-                                    NULL,
-                                    &guidInterface));
-                        }
-                    }
-                    else
-                    {
-                        tap_delete_interface(NULL, &guidInterface, &bRebootRequired);
-                    }
-
-                    if (bRebootRequired)
-                    {
-                        MsiSetMode(session->hInstall, MSIRUNMODE_REBOOTATEND, TRUE);
-                    }
-                }
-                break;
-            }
-            else if (_tcsicmp(op->value, pInterfaceOther->szName) == 0)
-            {
-                /* Interface with a same name found. */
-                for (LPCTSTR hwid = pInterfaceOther->szzHardwareIDs;; hwid += _tcslen(hwid) + 1)
-                {
-                    if (hwid[0] == 0)
-                    {
-                        /* This is not a TAP interface. */
-                        msg(M_NONFATAL, "%s: Interface with name \"%" PRIsLPTSTR "\" already exists", __FUNCTION__, pInterfaceOther->szName);
-                        dwResult = ERROR_ALREADY_EXISTS;
-                        break;
-                    }
-                    else if (
-                        _tcsicmp(hwid, TEXT(TAP_WIN_COMPONENT_ID)) == 0
-                        || _tcsicmp(hwid, TEXT("root\\") TEXT(TAP_WIN_COMPONENT_ID)) == 0)
-                    {
-                        /* This is a TAP interface. We already got what we wanted! */
-                        dwResult = ERROR_SUCCESS;
-                        break;
-                    }
-                }
-                break;
-            }
-        }
-
-        tap_free_interface_list(pInterfaceList);
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_tap_interface_delete(
-    _In_ struct tap_interface_node *pInterfaceList,
-    _In_ struct tap_interface_node *pInterface,
-    _Inout_ struct msica_session *session)
-{
-    if (pInterfaceList == NULL || pInterface == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    DWORD dwResult;
-
-    /* Delete the interface. */
-    BOOL bRebootRequired = FALSE;
-    dwResult = tap_delete_interface(NULL, &pInterface->guid, &bRebootRequired);
-    if (bRebootRequired)
-    {
-        MsiSetMode(session->hInstall, MSIRUNMODE_REBOOTATEND, TRUE);
-    }
-
-    if (session->rollback_enabled)
-    {
-        /*
-         * Schedule rollback action to create the interface back. Though it won't be exactly the same interface again.
-         *
-         * The previous version of this function did:
-         * - Execution Pass:       rename the interface to some temporary name
-         * - Commit/Rollback Pass: delete the interface / rename the interface back to original name
-         *
-         * However, the WiX Toolset's Diffx extension to install and remove drivers removed the TAP driver between the
-         * execution and commit passes. TAP driver removal makes all TAP interfaces unavailable and our CA couldn't find
-         * the interface to delete any more.
-         *
-         * While the system where OpenVPN was uninstalled didn't have any TAP interfaces any more as expected behaviour,
-         * the problem appears after reinstalling the OpenVPN. Some residue TAP interface registry keys remain on the
-         * system, causing the TAP interface to reappear as "Ethernet NN" interface next time the TAP driver is
-         * installed. This causes TAP interfaces to accumulate over cyclic install-uninstall-install...
-         *
-         * Therefore, it is better to remove the TAP interfaces before the TAP driver is removed, and reinstall the TAP
-         * interface back should the rollback be required. I wonder if the WiX Diffx extension supports execute/commit/
-         * rollback feature of MSI in the first place.
-         */
-        msica_op_seq_add_head(
-            &session->seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK],
-            msica_op_create_string(
-                msica_op_tap_interface_create,
-                0,
-                NULL,
-                pInterface->szName));
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_tap_interface_delete_by_name_exec(
-    _Inout_ const struct msica_op_string *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the name of the interface to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        MsiRecordSetString(hRecord, 1, TEXT("Deleting interface"));
-        MsiRecordSetString(hRecord, 2, op->value);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    /* Get available TUN/TAP interfaces. */
-    struct tap_interface_node *pInterfaceList = NULL;
-    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, FALSE);
-    if (dwResult == ERROR_SUCCESS)
-    {
-        /* Does interface exist? */
-        for (struct tap_interface_node *pInterface = pInterfaceList;; pInterface = pInterface->pNext)
-        {
-            if (pInterface == NULL)
-            {
-                /* Interface not found. We already got what we wanted! */
-                dwResult = ERROR_SUCCESS;
-                break;
-            }
-            else if (_tcsicmp(op->value, pInterface->szName) == 0)
-            {
-                /* Interface found. */
-                dwResult = msica_op_tap_interface_delete(
-                    pInterfaceList,
-                    pInterface,
-                    session);
-                break;
-            }
-        }
-
-        tap_free_interface_list(pInterfaceList);
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_tap_interface_delete_by_guid_exec(
-    _Inout_ const struct msica_op_guid *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the GUID of the interface to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        LPOLESTR szInterfaceId = NULL;
-        StringFromIID((REFIID)&op->value, &szInterfaceId);
-        MsiRecordSetString(hRecord, 1, TEXT("Deleting interface"));
-        MsiRecordSetString(hRecord, 2, szInterfaceId);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        CoTaskMemFree(szInterfaceId);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    /* Get all available interfaces. */
-    struct tap_interface_node *pInterfaceList = NULL;
-    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, TRUE);
-    if (dwResult == ERROR_SUCCESS)
-    {
-        /* Does interface exist? */
-        for (struct tap_interface_node *pInterface = pInterfaceList;; pInterface = pInterface->pNext)
-        {
-            if (pInterface == NULL)
-            {
-                /* Interface not found. We already got what we wanted! */
-                dwResult = ERROR_SUCCESS;
-                break;
-            }
-            else if (memcmp(&op->value, &pInterface->guid, sizeof(GUID)) == 0)
-            {
-                /* Interface found. */
-                dwResult = msica_op_tap_interface_delete(
-                    pInterfaceList,
-                    pInterface,
-                    session);
-                break;
-            }
-        }
-
-        tap_free_interface_list(pInterfaceList);
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_tap_interface_set_name_exec(
-    _Inout_ const struct msica_op_guid_string *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the GUID of the interface to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        LPOLESTR szInterfaceId = NULL;
-        StringFromIID((REFIID)&op->value_guid, &szInterfaceId);
-        MsiRecordSetString(hRecord, 1, TEXT("Setting interface name"));
-        MsiRecordSetString(hRecord, 2, szInterfaceId);
-        MsiRecordSetString(hRecord, 3, op->value_str);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        CoTaskMemFree(szInterfaceId);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    /* Get all available network interfaces. */
-    struct tap_interface_node *pInterfaceList = NULL;
-    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, TRUE);
-    if (dwResult == ERROR_SUCCESS)
-    {
-        /* Does interface exist? */
-        for (struct tap_interface_node *pInterface = pInterfaceList;; pInterface = pInterface->pNext)
-        {
-            if (pInterface == NULL)
-            {
-                /* Interface not found. */
-                LPOLESTR szInterfaceId = NULL;
-                StringFromIID((REFIID)&op->value_guid, &szInterfaceId);
-                msg(M_NONFATAL, "%s: %" PRIsLPOLESTR " interface not found", __FUNCTION__, szInterfaceId);
-                CoTaskMemFree(szInterfaceId);
-                dwResult = ERROR_FILE_NOT_FOUND;
-                break;
-            }
-            else if (memcmp(&op->value_guid, &pInterface->guid, sizeof(GUID)) == 0)
-            {
-                /* Interface found. */
-                for (struct tap_interface_node *pInterfaceOther = pInterfaceList;; pInterfaceOther = pInterfaceOther->pNext)
-                {
-                    if (pInterfaceOther == NULL)
-                    {
-                        /* No other interface with a same name found. All clear to rename the interface. */
-                        dwResult = tap_set_interface_name(&pInterface->guid, op->value_str);
-                        if (dwResult == ERROR_SUCCESS)
-                        {
-                            if (session->rollback_enabled)
-                            {
-                                /* Order rollback action to rename it back. */
-                                msica_op_seq_add_head(
-                                    &session->seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK],
-                                    msica_op_create_guid_string(
-                                        msica_op_tap_interface_set_name,
-                                        0,
-                                        NULL,
-                                        &pInterface->guid,
-                                        pInterface->szName));
-                            }
-                        }
-                        break;
-                    }
-                    else if (_tcsicmp(op->value_str, pInterfaceOther->szName) == 0)
-                    {
-                        /* Interface with a same name found. Duplicate interface names are not allowed. */
-                        msg(M_NONFATAL, "%s: Interface with name \"%" PRIsLPTSTR "\" already exists", __FUNCTION__, pInterfaceOther->szName);
-                        dwResult = ERROR_ALREADY_EXISTS;
-                        break;
-                    }
-                }
-                break;
-            }
-        }
-
-        tap_free_interface_list(pInterfaceList);
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_file_delete_exec(
-    _Inout_ const struct msica_op_string *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the name of the file to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        MsiRecordSetString(hRecord, 1, TEXT("Deleting file"));
-        MsiRecordSetString(hRecord, 2, op->value);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    DWORD dwResult;
-
-    if (session->rollback_enabled)
-    {
-        size_t sizeNameBackupLenZ = _tcslen(op->value) + 7 /*" (orig "*/ + 10 /*maximum int*/ + 1 /*")"*/ + 1 /*terminator*/;
-        LPTSTR szNameBackup = (LPTSTR)malloc(sizeNameBackupLenZ * sizeof(TCHAR));
-        if (szNameBackup == NULL)
-        {
-            msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, sizeNameBackupLenZ * sizeof(TCHAR));
-            return ERROR_OUTOFMEMORY;
-        }
-
-        int count = 0;
-
-        do
-        {
-            /* Rename the file to make a backup. */
-            _stprintf_s(
-                szNameBackup, sizeNameBackupLenZ,
-                TEXT("%s (orig %i)"),
-                op->value,
-                ++count);
-            dwResult = MoveFile(op->value, szNameBackup) ? ERROR_SUCCESS : GetLastError();
-        } while (dwResult == ERROR_ALREADY_EXISTS);
-
-        if (dwResult == ERROR_SUCCESS)
-        {
-            /* Schedule rollback action to restore from backup. */
-            msica_op_seq_add_head(
-                &session->seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK],
-                msica_op_create_multistring(
-                    msica_op_file_move,
-                    0,
-                    NULL,
-                    szNameBackup,
-                    op->value,
-                    NULL));
-
-            /* Schedule commit action to delete the backup. */
-            msica_op_seq_add_tail(
-                &session->seq_cleanup[MSICA_CLEANUP_ACTION_COMMIT],
-                msica_op_create_string(
-                    msica_op_file_delete,
-                    0,
-                    NULL,
-                    szNameBackup));
-        }
-        else if (dwResult == ERROR_FILE_NOT_FOUND) /* File does not exist: We already got what we wanted! */
-        {
-            dwResult = ERROR_SUCCESS;
-        }
-        else
-        {
-            msg(M_NONFATAL | M_ERRNO, "%s: MoveFile(\"%" PRIsLPTSTR "\", \"%" PRIsLPTSTR "\") failed", __FUNCTION__, op->value, szNameBackup);
-        }
-
-        free(szNameBackup);
-    }
-    else
-    {
-        /* Delete the file. */
-        dwResult = DeleteFile(op->value) ? ERROR_SUCCESS : GetLastError();
-        if (dwResult == ERROR_FILE_NOT_FOUND) /* File does not exist: We already got what we wanted! */
-        {
-            dwResult = ERROR_SUCCESS;
-        }
-        else if (dwResult != ERROR_SUCCESS)
-        {
-            msg(M_NONFATAL | M_ERRNO, "%s: DeleteFile(\"%" PRIsLPTSTR "\") failed", __FUNCTION__, op->value);
-        }
-    }
-
-    return dwResult;
-}
-
-
-static DWORD
-msica_op_file_move_exec(
-    _Inout_ const struct msica_op_multistring *op,
-    _Inout_ struct msica_session *session)
-{
-    if (op == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    /* Get source filename. */
-    LPCTSTR szNameSrc = op->value;
-    if (szNameSrc[0] == 0)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    /* Get destination filename. */
-    LPCTSTR szNameDst = szNameSrc + _tcslen(szNameSrc) + 1;
-    if (szNameDst[0] == 0)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    {
-        /* Report the name of the files to installer. */
-        MSIHANDLE hRecord = MsiCreateRecord(3);
-        MsiRecordSetString(hRecord, 1, TEXT("Moving file"));
-        MsiRecordSetString(hRecord, 2, szNameSrc);
-        MsiRecordSetString(hRecord, 3, szNameDst);
-        int iResult = MsiProcessMessage(session->hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
-        MsiCloseHandle(hRecord);
-        if (iResult == IDCANCEL)
-        {
-            return ERROR_INSTALL_USEREXIT;
-        }
-    }
-
-    DWORD dwResult = MoveFile(szNameSrc, szNameDst) ? ERROR_SUCCESS : GetLastError();
-    if (dwResult == ERROR_SUCCESS)
-    {
-        if (session->rollback_enabled)
-        {
-            /* Order rollback action to move it back. */
-            msica_op_seq_add_head(
-                &session->seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK],
-                msica_op_create_multistring(
-                    msica_op_file_move,
-                    0,
-                    NULL,
-                    szNameDst,
-                    szNameSrc,
-                    NULL));
-        }
-    }
-    else
-    {
-        msg(M_NONFATAL | M_ERRNO, "%s: MoveFile(\"%" PRIsLPTSTR "\", \"%" PRIsLPTSTR "\") failed", __FUNCTION__, szNameSrc, szNameDst);
-    }
-
-    return dwResult;
-}
-
-
-void
-openvpnmsica_session_init(
-    _Inout_ struct msica_session *session,
-    _In_ MSIHANDLE hInstall,
-    _In_ bool continue_on_error,
-    _In_ bool rollback_enabled)
-{
-    session->hInstall          = hInstall;
-    session->continue_on_error = continue_on_error;
-    session->rollback_enabled  = rollback_enabled;
-    for (size_t i = 0; i < MSICA_CLEANUP_ACTION_COUNT; i++)
-    {
-        msica_op_seq_init(&session->seq_cleanup[i]);
-    }
-}
-
-
-DWORD
-msica_op_seq_process(
-    _Inout_ const struct msica_op_seq *seq,
-    _Inout_ struct msica_session *session)
-{
-    DWORD dwResult;
-
-    if (seq == NULL || session == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    /* Tell the installer to use explicit progress messages. */
-    MSIHANDLE hRecordProg = MsiCreateRecord(3);
-    MsiRecordSetInteger(hRecordProg, 1, 1);
-    MsiRecordSetInteger(hRecordProg, 2, 1);
-    MsiRecordSetInteger(hRecordProg, 3, 0);
-    MsiProcessMessage(session->hInstall, INSTALLMESSAGE_PROGRESS, hRecordProg);
-
-    /* Prepare hRecordProg for progress messages. */
-    MsiRecordSetInteger(hRecordProg, 1, 2);
-    MsiRecordSetInteger(hRecordProg, 3, 0);
-
-    for (const struct msica_op *op = seq->head; op; op = op->next)
-    {
-        switch (op->type)
-        {
-            case msica_op_rollback_enable:
-                session->rollback_enabled = ((const struct msica_op_bool *)op)->value;
-                dwResult = ERROR_SUCCESS;
-                break;
-
-            case msica_op_tap_interface_create:
-                dwResult = msica_op_tap_interface_create_exec((const struct msica_op_string *)op, session);
-                break;
-
-            case msica_op_tap_interface_delete_by_name:
-                dwResult = msica_op_tap_interface_delete_by_name_exec((const struct msica_op_string *)op, session);
-                break;
-
-            case msica_op_tap_interface_delete_by_guid:
-                dwResult = msica_op_tap_interface_delete_by_guid_exec((const struct msica_op_guid *)op, session);
-                break;
-
-            case msica_op_tap_interface_set_name:
-                dwResult = msica_op_tap_interface_set_name_exec((const struct msica_op_guid_string *)op, session);
-                break;
-
-            case msica_op_file_delete:
-                dwResult = msica_op_file_delete_exec((const struct msica_op_string *)op, session);
-                break;
-
-            case msica_op_file_move:
-                dwResult = msica_op_file_move_exec((const struct msica_op_multistring *)op, session);
-                break;
-
-            default:
-                msg(M_NONFATAL, "%s: Unknown operation type (%x)", __FUNCTION__, op->type);
-                dwResult = ERROR_FILE_NOT_FOUND;
-        }
-
-        if (!session->continue_on_error && dwResult != ERROR_SUCCESS)
-        {
-            /* Operation failed. It should have sent error message to Installer. Therefore, just quit here. */
-            goto cleanup_hRecordProg;
-        }
-
-        /* Report progress and check for user cancellation. */
-        MsiRecordSetInteger(hRecordProg, 2, op->ticks);
-        if (MsiProcessMessage(session->hInstall, INSTALLMESSAGE_PROGRESS, hRecordProg) == IDCANCEL)
-        {
-            dwResult = ERROR_INSTALL_USEREXIT;
-            goto cleanup_hRecordProg;
-        }
-    }
-
-    dwResult = ERROR_SUCCESS;
-
-cleanup_hRecordProg:
-    MsiCloseHandle(hRecordProg);
-    return dwResult;
-}
diff --git a/src/openvpnmsica/msica_op.h b/src/openvpnmsica/msica_op.h
deleted file mode 100644
index eaf7596c..00000000
--- a/src/openvpnmsica/msica_op.h
+++ /dev/null
@@ -1,430 +0,0 @@ 
-/*
- *  openvpnmsica -- Custom Action DLL to provide OpenVPN-specific support to MSI packages
- *                  https://community.openvpn.net/openvpn/wiki/OpenVPNMSICA
- *
- *  Copyright (C) 2018 Simon Rozman <simon@rozman.si>
- *
- *  This program is free software; you can redistribute it and/or modify
- *  it under the terms of the GNU General Public License version 2
- *  as published by the Free Software Foundation.
- *
- *  This program is distributed in the hope that it will be useful,
- *  but WITHOUT ANY WARRANTY; without even the implied warranty of
- *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- *  GNU General Public License for more details.
- *
- *  You should have received a copy of the GNU General Public License along
- *  with this program; if not, write to the Free Software Foundation, Inc.,
- *  51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
- */
-
-#ifndef MSICA_OP_H
-#define MSICA_OP_H
-
-#include <windows.h>
-#include <msi.h>
-#include <stdarg.h>
-#include <stdbool.h>
-#include <tchar.h>
-#include "../tapctl/basic.h"
-
-#ifdef _MSC_VER
-#pragma warning(push)
-#pragma warning(disable: 4200) /* Using zero-sized arrays in struct/union. */
-#endif
-
-
-/**
- * Operation type macros
- */
-#define MSICA_MAKE_OP_TYPE(op, data)  (((op)<<4)|((data)&0xf))
-#define MSICA_OP_TYPE_OP(type)        ((unsigned int)(type)>>4)
-#define MSICA_OP_TYPE_DATA(type)      ((unsigned int)(type)&0xf)
-
-
-/**
- * Operation types
- */
-enum msica_op_type
-{
-    msica_op_rollback_enable              = MSICA_MAKE_OP_TYPE(0x1, 0x1),  /** Enable/disable rollback  | msica_op_bool */
-    msica_op_tap_interface_create         = MSICA_MAKE_OP_TYPE(0x2, 0x2),  /** Create TAP/TUN interface | msica_op_string */
-    msica_op_tap_interface_delete_by_name = MSICA_MAKE_OP_TYPE(0x3, 0x2),  /** Delete TAP/TUN interface | msica_op_string */
-    msica_op_tap_interface_delete_by_guid = MSICA_MAKE_OP_TYPE(0x3, 0x4),  /** Delete TAP/TUN interface | msica_op_guid */
-    msica_op_tap_interface_set_name       = MSICA_MAKE_OP_TYPE(0x4, 0x5),  /** Rename TAP/TUN interface | msica_op_guid_string */
-    msica_op_file_delete                  = MSICA_MAKE_OP_TYPE(0x5, 0x2),  /** Delete file              | msica_op_string */
-    msica_op_file_move                    = MSICA_MAKE_OP_TYPE(0x6, 0x3),  /** Move file                | msica_op_multistring (min 2 strings) */
-};
-
-
-/**
- * Operation data
- */
-struct msica_op
-{
-    enum msica_op_type type;  /** Operation type */
-    int ticks;                /** Number of ticks on the progress indicator this operation represents */
-    struct msica_op *next;    /** Pointer to the next operation in the sequence */
-};
-
-
-/**
- * Operation sequence
- */
-struct msica_op_seq
-{
-    struct msica_op *head;    /** Pointer to the first operation in the sequence */
-    struct msica_op *tail;    /** Pointer to the last operation in the sequence */
-};
-
-
-/**
- * Initializes operation sequence
- *
- * @param seq           Pointer to uninitialized operation sequence
- */
-void
-msica_op_seq_init(_Inout_ struct msica_op_seq *seq);
-
-
-/**
- * Frees operation sequence
- *
- * @param seq           Pointer to operation sequence
- */
-void
-msica_op_seq_free(_Inout_ struct msica_op_seq *seq);
-
-
-/**
- * Operation data (bool, 0x1)
- */
-struct msica_op_bool
-{
-    struct msica_op base;     /** Common operation data */
-    bool value;               /** Operation data boolean value */
-};
-
-
-/**
- * Allocates and fills a new msica_op_bool operation
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @param value         Boolean value
- *
- * @return              A new msica_op_bool operation. Must be added to a sequence list or
- *                      released using free() after use. The function returns a pointer to
- *                      msica_op to reduce type-casting in code.
- */
-struct msica_op *
-msica_op_create_bool(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ bool value);
-
-
-/**
- * Operation data (string, 0x2)
- */
-struct msica_op_string
-{
-    struct msica_op base;     /** Common operation data */
-    TCHAR value[];            /** Operation data string - the string must always be zero terminated. */
-};
-
-
-/**
- * Allocates and fills a new msica_op_string operation
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @param value         String value
- *
- * @return              A new msica_op_string operation. Must be added to a sequence list or
- *                      released using free() after use. The function returns a pointer to
- *                      msica_op to reduce type-casting in code.
- */
-struct msica_op *
-msica_op_create_string(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_z_ LPCTSTR value);
-
-
-/**
- * Operation data (multi-string, 0x3)
- */
-struct msica_op_multistring
-{
-    struct msica_op base;     /** Common operation data */
-    TCHAR value[];            /** Operation data strings - each string must always be zero terminated. The last string must be double terminated. */
-};
-
-
-/**
- * Allocates and fills a new msica_op_multistring operation
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @param arglist       List of non-empty strings. The last string must be NULL.
- *
- * @return              A new msica_op_string operation. Must be added to a sequence list or
- *                      released using free() after use. The function returns a pointer to
- *                      msica_op to reduce type-casting in code.
- */
-struct msica_op *
-msica_op_create_multistring_va(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ va_list arglist);
-
-
-/**
- * Operation data (GUID, 0x4)
- */
-struct msica_op_guid
-{
-    struct msica_op base;     /** Common operation data */
-    GUID value;               /** Operation data GUID */
-};
-
-
-/**
- * Allocates and fills a new msica_op_guid operation
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @param value         Pointer to GUID value
- *
- * @return              A new msica_op_guid operation. Must be added to a sequence list or
- *                      released using free() after use. The function returns a pointer to
- *                      msica_op to reduce type-casting in code.
- */
-struct msica_op *
-msica_op_create_guid(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ const GUID *value);
-
-
-/**
- * Operation data (guid-string, 0x5)
- */
-struct msica_op_guid_string
-{
-    struct msica_op base;     /** Common operation data */
-    GUID value_guid;          /** Operation data GUID */
-    TCHAR value_str[];        /** Operation data string - the string must always be zero terminated. */
-};
-
-
-/**
- * Allocates and fills a new msica_op_guid_string operation
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @param value_guid    Pointer to GUID value
- *
- * @param value_str     String value
- *
- * @return              A new msica_op_guid_string operation. Must be added to a sequence
- *                      list or released using free() after use. The function returns a
- *                      pointer to msica_op to reduce type-casting in code.
- */
-struct msica_op *
-msica_op_create_guid_string(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    _In_ const GUID *value_guid,
-    _In_z_ LPCTSTR value_str);
-
-
-/**
- * Allocates and fills a new msica_op_multistring operation. Strings must be non-empty. The
- * last string passed as the input parameter must be NULL.
- *
- * @param type          Operation type
- *
- * @param ticks         Number of ticks on the progress indicator this operation represents
- *
- * @param next          Pointer to the next operation in the sequence
- *
- * @return              A new msica_op_string operation. Must be added to a sequence list or
- *                      released using free() after use. The function returns a pointer to
- *                      msica_op to reduce type-casting in code.
- */
-static inline struct msica_op *
-msica_op_create_multistring(
-    _In_ enum msica_op_type type,
-    _In_ int ticks,
-    _In_opt_ struct msica_op *next,
-    ...)
-{
-    va_list arglist;
-    va_start(arglist, next);
-    struct msica_op *op = msica_op_create_multistring_va(type, ticks, next, arglist);
-    va_end(arglist);
-    return op;
-}
-
-
-/**
- * Is operation sequence empty
- *
- * @param seq           Pointer to operation sequence
- *
- * @return true if empty; false otherwise
- */
-static inline bool
-msica_op_seq_is_empty(_In_ const struct msica_op_seq *seq)
-{
-    return seq->head != NULL;
-}
-
-
-/**
- * Inserts operation(s) to the beginning of the operation sequence
- *
- * @param seq           Pointer to operation sequence
- *
- * @param operation     Pointer to the operation to insert. All operations in the list are
- *                      added until the list is terminated with msica_op.next field set to
- *                      NULL. Operations must be allocated using malloc().
- */
-void
-msica_op_seq_add_head(
-    _Inout_ struct msica_op_seq *seq,
-    _Inout_ struct msica_op *operation);
-
-
-/**
- * Appends operation(s) to the end of the operation sequence
- *
- * @param seq           Pointer to operation sequence
- *
- * @param operation     Pointer to the operation to append. All operations in the list are
- *                      added until the list is terminated with msica_op.next field set to
- *                      NULL. Operations must be allocated using malloc().
- */
-void
-msica_op_seq_add_tail(
-    _Inout_ struct msica_op_seq *seq,
-    _Inout_ struct msica_op *operation);
-
-
-/**
- * Saves the operation sequence to the file
- *
- * @param seq           Pointer to operation sequence
- *
- * @param hFile         Handle of the file opened with GENERIC_WRITE access
- *
- * @return ERROR_SUCCESS on success; An error code otherwise
- */
-DWORD
-msica_op_seq_save(
-    _In_ const struct msica_op_seq *seq,
-    _In_ HANDLE hFile);
-
-
-/**
- * Loads the operation sequence from the file
- *
- * @param seq           Pointer to uninitialized or empty operation sequence
- *
- * @param hFile         Handle of the file opened with GENERIC_READ access
- *
- * @return ERROR_SUCCESS on success; An error code otherwise
- */
-DWORD
-msica_op_seq_load(
-    _Inout_ struct msica_op_seq *seq,
-    _In_ HANDLE hFile);
-
-
-/**
- * Execution session constants
- */
-#define MSICA_CLEANUP_ACTION_COMMIT   0
-#define MSICA_CLEANUP_ACTION_ROLLBACK 1
-#define MSICA_CLEANUP_ACTION_COUNT    2
-
-
-/**
- * Execution session
- */
-struct msica_session
-{
-    MSIHANDLE hInstall;           /** Installer handle */
-    bool continue_on_error;       /** Continue execution on operation error? */
-    bool rollback_enabled;        /** Is rollback enabled? */
-    struct msica_op_seq seq_cleanup[MSICA_CLEANUP_ACTION_COUNT]; /** Commit/Rollback action operation sequence */
-};
-
-
-/**
- * Initializes execution session
- *
- * @param session       Pointer to an uninitialized execution session
- *
- * @param hInstall      Installer handle
- *
- * @param continue_on_error  Continue execution on operation error?
- *
- * @param rollback_enabled  Is rollback enabled?
- */
-void
-openvpnmsica_session_init(
-    _Inout_ struct msica_session *session,
-    _In_ MSIHANDLE hInstall,
-    _In_ bool continue_on_error,
-    _In_ bool rollback_enabled);
-
-
-/**
- * Executes all operations in sequence
- *
- * @param seq           Pointer to operation sequence
- *
- * @param session       MSI session. The execution updates its members, most notably
- *                      rollback_enabled and fills cleanup sequences with commit/rollback
- *                      operations.
- *
- * @return ERROR_SUCCESS on success; An error code otherwise
- */
-DWORD
-msica_op_seq_process(
-    _Inout_ const struct msica_op_seq *seq,
-    _Inout_ struct msica_session *session);
-
-#ifdef _MSC_VER
-#pragma warning(pop)
-#endif
-
-#endif /* ifndef MSICA_OP_H */
diff --git a/src/openvpnmsica/openvpnmsica.c b/src/openvpnmsica/openvpnmsica.c
index e1f0b77d..4c186b13 100644
--- a/src/openvpnmsica/openvpnmsica.c
+++ b/src/openvpnmsica/openvpnmsica.c
@@ -26,7 +26,7 @@ 
 #include <winsock2.h> /* Must be included _before_ <windows.h> */
 
 #include "openvpnmsica.h"
-#include "msica_op.h"
+#include "msica_arg.h"
 #include "msiex.h"
 
 #include "../tapctl/basic.h"
@@ -61,100 +61,32 @@ 
 
 
 /**
- * Cleanup actions
- */
-static const struct {
-    LPCTSTR szName;               /** Name of the cleanup action. This name is appended to the deferred custom action name (e.g. "InstallTAPInterfaces" >> "InstallTAPInterfacesCommit"). */
-    TCHAR szSuffix[3];            /** Two-character suffix to append to the cleanup operation sequence filename */
-} openvpnmsica_cleanup_action_seqs[MSICA_CLEANUP_ACTION_COUNT] =
-{
-    { TEXT("Commit"  ), TEXT("cm") }, /* MSICA_CLEANUP_ACTION_COMMIT   */
-    { TEXT("Rollback"), TEXT("rb") }, /* MSICA_CLEANUP_ACTION_ROLLBACK */
-};
-
-
-/**
- * Creates a new sequence file in the current user's temporary folder and sets MSI property
- * to its absolute path.
+ * Joins an argument sequence and sets it to the MSI property.
  *
  * @param hInstall      Handle to the installation provided to the DLL custom action
  *
- * @param szProperty    MSI property name to set to the absolute path of the sequence file.
+ * @param szProperty    MSI property name to set to the joined argument sequence.
  *
- * @param szFilename    String of minimum MAXPATH+1 characters where the zero-terminated
- *                      file absolute path is stored.
+ * @param seq           The argument sequence.
  *
  * @return ERROR_SUCCESS on success; An error code otherwise
  */
-static DWORD
-openvpnmsica_setup_sequence_filename(
+static UINT
+openvpnmsica_setup_sequence(
     _In_ MSIHANDLE hInstall,
     _In_z_ LPCTSTR szProperty,
-    _Out_z_cap_(MAXPATH + 1) LPTSTR szFilename)
+    _In_ struct msica_arg_seq *seq)
 {
-    DWORD dwResult;
-
-    if (szFilename == NULL)
-    {
-        return ERROR_BAD_ARGUMENTS;
-    }
-
-    /* Generate a random filename in the temporary folder. */
-    if (GetTempPath(MAX_PATH + 1, szFilename) == 0)
-    {
-        dwResult = GetLastError();
-        msg(M_NONFATAL | M_ERRNO, "%s: GetTempPath failed", __FUNCTION__);
-        return dwResult;
-    }
-    if (GetTempFileName(szFilename, szProperty, 0, szFilename) == 0)
-    {
-        dwResult = GetLastError();
-        msg(M_NONFATAL | M_ERRNO, "%s: GetTempFileName failed", __FUNCTION__);
-        return dwResult;
-    }
-
-    /* Store sequence filename to property for deferred custom action. */
-    dwResult = MsiSetProperty(hInstall, szProperty, szFilename);
-    if (dwResult != ERROR_SUCCESS)
+    UINT uiResult;
+    LPTSTR szSequence = msica_arg_seq_join(seq);
+    uiResult = MsiSetProperty(hInstall, szProperty, szSequence);
+    free(szSequence);
+    if (uiResult != ERROR_SUCCESS)
     {
-        SetLastError(dwResult); /* MSDN does not mention MsiSetProperty() to set GetLastError(). But we do have an error code. Set last error manually. */
+        SetLastError(uiResult); /* MSDN does not mention MsiSetProperty() to set GetLastError(). But we do have an error code. Set last error manually. */
         msg(M_NONFATAL | M_ERRNO, "%s: MsiSetProperty(\"%" PRIsLPTSTR "\") failed", __FUNCTION__, szProperty);
-        return dwResult;
-    }
-
-    /* Generate and store cleanup operation sequence filenames to properties. */
-    LPTSTR szExtension = PathFindExtension(szFilename);
-    TCHAR szFilenameEx[MAX_PATH + 1 /*dash*/ + 2 /*suffix*/ + 1 /*terminator*/];
-    size_t len_property_name = _tcslen(szProperty);
-    for (size_t i = 0; i < MSICA_CLEANUP_ACTION_COUNT; i++)
-    {
-        size_t len_action_name_z = _tcslen(openvpnmsica_cleanup_action_seqs[i].szName) + 1;
-        TCHAR *szPropertyEx = (TCHAR *)malloc((len_property_name + len_action_name_z) * sizeof(TCHAR));
-        if (szPropertyEx == NULL)
-        {
-            msg(M_FATAL, "%s: malloc(%u) failed", __FUNCTION__, (len_property_name + len_action_name_z) * sizeof(TCHAR));
-            return ERROR_OUTOFMEMORY;
-        }
-
-        memcpy(szPropertyEx, szProperty, len_property_name * sizeof(TCHAR));
-        memcpy(szPropertyEx + len_property_name, openvpnmsica_cleanup_action_seqs[i].szName, len_action_name_z * sizeof(TCHAR));
-        _stprintf_s(
-            szFilenameEx, _countof(szFilenameEx),
-            TEXT("%.*s-%.2s%s"),
-            (int)(szExtension - szFilename), szFilename,
-            openvpnmsica_cleanup_action_seqs[i].szSuffix,
-            szExtension);
-        dwResult = MsiSetProperty(hInstall, szPropertyEx, szFilenameEx);
-        if (dwResult != ERROR_SUCCESS)
-        {
-            SetLastError(dwResult); /* MSDN does not mention MsiSetProperty() to set GetLastError(). But we do have an error code. Set last error manually. */
-            msg(M_NONFATAL | M_ERRNO, "%s: MsiSetProperty(\"%" PRIsLPTSTR "\") failed", __FUNCTION__, szPropertyEx);
-            free(szPropertyEx);
-            return dwResult;
-        }
-        free(szPropertyEx);
+        return uiResult;
     }
-
     return ERROR_SUCCESS;
 }
 
@@ -613,6 +545,179 @@  cleanup_CoInitialize:
 }
 
 
+/**
+ * Schedules interface creation.
+ *
+ * When the rollback is enabled, the interface deletition is scheduled on rollback.
+ *
+ * @param seq           The argument sequence to pass to InstallTAPInterfaces custom action
+ *
+ * @param seqRollback   The argument sequence to pass to InstallTAPInterfacesRollback custom
+ *                      action. NULL when rollback is disabled.
+ *
+ * @param szDisplayName  Interface display name.
+ *
+ * @param iTicks        Pointer to an integer that represents amount of work (on progress
+ *                      indicator) the InstallTAPInterfaces will take. This function increments it
+ *                      by MSICA_INTERFACE_TICK_SIZE for each interface to create.
+ *
+ * @return ERROR_SUCCESS on success; An error code otherwise
+ */
+static DWORD
+openvpnmsica_schedule_interface_create(_Inout_ struct msica_arg_seq *seq, _Inout_opt_ struct msica_arg_seq *seqRollback, _In_z_ LPCTSTR szDisplayName, _Inout_ int *iTicks)
+{
+    /* Get all available network interfaces. */
+    struct tap_interface_node *pInterfaceList = NULL;
+    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, TRUE);
+    if (dwResult != ERROR_SUCCESS)
+    {
+        return dwResult;
+    }
+
+    /* Does interface exist? */
+    for (struct tap_interface_node *pInterfaceOther = pInterfaceList;; pInterfaceOther = pInterfaceOther->pNext)
+    {
+        if (pInterfaceOther == NULL)
+        {
+            /* No interface with a same name found. */
+            TCHAR szArgument[10 /*create=""|deleteN=""*/ + MAX_PATH /*szDisplayName*/ + 1 /*terminator*/];
+
+            /* InstallTAPInterfaces will create the interface. */
+            _stprintf_s(
+                szArgument, _countof(szArgument),
+                TEXT("create=\"%.*s\""),
+                MAX_PATH, szDisplayName);
+            msica_arg_seq_add_tail(seq, szArgument);
+
+            if (seqRollback)
+            {
+                /* InstallTAPInterfacesRollback will delete the interface. */
+                _stprintf_s(
+                    szArgument, _countof(szArgument),
+                    TEXT("deleteN=\"%.*s\""),
+                    MAX_PATH, szDisplayName);
+                msica_arg_seq_add_head(seqRollback, szArgument);
+            }
+
+            *iTicks += MSICA_INTERFACE_TICK_SIZE;
+            break;
+        }
+        else if (_tcsicmp(szDisplayName, pInterfaceOther->szName) == 0)
+        {
+            /* Interface with a same name found. */
+            for (LPCTSTR hwid = pInterfaceOther->szzHardwareIDs;; hwid += _tcslen(hwid) + 1)
+            {
+                if (hwid[0] == 0)
+                {
+                    /* This is not a TAP interface. */
+                    msg(M_NONFATAL, "%s: Interface with name \"%" PRIsLPTSTR "\" already exists", __FUNCTION__, pInterfaceOther->szName);
+                    dwResult = ERROR_ALREADY_EXISTS;
+                    goto cleanup_pInterfaceList;
+                }
+                else if (
+                    _tcsicmp(hwid, TEXT(TAP_WIN_COMPONENT_ID)) == 0
+                    || _tcsicmp(hwid, TEXT("root\\") TEXT(TAP_WIN_COMPONENT_ID)) == 0)
+                {
+                    /* This is a TAP-Windows6 interface. We already have what we want! */
+                    break;
+                }
+            }
+            break; /* Interface names are unique. There should be no other interface with this name. */
+        }
+    }
+
+cleanup_pInterfaceList:
+    tap_free_interface_list(pInterfaceList);
+    return dwResult;
+}
+
+
+/**
+ * Schedules interface deletion.
+ *
+ * When the rollback is enabled, the interface deletition is scheduled as: disable in
+ * UninstallTAPInterfaces, enable on rollback, delete on commit.
+ *
+ * When rollback is disabled, the interface deletition is scheduled as delete in
+ * UninstallTAPInterfaces.
+ *
+ * @param seq           The argument sequence to pass to UninstallTAPInterfaces custom action
+ *
+ * @param seqCommit     The argument sequence to pass to UninstallTAPInterfacesCommit custom
+ *                      action. NULL when rollback is disabled.
+ *
+ * @param seqRollback   The argument sequence to pass to UninstallTAPInterfacesRollback custom
+ *                      action. NULL when rollback is disabled.
+ *
+ * @param szDisplayName  Interface display name.
+ *
+ * @param iTicks        Pointer to an integer that represents amount of work (on progress
+ *                      indicator) the UninstallTAPInterfaces will take. This function increments
+ *                      it by MSICA_INTERFACE_TICK_SIZE for each interface to delete.
+ *
+ * @return ERROR_SUCCESS on success; An error code otherwise
+ */
+static DWORD
+openvpnmsica_schedule_interface_delete(_Inout_ struct msica_arg_seq *seq, _Inout_opt_ struct msica_arg_seq *seqCommit, _Inout_opt_ struct msica_arg_seq *seqRollback, _In_z_ LPCTSTR szDisplayName, _Inout_ int *iTicks)
+{
+    /* Get available TUN/TAP interfaces. */
+    struct tap_interface_node *pInterfaceList = NULL;
+    DWORD dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, FALSE);
+    if (dwResult != ERROR_SUCCESS)
+    {
+        return dwResult;
+    }
+
+    /* Does interface exist? */
+    for (struct tap_interface_node *pInterface = pInterfaceList; pInterface != NULL; pInterface = pInterface->pNext)
+    {
+        if (_tcsicmp(szDisplayName, pInterface->szName) == 0)
+        {
+            /* Interface found. */
+            TCHAR szArgument[8 /*disable=|enable=|delete=*/ + 38 /*{xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx}*/ + 1 /*terminator*/];
+            if (seqCommit && seqRollback)
+            {
+                /* UninstallTAPInterfaces will disable the interface. */
+                _stprintf_s(
+                    szArgument, _countof(szArgument),
+                    TEXT("disable=") TEXT(PRIXGUID),
+                    PRIGUID_PARAM(pInterface->guid));
+                msica_arg_seq_add_tail(seq, szArgument);
+
+                /* UninstallTAPInterfacesRollback will re-enable the interface. */
+                _stprintf_s(
+                    szArgument, _countof(szArgument),
+                    TEXT("enable=") TEXT(PRIXGUID),
+                    PRIGUID_PARAM(pInterface->guid));
+                msica_arg_seq_add_head(seqRollback, szArgument);
+
+                /* UninstallTAPInterfacesCommit will delete the interface. */
+                _stprintf_s(
+                    szArgument, _countof(szArgument),
+                    TEXT("delete=") TEXT(PRIXGUID),
+                    PRIGUID_PARAM(pInterface->guid));
+                msica_arg_seq_add_tail(seqCommit, szArgument);
+            }
+            else
+            {
+                /* UninstallTAPInterfaces will delete the interface. */
+                _stprintf_s(
+                    szArgument, _countof(szArgument),
+                    TEXT("delete=") TEXT(PRIXGUID),
+                    PRIGUID_PARAM(pInterface->guid));
+                msica_arg_seq_add_tail(seq, szArgument);
+            }
+
+            iTicks += MSICA_INTERFACE_TICK_SIZE;
+            break; /* Interface names are unique. There should be no other interface with this name. */
+        }
+    }
+
+    tap_free_interface_list(pInterfaceList);
+    return dwResult;
+}
+
+
 UINT __stdcall
 EvaluateTAPInterfaces(_In_ MSIHANDLE hInstall)
 {
@@ -627,43 +732,30 @@  EvaluateTAPInterfaces(_In_ MSIHANDLE hInstall)
 
     OPENVPNMSICA_SAVE_MSI_SESSION(hInstall);
 
-    /* List of deferred custom actions EvaluateTAPInterfaces prepares operation sequence for. */
-    static const LPCTSTR szActionNames[] =
-    {
-        TEXT("InstallTAPInterfaces"),
-        TEXT("UninstallTAPInterfaces"),
-    };
-    struct msica_op_seq exec_seq[_countof(szActionNames)];
-    for (size_t i = 0; i < _countof(szActionNames); i++)
-    {
-        msica_op_seq_init(&exec_seq[i]);
-    }
-
-    {
-        /* Check and store the rollback enabled state. */
-        TCHAR szValue[128];
-        DWORD dwLength = _countof(szValue);
-        bool enable_rollback = MsiGetProperty(hInstall, TEXT("RollbackDisabled"), szValue, &dwLength) == ERROR_SUCCESS ?
-                               _ttoi(szValue) || _totlower(szValue[0]) == TEXT('y') ? false : true :
-                               true;
-        for (size_t i = 0; i < _countof(szActionNames); i++)
-        {
-            msica_op_seq_add_tail(
-                &exec_seq[i],
-                msica_op_create_bool(
-                    msica_op_rollback_enable,
-                    0,
-                    NULL,
-                    enable_rollback));
-        }
-    }
+    struct msica_arg_seq
+        seqInstallTAPInterfaces,
+        seqInstallTAPInterfacesCommit,
+        seqInstallTAPInterfacesRollback,
+        seqUninstallTAPInterfaces,
+        seqUninstallTAPInterfacesCommit,
+        seqUninstallTAPInterfacesRollback;
+    msica_arg_seq_init(&seqInstallTAPInterfaces);
+    msica_arg_seq_init(&seqInstallTAPInterfacesCommit);
+    msica_arg_seq_init(&seqInstallTAPInterfacesRollback);
+    msica_arg_seq_init(&seqUninstallTAPInterfaces);
+    msica_arg_seq_init(&seqUninstallTAPInterfacesCommit);
+    msica_arg_seq_init(&seqUninstallTAPInterfacesRollback);
+
+    /* Check rollback state. */
+    bool bRollbackEnabled = MsiEvaluateCondition(hInstall, TEXT("RollbackDisabled")) != MSICONDITION_TRUE;
 
     /* Open MSI database. */
     MSIHANDLE hDatabase = MsiGetActiveDatabase(hInstall);
     if (hDatabase == 0)
     {
         msg(M_NONFATAL, "%s: MsiGetActiveDatabase failed", __FUNCTION__);
-        uiResult = ERROR_INVALID_HANDLE; goto cleanup_exec_seq;
+        uiResult = ERROR_INVALID_HANDLE;
+        goto cleanup_exec_seq;
     }
 
     /* Check if TAPInterface table exists. If it doesn't exist, there's nothing to do. */
@@ -758,6 +850,8 @@  EvaluateTAPInterfaces(_In_ MSIHANDLE hInstall)
 
         if (iAction > INSTALLSTATE_BROKEN)
         {
+            int iTicks = 0;
+
             if (iAction >= INSTALLSTATE_LOCAL)
             {
                 /* Read and evaluate interface condition (`Condition` is field #3). */
@@ -793,29 +887,35 @@  EvaluateTAPInterfaces(_In_ MSIHANDLE hInstall)
                 free(szValue);
 
                 /* Component is or should be installed. Schedule interface creation. */
-                msica_op_seq_add_tail(
-                    &exec_seq[0],
-                    msica_op_create_string(
-                        msica_op_tap_interface_create,
-                        MSICA_INTERFACE_TICK_SIZE,
-                        NULL,
-                        szDisplayNameEx));
+                if (openvpnmsica_schedule_interface_create(
+                        &seqInstallTAPInterfaces,
+                        bRollbackEnabled ? &seqInstallTAPInterfacesRollback : NULL,
+                        szDisplayNameEx,
+                        &iTicks) != ERROR_SUCCESS)
+                {
+                    uiResult = ERROR_INSTALL_FAILED;
+                    goto cleanup_szDisplayName;
+                }
             }
             else
             {
-                /* Component is installed, but should be degraded to advertised/removed. Schedule interface deletition. */
-                msica_op_seq_add_tail(
-                    &exec_seq[1],
-                    msica_op_create_string(
-                        msica_op_tap_interface_delete_by_name,
-                        MSICA_INTERFACE_TICK_SIZE,
-                        NULL,
-                        szDisplayNameEx));
+                /* Component is installed, but should be degraded to advertised/removed. Schedule interface deletition.
+                 *
+                 * Note: On interface removal (product is being uninstalled), we tolerate dwResult error.
+                 * Better a partial uninstallation than no uninstallation at all.
+                 */
+                openvpnmsica_schedule_interface_delete(
+                    &seqUninstallTAPInterfaces,
+                    bRollbackEnabled ? &seqUninstallTAPInterfacesCommit : NULL,
+                    bRollbackEnabled ? &seqUninstallTAPInterfacesRollback : NULL,
+                    szDisplayNameEx,
+                    &iTicks);
             }
 
-            /* The amount of tick space to add for each interface to progress indicator. */
+            /* Arrange the amount of tick space to add to the progress indicator.
+             * Do this within the loop to poll for user cancellation. */
             MsiRecordSetInteger(hRecordProg, 1, 3 /* OP3 = Add ticks to the expected total number of progress of the progress bar */);
-            MsiRecordSetInteger(hRecordProg, 2, MSICA_INTERFACE_TICK_SIZE);
+            MsiRecordSetInteger(hRecordProg, 2, iTicks);
             if (MsiProcessMessage(hInstall, INSTALLMESSAGE_PROGRESS, hRecordProg) == IDCANCEL)
             {
                 uiResult = ERROR_INSTALL_USEREXIT;
@@ -833,59 +933,19 @@  cleanup_hRecord:
         }
     }
 
-    /*
-     * Write sequence files.
-     * The InstallTAPInterfaces and UninstallTAPInterfaces are deferred custom actions, thus all this information
-     * will be unavailable to them. Therefore save all required operations and their info to sequence files.
-     */
-    TCHAR szSeqFilename[_countof(szActionNames)][MAX_PATH + 1];
-    for (size_t i = 0; i < _countof(szActionNames); i++)
+    /* Store deferred custom action parameters. */
+    if ((uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("InstallTAPInterfaces"          ), &seqInstallTAPInterfaces          )) != ERROR_SUCCESS
+        || (uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("InstallTAPInterfacesCommit"    ), &seqInstallTAPInterfacesCommit    )) != ERROR_SUCCESS
+        || (uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("InstallTAPInterfacesRollback"  ), &seqInstallTAPInterfacesRollback  )) != ERROR_SUCCESS
+        || (uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("UninstallTAPInterfaces"        ), &seqUninstallTAPInterfaces        )) != ERROR_SUCCESS
+        || (uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("UninstallTAPInterfacesCommit"  ), &seqUninstallTAPInterfacesCommit  )) != ERROR_SUCCESS
+        || (uiResult = openvpnmsica_setup_sequence(hInstall, TEXT("UninstallTAPInterfacesRollback"), &seqUninstallTAPInterfacesRollback)) != ERROR_SUCCESS)
     {
-        szSeqFilename[i][0] = 0;
-    }
-    for (size_t i = 0; i < _countof(szActionNames); i++)
-    {
-        uiResult = openvpnmsica_setup_sequence_filename(hInstall, szActionNames[i], szSeqFilename[i]);
-        if (uiResult != ERROR_SUCCESS)
-        {
-            goto cleanup_szSeqFilename;
-        }
-        HANDLE hSeqFile = CreateFile(
-            szSeqFilename[i],
-            GENERIC_WRITE,
-            FILE_SHARE_READ,
-            NULL,
-            CREATE_ALWAYS,
-            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
-            NULL);
-        if (hSeqFile == INVALID_HANDLE_VALUE)
-        {
-            uiResult = GetLastError();
-            msg(M_NONFATAL | M_ERRNO, "%s: CreateFile(\"%.*" PRIsLPTSTR "\") failed", __FUNCTION__, _countof(szSeqFilename[i]), szSeqFilename[i]);
-            goto cleanup_szSeqFilename;
-        }
-        uiResult = msica_op_seq_save(&exec_seq[i], hSeqFile);
-        CloseHandle(hSeqFile);
-        if (uiResult != ERROR_SUCCESS)
-        {
-            goto cleanup_szSeqFilename;
-        }
+        goto cleanup_hRecordProg;
     }
 
     uiResult = ERROR_SUCCESS;
 
-cleanup_szSeqFilename:
-    if (uiResult != ERROR_SUCCESS)
-    {
-        /* Clean-up sequence files. */
-        for (size_t i = _countof(szActionNames); i--; )
-        {
-            if (szSeqFilename[i][0])
-            {
-                DeleteFile(szSeqFilename[i]);
-            }
-        }
-    }
 cleanup_hRecordProg:
     MsiCloseHandle(hRecordProg);
 cleanup_hViewST_close:
@@ -895,10 +955,12 @@  cleanup_hViewST:
 cleanup_hDatabase:
     MsiCloseHandle(hDatabase);
 cleanup_exec_seq:
-    for (size_t i = 0; i < _countof(szActionNames); i++)
-    {
-        msica_op_seq_free(&exec_seq[i]);
-    }
+    msica_arg_seq_free(&seqInstallTAPInterfaces);
+    msica_arg_seq_free(&seqInstallTAPInterfacesCommit);
+    msica_arg_seq_free(&seqInstallTAPInterfacesRollback);
+    msica_arg_seq_free(&seqUninstallTAPInterfaces);
+    msica_arg_seq_free(&seqUninstallTAPInterfacesCommit);
+    msica_arg_seq_free(&seqUninstallTAPInterfacesRollback);
     if (bIsCoInitialized)
     {
         CoUninitialize();
@@ -907,6 +969,27 @@  cleanup_exec_seq:
 }
 
 
+/**
+ * Parses string encoded GUID.
+ *
+ * @param szArg         Zero terminated string where the GUID string starts
+ *
+ * @param guid          Pointer to GUID that receives parsed value
+ *
+ * @return TRUE on success; FALSE otherwise
+ */
+static BOOL
+openvpnmsica_parse_guid(_In_z_ LPCWSTR szArg, _Out_ GUID *guid)
+{
+    if (swscanf_s(szArg, _L(PRIXGUID), PRIGUID_PARAM_REF(*guid)) != 11)
+    {
+        msg(M_NONFATAL | M_ERRNO, "%s: swscanf_s(\"%ls\") failed", __FUNCTION__, szArg);
+        return FALSE;
+    }
+    return TRUE;
+}
+
+
 UINT __stdcall
 ProcessDeferredAction(_In_ MSIHANDLE hInstall)
 {
@@ -923,158 +1006,172 @@  ProcessDeferredAction(_In_ MSIHANDLE hInstall)
 
     BOOL bIsCleanup = MsiGetMode(hInstall, MSIRUNMODE_COMMIT) || MsiGetMode(hInstall, MSIRUNMODE_ROLLBACK);
 
-    /* Get sequence filename and open the file. */
-    LPTSTR szSeqFilename = NULL;
-    uiResult = msi_get_string(hInstall, TEXT("CustomActionData"), &szSeqFilename);
+    /* Get sequence arguments. Always Unicode as CommandLineToArgvW() is available as Unicode-only. */
+    LPWSTR szSequence = NULL;
+    uiResult = msi_get_string(hInstall, L"CustomActionData", &szSequence);
     if (uiResult != ERROR_SUCCESS)
     {
         goto cleanup_CoInitialize;
     }
-    struct msica_op_seq seq = { .head = NULL, .tail = NULL };
+    int nArgs;
+    LPWSTR *szArg = CommandLineToArgvW(szSequence, &nArgs);
+    if (szArg == NULL)
     {
-        HANDLE hSeqFile = CreateFile(
-            szSeqFilename,
-            GENERIC_READ,
-            FILE_SHARE_READ,
-            NULL,
-            OPEN_EXISTING,
-            FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
-            NULL);
-        if (hSeqFile == INVALID_HANDLE_VALUE)
+        uiResult = GetLastError();
+        msg(M_NONFATAL | M_ERRNO, "%s: CommandLineToArgvW(\"%ls\") failed", __FUNCTION__, szSequence);
+        goto cleanup_szSequence;
+    }
+
+    /* Tell the installer to use explicit progress messages. */
+    MSIHANDLE hRecordProg = MsiCreateRecord(3);
+    MsiRecordSetInteger(hRecordProg, 1, 1);
+    MsiRecordSetInteger(hRecordProg, 2, 1);
+    MsiRecordSetInteger(hRecordProg, 3, 0);
+    MsiProcessMessage(hInstall, INSTALLMESSAGE_PROGRESS, hRecordProg);
+
+    /* Prepare hRecordProg for progress messages. */
+    MsiRecordSetInteger(hRecordProg, 1, 2);
+    MsiRecordSetInteger(hRecordProg, 3, 0);
+
+    BOOL bRebootRequired = FALSE;
+
+    for (int i = 1 /*CommandLineToArgvW injects msiexec.exe as szArg[0]*/; i < nArgs; ++i)
+    {
+        DWORD dwResult = ERROR_SUCCESS;
+
+        if (wcsncmp(szArg[i], L"create=", 7) == 0)
         {
-            uiResult = GetLastError();
-            if (uiResult == ERROR_FILE_NOT_FOUND && bIsCleanup)
+            /* Create an interface with a given name. */
+            LPCWSTR szName = szArg[i] + 7;
+
             {
-                /*
-                 * Sequence file not found and this is rollback/commit action. Either of the following scenarios are possible:
-                 * - The delayed action failed to save the rollback/commit sequence to file. The delayed action performed cleanup itself. No further operation is required.
-                 * - Somebody removed the rollback/commit file between delayed action and rollback/commit action. No further operation is possible.
-                 */
-                uiResult = ERROR_SUCCESS;
-                goto cleanup_szSeqFilename;
+                /* Report the name of the interface to installer. */
+                MSIHANDLE hRecord = MsiCreateRecord(3);
+                MsiRecordSetString(hRecord, 1, TEXT("Creating interface"));
+                MsiRecordSetString(hRecord, 2, szName);
+                int iResult = MsiProcessMessage(hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
+                MsiCloseHandle(hRecord);
+                if (iResult == IDCANCEL)
+                {
+                    uiResult = ERROR_INSTALL_USEREXIT;
+                    goto cleanup;
+                }
             }
-            msg(M_NONFATAL | M_ERRNO, "%s: CreateFile(\"%" PRIsLPTSTR "\") failed", __FUNCTION__, szSeqFilename);
-            goto cleanup_szSeqFilename;
-        }
 
-        /* Load sequence. */
-        uiResult = msica_op_seq_load(&seq, hSeqFile);
-        CloseHandle(hSeqFile);
-        if (uiResult != ERROR_SUCCESS)
-        {
-            goto cleanup_seq;
+            GUID guidInterface;
+            dwResult = tap_create_interface(NULL, NULL, NULL, &bRebootRequired, &guidInterface);
+            if (dwResult == ERROR_SUCCESS)
+            {
+                /* Set interface name. */
+                dwResult = tap_set_interface_name(&guidInterface, szName);
+                if (dwResult != ERROR_SUCCESS)
+                {
+                    tap_delete_interface(NULL, &guidInterface, &bRebootRequired);
+                }
+            }
         }
-    }
-
-    /* Prepare session context. */
-    struct msica_session session;
-    openvpnmsica_session_init(
-        &session,
-        hInstall,
-        bIsCleanup, /* In case of commit/rollback, continue sequence on error, to do as much cleanup as possible. */
-        false);
-
-    /* Execute sequence. */
-    uiResult = msica_op_seq_process(&seq, &session);
-    if (!bIsCleanup)
-    {
-        /*
-         * Save cleanup scripts of delayed action regardless of action's execution status.
-         * Rollback action MUST be scheduled in InstallExecuteSequence before this action! Otherwise cleanup won't be performed in case this action execution failed.
-         */
-        DWORD dwResultEx; /* Don't overwrite uiResult. */
-        LPCTSTR szExtension = PathFindExtension(szSeqFilename);
-        TCHAR szFilenameEx[MAX_PATH + 1 /*dash*/ + 2 /*suffix*/ + 1 /*terminator*/];
-        for (size_t i = 0; i < MSICA_CLEANUP_ACTION_COUNT; i++)
+        else if (wcsncmp(szArg[i], L"deleteN=", 8) == 0)
         {
-            _stprintf_s(
-                szFilenameEx, _countof(szFilenameEx),
-                TEXT("%.*s-%.2s%s"),
-                (int)(szExtension - szSeqFilename), szSeqFilename,
-                openvpnmsica_cleanup_action_seqs[i].szSuffix,
-                szExtension);
-
-            /* After commit, delete rollback file. After rollback, delete commit file. */
-            msica_op_seq_add_tail(
-                &session.seq_cleanup[MSICA_CLEANUP_ACTION_COUNT - 1 - i],
-                msica_op_create_string(
-                    msica_op_file_delete,
-                    0,
-                    NULL,
-                    szFilenameEx));
+            /* Delete the interface by name. */
+            LPCWSTR szName = szArg[i] + 8;
+
+            {
+                /* Report the name of the interface to installer. */
+                MSIHANDLE hRecord = MsiCreateRecord(3);
+                MsiRecordSetString(hRecord, 1, TEXT("Deleting interface"));
+                MsiRecordSetString(hRecord, 2, szName);
+                int iResult = MsiProcessMessage(hInstall, INSTALLMESSAGE_ACTIONDATA, hRecord);
+                MsiCloseHandle(hRecord);
+                if (iResult == IDCANCEL)
+                {
+                    uiResult = ERROR_INSTALL_USEREXIT;
+                    goto cleanup;
+                }
+            }
+
+            /* Get available TUN/TAP interfaces. */
+            struct tap_interface_node *pInterfaceList = NULL;
+            dwResult = tap_list_interfaces(NULL, NULL, &pInterfaceList, FALSE);
+            if (dwResult == ERROR_SUCCESS)
+            {
+                /* Does the interface exist? */
+                for (struct tap_interface_node *pInterface = pInterfaceList; pInterface != NULL; pInterface = pInterface->pNext)
+                {
+                    if (_tcsicmp(szName, pInterface->szName) == 0)
+                    {
+                        /* Interface found. */
+                        dwResult = tap_delete_interface(NULL, &pInterface->guid, &bRebootRequired);
+                        break;
+                    }
+                }
+
+                tap_free_interface_list(pInterfaceList);
+            }
         }
-        for (size_t i = 0; i < MSICA_CLEANUP_ACTION_COUNT; i++)
+        else if (wcsncmp(szArg[i], L"delete=", 7) == 0)
         {
-            _stprintf_s(
-                szFilenameEx, _countof(szFilenameEx),
-                TEXT("%.*s-%.2s%s"),
-                (int)(szExtension - szSeqFilename), szSeqFilename,
-                openvpnmsica_cleanup_action_seqs[i].szSuffix,
-                szExtension);
-
-            /* Save the cleanup sequence file. */
-            HANDLE hSeqFile = CreateFile(
-                szFilenameEx,
-                GENERIC_WRITE,
-                FILE_SHARE_READ,
-                NULL,
-                CREATE_ALWAYS,
-                FILE_ATTRIBUTE_NORMAL | FILE_FLAG_SEQUENTIAL_SCAN,
-                NULL);
-            if (hSeqFile == INVALID_HANDLE_VALUE)
+            /* Delete the interface by GUID. */
+            GUID guid;
+            if (!openvpnmsica_parse_guid(szArg[i] + 7, &guid))
             {
-                dwResultEx = GetLastError();
-                msg(M_NONFATAL | M_ERRNO, "%s: CreateFile(\"%.*" PRIsLPTSTR "\") failed", __FUNCTION__, _countof(szFilenameEx), szFilenameEx);
-                goto cleanup_session;
+                goto invalid_argument;
             }
-            dwResultEx = msica_op_seq_save(&session.seq_cleanup[i], hSeqFile);
-            CloseHandle(hSeqFile);
-            if (dwResultEx != ERROR_SUCCESS)
+            dwResult = tap_delete_interface(NULL, &guid, &bRebootRequired);
+        }
+        else if (wcsncmp(szArg[i], L"enable=", 7) == 0)
+        {
+            /* Enable the interface. */
+            GUID guid;
+            if (!openvpnmsica_parse_guid(szArg[i] + 7, &guid))
             {
-                goto cleanup_session;
+                goto invalid_argument;
             }
+            dwResult = tap_enable_interface(NULL, &guid, TRUE, &bRebootRequired);
         }
-
-cleanup_session:
-        if (dwResultEx != ERROR_SUCCESS)
+        else if (wcsncmp(szArg[i], L"disable=", 8) == 0)
         {
-            /* The commit and/or rollback scripts were not written to file successfully. Perform the cleanup immediately. */
-            struct msica_session session_cleanup;
-            openvpnmsica_session_init(
-                &session_cleanup,
-                hInstall,
-                true,
-                false);
-            msica_op_seq_process(&session.seq_cleanup[MSICA_CLEANUP_ACTION_ROLLBACK], &session_cleanup);
-
-            szExtension = PathFindExtension(szSeqFilename);
-            for (size_t i = 0; i < MSICA_CLEANUP_ACTION_COUNT; i++)
+            /* Disable the interface. */
+            GUID guid;
+            if (!openvpnmsica_parse_guid(szArg[i] + 8, &guid))
             {
-                _stprintf_s(
-                    szFilenameEx, _countof(szFilenameEx),
-                    TEXT("%.*s-%.2s%s"),
-                    (int)(szExtension - szSeqFilename), szSeqFilename,
-                    openvpnmsica_cleanup_action_seqs[i].szSuffix,
-                    szExtension);
-                DeleteFile(szFilenameEx);
+                goto invalid_argument;
             }
+            dwResult = tap_enable_interface(NULL, &guid, FALSE, &bRebootRequired);
         }
-    }
-    else
-    {
-        /* No cleanup after cleanup support. */
-        uiResult = ERROR_SUCCESS;
+        else
+        {
+            goto invalid_argument;
+        }
+
+        if (dwResult != ERROR_SUCCESS && !bIsCleanup /* Ignore errors in case of commit/rollback to do as much work as possible. */)
+        {
+            uiResult = ERROR_INSTALL_FAILURE;
+            goto cleanup;
+        }
+
+        /* Report progress and check for user cancellation. */
+        MsiRecordSetInteger(hRecordProg, 2, MSICA_INTERFACE_TICK_SIZE);
+        if (MsiProcessMessage(hInstall, INSTALLMESSAGE_PROGRESS, hRecordProg) == IDCANCEL)
+        {
+            dwResult = ERROR_INSTALL_USEREXIT;
+            goto cleanup;
+        }
+
+        continue;
+
+invalid_argument:
+        msg(M_NONFATAL, "%s: Ignoring invalid argument: %ls", __FUNCTION__, szArg[i]);
     }
 
-    for (size_t i = MSICA_CLEANUP_ACTION_COUNT; i--; )
+cleanup:
+    if (bRebootRequired)
     {
-        msica_op_seq_free(&session.seq_cleanup[i]);
+        MsiSetMode(hInstall, MSIRUNMODE_REBOOTATEND, TRUE);
     }
-    DeleteFile(szSeqFilename);
-cleanup_seq:
-    msica_op_seq_free(&seq);
-cleanup_szSeqFilename:
-    free(szSeqFilename);
+    MsiCloseHandle(hRecordProg);
+    LocalFree(szArg);
+cleanup_szSequence:
+    free(szSequence);
 cleanup_CoInitialize:
     if (bIsCoInitialized)
     {
diff --git a/src/openvpnmsica/openvpnmsica.vcxproj b/src/openvpnmsica/openvpnmsica.vcxproj
index afa4faec..4b429806 100644
--- a/src/openvpnmsica/openvpnmsica.vcxproj
+++ b/src/openvpnmsica/openvpnmsica.vcxproj
@@ -116,7 +116,7 @@ 
     <ClCompile Include="..\tapctl\tap.c" />
     <ClCompile Include="dllmain.c" />
     <ClCompile Include="msiex.c" />
-    <ClCompile Include="msica_op.c" />
+    <ClCompile Include="msica_arg.c" />
     <ClCompile Include="openvpnmsica.c" />
   </ItemGroup>
   <ItemGroup>
@@ -124,7 +124,7 @@ 
     <ClInclude Include="..\tapctl\error.h" />
     <ClInclude Include="..\tapctl\tap.h" />
     <ClInclude Include="msiex.h" />
-    <ClInclude Include="msica_op.h" />
+    <ClInclude Include="msica_arg.h" />
     <ClInclude Include="openvpnmsica.h" />
   </ItemGroup>
   <ItemGroup>
diff --git a/src/openvpnmsica/openvpnmsica.vcxproj.filters b/src/openvpnmsica/openvpnmsica.vcxproj.filters
index d0b6dcf0..cb050f97 100644
--- a/src/openvpnmsica/openvpnmsica.vcxproj.filters
+++ b/src/openvpnmsica/openvpnmsica.vcxproj.filters
@@ -27,7 +27,7 @@ 
     <ClCompile Include="openvpnmsica.c">
       <Filter>Source Files</Filter>
     </ClCompile>
-    <ClCompile Include="msica_op.c">
+    <ClCompile Include="msica_arg.c">
       <Filter>Source Files</Filter>
     </ClCompile>
     <ClCompile Include="..\tapctl\tap.c">
@@ -41,7 +41,7 @@ 
     <ClInclude Include="msiex.h">
       <Filter>Header Files</Filter>
     </ClInclude>
-    <ClInclude Include="msica_op.h">
+    <ClInclude Include="msica_arg.h">
       <Filter>Header Files</Filter>
     </ClInclude>
     <ClInclude Include="..\tapctl\tap.h">
diff --git a/src/tapctl/basic.h b/src/tapctl/basic.h
index bfbcc30d..a0a88511 100644
--- a/src/tapctl/basic.h
+++ b/src/tapctl/basic.h
@@ -23,12 +23,20 @@ 
 #define BASIC_H
 
 #ifdef _UNICODE
-#define PRIsLPTSTR "ls"
-#define PRIsLPOLESTR  "ls"
+#define PRIsLPTSTR      "ls"
+#define PRIsLPOLESTR    "ls"
 #else
-#define PRIsLPTSTR "s"
-#define PRIsLPOLESTR  "ls"
+#define PRIsLPTSTR      "s"
+#define PRIsLPOLESTR    "ls"
 #endif
+#define PRIXGUID        "{%08lX-%04hX-%04hX-%02hhX%02hhX-%02hhX%02hhX%02hhX%02hhX%02hhX%02hhX}"
+#define PRIGUID_PARAM(g) \
+    (g).Data1, (g).Data2, (g).Data3, (g).Data4[0], (g).Data4[1], (g).Data4[2], (g).Data4[3], (g).Data4[4], (g).Data4[5], (g).Data4[6], (g).Data4[7]
+#define PRIGUID_PARAM_REF(g) \
+    &(g).Data1, &(g).Data2, &(g).Data3, &(g).Data4[0], &(g).Data4[1], &(g).Data4[2], &(g).Data4[3], &(g).Data4[4], &(g).Data4[5], &(g).Data4[6], &(g).Data4[7]
+
+#define __L(q)          L ## q
+#define _L(q)           __L(q)
 
 #ifndef _In_
 #define _In_
@@ -42,6 +50,9 @@ 
 #ifndef _Inout_
 #define _Inout_
 #endif
+#ifndef _Inout_opt_
+#define _Inout_opt_
+#endif
 #ifndef _Out_
 #define _Out_
 #endif
diff --git a/src/tapctl/tap.c b/src/tapctl/tap.c
index 576f6740..d4631679 100644
--- a/src/tapctl/tap.c
+++ b/src/tapctl/tap.c
@@ -31,6 +31,7 @@ 
 #include <cfgmgr32.h>
 #include <objbase.h>
 #include <setupapi.h>
+#include <stdio.h>
 #include <tchar.h>
 
 #ifdef _MSC_VER