[Openvpn-devel,v1] Remove --memstats feature

diff --git a/CMakeLists.txt b/CMakeLists.txt
index bf754f3..c9301e6 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -490,8 +490,6 @@ 
     src/openvpn/mroute.h
     src/openvpn/mss.c
     src/openvpn/mss.h
-    src/openvpn/mstats.c
-    src/openvpn/mstats.h
     src/openvpn/mtcp.c
     src/openvpn/mtcp.h
     src/openvpn/mtu.c
diff --git a/Changes.rst b/Changes.rst
index 4feacad2..41af103 100644
--- a/Changes.rst
+++ b/Changes.rst
@@ -217,6 +217,11 @@ 
     ``--allow-compression yes`` is now an alias for
     ``--allow-compression asym``.
 
+``--memstats`` feature removed
+    The ``--mememstat`` was largely undocumented and there is no known
+    user of this feature.  This feature provided very limited statistics
+    (number of users, link bytes read/written) and we do not except any
+    usage because of this.
 
 User-visible Changes
 --------------------
diff --git a/src/openvpn/Makefile.am b/src/openvpn/Makefile.am
index dc58cd1..db87dfc 100644
--- a/src/openvpn/Makefile.am
+++ b/src/openvpn/Makefile.am
@@ -90,7 +90,6 @@ 
 	mbedtls_compat.h \
 	mroute.c mroute.h \
 	mss.c mss.h \
-	mstats.c mstats.h \
 	mtcp.c mtcp.h \
 	mtu.c mtu.h \
 	mudp.c mudp.h \
diff --git a/src/openvpn/error.c b/src/openvpn/error.c
index 735d259..bd588d4 100644
--- a/src/openvpn/error.c
+++ b/src/openvpn/error.c
@@ -37,8 +37,6 @@ 
 #include "status.h"
 #include "integer.h"
 #include "ps.h"
-#include "mstats.h"
-
 
 #if SYSLOG_CAPABILITY
 #ifndef LOG_OPENVPN
@@ -723,10 +721,6 @@ 
         }
 #endif
 
-#ifdef ENABLE_MEMSTATS
-        mstats_close();
-#endif
-
 #ifdef ABORT_ON_ERROR
         if (status == OPENVPN_EXIT_STATUS_ERROR)
         {
diff --git a/src/openvpn/forward.c b/src/openvpn/forward.c
index 7f72000..5bbac13 100644
--- a/src/openvpn/forward.c
+++ b/src/openvpn/forward.c
@@ -44,8 +44,6 @@ 
 
 #include "memdbg.h"
 
-#include "mstats.h"
-
 counter_type link_read_bytes_global;  /* GLOBAL */
 counter_type link_write_bytes_global; /* GLOBAL */
 
@@ -992,12 +990,6 @@ 
     {
         c->c2.link_read_bytes += c->c2.buf.len;
         link_read_bytes_global += c->c2.buf.len;
-#ifdef ENABLE_MEMSTATS
-        if (mmap_stats)
-        {
-            mmap_stats->link_read_bytes = link_read_bytes_global;
-        }
-#endif
         c->c2.original_recv_size = c->c2.buf.len;
     }
     else
@@ -1821,12 +1813,6 @@ 
                 c->c2.max_send_size_local = max_int(size, c->c2.max_send_size_local);
                 c->c2.link_write_bytes += size;
                 link_write_bytes_global += size;
-#ifdef ENABLE_MEMSTATS
-                if (mmap_stats)
-                {
-                    mmap_stats->link_write_bytes = link_write_bytes_global;
-                }
-#endif
             }
         }
 
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index aa2611d..1bdaf27 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -44,7 +44,6 @@ 
 #include "ps.h"
 #include "lladdr.h"
 #include "ping.h"
-#include "mstats.h"
 #include "ssl_verify.h"
 #include "ssl_ncp.h"
 #include "tls_crypt.h"
@@ -908,22 +907,6 @@ 
     return false;
 #endif
 
-#ifdef MSTATS_TEST
-    {
-        int i;
-        mstats_open("/dev/shm/mstats.dat");
-        for (i = 0; i < 30; ++i)
-        {
-            mmap_stats->n_clients += 1;
-            mmap_stats->link_write_bytes += 8;
-            mmap_stats->link_read_bytes += 16;
-            sleep(1);
-        }
-        mstats_close();
-        return false;
-    }
-#endif
-
     return true;
 }
 
@@ -1233,13 +1216,6 @@ 
             }
         }
 
-#ifdef ENABLE_MEMSTATS
-        if (c->first_time && c->options.memstats_fn)
-        {
-            mstats_open(c->options.memstats_fn);
-        }
-#endif
-
 #ifdef ENABLE_SELINUX
         /* Apply a SELinux context in order to restrict what OpenVPN can do
          * to _only_ what it is supposed to do after initialization is complete
diff --git a/src/openvpn/mstats.c b/src/openvpn/mstats.c
deleted file mode 100644
index bd6316c..0000000
--- a/src/openvpn/mstats.c
+++ /dev/null
@@ -1,124 +0,0 @@ 
-/*
- *  OpenVPN -- An application to securely tunnel IP networks
- *             over a single TCP/UDP port, with support for SSL/TLS-based
- *             session authentication and key exchange,
- *             packet encryption, packet authentication, and
- *             packet compression.
- *
- *  Copyright (C) 2002-2025 OpenVPN Inc <sales@openvpn.net>
- *
- *  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, see <https://www.gnu.org/licenses/>.
- */
-
-/*
- * Maintain usage stats in a memory-mapped file
- */
-
-#ifdef HAVE_CONFIG_H
-#include "config.h"
-#endif
-
-#include "syshead.h"
-
-#if defined(ENABLE_MEMSTATS)
-
-#include <sys/mman.h>
-
-#include "error.h"
-#include "misc.h"
-#include "mstats.h"
-
-#include "memdbg.h"
-
-volatile struct mmap_stats *mmap_stats = NULL; /* GLOBAL */
-static char mmap_fn[128];
-
-void
-mstats_open(const char *fn)
-{
-    void *data;
-    ssize_t stat;
-    int fd;
-    struct mmap_stats ms;
-
-    if (mmap_stats) /* already called? */
-    {
-        return;
-    }
-
-    /* verify that filename is not too long */
-    if (strlen(fn) >= sizeof(mmap_fn))
-    {
-        msg(M_FATAL, "mstats_open: filename too long");
-    }
-
-    /* create file that will be memory mapped */
-    fd = open(fn, O_CREAT | O_TRUNC | O_RDWR, S_IRUSR | S_IWUSR);
-    if (fd < 0)
-    {
-        msg(M_ERR, "mstats_open: cannot open: %s", fn);
-        return;
-    }
-
-    /* set the file to the correct size to contain a
-     * struct mmap_stats, and zero it */
-    CLEAR(ms);
-    ms.state = MSTATS_ACTIVE;
-    stat = write(fd, &ms, sizeof(ms));
-    if (stat != sizeof(ms))
-    {
-        msg(M_ERR, "mstats_open: write error: %s", fn);
-        close(fd);
-        return;
-    }
-
-    /* mmap the file */
-    data = mmap(NULL, sizeof(struct mmap_stats), PROT_READ | PROT_WRITE, MAP_SHARED, fd, 0);
-    if (data == MAP_FAILED)
-    {
-        msg(M_ERR, "mstats_open: write error: %s", fn);
-        close(fd);
-        return;
-    }
-
-    /* close the fd (mmap now controls the file) */
-    if (close(fd))
-    {
-        msg(M_ERR, "mstats_open: close error: %s", fn);
-    }
-
-    /* save filename so we can delete it later */
-    strcpy(mmap_fn, fn);
-
-    /* save a global pointer to memory-mapped region */
-    mmap_stats = (struct mmap_stats *)data;
-
-    msg(M_INFO, "memstats data will be written to %s", fn);
-}
-
-void
-mstats_close(void)
-{
-    if (mmap_stats)
-    {
-        mmap_stats->state = MSTATS_EXPIRED;
-        if (munmap((void *)mmap_stats, sizeof(struct mmap_stats)))
-        {
-            msg(M_WARN | M_ERRNO, "mstats_close: munmap error");
-        }
-        platform_unlink(mmap_fn);
-        mmap_stats = NULL;
-    }
-}
-
-#endif /* if defined(ENABLE_MEMSTATS) */
diff --git a/src/openvpn/mstats.h b/src/openvpn/mstats.h
deleted file mode 100644
index c38b0f2..0000000
--- a/src/openvpn/mstats.h
+++ /dev/null
@@ -1,51 +0,0 @@ 
-/*
- *  OpenVPN -- An application to securely tunnel IP networks
- *             over a single TCP/UDP port, with support for SSL/TLS-based
- *             session authentication and key exchange,
- *             packet encryption, packet authentication, and
- *             packet compression.
- *
- *  Copyright (C) 2002-2025 OpenVPN Inc <sales@openvpn.net>
- *
- *  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, see <https://www.gnu.org/licenses/>.
- */
-
-/*
- * Maintain usage stats in a memory-mapped file
- */
-
-#if !defined(OPENVPN_MEMSTATS_H) && defined(ENABLE_MEMSTATS)
-#define OPENVPN_MEMSTATS_H
-
-#include "basic.h"
-
-/* this struct is mapped to the file */
-struct mmap_stats
-{
-    counter_type link_read_bytes; /* counter_type can be assumed to be a uint64_t */
-    counter_type link_write_bytes;
-    int n_clients;
-
-#define MSTATS_UNDEF   0
-#define MSTATS_ACTIVE  1
-#define MSTATS_EXPIRED 2
-    int state;
-};
-
-extern volatile struct mmap_stats *mmap_stats; /* GLOBAL */
-
-void mstats_open(const char *fn);
-
-void mstats_close(void);
-
-#endif /* if !defined(OPENVPN_MEMSTATS_H) && defined(ENABLE_MEMSTATS) */
diff --git a/src/openvpn/multi.c b/src/openvpn/multi.c
index 285671d..e243843 100644
--- a/src/openvpn/multi.c
+++ b/src/openvpn/multi.c
@@ -37,7 +37,6 @@ 
 #include "run_command.h"
 #include "otime.h"
 #include "gremlin.h"
-#include "mstats.h"
 #include "ssl_verify.h"
 #include "ssl_ncp.h"
 #include "vlan.h"
@@ -80,17 +79,6 @@ 
 }
 #endif
 
-static inline void
-update_mstat_n_clients(const int n_clients)
-{
-#ifdef ENABLE_MEMSTATS
-    if (mmap_stats)
-    {
-        mmap_stats->n_clients = n_clients;
-    }
-#endif
-}
-
 static bool
 learn_address_script(const struct multi_context *m, const struct multi_instance *mi, const char *op,
                      const struct mroute_addr *addr)
@@ -589,7 +577,6 @@ 
 
     /* adjust current client connection count */
     m->n_clients += mi->n_clients_delta;
-    update_mstat_n_clients(m->n_clients);
     mi->n_clients_delta = 0;
 
     /* prevent dangling pointers */
@@ -2799,7 +2786,6 @@ 
 
     /* increment number of current authenticated clients */
     ++m->n_clients;
-    update_mstat_n_clients(m->n_clients);
     --mi->n_clients_delta;
 
 #ifdef ENABLE_MANAGEMENT
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index 9c02a8c..ecf9374 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -323,9 +323,6 @@ 
     "                  via a VRF present on the system.\n"
 #endif
     "--txqueuelen n  : Set the tun/tap TX queue length to n (Linux only).\n"
-#ifdef ENABLE_MEMSTATS
-    "--memstats file : Write live usage stats to memory mapped binary file.\n"
-#endif
     "--mlock         : Disable Paging -- ensures key material and tunnel\n"
     "                  data will never be written to disk.\n"
     "--up cmd        : Run command cmd after successful tun device open.\n"
@@ -6333,13 +6330,6 @@ 
         options->log = true;
         redirect_stdout_stderr(p[1], true);
     }
-#ifdef ENABLE_MEMSTATS
-    else if (streq(p[0], "memstats") && p[1] && !p[2])
-    {
-        VERIFY_PERMISSION(OPT_P_GENERAL);
-        options->memstats_fn = p[1];
-    }
-#endif
     else if (streq(p[0], "mlock") && !p[1])
     {
         VERIFY_PERMISSION(OPT_P_GENERAL);
diff --git a/src/openvpn/options.h b/src/openvpn/options.h
index 125e524..9d2ff9f 100644
--- a/src/openvpn/options.h
+++ b/src/openvpn/options.h
@@ -336,10 +336,6 @@ 
 
     bool mtu_test;
 
-#ifdef ENABLE_MEMSTATS
-    char *memstats_fn;
-#endif
-
     bool mlock;
 
     int keepalive_ping; /* a proxy for ping/ping-restart */
diff --git a/src/openvpn/syshead.h b/src/openvpn/syshead.h
index 26a553b..90045a9 100644
--- a/src/openvpn/syshead.h
+++ b/src/openvpn/syshead.h
@@ -528,13 +528,6 @@ 
 #define USE_COMP
 #endif
 
-/*
- * Enable --memstats option
- */
-#ifdef TARGET_LINUX
-#define ENABLE_MEMSTATS
-#endif
-
 #ifdef _MSC_VER
 #ifndef PATH_MAX
 #define PATH_MAX MAX_PATH