diff mbox series

[Openvpn-devel,v1] Clean up documentation for --tun-mtu-max

Message ID 20250823153652.30938-1-gert@greenie.muc.de
State New
Headers show
Series [Openvpn-devel,v1] Clean up documentation for --tun-mtu-max | expand

Commit Message

Gert Doering Aug. 23, 2025, 3:36 p.m. UTC 
From: Frank Lichtenheld <frank@lichtenheld.com>

There was some confusion about how the option
was called...

Change-Id: I5e240c35cd4236e1d845195e4634fd5008f61814
Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
Acked-by: Gert Doering <gert@greenie.muc.de>
---

This change was reviewed on Gerrit and approved by at least one
developer. I request to merge it to master.

Gerrit URL: https://gerrit.openvpn.net/c/openvpn/+/1152
This mail reflects revision 1 of this Change.

Acked-by according to Gerrit (reflected above):
Gert Doering <gert@greenie.muc.de>

Comments

Gert Doering Aug. 23, 2025, 3:43 p.m. UTC | #1 
This all makes sense - thanks for spotting.  No idea what we were looking
at when merging the original patch...

Not sure introducing the extra define improves readability (the old context
made it quite clear that "1600" is not "a random number out of thin air")
- but since TUN_MTU_DEFAULT has a define in mtu.h, why not.

Your patch has been applied to the master branch.

commit 5c4744f28e2adb3fc8f6fb3b3c8ffe22636eb0a0
Author: Frank Lichtenheld
Date:   Sat Aug 23 17:36:46 2025 +0200

     Clean up documentation for --tun-mtu-max

     Signed-off-by: Frank Lichtenheld <frank@lichtenheld.com>
     Acked-by: Gert Doering <gert@greenie.muc.de>
     Message-Id: <20250823153652.30938-1-gert@greenie.muc.de>
     URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg32663.html
     Signed-off-by: Gert Doering <gert@greenie.muc.de>


--
kind regards,

Gert Doering
diff mbox series

Patch

diff --git a/doc/man-sections/vpn-network-options.rst b/doc/man-sections/vpn-network-options.rst
index 4a64e8d..2a06ef6 100644
--- a/doc/man-sections/vpn-network-options.rst
+++ b/doc/man-sections/vpn-network-options.rst
@@ -587,7 +587,7 @@ 
   packets larger than ``tun-mtu`` (e.g. Linux and FreeBSD) but other platforms
   (like macOS) limit received packets to the same size as the MTU.
 
---tun-max-mtu maxmtu
+--tun-mtu-max maxmtu
   This configures the maximum MTU size that a server can push to ``maxmtu``,
   by configuring the internal buffers to allow at least this packet size.
   The default for ``maxmtu`` is 1600. Currently, only increasing beyond 1600
diff --git a/src/openvpn/init.c b/src/openvpn/init.c
index 5583274..9dd3b96 100644
--- a/src/openvpn/init.c
+++ b/src/openvpn/init.c
@@ -2916,7 +2916,7 @@ 
 
     /* We always allow at least 1600 MTU packets to be received in our buffer
      * space to allow server to push "baby giant" MTU sizes */
-    frame->tun_max_mtu = max_int(1600, frame->tun_max_mtu);
+    frame->tun_max_mtu = max_int(TUN_MTU_MAX_MIN, frame->tun_max_mtu);
 
     size_t payload_size = frame->tun_max_mtu;
 
diff --git a/src/openvpn/mtu.h b/src/openvpn/mtu.h
index 925ef0b..c092461 100644
--- a/src/openvpn/mtu.h
+++ b/src/openvpn/mtu.h
@@ -69,6 +69,11 @@ 
 #define TUN_MTU_DEFAULT 1500
 
 /*
+ * Minimum maximum MTU
+ */
+#define TUN_MTU_MAX_MIN 1600
+
+/*
  * MTU Defaults for TAP devices
  */
 #define TAP_MTU_EXTRA_DEFAULT 32
diff --git a/src/openvpn/options.c b/src/openvpn/options.c
index e9584a8..0b16c5a 100644
--- a/src/openvpn/options.c
+++ b/src/openvpn/options.c
@@ -297,6 +297,7 @@ 
     "--tun-mtu-extra n : Assume that tun/tap device might return as many\n"
     "                  as n bytes more than the tun-mtu size on read\n"
     "                  (default TUN=0 TAP=%d).\n"
+    "--tun-mtu-max n : Maximum pushable MTU (default and minimum=%d).\n"
     "--link-mtu n    : Take the TCP/UDP device MTU to be n and derive the tun MTU\n"
     "                  from it.\n"
     "--mtu-disc type : Should we do Path MTU discovery on TCP/UDP channel?\n"
@@ -4844,8 +4845,9 @@ 
 
     fprintf(fp, usage_message, title_string, o.ce.connect_retry_seconds,
             o.ce.connect_retry_seconds_max, o.ce.local_port, o.ce.remote_port, TUN_MTU_DEFAULT,
-            TAP_MTU_EXTRA_DEFAULT, o.verbosity, o.authname, o.replay_window, o.replay_time,
-            o.tls_timeout, o.renegotiate_seconds, o.handshake_window, o.transition_window);
+            TAP_MTU_EXTRA_DEFAULT, TUN_MTU_MAX_MIN, o.verbosity, o.authname, o.replay_window,
+            o.replay_time, o.tls_timeout, o.renegotiate_seconds, o.handshake_window,
+            o.transition_window);
     fflush(fp);
 
 #endif                                       /* ENABLE_SMALL */
@@ -7011,7 +7013,7 @@ 
             options->ce.occ_mtu = 0;
         }
     }
-    else if (streq(p[0], "tun-mtu-max") && p[1] && !p[3])
+    else if (streq(p[0], "tun-mtu-max") && p[1] && !p[2])
     {
         VERIFY_PERMISSION(OPT_P_MTU | OPT_P_CONNECTION);
         int max_mtu = positive_atoi(p[1], msglevel);
diff --git a/src/openvpn/push.c b/src/openvpn/push.c
index 889b268..4f6adfc 100644
--- a/src/openvpn/push.c
+++ b/src/openvpn/push.c
@@ -721,7 +721,7 @@ 
         {
             msg(M_WARN,
                 "Warning: reported maximum MTU from client (%d) is lower "
-                "than MTU used on the server (%d). Add tun-max-mtu %d "
+                "than MTU used on the server (%d). Add tun-mtu-max %d "
                 "to client configuration.",
                 client_max_mtu, o->ce.tun_mtu, o->ce.tun_mtu);
         }