FreeBSD MTU issue w/fix

[tickerguy]

softether-4.38.9760
Server
FreeBSD 13.1-STABLE
64-bit AMD

The server attempts to modify the MTU of the local interface so as to use jumbo frames if the attempted transmission will be more than the default (typically 1500 bytes for an Ethernet controller.) This behavior is disabled if the interface is opened raw, but that is only supported on Linux.

On FreeBSD this results in multiple attempts to reset the MTU higher, and then complaints when even the interfaces maximum jumbo frame size is insufficient.

Expected behavior:
The server should function normally.

Actual behavior:
The server repeatedly attempts to modify the MTU, each of which attempts results in an up/down and is wildly destructive to network traffic and other services on the machine.

Steps to reproduce

Start server on FreeBSD (loaded from packages, or built from ports.)

Note repeated up/downs in the dmesg log and complaints in the server logfiles about MTU size.

Patch -

The following patch against src/Cedar/BridgeUnix.c resolves the problem by disabling the MTU reset function if and only if the software is compiled on FreeBSD.

*** BridgeUnix.c.orig   Tue Oct 18 14:16:09 2022
--- BridgeUnix.c        Tue Oct 18 13:31:05 2022
***************
*** 887,893 ****
--- 887,897 ----
        {
                return false;
        }
+ #ifndef       __FreeBSD__
        return true;
+ #else
+       return false;
+ #endif
  #else // defined(UNIX_LINUX) || defined(UNIX_BSD) || defined(UNIX_SOLARIS)
        return false;
  #endif        // defined(UNIX_LINUX) || defined(UNIX_BSD) || defined(UNIX_SOLARIS)

[shipitsin-ilia]

@tickerguy , please create a PR.

also, please notice that this repo belongs to "SE VPN Developer Edition" (versioned 5.x.x), code is aligned to stable edition, but accepting PR will not propse changes to stable edition automatically. i.e. you will need to test 5.x.x built from git master.

@metalefty , I recall you run SE VPN on freebsd, can you please review these changes ?

[metalefty]

Yes, I will review after @tickerguy creates a PR for 5.x.

[metalefty]

References:

• https://www.vpnusers.com/viewtopic.php?f=7&t=67841
• https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=267178

[tickerguy]

Done (I think -- last time I set up a pull it was through Jira, so hope I did it right :-))

On 10/19/2022 06:14, metalefty wrote: Yes, I will review after @tickerguy <https://github.com/tickerguy> creates a PR for 5.x. — Reply to this email directly, view it on GitHub <#1677 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/ADJVXIH5W3BESEVDQTOV4F3WD7CY3ANCNFSM6AAAAAARIQJ54M>. You are receiving this because you were mentioned.Message ID: ***@***.***>

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