Date: Fri, 23 Aug 2019 17:32:12 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 240059] Min MTU for a interface GIF interface is to high Message-ID: <bug-240059-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=3D240059 Bug ID: 240059 Summary: Min MTU for a interface GIF interface is to high Product: Base System Version: 12.0-STABLE Hardware: Any OS: Any Status: New Severity: Affects Only Me Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: sirl33tname@gmail.com The Min MTU for a GIF interface is 1280. See:=20 https://github.com/freebsd/freebsd/blob/c4ed3acb9f59d3498905e95d5d445c5046f= dfdb6/sys/net/if_gif.h#L80-L82 #define GIF_MTU_MIN (1280) /* Minimum MTU */ There are some cases where this is still to high.=20 And to quote the man page: If the outer protocol is IPv6, path MTU discovery for encapsulated packets may affect communication over the interface. The first bigger- than-pmtu packet may be lost. To avoid the problem, you may want to set the interface MTU for gif to 1240 or smaller, when the outer header is IPv6 and the inner header is IPv4. So I would expect that it is possible to set the MTU for a GIF interface lo= wer than 1280. --=20 You are receiving this mail because: You are the assignee for the bug.=
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