Date: Mon, 10 May 2021 13:33:51 +0000 From: bugzilla-noreply@freebsd.org To: bugs@FreeBSD.org Subject: [Bug 255749] jumbo frame support of IPv6 vlan interfaces is broken Message-ID: <bug-255749-227@https.bugs.freebsd.org/bugzilla/>
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https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=255749 Bug ID: 255749 Summary: jumbo frame support of IPv6 vlan interfaces is broken Product: Base System Version: 13.0-RELEASE Hardware: Any OS: Any Status: New Severity: Affects Some People Priority: --- Component: kern Assignee: bugs@FreeBSD.org Reporter: topical@gmx.net If you have an interface with jumbo frame support enabled and create a vlan, mtu is not inherited by its IPv6 vlan interface. IPv4 is unaffected. Setup: change mtu of an interface to 9k, create a vlan sub interface and (optionally) activate it: # ifconfig vtnet0 mtu 9000 # ifconfig vtnet0.1000 create # ifconfig vtnet0.1000 up Check state with "ifconfig" vtnet0: flags=8863<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000 ... vtnet0.1000: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 9000 Check ipv6 mtu: # ndp -i vtnet0.1000 linkmtu=0, maxmtu=1500, curhlim=64, basereachable=30s0ms, reachable=19s, retrans=1s0ms ... You see that "maxmtu=1500". So, this host never uses IPv6 with Jumbo frames on this vlan. To make things worse: Mellanox cards don't like that scenario and have massive packet loss (but this is another story). To fix it, you need to temporarily change mtu of vlan interface # ifconfig vtnet0.1000 mtu 8000 # ifconfig vtnet0.1000 mtu 9000 # ndp -i vtnet0.1000 linkmtu=0, maxmtu=9000, curhlim=64, basereachable=30s0ms, reachable=19s, retrans=1s0ms -- You are receiving this mail because: You are the assignee for the bug.home | help
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