FreeBSD write to network: Input/output error with jumbo frames

[andrewbasterfield]

vblade running on FreeBSD 10.2-RELEASE x86_64, client is Linux. The 2 boxes have jumbo frames enabled and will happily ping at ~9000 bytes

When I set the MTU to 4131 all is fine; I get 3584 byte data frames
When I set the MTU to 4132 the frame size jumps to 4096 and vblade exits with
write to network: Input/output error

Presumably there is some limitation on FreeBSD with >4096 byte writes to BPF device; I haven't been able to find any reference to this limitation and if it is tweakable. Any suggestions?

[ecashin]

I don't have much experience with AoE on FreeBSD. You might be able to
find some information by searching the archives of the aoetools-discuss
mailing list, hosted at sourceforge and archived elsewhere, including
gmane, I believe.

On 10/10/2015 03:37 PM, Andrew Basterfield wrote:

vblade running on FreeBSD 10.2-RELEASE x86_64, client is Linux. The 2
boxes have jumbo frames enabled and will happily ping at ~9000 bytes

When I set the MTU to 4131 all is fine; I get 3584 byte data frames
When I set the MTU to 4132 the frame size jumps to 4096 and vblade
exits with
write to network: Input/output error

Presumably there is some limitation on FreeBSD with >4096 byte writes
to BPF device; I haven't been able to find any reference to this
limitation and if it is tweakable. Any suggestions?

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[andrewbasterfield]

Have taken it to FreeBSD mailing lists; will update with any progress

[andrewbasterfield]

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=205164

[carton-of-mice]

Hello. I haven't tracked the project lately. Due to insufficient dog-food-ing, this slipped by.
FreeBSD indeed, as the other BSDs, limits BPF writes to one mbuf (have not checked reads, but behaviour probably matches). I'm going to file a PR to cap MTU at page size, but I'm not sure if a full-sized jumbo frame workaround is available.