Comment 44 for bug 1720126

Just a note:

There are theoretical and practical upper limits to the number of Virtual Functions per PF (256 from some sources)[1], so setting a static maximum buffer size is a justifiable option. That moves the burden over to ensuring that the response per VF doesn't grow in the future.

Libvirt had similar issues (it used libnl) until it enabled message peeking by default. Unfortunately the only way to solve this issue in all cases without performance penalty is to alter the kernel's message truncation handling mechanism to not free the skb if MSG_TRUNC occurred. [1]

It's possible to put in a retry on truncation, resizing the receive buffer to fit the response, BUT since that's two unrelated syscalls, it leaves me feeling a bit queasy.

[1] http://windowsitpro.com/systems-management/q-what-sr-iov
[2] http://man7.org/linux/man-pages/man2/recv.2.html