UDP receive buffer size on OpenBSD?

[mrusme]

Hey there,

I'm running into an issue on OpenBSD where I get the following output:

failed to increase receive buffer size (wanted: 2048 kiB, got 0 kiB). See https://github.com/lucas-clemente/quic-go/wiki/UDP-Receive-Buffer-Size for details.

Unfortunately the linked documentation doesn't describe how to do so. Also, resources that I found (e.g. https://comp.unix.bsd.openbsd.misc.narkive.com/X8fbptCR/how-to-raise-the-maxsockbuf-in-openbsd) doesn't seem to provide a feasible solution to this.

Is there a way quic-go can circumvent this issue?

Thank you!

[marten-seemann]

I don’t have any experience with OpenBSD. A PR would be appreciated.

[shassard]

I've just tested this on OpenBSD 7.2 amd64 and have taken the following notes:

The correct sysctl to change is:

sysctl net.inet.udp.recvspace=...

While the maximum value supported by the kernel is 2147483647, resolving DNS hostnames via dig fails when the value is set beyond 2048000.

The maximum value doesn't seem to be affected by allocating more memory to the system (8GB vs 16GB available to the host at boot time).