On 05/20/2016 10:07 AM, Jonathan Morton wrote:

On 20 May, 2016, at 20:01, Rick Jones <rick.jon...@hpe.com> wrote:

But I haven't seen that EMSGSIZE happen with netperf UDP tests -
could be though I've never run them in an environment which
triggered PTMUD.

It’s entirely possible that netperf and/or iperf3 are (ab)using the
IP_MTU_DISCOVERY socket option mentioned.

I cannot speak to iperf, but netperf doesn't manipulate IP_MTU_DISCOVERY. It will set IP_RECVERR for a UDP_STREAM test, and will by default set SO_DONTROUTE (*) for UDP_STREAM but no IP_MTU_DISCOVERY.

happy benchmarking,

rick jones

* QA engineers doing link up/down testing with UDP_STREAM on test systems not air-gapped from the production networks are dangerous creatures...

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