error - socket buffer size not set correctly

[arainero]

Context

I am trying to do an iperf test from my machine 192.168.1.50 to another machine 192.168.1.220. The following test will give the error "error - socket buffer size not set correctly":

iperf3 -c 192.168.1.220 -w 512K

This command will work when -w is set to 416k, anything higher and that error is displayed. I did a little poking around and I thought it was due to my tcp session window being too small, but it doesn't appear to be the case.

These are some of the sysctl values:

net.core.rmem_max = 16777216
net.core.rmem_default = 212992
net.core.wmem_max = 212992
net.ipv4.tcp_rmem = 4096        87380   16777216
net.ipv4.tcp_wmem = 4096        16384   16777216

I am however able to do this test successfully in the other direction. So I believe this has to do with some type of setting on this machine, which I don't know what it may be.

Any help will be appreciated on this.

Thank you!

• Version of iperf3:
  iperf 3.1.7
  Linux 3450asterisk 3.10.0-123.9.3.el7.x86_64 setting of window size should be explicit #1 SMP Thu Nov 6 15:06:03 UTC 2014 x86_64
  Optional features available: CPU affinity setting, IPv6 flow label, TCP congestion algorithm setting, sendfile / zerocopy, socket pacing

• Hardware:
  Onboard NIC, 8 GB ram, Xeon E3-1271

• Operating system (and distribution, if any):
  CentOS 7

Bug Report

• Expected Behavior
  iperf should be able to handle that window size

• Actual Behavior
  iperf throws an error when window size is greater than 416k

• Steps to Reproduce
  Try to do an iperf test with a window size greater than 416k

[bmah888]

I thought I had written a response to this but I didn't, apparently.

You might want to try increasing the size of net.core.wmem_max, which still seems to have a fairly low/default value.

Some other tips on tuning a Linux kernel (which covers setting the socket buffer sizes) can be found here:

http://fasterdata.es.net/host-tuning/linux/

Finally you may want to consider using a newer version of iperf3 (iperf 3.6 is current as of this writing). If I remember correctly, some newer versions have some fixes in the socket buffer setting code, although offhand, I remember whether they are directly applicable to this problem.

[arainero]

That's a good read, thanks.

[bmah888]

Closing this issue as I think the question was resolved.