[ofa-general] Ipoib child interfaces are created in dgram mode, even if the config file (and main interface) specify connected mode.

[Mike Heinz]

One of our testers recently reported that he was getting different performance numbers from IPOIB depending on whether he was using interface ib0 or  a child interface he had created with /sys/class/netib0/create_child.

Investigating, I noticed that the two interfaces have different MTU sizes:

ib0       Link encap:UNSPEC  HWaddr 80-00-00-02-FE-80-00-00-00-00-00-00-00-00-00-00
          inet addr:172.21.33.58  Bcast:172.21.255.255  Mask:255.255.0.0
          inet6 addr: fe80::211:7500:ff:8fa4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:65520  Metric:1
          RX packets:76 errors:0 dropped:0 overruns:0 frame:0
          TX packets:23147668 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:256
          RX bytes:5284 (5.1 Kb)  TX bytes:17365044664 (16560.5 Mb)

ib0.9001  Link encap:UNSPEC  HWaddr 80-00-00-06-FE-80-00-00-00-00-00-00-00-00-00-00
          inet addr:172.21.34.58  Bcast:172.21.255.255  Mask:255.255.0.0
          inet6 addr: fe80::211:7500:ff:8fa4/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:2044  Metric:1
          RX packets:60413619 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:256
          RX bytes:112572449188 (107357.4 Mb)  TX bytes:0 (0.0 b)


This leads me to believe that the child interface is in datagram mode even though the parent is in connected mode.

Is this expected behavior? Is there a way to change this?

--
Michael Heinz
Principal Engineer, Qlogic Corporation
King of Prussia, Pennsylvania
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