[openib-general] IPoIB odd loopback packet from arp

[Todd Bowman]

Using the OFED 1.0 and OFED 1.1 stack I have notice some rcvswrelay errors.
I have tracked it down to the arp request.  I can reproduce the problem with
the following steps:

( I have used both 2.6.14.14 and 2.6.18.1 kernels)

ib109> arp -d ib110
ib109> ping ib110 -c 2

# ib_ipoib module debug
13:15:46 ib109 kernel: ib0: sending packet, length=60 address=f6187200
qpn=0xffffff
13:15:46 ib109 kernel: ib0: called: id 34, op 0, status: 0
13:15:46 ib109 kernel: ib0: send complete, wrid 34
13:15:46 ib109 kernel: ib0: called: id -2147483623, op 128, status: 0
13:15:46 ib109 kernel: ib0: received 100 bytes, SLID 0x0369
13:15:46 ib109 kernel: ib0: dropping loopback packet
13:15:46 ib109 kernel: ib0: called: id -2147483622, op 128, status: 0
13:15:46 ib109 kernel: ib0: received 100 bytes, SLID 0x016d
13:15:46 ib109 kernel: ib0: sending packet, length=88 address=f6e57520
qpn=0x000404
13:15:46 ib109 kernel: ib0: called: id 35, op 0, status: 0
13:15:46 ib109 kernel: ib0: send complete, wrid 35
13:15:46 ib109 kernel: ib0: called: id -2147483621, op 128, status: 0
13:15:46 ib109 kernel: ib0: received 128 bytes, SLID 0x016d
13:15:47 ib109 kernel: ib0: sending packet, length=88 address=f6e57520
qpn=0x000404
13:15:47 ib109 kernel: ib0: called: id 36, op 0, status: 0
13:15:47 ib109 kernel: ib0: send complete, wrid 36
13:15:47 ib109 kernel: ib0: called: id -2147483620, op 128, status: 0
13:15:47 ib109 kernel: ib0: received 128 bytes, SLID 0x016d
13:15:51 ib109 kernel: ib0: called: id -2147483619, op 128, status: 0
13:15:51 ib109 kernel: ib0: received 100 bytes, SLID 0x016d
13:15:51 ib109 kernel: ib0: sending packet, length=60 address=f6e57520
qpn=0x000404
13:15:51 ib109 kernel: ib0: called: id 37, op 0, status: 0
13:15:51 ib109 kernel: ib0: send complete, wrid 37

# tcpdump -i ib0
13:15:46.977578 arp who-has ib110 tell ib109 hardware #32
13:15:46.977682 arp reply ib110 is-at
00:00:04:04:fe:80:00:00:00:00:00:00:00:08:f1:04:03:96:11:59 hardware #32
13:15:46.977710 IP ib109 > ib110: icmp 64: echo request seq 0
13:15:46.977790 IP ib110 > ib109: icmp 64: echo reply seq 0
13:15:47.977772 IP ib109 > ib110: icmp 64: echo request seq 1
13:15:47.977892 IP ib110 > ib109: icmp 64: echo reply seq 1
13:15:51.977076 arp who-has ib109 tell ib110 hardware #32
13:15:51.977094 arp reply ib109 is-at
00:02:00:14:fe:80:00:00:00:00:00:00:00:02:c9:02:00:00:3b:31 hardware #32

# error dump
rcvswrelayerrors:1 MT47396 Infiniscale-III 0x2c9010b022090[1]   <-------->
ib109 HCA-1 0x2c90200003b30[1]

1) The ping is successful and the arp table is populated so Is this really a
problem or a false positive?
2) The second arp does not generate an error (the error dump reports all new
errors in switches). Why?

Any ideas?

Thanks in advance.

Todd
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