[openib-general] IPoIB odd loopback packet from arp

[Eli Cohen]

Todd,
This does not look like an error. The first arp is a broadcast
(qpn=ffffff) so it is received in at the sending interface and is
dropped. The second on is a unicast arp (qpn=0x000404) so it is not
received at the local interface. 


On Mon, 2006-10-23 at 13:48 -0600, Todd Bowman wrote:
> 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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