Re: Bad interaction of SO_BINDTODEVICE and ARP in Linux 2.4.10

Re: Bad interaction of SO_BINDTODEVICE and ARP in Linux 2.4.10

[Joerg Pommnitz]

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Hi Lists,
I worked around my previous problem by deleting the routing
entry that sent packets for my subnet directly to their
destination. Using our default router works (somewhat).

I can now see the ICMP packets on eth1:

jpo> /sbin/ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:E0:4C:71:05:92
          inet addr:10.1.12.87  Bcast:10.1.12.255  Mask:255.255.255.0
eth1      Link encap:Ethernet  HWaddr 00:E0:4C:71:05:91
          inet addr:10.1.12.151  Bcast:10.1.12.255  Mask:255.255.255.0
jpo> netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt
Iface
0.0.0.0         10.1.12.1       0.0.0.0         UG       40 0          0
eth0

jpo> ping -I eth0 10.1.12.151
jpo> sudo /usr/sbin/tcpdump -i eth1 host 10.1.12.151 -n
tcpdump: listening on eth1
20:40:46.289402 10.1.12.87 > 10.1.12.151: icmp: echo request (DF)
20:40:47.289402 10.1.12.87 > 10.1.12.151: icmp: echo request (DF)
20:40:48.289402 10.1.12.87 > 10.1.12.151: icmp: echo request (DF)
20:40:49.289402 10.1.12.87 > 10.1.12.151: icmp: echo request (DF)
20:40:50.289402 10.1.12.87 > 10.1.12.151: icmp: echo request (DF)

It seems that no answer is sent at all. Any ideas?

Regards
  Jörg

=====
-- 
Regards
       Joerg


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Bad interaction of SO_BINDTODEVICE and ARP in Linux 2.4.10

[Joerg Pommnitz]

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On the advise of a coworker I'm resending this message with
a more sexy Subject line. The previous one did sound too newbieish...


Hi List,
I have the following setup:
One host with two interfaces (eth0, eth1):

eth0      Link encap:Ethernet  HWaddr 00:E0:4C:71:05:92
          inet addr:10.1.12.87  Bcast:10.1.12.255  Mask:255.255.255.0
          inet6 addr: fe80::2e0:4cff:fe71:592/10 Scope:Link
          UP BROADCAST NOTRAILERS RUNNING  MTU:1500  Metric:1
          RX packets:4512 errors:0 dropped:0 overruns:0 frame:0
          TX packets:4034 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:345507 (337.4 Kb)  TX bytes:407841 (398.2 Kb)
          Interrupt:11 Base address:0x5000

eth1      Link encap:Ethernet  HWaddr 00:E0:4C:71:05:91
          inet addr:10.1.12.151  Bcast:10.1.12.255  Mask:255.255.255.0
          inet6 addr: fe80::2e0:4cff:fe71:591/10 Scope:Link
          UP BROADCAST NOTRAILERS RUNNING  MTU:1500  Metric:1
          RX packets:2709 errors:0 dropped:0 overruns:0 frame:0
          TX packets:16 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:239132 (233.5 Kb)  TX bytes:2646 (2.5 Kb)
          Interrupt:10 Base address:0x7000

when I do 
ping -I eth0 10.1.12.151
I don't get a reply but ARP requests like this:

19:23:59.219402 arp who-has 10.1.12.151 tell 10.1.12.87
19:24:00.219402 arp who-has 10.1.12.151 tell 10.1.12.87
19:24:01.219402 arp who-has 10.1.12.151 tell 10.1.12.87
19:24:02.219402 arp who-has 10.1.12.151 tell 10.1.12.87

So the host tries to resolve its own MAC address and does
not answer itself. Manually setting the ARP entry fails
as well.

Question: Should this work at all? If yes, is there a fix?

Regards
  Jörg



=====
-- 
Regards
       Joerg


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