netdev - Re: Ping Is Broken

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Date:	Mon, 12 Oct 2009 23:28:56 +0200
From:	Jarek Poplawski <jarkao2@...il.com>
To:	Brian Haley <brian.haley@...com>
CC:	Rob.Townley@...il.com, netdev@...r.kernel.org,
	Omaha Linux User Group <olug@...g.org>,
	CentOS mailing list <centos@...tos.org>
Subject: Re: Ping Is Broken

Brian Haley wrote, On 10/12/2009 10:36 PM:

> Rob Townley wrote:

...

>> ping -c 2 -B -I  eth0 208.67.222.222
>> PING 208.67.222.222 (208.67.222.222) from 4.3.2.8 eth0: 56(84) bytes of data.
>> From 4.3.2.8 icmp_seq=1 Destination Host Unreachable
>> From 4.3.2.8 icmp_seq=2 Destination Host Unreachable
> 
> In this case ping is doing an SO_BINDTODEVICE to eth0, so the kernel is going
> to force the packets out of it, even if it isn't the "correct" interface.  If
> you ran tcpdump you'd probably see an ARP resolution failure, or an ICMP from
> a gateway.
> 
> This confusion could be cleared-up on the man page.  What did you expect to
> happen in this case?

Actually, ping could do it other way: trying to connect with eth0's
IP address(es). (Then we would need another option for using a dev
like now.)

Jarek P.
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