Hi, I have a multi-homed system like this: eth1: 1.2.3.4 GW: 1.2.3.1 eth2: 2.3.4.5 GW: 2.3.4.1 route ouput snippet is: default 2.3.4.1 0.0.0.0 UG 3 0 0 eth2 default 1.2.3.1 0.0.0.0 UG 4 0 0 eth1 default 2.3.4.1 0.0.0.0 UG 4 0 0 eth2 When I run traceroute -i eth1 5.4.3.2, the UDP packets are routed out eth2. Has anybody seen this behaviour with traceroute?? I have done some debugging, and believe this to be an ipv4 kernel bug. My research came up with the following: By the traceroute source code, it uses raw sockets and relies on IP_HDRINCL (which is defined in the kernel source <netinet/in.h>) to select the routing interface and does not bind the socket to the source IP address. I hacked the traceroute source code to do a bind if the -i or -s options are used, and the correct GW is used. I am using a 2.4.29 kernel and have traced through the kernel and in .../net/ipv4/raw.c, raw_sendmsg() does not read the data to get the IP header and the source address, which then results in a 0.0.0.0 source address and hence the routing, ip_route_output(), pulls the default gateway with the lowest metric, in this case eth2. I have also used a 2.6.21 kernel and similiar behaviour happens. The 2.6.21 kernel source code does not read the IP header from the data either. Am I reading/interpreting the source code correctly? Any other suggestions/more information would be great. Cheers, Mick -- -- Mick McCreath Sr Engineer Secure Computing® your trusted source for enterprise security™ www.securecomputing.com NASDAQ: SCUR 61 7 3435 2803 (Direct Phone) mick_mccreath@xxxxxxxxxxxxxxxxxxx Secure Computing Corporation 825 Stanley Street Woolloongabba Queensland 4102 Australia The information contained in this email message may be privileged, confidential and protected from disclosure. If you are not the intended recipient, any review, dissemination, distribution or copying is strictly prohibited. If you have received this email message in error, please notify the sender by reply email and delete the message and any attachments. - To unsubscribe from this list: send the line "unsubscribe linux-net" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
