I have a piece of code that is trying to use sendmsg() on a raw socket to inject a UDP packet onto an ethernet link. The destination IP address is set to another machine on the same subnet, and the packet arrives at its destination. Thus far all is well. However, inspection of the ethernet headers using tcpdump shows that rather than being addressed directly to the MAC address of the destination, the packet is instead being sent to the gateway, which then appears to forward it on to the destination. It almost appears as though the kernel doesn't realize that the IP address is on the same subnet. Here's where it gets interesting. I grabbed what I thought was all the socket setup and sending code from the misbehaving application and stuck them into a tiny program that builds and sends empty packets with arbitrary source and destination addresses. Tcpdump shows this program behaving as expected--ie the destination MAC address in the ethernet header is set to the MAC address of the destination, not the MAC address of the gateway. Does anyone have any clue what might be going on? I'm almost ready to try strace and kernel debugging.... Thanks, Chris -- Chris Friesen | MailStop: 043/33/F10 Nortel Networks | work: (613) 765-0557 3500 Carling Avenue | fax: (613) 765-2986 Nepean, ON K2H 8E9 Canada | email: cfriesen@nortelnetworks.com - : send the line "unsubscribe linux-net" in the body of a message to majordomo@vger.kernel.org
