You're probably getting stuck on the rp_filter (packets coming in on a different interface than the reply would go out of). You can test this by enabling log_martians and disable it if you wish. Are you actually modifying the packets? If not, I'd suggest using netfiler with the DNAT target. Hope this helps, On Sun, Oct 26, 2003 at 10:54:58PM +0100, bit.gossip@libero.it wrote: > I am developing in C on RH9 with kernel 2.4.20-20.9 > I want to write a program that receives an UDP stream and send it to another > destination with the same source IP as it is received. This obviously means > spoofing the source IP address. > Issuing: > echo 1 > /proc/sys/net/ipv4/ip_nonlocal_bind > I am able to bind the socket to the foreign address (socket(AF_INET, SOCK_DGRAM, > IPPROTO_UDP)) > But then the sendto fails with an 'invalid argument' error. > > I have tried the following hack: > create a dummy interface with the address to be spoofed, for instance lo:1 > in this case the sendto works correctly sending datagrams with the spoofed source IP > > ... but the recvfrom stops working and doesn't receive any datagram from that > same address :-( > > Any suggestion on how can I do it? > Thanks, > Luca. > > - > : send the line "unsubscribe linux-net" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- Martijn van Oosterhout <kleptog@svana.org> http://svana.org/kleptog/ > "All that is needed for the forces of evil to triumph is for enough good > men to do nothing." - Edmond Burke > "The penalty good people pay for not being interested in politics is to be > governed by people worse than themselves." - Plato
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