Disclaimer: I know this is a *development* list, but I feel the answer lies deep down in the ipv4 routing code, so it's more likely that I find help here.
That being said, I have two TUN interfaces that are "cross-connected" in user space (i.e. whatever is read on the socket corresponding to either interface is written to the socket of the other interface). The problem: if I assign IPv4 addresses to both TUN interfaces, local traffic to either address flows through the loopback interface. Getting packets to be routed through the TUN interfaces is easy. The real challenge is to get packets to be accepted/processed as input packets when they pop out of the opposite TUN interface. I tracked down the problem to ip_route_input_slow() in net/ipv4/route.c What I tried so far: 1. Remove the implicit routes from the local table. This apparently causes packets to be silently dropped by ip_route_input_slow(), since it looks for a corresponding route and only delivers packets locally if a local route is found. 2. Keep implicit routes in the local table, change the priority of the "lookup local" ip rule, mark *output* packets with iptables and add a higher priority rule to lookup the main table for marked packets. By doing that, the main table is looked up on the egress path and packets are routed through the TUN interface. When packets pop out of the opposite TUN interface, they are no longer marked (because they are actually different packets), so ingress routing correctly looks up the local table. The next problem is that packets are seen as "martians" and dropped, most probably because of __fib_validate_source() failing due to the fact that the input interface is not the expected one. This is where I stopped. Any idea or help would be highly appreciated. Please CC my private address (I am not subscribed to the list). Thanks in advance! -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
