Hi, Pranay, First, let's assume that you are talking about IPv4, though you did not mention it explicitly. (The principles in IPv6 are quite similar, though) A packet is sent out in the usual case with the ip_queue_xmit() method. The ip_queue_xmit() method calls the ip_route_output_ports() method in order to perform a lookup in the IPv4 routing tables. see: http://lxr.free-electrons.com/source/net/ipv4/ip_output.c#L352 The results of this IPv4 routing lookup determines on which network device (net_device) the packet will be sent. You should look at the code of ip_route_output_ports() method in net/ipv4/route.c in order to understand the IPv4 routing subsystem and the IPv4 routing lookup. Packets can, under certain circumstances, be sent by the ip_send_skb() method, but this happens when the flow (which consists also of the net_device to be used) is known before. Best Regards, Rami Rosen http://ramirose.wix.com/ramirosen On Sat, May 3, 2014 at 11:33 AM, Pranay Srivastava <pranjas@xxxxxxxxx> wrote: > Hi, > > This is probably a stupid question, but i'm not able to find the > answer. How does the networking subsystem decides which device to use > for sending the skb. Can some one please guide me to the particular > code. I seem to get lost in there :( > > -- > ---P.K.S > > _______________________________________________ > Kernelnewbies mailing list > Kernelnewbies@xxxxxxxxxxxxxxxxx > http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies _______________________________________________ Kernelnewbies mailing list Kernelnewbies@xxxxxxxxxxxxxxxxx http://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
