net: Use sk_mark for routing lookup in more places

This patch against v2.6.31 adds support for route lookup using sk_mark in some 
more places. The benefits from this patch are the following.
First, SO_MARK option now has effect on UDP sockets too.
Second, ip_queue_xmit() and inet_sk_rebuild_header() could fail to do routing 
lookup correctly if TCP sockets with SO_MARK were used.

Signed-off-by: Atis Elsts <atis@mikrotik.com>
Acked-by: Eric Dumazet <eric.dumazet@gmail.com>

net/ipv4/af_inet.c

@@ -1119,6 +1119,7 @@ int inet_sk_rebuild_header(struct sock *sk)
 {
 	struct flowi fl = {
 		.oif = sk->sk_bound_dev_if,
+		.mark = sk->sk_mark,
 		.nl_u = {
 			.ip4_u = {
 				.daddr	= daddr,

net/ipv4/ip_output.c

@@ -335,6 +335,7 @@ int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 
 		{
 			struct flowi fl = { .oif = sk->sk_bound_dev_if,
+					    .mark = sk->sk_mark,
 					    .nl_u = { .ip4_u =
 						      { .daddr = daddr,
 							.saddr = inet->saddr,

net/ipv4/udp.c

@@ -696,6 +696,7 @@ int udp_sendmsg(struct kiocb *iocb, struct sock *sk, struct msghdr *msg,
 
 	if (rt == NULL) {
 		struct flowi fl = { .oif = ipc.oif,
+				    .mark = sk->sk_mark,
 				    .nl_u = { .ip4_u =
 					      { .daddr = faddr,
 						.saddr = saddr,