ipv4: Make Netfilter's ip_route_me_harder() non-local address compatible

Netfilter's ip_route_me_harder() tries to re-route packets either
generated or re-routed by Netfilter. This patch changes
ip_route_me_harder() to handle packets from non-locally-bound sockets
with IP_TRANSPARENT set as local and to set the appropriate flowi
flags when re-doing the routing lookup.

Signed-off-by: KOVACS Krisztian <hidden@sch.bme.hu>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ip.h

@@ -29,6 +29,7 @@
 
 #include <net/inet_sock.h>
 #include <net/snmp.h>
+#include <net/flow.h>
 
 struct sock;
 
@@ -149,6 +150,11 @@ struct ip_reply_arg {
 
 #define IP_REPLY_ARG_NOSRCCHECK 1
 
+static inline __u8 ip_reply_arg_flowi_flags(const struct ip_reply_arg *arg)
+{
+	return (arg->flags & IP_REPLY_ARG_NOSRCCHECK) ? FLOWI_FLAG_ANYSRC : 0;
+}
+
 void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *arg,
 		   unsigned int len); 
 

net/ipv4/inet_connection_sock.c

@@ -335,6 +335,7 @@ struct dst_entry* inet_csk_route_req(struct sock *sk,
 					.saddr = ireq->loc_addr,
 					.tos = RT_CONN_FLAGS(sk) } },
 			    .proto = sk->sk_protocol,
+			    .flags = inet_sk_flowi_flags(sk),
 			    .uli_u = { .ports =
 				       { .sport = inet_sk(sk)->sport,
 					 .dport = ireq->rmt_port } } };

net/ipv4/ip_output.c

@@ -340,6 +340,7 @@ int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
 							.saddr = inet->saddr,
 							.tos = RT_CONN_FLAGS(sk) } },
 					    .proto = sk->sk_protocol,
+					    .flags = inet_sk_flowi_flags(sk),
 					    .uli_u = { .ports =
 						       { .sport = inet->sport,
 							 .dport = inet->dport } } };
@@ -1371,7 +1372,8 @@ void ip_send_reply(struct sock *sk, struct sk_buff *skb, struct ip_reply_arg *ar
 				    .uli_u = { .ports =
 					       { .sport = tcp_hdr(skb)->dest,
 						 .dport = tcp_hdr(skb)->source } },
-				    .proto = sk->sk_protocol };
+				    .proto = sk->sk_protocol,
+				    .flags = ip_reply_arg_flowi_flags(arg) };
 		security_skb_classify_flow(skb, &fl);
 		if (ip_route_output_key(sock_net(sk), &rt, &fl))
 			return;

net/ipv4/netfilter.c

@@ -20,6 +20,8 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 	unsigned int type;
 
 	type = inet_addr_type(&init_net, iph->saddr);
+	if (skb->sk && inet_sk(skb->sk)->transparent)
+		type = RTN_LOCAL;
 	if (addr_type == RTN_UNSPEC)
 		addr_type = type;
 
@@ -33,6 +35,7 @@ int ip_route_me_harder(struct sk_buff *skb, unsigned addr_type)
 		fl.nl_u.ip4_u.tos = RT_TOS(iph->tos);
 		fl.oif = skb->sk ? skb->sk->sk_bound_dev_if : 0;
 		fl.mark = skb->mark;
+		fl.flags = skb->sk ? inet_sk_flowi_flags(skb->sk) : 0;
 		if (ip_route_output_key(&init_net, &rt, &fl) != 0)
 			return -1;
 

net/ipv4/syncookies.c

@@ -16,6 +16,7 @@
 #include <linux/cryptohash.h>
 #include <linux/kernel.h>
 #include <net/tcp.h>
+#include <net/route.h>
 
 /* Timestamps: lowest 9 bits store TCP options */
 #define TSBITS 9
@@ -337,6 +338,7 @@ struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb,
 						.saddr = ireq->loc_addr,
 						.tos = RT_CONN_FLAGS(sk) } },
 				    .proto = IPPROTO_TCP,
+				    .flags = inet_sk_flowi_flags(sk),
 				    .uli_u = { .ports =
 					       { .sport = th->dest,
 						 .dport = th->source } } };