[NETFILTER]: Use conntrack information to determine if packet was NATed

Preparation for IPsec support for NAT:
Use conntrack information instead of saving the saving and comparing the
addresses to determine if a packet was NATed and needs to be rerouted to
make it easier to extend the key.

Signed-off-by: Patrick McHardy <kaber@trash.net>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/netfilter/ip_nat_standalone.c b/net/ipv4/netfilter/ip_nat_standalone.c
index f04111f..1bb5089 100644 (file)
--- a/net/ipv4/netfilter/ip_nat_standalone.c
+++ b/net/ipv4/netfilter/ip_nat_standalone.c
@@ -162,18 +162,20 @@ ip_nat_in(unsigned int hooknum,
           const struct net_device *out,
           int (*okfn)(struct sk_buff *))
 {
-       u_int32_t saddr, daddr;
+       struct ip_conntrack *ct;
+       enum ip_conntrack_info ctinfo;
        unsigned int ret;
 
-       saddr = (*pskb)->nh.iph->saddr;
-       daddr = (*pskb)->nh.iph->daddr;
-
        ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
        if (ret != NF_DROP && ret != NF_STOLEN
-           && ((*pskb)->nh.iph->saddr != saddr
-               || (*pskb)->nh.iph->daddr != daddr)) {
-               dst_release((*pskb)->dst);
-               (*pskb)->dst = NULL;
+           && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) {
+               enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+
+               if (ct->tuplehash[dir].tuple.src.ip !=
+                   ct->tuplehash[!dir].tuple.dst.ip) {
+                       dst_release((*pskb)->dst);
+                       (*pskb)->dst = NULL;
+               }
        }
        return ret;
 }
@@ -200,7 +202,8 @@ ip_nat_local_fn(unsigned int hooknum,
                const struct net_device *out,
                int (*okfn)(struct sk_buff *))
 {
-       u_int32_t saddr, daddr;
+       struct ip_conntrack *ct;
+       enum ip_conntrack_info ctinfo;
        unsigned int ret;
 
        /* root is playing with raw sockets. */
@@ -208,14 +211,15 @@ ip_nat_local_fn(unsigned int hooknum,
            || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
                return NF_ACCEPT;
 
-       saddr = (*pskb)->nh.iph->saddr;
-       daddr = (*pskb)->nh.iph->daddr;
-
        ret = ip_nat_fn(hooknum, pskb, in, out, okfn);
        if (ret != NF_DROP && ret != NF_STOLEN
-           && ((*pskb)->nh.iph->saddr != saddr
-               || (*pskb)->nh.iph->daddr != daddr))
-               return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
+           && (ct = ip_conntrack_get(*pskb, &ctinfo)) != NULL) {
+               enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
+
+               if (ct->tuplehash[dir].tuple.dst.ip !=
+                   ct->tuplehash[!dir].tuple.src.ip)
+                       return ip_route_me_harder(pskb) == 0 ? ret : NF_DROP;
+       }
        return ret;
 }