[NETFILTER]: Call POST_ROUTING hook before fragmentation

Call POST_ROUTING hook before fragmentation to get rid of the okfn use
in ip_refrag and save the useless fragmentation/defragmentation step
when NAT is used.

The patch introduces one user-visible change, the POSTROUTING chain
in the mangle table gets entire packets, not fragments, which should
simplify use of the MARK and CLASSIFY targets for queueing as a nice
side-effect.

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

4 files changed, 16 insertions, 83 deletions

diff --git a/net/ipv4/ip_output.c b/net/ipv4/ip_output.c
index 2a830de3a699..71da31818cfc 100644
--- a/net/ipv4/ip_output.c
+++ b/net/ipv4/ip_output.c
@@ -202,13 +202,11 @@ static inline int ip_finish_output2(struct sk_buff *skb)
 
 static inline int ip_finish_output(struct sk_buff *skb)
 {
-        struct net_device *dev = skb->dst->dev;
-
-        skb->dev = dev;
-        skb->protocol = htons(ETH_P_IP);
-
-        return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
-                       ip_finish_output2);
+        if (skb->len > dst_mtu(skb->dst) &&
+            !(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
+                return ip_fragment(skb, ip_finish_output2);
+        else
+                return ip_finish_output2(skb);
 }
 
 int ip_mc_output(struct sk_buff *skb)
@@ -265,21 +263,21 @@ int ip_mc_output(struct sk_buff *skb)
                                 newskb->dev, ip_dev_loopback_xmit);
         }
 
-        if (skb->len > dst_mtu(&rt->u.dst))
-                return ip_fragment(skb, ip_finish_output);
-        else
-                return ip_finish_output(skb);
+        return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, skb->dev,
+                       ip_finish_output);
 }
 
 int ip_output(struct sk_buff *skb)
 {
+        struct net_device *dev = skb->dst->dev;
+
         IP_INC_STATS(IPSTATS_MIB_OUTREQUESTS);
 
-        if (skb->len > dst_mtu(skb->dst) &&
-                !(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
-                return ip_fragment(skb, ip_finish_output);
-        else
-                return ip_finish_output(skb);
+        skb->dev = dev;
+        skb->protocol = htons(ETH_P_IP);
+
+        return NF_HOOK(PF_INET, NF_IP_POST_ROUTING, skb, NULL, dev,
+                       ip_finish_output);
 }
 
 int ip_queue_xmit(struct sk_buff *skb, int ipfragok)
diff --git a/net/ipv4/netfilter/ip_conntrack_standalone.c b/net/ipv4/netfilter/ip_conntrack_standalone.c
index a88bcc551244..7ba97783e741 100644
--- a/net/ipv4/netfilter/ip_conntrack_standalone.c
+++ b/net/ipv4/netfilter/ip_conntrack_standalone.c
@@ -451,30 +451,6 @@ static unsigned int ip_conntrack_defrag(unsigned int hooknum,
         return NF_ACCEPT;
 }
 
-static unsigned int ip_refrag(unsigned int hooknum,
-                              struct sk_buff **pskb,
-                              const struct net_device *in,
-                              const struct net_device *out,
-                              int (*okfn)(struct sk_buff *))
-{
-        struct rtable *rt = (struct rtable *)(*pskb)->dst;
-
-        /* We've seen it coming out the other side: confirm */
-        if (ip_confirm(hooknum, pskb, in, out, okfn) != NF_ACCEPT)
-                return NF_DROP;
-
-        /* Local packets are never produced too large for their
-           interface.  We degfragment them at LOCAL_OUT, however,
-           so we have to refragment them here. */
-        if ((*pskb)->len > dst_mtu(&rt->u.dst) &&
-            !skb_shinfo(*pskb)->tso_size) {
-                /* No hook can be after us, so this should be OK. */
-                ip_fragment(*pskb, okfn);
-                return NF_STOLEN;
-        }
-        return NF_ACCEPT;
-}
-
 static unsigned int ip_conntrack_local(unsigned int hooknum,
                                        struct sk_buff **pskb,
                                        const struct net_device *in,
@@ -544,7 +520,7 @@ static struct nf_hook_ops ip_conntrack_helper_in_ops = {
 
 /* Refragmenter; last chance. */
 static struct nf_hook_ops ip_conntrack_out_ops = {
-        .hook           = ip_refrag,
+        .hook           = ip_confirm,
         .owner          = THIS_MODULE,
         .pf             = PF_INET,
         .hooknum        = NF_IP_POST_ROUTING,
diff --git a/net/ipv4/netfilter/ip_nat_standalone.c b/net/ipv4/netfilter/ip_nat_standalone.c
index 30cd4e18c129..f04111f74e09 100644
--- a/net/ipv4/netfilter/ip_nat_standalone.c
+++ b/net/ipv4/netfilter/ip_nat_standalone.c
@@ -190,23 +190,6 @@ ip_nat_out(unsigned int hooknum,
             || (*pskb)->nh.iph->ihl * 4 < sizeof(struct iphdr))
                 return NF_ACCEPT;
 
-        /* We can hit fragment here; forwarded packets get
-           defragmented by connection tracking coming in, then
-           fragmented (grr) by the forward code.
-
-           In future: If we have nfct != NULL, AND we have NAT
-           initialized, AND there is no helper, then we can do full
-           NAPT on the head, and IP-address-only NAT on the rest.
-
-           I'm starting to have nightmares about fragments.  */
-
-        if ((*pskb)->nh.iph->frag_off & htons(IP_MF|IP_OFFSET)) {
-                *pskb = ip_ct_gather_frags(*pskb, IP_DEFRAG_NAT_OUT);
-
-                if (!*pskb)
-                        return NF_STOLEN;
-        }
-
         return ip_nat_fn(hooknum, pskb, in, out, okfn);
 }
 
diff --git a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
index 385867efd481..1d36e8effe4f 100644
--- a/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
+++ b/net/ipv4/netfilter/nf_conntrack_l3proto_ipv4.c
@@ -180,30 +180,6 @@ static unsigned int ipv4_conntrack_defrag(unsigned int hooknum,
         return NF_ACCEPT;
 }
 
-static unsigned int ipv4_refrag(unsigned int hooknum,
-                                struct sk_buff **pskb,
-                                const struct net_device *in,
-                                const struct net_device *out,
-                                int (*okfn)(struct sk_buff *))
-{
-        struct rtable *rt = (struct rtable *)(*pskb)->dst;
-
-        /* We've seen it coming out the other side: confirm */
-        if (ipv4_confirm(hooknum, pskb, in, out, okfn) != NF_ACCEPT)
-                return NF_DROP;
-
-        /* Local packets are never produced too large for their
-           interface.  We degfragment them at LOCAL_OUT, however,
-           so we have to refragment them here. */
-        if ((*pskb)->len > dst_mtu(&rt->u.dst) &&
-            !skb_shinfo(*pskb)->tso_size) {
-                /* No hook can be after us, so this should be OK. */
-                ip_fragment(*pskb, okfn);
-                return NF_STOLEN;
-        }
-        return NF_ACCEPT;
-}
-
 static unsigned int ipv4_conntrack_in(unsigned int hooknum,
                                       struct sk_buff **pskb,
                                       const struct net_device *in,
@@ -283,7 +259,7 @@ static struct nf_hook_ops ipv4_conntrack_helper_in_ops = {
 
 /* Refragmenter; last chance. */
 static struct nf_hook_ops ipv4_conntrack_out_ops = {
-        .hook           = ipv4_refrag,
+        .hook           = ipv4_confirm,
         .owner          = THIS_MODULE,
         .pf             = PF_INET,
         .hooknum        = NF_IP_POST_ROUTING,