[NETFILTER]: Fix fragmentation issues with bridge netfilter

The conntrack code doesn't do re-fragmentation of defragmented packets
anymore but relies on fragmentation in the IP layer. Purely bridged
packets don't pass through the IP layer, so the bridge netfilter code
needs to take care of fragmentation itself.

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

include/net/ip.h

@@ -95,6 +95,7 @@ extern int		ip_local_deliver(struct sk_buff *skb);
 extern int		ip_mr_input(struct sk_buff *skb);
 extern int		ip_output(struct sk_buff *skb);
 extern int		ip_mc_output(struct sk_buff *skb);
+extern int		ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff *));
 extern int		ip_do_nat(struct sk_buff *skb);
 extern void		ip_send_check(struct iphdr *ip);
 extern int		ip_queue_xmit(struct sk_buff *skb, int ipfragok);

net/bridge/br_netfilter.c

@@ -765,6 +765,15 @@ out:
 	return NF_STOLEN;
 }
 
+static int br_nf_dev_queue_xmit(struct sk_buff *skb)
+{
+	if (skb->protocol == htons(ETH_P_IP) &&
+	    skb->len > skb->dev->mtu &&
+	    !(skb_shinfo(skb)->ufo_size || skb_shinfo(skb)->tso_size))
+		return ip_fragment(skb, br_dev_queue_push_xmit);
+	else
+		return br_dev_queue_push_xmit(skb);
+}
 
 /* PF_BRIDGE/POST_ROUTING ********************************************/
 static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff **pskb,
@@ -824,7 +833,7 @@ static unsigned int br_nf_post_routing(unsigned int hook, struct sk_buff **pskb,
 		realoutdev = nf_bridge->netoutdev;
 #endif
 	NF_HOOK(pf, NF_IP_POST_ROUTING, skb, NULL, realoutdev,
-		br_dev_queue_push_xmit);
+		br_nf_dev_queue_xmit);
 
 	return NF_STOLEN;
 
@@ -869,7 +878,7 @@ static unsigned int ip_sabotage_out(unsigned int hook, struct sk_buff **pskb,
 
 	if ((out->hard_start_xmit == br_dev_xmit &&
 	     okfn != br_nf_forward_finish &&
-	     okfn != br_nf_local_out_finish && okfn != br_dev_queue_push_xmit)
+	     okfn != br_nf_local_out_finish && okfn != br_nf_dev_queue_xmit)
 #if defined(CONFIG_VLAN_8021Q) || defined(CONFIG_VLAN_8021Q_MODULE)
 	    || ((out->priv_flags & IFF_802_1Q_VLAN) &&
 		VLAN_DEV_INFO(out)->real_dev->hard_start_xmit == br_dev_xmit)

net/ipv4/ip_output.c

@@ -86,8 +86,6 @@
 
 int sysctl_ip_default_ttl = IPDEFTTL;
 
-static int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*));
-
 /* Generate a checksum for an outgoing IP datagram. */
 __inline__ void ip_send_check(struct iphdr *iph)
 {
@@ -421,7 +419,7 @@ static void ip_copy_metadata(struct sk_buff *to, struct sk_buff *from)
  *	single device frame, and queue such a frame for sending.
  */
 
-static int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
+int ip_fragment(struct sk_buff *skb, int (*output)(struct sk_buff*))
 {
 	struct iphdr *iph;
 	int raw = 0;
@@ -673,6 +671,8 @@ fail:
 	return err;
 }
 
+EXPORT_SYMBOL(ip_fragment);
+
 int
 ip_generic_getfrag(void *from, char *to, int offset, int len, int odd, struct sk_buff *skb)
 {