bridge: Save frag_max_size between PRE_ROUTING and POST_ROUTING

As we may defragment the packet in IPv4 PRE_ROUTING and refragment
it after POST_ROUTING we should save the value of frag_max_size.

This is still very wrong as the bridge is supposed to leave the
packets intact, meaning that the right thing to do is to use the
original frag_list for fragmentation.

Unfortunately we don't currently guarantee that the frag_list is
left untouched throughout netfilter so until this changes this is
the best we can do.

There is also a spot in FORWARD where it appears that we can
forward a packet without going through fragmentation, mark it
so that we can fix it later.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 15 insertions, 0 deletions

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index a615264cf01a..4063898cf8aa 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -404,6 +404,7 @@ static int br_nf_pre_routing_finish_bridge(struct sk_buff *skb)
                                                          ETH_HLEN-ETH_ALEN);
                         /* tell br_dev_xmit to continue with forwarding */
                         nf_bridge->mask |= BRNF_BRIDGED_DNAT;
+                        /* FIXME Need to refragment */
                         ret = neigh->output(neigh, skb);
                 }
                 neigh_release(neigh);
@@ -459,6 +460,10 @@ static int br_nf_pre_routing_finish(struct sk_buff *skb)
         struct nf_bridge_info *nf_bridge = skb->nf_bridge;
         struct rtable *rt;
         int err;
+        int frag_max_size;
+
+        frag_max_size = IPCB(skb)->frag_max_size;
+        BR_INPUT_SKB_CB(skb)->frag_max_size = frag_max_size;
 
         if (nf_bridge->mask & BRNF_PKT_TYPE) {
                 skb->pkt_type = PACKET_OTHERHOST;
@@ -863,13 +868,19 @@ static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 {
         int ret;
+        int frag_max_size;
 
+        /* This is wrong! We should preserve the original fragment
+         * boundaries by preserving frag_list rather than refragmenting.
+         */
         if (skb->protocol == htons(ETH_P_IP) &&
             skb->len + nf_bridge_mtu_reduction(skb) > skb->dev->mtu &&
             !skb_is_gso(skb)) {
+                frag_max_size = BR_INPUT_SKB_CB(skb)->frag_max_size;
                 if (br_parse_ip_options(skb))
                         /* Drop invalid packet */
                         return NF_DROP;
+                IPCB(skb)->frag_max_size = frag_max_size;
                 ret = ip_fragment(skb, br_dev_queue_push_xmit);
         } else
                 ret = br_dev_queue_push_xmit(skb);
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index b6c04cbcfdc5..2398369c6dda 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -305,10 +305,14 @@ struct net_bridge
 
 struct br_input_skb_cb {
         struct net_device *brdev;
+
 #ifdef CONFIG_BRIDGE_IGMP_SNOOPING
         int igmp;
         int mrouters_only;
 #endif
+
+        u16 frag_max_size;
+
 #ifdef CONFIG_BRIDGE_VLAN_FILTERING
         bool vlan_filtered;
 #endif