bridge: move mac header copying into br_netfilter

The mac header only has to be copied back into the skb for
fragments generated by ip_fragment(), which only happens
for bridge forwarded packets with nf-call-iptables=1 && active nf_defrag.

Signed-off-by: Florian Westphal <fw@strlen.de>
Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

2 files changed, 29 insertions, 4 deletions

diff --git a/net/bridge/br_forward.c b/net/bridge/br_forward.c
index f96933a823e3..32541d4f72e8 100644
--- a/net/bridge/br_forward.c
+++ b/net/bridge/br_forward.c
@@ -37,9 +37,7 @@ static inline int should_deliver(const struct net_bridge_port *p,
 
 int br_dev_queue_push_xmit(struct sk_buff *skb)
 {
-        /* ip_fragment doesn't copy the MAC header */
-        if (nf_bridge_maybe_copy_header(skb) ||
-            !is_skb_forwardable(skb->dev, skb)) {
+        if (!is_skb_forwardable(skb->dev, skb)) {
                 kfree_skb(skb);
         } else {
                 skb_push(skb, ETH_HLEN);
diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 0ee453fad3de..e5479112c4a3 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -764,6 +764,33 @@ static unsigned int br_nf_forward_arp(const struct nf_hook_ops *ops,
 }
 
 #if IS_ENABLED(CONFIG_NF_DEFRAG_IPV4)
+static bool nf_bridge_copy_header(struct sk_buff *skb)
+{
+        int err;
+        unsigned int header_size;
+
+        nf_bridge_update_protocol(skb);
+        header_size = ETH_HLEN + nf_bridge_encap_header_len(skb);
+        err = skb_cow_head(skb, header_size);
+        if (err)
+                return false;
+
+        skb_copy_to_linear_data_offset(skb, -header_size,
+                                       skb->nf_bridge->data, header_size);
+        __skb_push(skb, nf_bridge_encap_header_len(skb));
+        return true;
+}
+
+static int br_nf_push_frag_xmit(struct sk_buff *skb)
+{
+        if (!nf_bridge_copy_header(skb)) {
+                kfree_skb(skb);
+                return 0;
+        }
+
+        return br_dev_queue_push_xmit(skb);
+}
+
 static int br_nf_dev_queue_xmit(struct sk_buff *skb)
 {
         int ret;
@@ -780,7 +807,7 @@ static int br_nf_dev_queue_xmit(struct sk_buff *skb)
                         /* Drop invalid packet */
                         return NF_DROP;
                 IPCB(skb)->frag_max_size = frag_max_size;
-                ret = ip_fragment(skb, br_dev_queue_push_xmit);
+                ret = ip_fragment(skb, br_nf_push_frag_xmit);
         } else
                 ret = br_dev_queue_push_xmit(skb);