Subject: Re: [NETFILTER]: Fix skb->nf_bridge lifetime issues

From: Patrick McHardy <[email-masked]>
Date: Mon, 20 Feb 2006 10:33:34 +0100

Patrick McHardy wrote:
> Bart, can you please have a look at this patch and ACK/NACK it?
> We have a bugreport in the netfilter bugzilla of broken conntrack
> with tunnels on top of bridge devices (#448), which should be cured
> by this patch.
> 
> +static inline void nf_reset(struct sk_buff *skb)
> +{
> +	nf_conntrack_put(skb->nfct);
> +	skb->nfct = NULL;
> +#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
> +	nf_conntrack_put_reasm(skb->nfct_reasm);
> +	skb->nfct_reasm = NULL;
> +#endif
> +#ifdef CONFIG_BRIDGE_NETFILTER
> +	nf_bridge_put(skb->nfct);
> +	skb->nfct = NULL;
> +#endif
> +}

This time compile tested and s/nfct/nf_bridge/ above.
[NETFILTER]: Fix skb->nf_bridge lifetime issues

The bridge netfilter code simulates the NF_IP_PRE_ROUTING hook and skips
the real hook by registering with high priority and returning NF_STOP if
skb->nf_bridge is present and the BRNF_NF_BRIDGE_PREROUTING flag is not
set. The flag is only set during the simulated hook.

Because skb->nf_bridge is only freed when the packet is destroyed, the
packet will not only skip the first invocation of NF_IP_PRE_ROUTING, but
in the case of tunnel devices on top of the bridge also all further ones.
Forwarded packets from a bridge encapsulated by a tunnel device and sent
as locally outgoing packet will also still have the incorrect bridge
information from the input path attached.

We already have nf_reset calls on all RX/TX paths of tunnel devices,
so simply reset the nf_bridge field there too. As an added bonus,
the bridge information for locally delivered packets is now also freed
when the packet is queued to a socket.

Signed-off-by: Patrick McHardy <[email-masked]>

---
commit 5e5c34345f3ead2608e38d75f998dfeb7bb5df1c
tree 17bbdf2d4efc19888ec4fc0fd27c544677bd1949
parent 337ba256a7e68f174a88ffba805b40622297fc22
author Patrick McHardy <[email-masked]> Mon, 20 Feb 2006 10:33:14 +0100
committer Patrick McHardy <[email-masked]> Mon, 20 Feb 2006 10:33:14 +0100

 include/linux/skbuff.h          |   24 ++++++++++++++----------
 net/ipv4/netfilter/ipt_REJECT.c |    4 ----
 2 files changed, 14 insertions(+), 14 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 838ce0f..1a26110 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -1351,16 +1351,6 @@ static inline void nf_conntrack_put_reas
 		kfree_skb(skb);
 }
 #endif
-static inline void nf_reset(struct sk_buff *skb)
-{
-	nf_conntrack_put(skb->nfct);
-	skb->nfct = NULL;
-#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
-	nf_conntrack_put_reasm(skb->nfct_reasm);
-	skb->nfct_reasm = NULL;
-#endif
-}
-
 #ifdef CONFIG_BRIDGE_NETFILTER
 static inline void nf_bridge_put(struct nf_bridge_info *nf_bridge)
 {
@@ -1373,6 +1363,20 @@ static inline void nf_bridge_get(struct 
 		atomic_inc(&nf_bridge->use);
 }
 #endif /* CONFIG_BRIDGE_NETFILTER */
+static inline void nf_reset(struct sk_buff *skb)
+{
+	nf_conntrack_put(skb->nfct);
+	skb->nfct = NULL;
+#if defined(CONFIG_NF_CONNTRACK) || defined(CONFIG_NF_CONNTRACK_MODULE)
+	nf_conntrack_put_reasm(skb->nfct_reasm);
+	skb->nfct_reasm = NULL;
+#endif
+#ifdef CONFIG_BRIDGE_NETFILTER
+	nf_bridge_put(skb->nf_bridge);
+	skb->nf_bridge = NULL;
+#endif
+}
+
 #else /* CONFIG_NETFILTER */
 static inline void nf_reset(struct sk_buff *skb) {}
 #endif /* CONFIG_NETFILTER */
diff --git a/net/ipv4/netfilter/ipt_REJECT.c b/net/ipv4/netfilter/ipt_REJECT.c
index 26ea6c1..9d3b357 100644
--- a/net/ipv4/netfilter/ipt_REJECT.c
+++ b/net/ipv4/netfilter/ipt_REJECT.c
@@ -154,10 +154,6 @@ static void send_reset(struct sk_buff *o
 	/* This packet will not be the same as the other: clear nf fields */
 	nf_reset(nskb);
 	nskb->nfmark = 0;
-#ifdef CONFIG_BRIDGE_NETFILTER
-	nf_bridge_put(nskb->nf_bridge);
-	nskb->nf_bridge = NULL;
-#endif
 
 	tcph = (struct tcphdr *)((u_int32_t*)nskb->nh.iph + nskb->nh.iph->ihl);