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SubjectRe: [PATCH net-next-2.6] net/ipv4: push IP options to CB in ip_fragment
Le lundi 30 août 2010 à 19:21 -0400, Bandan Das a écrit :
> >
> > I wonder if we want this.
> >
> > Maybe setting skb->local_df = 1 in bridge should be enough ?
> >
> >
> Thanks Eric for looking at this. Indeed, setting local_df to 1 seems to be enough! I will
> respin and post a different patch.

Reading this stuff again, I wonder if we should not revert commit
17762060c25590bfddd and use a different trick

Author: Herbert Xu <>
Date: Mon Jul 5 21:29:28 2010 +0000

bridge: Clear IPCB before possible entry into IP stack

The bridge protocol lives dangerously by having incestuous relations
with the IP stack. In this instance an abomination has been created
where a bogus IPCB area from a bridged packet leads to a crash in
the IP stack because it's interpreted as IP options.

This patch papers over the problem by clearing the IPCB area in that
particular spot. To fix this properly we'd also need to parse any
IP options if present but I'm way too lazy for that.

Signed-off-by: Herbert Xu <>
Signed-off-by: David S. Miller <>

We could have a padding in front of struct br_input_skb_cb to make sure
we dont overwrite IP (4|6) CB in bridge ?

Something like this untested patch :

diff --git a/net/bridge/br_netfilter.c b/net/bridge/br_netfilter.c
index 2c911c0..9fdf1b1 100644
--- a/net/bridge/br_netfilter.c
+++ b/net/bridge/br_netfilter.c
@@ -598,9 +598,6 @@ static unsigned int br_nf_pre_routing(unsigned int hook, struct sk_buff *skb,

pskb_trim_rcsum(skb, len);

- /* BUG: Should really parse the IP options here. */
- memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
if (!nf_bridge_alloc(skb))
return NF_DROP;
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index 75c90ed..b27163a 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -18,6 +18,7 @@
#include <linux/netpoll.h>
#include <linux/u64_stats_sync.h>
#include <net/route.h>
+#include <linux/ipv6.h>

#define BR_HASH_BITS 8
#define BR_HASH_SIZE (1 << BR_HASH_BITS)
@@ -244,6 +245,8 @@ struct net_bridge

struct br_input_skb_cb {
+ struct inet6_skb_parm pad;
struct net_device *brdev;
int igmp;

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