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Re: 2.6.0-test9 : bridge freezes

To: "David S. Miller" <davem@xxxxxxxxxx>, Steve Hill <steve@xxxxxxxxxxxx>
Subject: Re: 2.6.0-test9 : bridge freezes
From: Bart De Schuymer <bdschuym@xxxxxxxxxx>
Date: Tue, 16 Dec 2003 08:43:58 +0100
Cc: netdev@xxxxxxxxxxx
In-reply-to: <>
References: <Pine.LNX.4.44.0312151304350.8670-200000@sorbus2.navaho> <>
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On Tuesday 16 December 2003 02:17, David S. Miller wrote:
> There must be something in particular that the IPV4 fragmentation code
> is doing that makes these fragment reference drops get forgotten.  Hmmm...
> I just noticed that both bridge netfilter and IPV4 fragmentation make much
> use of the skb->cb[] control block, this may be the true source of the
> troubles.
> In fact, since bridge netfilter expects pointers to be there, I'm surprised
> this does not cause a crash.

It only expects a pointer in br_nf_forward_finish() for ARP traffic. I
checked and the ARP code doesn't use the control buffer.
For IP traffic, it uses the control buffer just before and just after
the call to the IP PRE_ROUTING hook.
OK, I just looked at the ip_fragment.c code and it uses the control buffer
too. You are truly amazing. I'll use skbuff.c::nf_bridge_info instead.

Steve, does this patch fix things? Of course, first remove your code from
ip_fragment.c. I haven't tested this patch yet, this will have to wait
until this evening.
Dave, I'll cook up a slightly different patch for you later, I think
nf_bridge->hh is now a bad name, I'll change it into nf_bridge->data.


--- linux-2.6.0-test11-bk10/net/bridge/br_netfilter.c.old       2003-12-16 
08:33:35.000000000 +0100
+++ linux-2.6.0-test11-bk10/net/bridge/br_netfilter.c   2003-12-16 
08:34:12.000000000 +0100
@@ -38,11 +38,9 @@
 #define skb_origaddr(skb)       (((struct bridge_skb_cb *) \
-                                (skb->cb))->daddr.ipv4)
+                                (skb->nf_bridge->hh))->daddr.ipv4)
 #define store_orig_dstaddr(skb)         (skb_origaddr(skb) = 
 #define dnat_took_place(skb)    (skb_origaddr(skb) != (skb)->nh.iph->daddr)
-#define clear_cb(skb)           (memset(&skb_origaddr(skb), 0, \
-                                sizeof(struct bridge_skb_cb)))
 #define has_bridge_parent(device)      ((device)->br_port != NULL)
 #define bridge_parent(device)          ((device)->br_port->br->dev)
@@ -203,7 +201,6 @@ bridged_dnat:
                                nf_bridge->mask |= BRNF_BRIDGED_DNAT;
                                skb->dev = nf_bridge->physindev;
-                               clear_cb(skb);
                                if (skb->protocol ==
                                    __constant_htons(ETH_P_8021Q)) {
                                        skb_push(skb, VLAN_HLEN);
@@ -224,7 +221,6 @@ bridged_dnat:
-       clear_cb(skb);
        skb->dev = nf_bridge->physindev;
        if (skb->protocol == __constant_htons(ETH_P_8021Q)) {
                skb_push(skb, VLAN_HLEN);

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