netdev - [PATCH net-next 1/2] net: reset mac header in dev_start

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Message-ID: <1360131740.28557.25.camel@edumazet-glaptop>
Date:	Tue, 05 Feb 2013 22:22:20 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	David Miller <davem@...emloft.net>
Cc:	netdev <netdev@...r.kernel.org>,
	Ben Greear <greearb@...delatech.com>
Subject: [PATCH net-next 1/2] net: reset mac header in dev_start_xmit()

From: Eric Dumazet <edumazet@...gle.com>

On 64 bit arches :

There is a off-by-one error in qdisc_pkt_len_init() because
mac_header is not set in xmit path.

skb_mac_header() returns an out of bound value that was
harmless because hdr_len is an 'unsigned int'

On 32bit arches, the error is abysmal.

This patch is also a prereq for "macvlan: add multicast filter"

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
Cc: Ben Greear <greearb@...delatech.com>
---
 net/core/dev.c |    2 ++
 1 file changed, 2 insertions(+)

diff --git a/net/core/dev.c b/net/core/dev.c
index a87bc74..0b888b5 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2799,6 +2799,8 @@ int dev_queue_xmit(struct sk_buff *skb)
 	struct Qdisc *q;
 	int rc = -ENOMEM;
 
+	skb_reset_mac_header(skb);
+
 	/* Disable soft irqs for various locks below. Also
 	 * stops preemption for RCU.
 	 */


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