Subject: Re: 2.6.18-rc6 memory mapped pcap truncates outgoing TCP packets, but not icmp

From: Patrick McHardy <[email-masked]>
Date: Fri, 15 Sep 2006 22:16:17 +0200

bert hubert wrote:
>>It appears to be intentionally, but I don't see a reason for it.
>>Can you try if this patch makes it work as expected?
> 
> 
>>[PACKET]: Don't truncate non-linear skbs with mmaped IO
>>
>>Non-linear skbs are truncated to their linear part with mmaped IO.
>>Fix by using skb_copy_bits instead of memcpy.
> 
> 
> Works very well for me! I hope this can make it into 2.6.18.

That would be fine with me, lets see what Dave thinks.

[PACKET]: Don't truncate non-linear skbs with mmaped IO

Non-linear skbs are truncated to their linear part with mmaped IO.
Fix by using skb_copy_bits instead of memcpy.

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

---
commit 6e184976552a407c331f9b4e52b2c26fcae46ee7
tree 1bb4fc2b65179a51e795dc07908277b83cc0921a
parent 9f737633e6ee54fc174282d49b2559bd2208391d
author Patrick McHardy <[email-masked]> Thu, 14 Sep 2006 11:59:09 +0200
committer Patrick McHardy <[email-masked]> Thu, 14 Sep 2006 11:59:09 +0200

 net/packet/af_packet.c |    4 +---
 1 files changed, 1 insertions(+), 3 deletions(-)

diff --git a/net/packet/af_packet.c b/net/packet/af_packet.c
index f9cef36..4172a52 100644
--- a/net/packet/af_packet.c
+++ b/net/packet/af_packet.c
@@ -626,8 +626,6 @@ static int tpacket_rcv(struct sk_buff *s
 		if ((int)snaplen < 0)
 			snaplen = 0;
 	}
-	if (snaplen > skb->len-skb->data_len)
-		snaplen = skb->len-skb->data_len;
 
 	spin_lock(&sk->sk_receive_queue.lock);
 	h = (struct tpacket_hdr *)packet_lookup_frame(po, po->head);
@@ -644,7 +642,7 @@ static int tpacket_rcv(struct sk_buff *s
 		status &= ~TP_STATUS_LOSING;
 	spin_unlock(&sk->sk_receive_queue.lock);
 
-	memcpy((u8*)h + macoff, skb->data, snaplen);
+	skb_copy_bits(skb, 0, (u8*)h + macoff, snaplen);
 
 	h->tp_len = skb->len;
 	h->tp_snaplen = snaplen;