[Xen-devel] [PATCH] netfront/back: do not mark packets of length < MSS as GSO

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

# HG changeset patch
# User Ian Campbell <ian.campbell@xxxxxxxxxx>
# Date 1231847296 0
# Node ID 5b29f1081b2061cf56fa57ed67fef25cc1426a57
# Parent  28acedb66302a29c9ef14a3084b4736d3fc192f1
netfront/back: do not mark packets of length < MSS as GSO

Linux assumes that skbs marked for GSO are longer than MSS. In
particular tcp_tso_segment assumes that skb_segment will return a
chain of at least 2 skbs.

Both netfront and back should therefor not pass such a packet up the
stack.

Signed-off-by: Ian Campbell <ian.campbell@xxxxxxxxxx>

diff -r 28acedb66302 -r 5b29f1081b20 drivers/xen/netback/netback.c
--- a/drivers/xen/netback/netback.c     Wed Jan 07 12:21:54 2009 +0900
+++ b/drivers/xen/netback/netback.c     Tue Jan 13 11:48:16 2009 +0000
@@ -1345,6 +1345,9 @@ static void net_tx_action(unsigned long 
                        skb_shinfo(skb)->frags[0].page = (void *)~0UL;
                }
 
+               if (skb->data_len < skb_shinfo(skb)->gso_size)
+                       skb_shinfo(skb)->gso_size = 0;
+
                __skb_queue_tail(&tx_queue, skb);
 
                pending_cons++;
diff -r 28acedb66302 -r 5b29f1081b20 drivers/xen/netfront/netfront.c
--- a/drivers/xen/netfront/netfront.c   Wed Jan 07 12:21:54 2009 +0900
+++ b/drivers/xen/netfront/netfront.c   Tue Jan 13 11:48:16 2009 +0000
@@ -1439,6 +1439,10 @@ err:
                np->stats.rx_packets++;
                np->stats.rx_bytes += skb->len;
 
+#ifdef HAVE_TSO
+               if (skb->data_len < skb_shinfo(skb)->gso_size)
+                       skb_shinfo(skb)->gso_size = 0;
+#endif
                __skb_queue_tail(&rxq, skb);
 
                np->rx.rsp_cons = ++i;

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