net: core: don't account for udp header size when computing seglen

In case of tcp, gso_size contains the tcpmss. For UFO (udp fragmentation offloading) skbs, gso_size is the fragment payload size, i.e. we must not account for udp header size. Otherwise, when using virtio drivers, a to-be-forwarded UFO GSO packet will be needlessly fragmented in the forward path, because we think its individual segments are too large for the outgoing link. Fixes: fe6cc55 ("net: ip, ipv6: handle gso skbs in forwarding path") Cc: Eric Dumazet <[email protected]> Reported-by: Tobias Brunner <[email protected]> Signed-off-by: Florian Westphal <[email protected]> Signed-off-by: David S. Miller <[email protected]>
ambv · Apr 11, 2014 · 6d39d58 · 6d39d58
1 parent f34c4a3
commit 6d39d58
Showing 1 changed file with 7 additions and 5 deletions.
diff --git a/net/core/skbuff.c b/net/core/skbuff.c
@@ -3937,12 +3937,14 @@ EXPORT_SYMBOL_GPL(skb_scrub_packet);
 unsigned int skb_gso_transport_seglen(const struct sk_buff *skb)
 {
 	const struct skb_shared_info *shinfo = skb_shinfo(skb);
-	unsigned int hdr_len;
 
 	if (likely(shinfo->gso_type & (SKB_GSO_TCPV4 | SKB_GSO_TCPV6)))
-		hdr_len = tcp_hdrlen(skb);
-	else
-		hdr_len = sizeof(struct udphdr);
-	return hdr_len + shinfo->gso_size;
+		return tcp_hdrlen(skb) + shinfo->gso_size;
+
+	/* UFO sets gso_size to the size of the fragmentation
+	 * payload, i.e. the size of the L4 (UDP) header is already
+	 * accounted for.
+	 */
+	return shinfo->gso_size;
 }
 EXPORT_SYMBOL_GPL(skb_gso_transport_seglen);