ip_gre: Make o_seqno start from 0 in native mode

For GRE and GRETAP devices, currently o_seqno starts from 1 in native mode. According to RFC 2890 2.2., "The first datagram is sent with a sequence number of 0." Fix it. It is worth mentioning that o_seqno already starts from 0 in collect_md mode, see gre_fb_xmit(), where tunnel->o_seqno is passed to gre_build_header() before getting incremented. Fixes: 1da177e4c3f4 ("Linux-2.6.12-rc2") Signed-off-by: Peilin Ye <[email protected]> Acked-by: William Tu <[email protected]> Signed-off-by: David S. Miller <[email protected]>
majek · Apr 25, 2022 · ff827be · ff827be
1 parent 9810c58
commit ff827be
Showing 1 changed file with 3 additions and 5 deletions.
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
@@ -459,14 +459,12 @@ static void __gre_xmit(struct sk_buff *skb, struct net_device *dev,
 		       __be16 proto)
 {
 	struct ip_tunnel *tunnel = netdev_priv(dev);
-
-	if (tunnel->parms.o_flags & TUNNEL_SEQ)
-		tunnel->o_seqno++;
+	__be16 flags = tunnel->parms.o_flags;
 
 	/* Push GRE header. */
 	gre_build_header(skb, tunnel->tun_hlen,
-			 tunnel->parms.o_flags, proto, tunnel->parms.o_key,
-			 htonl(tunnel->o_seqno));
+			 flags, proto, tunnel->parms.o_key,
+			 (flags & TUNNEL_SEQ) ? htonl(tunnel->o_seqno++) : 0);
 
 	ip_tunnel_xmit(skb, dev, tnl_params, tnl_params->protocol);
 }