ip6_gre: Make o_seqno start from 0 in native mode

For IP6GRE and IP6GRETAP 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 the "if (tunnel->parms.collect_md)" clause in __gre6_xmit(), where tunnel->o_seqno is passed to gre_build_header() before getting incremented. Fixes: c12b395 ("gre: Support GRE over IPv6") Signed-off-by: Peilin Ye <[email protected]> Acked-by: William Tu <[email protected]> Signed-off-by: David S. Miller <[email protected]>
kawasaki · Apr 25, 2022 · fde98ae · fde98ae
1 parent ff827be
commit fde98ae
Showing 1 changed file with 5 additions and 6 deletions.
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
@@ -724,6 +724,7 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 {
 	struct ip6_tnl *tunnel = netdev_priv(dev);
 	__be16 protocol;
+	__be16 flags;
 
 	if (dev->type == ARPHRD_ETHER)
 		IPCB(skb)->flags = 0;
@@ -739,7 +740,6 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 	if (tunnel->parms.collect_md) {
 		struct ip_tunnel_info *tun_info;
 		const struct ip_tunnel_key *key;
-		__be16 flags;
 		int tun_hlen;
 
 		tun_info = skb_tunnel_info_txcheck(skb);
@@ -770,15 +770,14 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 						      : 0);
 
 	} else {
-		if (tunnel->parms.o_flags & TUNNEL_SEQ)
-			tunnel->o_seqno++;
-
 		if (skb_cow_head(skb, dev->needed_headroom ?: tunnel->hlen))
 			return -ENOMEM;
 
-		gre_build_header(skb, tunnel->tun_hlen, tunnel->parms.o_flags,
+		flags = tunnel->parms.o_flags;
+
+		gre_build_header(skb, tunnel->tun_hlen, flags,
 				 protocol, tunnel->parms.o_key,
-				 htonl(tunnel->o_seqno));
+				 (flags & TUNNEL_SEQ) ? htonl(tunnel->o_seqno++) : 0);
 	}
 
 	return ip6_tnl_xmit(skb, dev, dsfield, fl6, encap_limit, pmtu,