This is a note to let you know that I've just added the patch titled ip6_gre: Make o_seqno start from 0 in native mode to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: ip6_gre-make-o_seqno-start-from-0-in-native-mode.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@xxxxxxxxxxxxxxx> know about it. commit 3246d91e01c1ce08d4ee55dae6ca9a536dbdf1af Author: Peilin Ye <peilin.ye@xxxxxxxxxxxxx> Date: Thu Apr 21 15:08:38 2022 -0700 ip6_gre: Make o_seqno start from 0 in native mode [ Upstream commit fde98ae91f79cab4e020f40c35ed23cbdc59661c ] 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: c12b395a4664 ("gre: Support GRE over IPv6") Signed-off-by: Peilin Ye <peilin.ye@xxxxxxxxxxxxx> Acked-by: William Tu <u9012063@xxxxxxxxx> Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx> Stable-dep-of: d80fc101d2eb ("erspan: get the proto with the md version for collect_md") Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx> diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c index a1fd3c9c1da3e..e3c65e7681ad4 100644 --- a/net/ipv6/ip6_gre.c +++ b/net/ipv6/ip6_gre.c @@ -711,6 +711,7 @@ 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; @@ -726,7 +727,6 @@ 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(skb); @@ -758,15 +758,14 @@ 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,