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[5.15,098/177] ip_gre: Make o_seqno start from 0 in native mode

Message ID 20220504153101.902753048@linuxfoundation.org
State New
Headers show
Series None | expand

Commit Message

Greg KH May 4, 2022, 4:44 p.m. UTC 
From: Peilin Ye <peilin.ye@bytedance.com>

[ Upstream commit ff827beb706ed719c766acf36449801ded0c17fc ]

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 <peilin.ye@bytedance.com>
Acked-by: William Tu <u9012063@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 net/ipv4/ip_gre.c | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)
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Patch

diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index e7f3e37e4aa8..4b7d7ed4bab8 100644
--- 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);
 }