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From:   Peilin Ye <yepeilin.cs@gmail.com>
To:     "David S. Miller" <davem@davemloft.net>,
        Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>,
        David Ahern <dsahern@kernel.org>,
        Jakub Kicinski <kuba@kernel.org>
Cc:     Peilin Ye <peilin.ye@bytedance.com>,
        William Tu <u9012063@gmail.com>,
        Cong Wang <cong.wang@bytedance.com>,
        Feng Zhou <zhoufeng.zf@bytedance.com>,
        Peilin Ye <yepeilin.cs@gmail.com>, netdev@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: [PATCH v2 net 1/2] ip6_gre: Avoid updating tunnel->tun_hlen in __gre6_xmit()
Date:   Thu, 14 Apr 2022 13:34:26 -0700
Message-Id: <c5b7dc6020c93a1e7b40bc472fcdb6429999473e.1649967496.git.peilin.ye@bytedance.com>
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From: Peilin Ye <peilin.ye@bytedance.com>

Do not update tunnel->tun_hlen in data plane code.  Use a local variable
instead, just like "tunnel_hlen" in net/ipv4/ip_gre.c:gre_fb_xmit().

Co-developed-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Peilin Ye <peilin.ye@bytedance.com>
---
v1: https://lore.kernel.org/netdev/c5b7dc6020c93a1e7b40bc472fcdb6429999473e.1649715555.git.peilin.ye@bytedance.com

(no change since v1)

 net/ipv6/ip6_gre.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 8753e9cec326..b43a46449130 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -743,6 +743,7 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 		struct ip_tunnel_info *tun_info;
 		const struct ip_tunnel_key *key;
 		__be16 flags;
+		int tun_hlen;
 
 		tun_info = skb_tunnel_info_txcheck(skb);
 		if (IS_ERR(tun_info) ||
@@ -760,9 +761,9 @@ static netdev_tx_t __gre6_xmit(struct sk_buff *skb,
 		dsfield = key->tos;
 		flags = key->tun_flags &
 			(TUNNEL_CSUM | TUNNEL_KEY | TUNNEL_SEQ);
-		tunnel->tun_hlen = gre_calc_hlen(flags);
+		tun_hlen = gre_calc_hlen(flags);
 
-		gre_build_header(skb, tunnel->tun_hlen,
+		gre_build_header(skb, tun_hlen,
 				 flags, protocol,
 				 tunnel_id_to_key32(tun_info->key.tun_id),
 				 (flags & TUNNEL_SEQ) ? htonl(tunnel->o_seqno++)
-- 
2.20.1