netdev - [PATCH ipsec] esp6: get the right proto for transport mode in esp6_gso

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Message-Id: <7f50634c051299833413aa8478083d061443cc7c.1586509616.git.lucien.xin@gmail.com>
Date:   Fri, 10 Apr 2020 17:06:56 +0800
From:   Xin Long <lucien.xin@...il.com>
To:     netdev@...r.kernel.org
Cc:     Steffen Klassert <steffen.klassert@...unet.com>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        "David S. Miller" <davem@...emloft.net>,
        Sabrina Dubroca <sd@...asysnail.net>
Subject: [PATCH ipsec] esp6: get the right proto for transport mode in esp6_gso_encap

For transport mode, when ipv6 nexthdr is set, the packet format might
be like:

    ----------------------------------------------------
    |        | dest |     |     |      |  ESP    | ESP |
    | IP6 hdr| opts.| ESP | TCP | Data | Trailer | ICV |
    ----------------------------------------------------

What it wants to get for x-proto in esp6_gso_encap() is the proto that
will be set in ESP nexthdr. So it should skip all ipv6 nexthdrs and
get the real transport protocol. Othersize, the wrong proto number
will be set into ESP nexthdr.

This patch is to skip all ipv6 nexthdrs by calling ipv6_skip_exthdr()
in esp6_gso_encap().

Fixes: 7862b4058b9f ("esp: Add gso handlers for esp4 and esp6")
Signed-off-by: Xin Long <lucien.xin@...il.com>
---
 net/ipv6/esp6_offload.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/net/ipv6/esp6_offload.c b/net/ipv6/esp6_offload.c
index 8eab2c8..b828508 100644
--- a/net/ipv6/esp6_offload.c
+++ b/net/ipv6/esp6_offload.c
@@ -123,9 +123,16 @@ static void esp6_gso_encap(struct xfrm_state *x, struct sk_buff *skb)
 	struct ip_esp_hdr *esph;
 	struct ipv6hdr *iph = ipv6_hdr(skb);
 	struct xfrm_offload *xo = xfrm_offload(skb);
-	int proto = iph->nexthdr;
+	u8 proto = iph->nexthdr;
 
 	skb_push(skb, -skb_network_offset(skb));
+
+	if (x->outer_mode.encap == XFRM_MODE_TRANSPORT) {
+		__be16 frag;
+
+		ipv6_skip_exthdr(skb, sizeof(struct ipv6hdr), &proto, &frag);
+	}
+
 	esph = ip_esp_hdr(skb);
 	*skb_mac_header(skb) = IPPROTO_ESP;
 
-- 
2.1.0