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Date:   Wed, 29 Apr 2020 14:59:22 -0600
From:   "Jason A. Donenfeld" <Jason@...c4.com>
To:     netdev@...r.kernel.org, davem@...emloft.net
Cc:     Toke Høiland-Jørgensen <toke@...hat.com>,
        Olivier Tilmans <olivier.tilmans@...ia-bell-labs.com>,
        Dave Taht <dave.taht@...il.com>,
        "Rodney W . Grimes" <ietf@...rsh.dnsmgr.net>,
        "Jason A . Donenfeld" <Jason@...c4.com>
Subject: [PATCH net 3/3] wireguard: receive: use tunnel helpers for decapsulating ECN markings

From: Toke Høiland-Jørgensen <toke@...hat.com>

WireGuard currently only propagates ECN markings on tunnel decap according
to the old RFC3168 specification. However, the spec has since been updated
in RFC6040 to recommend slightly different decapsulation semantics. This
was implemented in the kernel as a set of common helpers for ECN
decapsulation, so let's just switch over WireGuard to using those, so it
can benefit from this enhancement and any future tweaks. We do not drop
packets with invalid ECN marking combinations, because WireGuard is
frequently used to work around broken ISPs, which could be doing that.

Fixes: e7096c131e51 ("net: WireGuard secure network tunnel")
Reported-by: Olivier Tilmans <olivier.tilmans@...ia-bell-labs.com>
Cc: Dave Taht <dave.taht@...il.com>
Cc: Rodney W. Grimes <ietf@...rsh.dnsmgr.net>
Signed-off-by: Toke Høiland-Jørgensen <toke@...hat.com>
Signed-off-by: Jason A. Donenfeld <Jason@...c4.com>
---
 drivers/net/wireguard/receive.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/drivers/net/wireguard/receive.c b/drivers/net/wireguard/receive.c
index da3b782ab7d3..267f202f1931 100644
--- a/drivers/net/wireguard/receive.c
+++ b/drivers/net/wireguard/receive.c
@@ -393,13 +393,11 @@ static void wg_packet_consume_data_done(struct wg_peer *peer,
 		len = ntohs(ip_hdr(skb)->tot_len);
 		if (unlikely(len < sizeof(struct iphdr)))
 			goto dishonest_packet_size;
-		if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
-			IP_ECN_set_ce(ip_hdr(skb));
+		INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ip_hdr(skb)->tos);
 	} else if (skb->protocol == htons(ETH_P_IPV6)) {
 		len = ntohs(ipv6_hdr(skb)->payload_len) +
 		      sizeof(struct ipv6hdr);
-		if (INET_ECN_is_ce(PACKET_CB(skb)->ds))
-			IP6_ECN_set_ce(skb, ipv6_hdr(skb));
+		INET_ECN_decapsulate(skb, PACKET_CB(skb)->ds, ipv6_get_dsfield(ipv6_hdr(skb)));
 	} else {
 		goto dishonest_packet_type;
 	}
-- 
2.26.2

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