netdev - [PATCH net-next] net: geneve: accept every ethertype

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Date:   Sun, 12 Mar 2023 17:37:26 +0100
From:   Josef Miegl <josef@...gl.cz>
To:     unlisted-recipients:; (no To-header on input)
Cc:     Eyal Birger <eyal.birger@...il.com>, Josef Miegl <josef@...gl.cz>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH net-next] net: geneve: accept every ethertype

The Geneve encapsulation, as defined in RFC 8926, has a Protocol Type
field, which states the Ethertype of the payload appearing after the
Geneve header.

Commit 435fe1c0c1f7 ("net: geneve: support IPv4/IPv6 as inner protocol")
introduced a new IFLA_GENEVE_INNER_PROTO_INHERIT flag that allowed the
use of other Ethertypes than Ethernet. However, it imposed a restriction
that prohibits receiving payloads other than IPv4, IPv6 and Ethernet.

This patch removes this restriction, making it possible to receive any
Ethertype as a payload, if the IFLA_GENEVE_INNER_PROTO_INHERIT flag is
set.

This is especially useful if one wants to encapsulate MPLS, because with
this patch the control-plane traffic (IP, IS-IS) and the data-plane
traffic (MPLS) can be encapsulated without an Ethernet frame, making
lightweight overlay networks a possibility.

Signed-off-by: Josef Miegl <josef@...gl.cz>
---
 drivers/net/geneve.c | 9 ++-------
 1 file changed, 2 insertions(+), 7 deletions(-)

diff --git a/drivers/net/geneve.c b/drivers/net/geneve.c
index 89ff7f8e8c7e..32684e94eb4f 100644
--- a/drivers/net/geneve.c
+++ b/drivers/net/geneve.c
@@ -365,13 +365,6 @@ static int geneve_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	if (unlikely(geneveh->ver != GENEVE_VER))
 		goto drop;

-	inner_proto = geneveh->proto_type;
-
-	if (unlikely((inner_proto != htons(ETH_P_TEB) &&
-		      inner_proto != htons(ETH_P_IP) &&
-		      inner_proto != htons(ETH_P_IPV6))))
-		goto drop;
-
 	gs = rcu_dereference_sk_user_data(sk);
 	if (!gs)
 		goto drop;
@@ -380,6 +373,8 @@ static int geneve_udp_encap_recv(struct sock *sk, struct sk_buff *skb)
 	if (!geneve)
 		goto drop;

+	inner_proto = geneveh->proto_type;
+
 	if (unlikely((!geneve->cfg.inner_proto_inherit &&
 		      inner_proto != htons(ETH_P_TEB)))) {
 		geneve->dev->stats.rx_dropped++;
-- 
2.37.1