geneve: Fix incorrect inner network header offset when innerprotoinherit is set

jira LE-1733
bugfix geneve_fixes
commit c6ae073

When innerprotoinherit is set, the tunneled packets do not have an inner
Ethernet header.
Change 'maclen' to not always assume the header length is ETH_HLEN, as
there might not be a MAC header.

This resolves issues with drivers (e.g. mlx5, in
mlx5e_tx_tunnel_accel()) who rely on the skb inner network header offset
to be correct, and use it for TX offloads.

Fixes: d8a6213 ("geneve: fix header validation in geneve[6]_xmit_skb")
	Signed-off-by: Gal Pressman <gal@nvidia.com>
	Signed-off-by: Tariq Toukan <tariqt@nvidia.com>
	Reviewed-by: Wojciech Drewek <wojciech.drewek@intel.com>
	Signed-off-by: David S. Miller <davem@davemloft.net>
(cherry picked from commit c6ae073)
Signed-off-by: Jonathan Maple <jmaple@ciq.com>

Author: PlaidCat

drivers/net/geneve.c

@@ -908,6 +908,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 			   struct geneve_dev *geneve,
 			   const struct ip_tunnel_info *info)
 {
+	bool inner_proto_inherit = geneve->cfg.inner_proto_inherit;
 	bool xnet = !net_eq(geneve->net, dev_net(geneve->dev));
 	struct geneve_sock *gs4 = rcu_dereference(geneve->sock4);
 	const struct ip_tunnel_key *key = &info->key;
@@ -919,7 +920,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 	__be16 sport;
 	int err;
 
-	if (!skb_vlan_inet_prepare(skb))
+	if (!skb_vlan_inet_prepare(skb, inner_proto_inherit))
 		return -EINVAL;
 
 	sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
@@ -992,7 +993,7 @@ static int geneve_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 	}
 
 	err = geneve_build_skb(&rt->dst, skb, info, xnet, sizeof(struct iphdr),
-			       geneve->cfg.inner_proto_inherit);
+			       inner_proto_inherit);
 	if (unlikely(err))
 		return err;
 
@@ -1008,6 +1009,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 			    struct geneve_dev *geneve,
 			    const struct ip_tunnel_info *info)
 {
+	bool inner_proto_inherit = geneve->cfg.inner_proto_inherit;
 	bool xnet = !net_eq(geneve->net, dev_net(geneve->dev));
 	struct geneve_sock *gs6 = rcu_dereference(geneve->sock6);
 	const struct ip_tunnel_key *key = &info->key;
@@ -1017,7 +1019,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 	__be16 sport;
 	int err;
 
-	if (!skb_vlan_inet_prepare(skb))
+	if (!skb_vlan_inet_prepare(skb, inner_proto_inherit))
 		return -EINVAL;
 
 	sport = udp_flow_src_port(geneve->net, skb, 1, USHRT_MAX, true);
@@ -1072,7 +1074,7 @@ static int geneve6_xmit_skb(struct sk_buff *skb, struct net_device *dev,
 		ttl = ttl ? : ip6_dst_hoplimit(dst);
 	}
 	err = geneve_build_skb(dst, skb, info, xnet, sizeof(struct ipv6hdr),
-			       geneve->cfg.inner_proto_inherit);
+			       inner_proto_inherit);
 	if (unlikely(err))
 		return err;
 

include/net/ip_tunnels.h

@@ -347,9 +347,10 @@ static inline bool pskb_inet_may_pull(struct sk_buff *skb)
 
 /* Variant of pskb_inet_may_pull().
  */
-static inline bool skb_vlan_inet_prepare(struct sk_buff *skb)
+static inline bool skb_vlan_inet_prepare(struct sk_buff *skb,
+					 bool inner_proto_inherit)
 {
-	int nhlen = 0, maclen = ETH_HLEN;
+	int nhlen = 0, maclen = inner_proto_inherit ? 0 : ETH_HLEN;
 	__be16 type = skb->protocol;
 
 	/* Essentially this is skb_protocol(skb, true)