kernel: 5.4: import wireguard backport

Rather than using the clunky, old, slower wireguard-linux-compat out of
tree module, this commit does a patch-by-patch backport of upstream's
wireguard to 5.4. This specific backport is in widespread use, being
part of SUSE's enterprise kernel, Oracle's enterprise kernel, Google's
Android kernel, Gentoo's distro kernel, and probably more I've forgotten
about. It's definately the "more proper" way of adding wireguard to a
kernel than the ugly compat.h hell of the wireguard-linux-compat repo.
And most importantly for OpenWRT, it allows using the same module
configuration code for 5.10 as for 5.4, with no need for bifurcation.

These patches are from the backport tree which is maintained in the
open here: https://git.zx2c4.com/wireguard-linux/log/?h=backport-5.4.y
I'll be sending PRs to update this as needed.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/080-wireguard-0112-wireguard-queueing-make-use-of-ip_tunnel_parse_proto.patch b/target/linux/generic/backport-5.4/080-wireguard-0112-wireguard-queueing-make-use-of-ip_tunnel_parse_proto.patch
new file mode 100644
index 0000000000..1f8766c9e1
--- /dev/null
+++ b/target/linux/generic/backport-5.4/080-wireguard-0112-wireguard-queueing-make-use-of-ip_tunnel_parse_proto.patch
@@ -0,0 +1,69 @@
+From 83313326c87e7c1aacebce4f8411505e2b68bf25 Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Mon, 29 Jun 2020 19:06:21 -0600
+Subject: [PATCH 112/124] wireguard: queueing: make use of
+ ip_tunnel_parse_protocol
+
+commit 1a574074ae7d1d745c16f7710655f38a53174c27 upstream.
+
+Now that wg_examine_packet_protocol has been added for general
+consumption as ip_tunnel_parse_protocol, it's possible to remove
+wg_examine_packet_protocol and simply use the new
+ip_tunnel_parse_protocol function directly.
+
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+---
+ drivers/net/wireguard/queueing.h | 19 ++-----------------
+ drivers/net/wireguard/receive.c  |  2 +-
+ 2 files changed, 3 insertions(+), 18 deletions(-)
+
+--- a/drivers/net/wireguard/queueing.h
++++ b/drivers/net/wireguard/queueing.h
+@@ -11,6 +11,7 @@
+ #include <linux/skbuff.h>
+ #include <linux/ip.h>
+ #include <linux/ipv6.h>
++#include <net/ip_tunnels.h>
+ 
+ struct wg_device;
+ struct wg_peer;
+@@ -65,25 +66,9 @@ struct packet_cb {
+ #define PACKET_CB(skb) ((struct packet_cb *)((skb)->cb))
+ #define PACKET_PEER(skb) (PACKET_CB(skb)->keypair->entry.peer)
+ 
+-/* Returns either the correct skb->protocol value, or 0 if invalid. */
+-static inline __be16 wg_examine_packet_protocol(struct sk_buff *skb)
+-{
+-	if (skb_network_header(skb) >= skb->head &&
+-	    (skb_network_header(skb) + sizeof(struct iphdr)) <=
+-		    skb_tail_pointer(skb) &&
+-	    ip_hdr(skb)->version == 4)
+-		return htons(ETH_P_IP);
+-	if (skb_network_header(skb) >= skb->head &&
+-	    (skb_network_header(skb) + sizeof(struct ipv6hdr)) <=
+-		    skb_tail_pointer(skb) &&
+-	    ipv6_hdr(skb)->version == 6)
+-		return htons(ETH_P_IPV6);
+-	return 0;
+-}
+-
+ static inline bool wg_check_packet_protocol(struct sk_buff *skb)
+ {
+-	__be16 real_protocol = wg_examine_packet_protocol(skb);
++	__be16 real_protocol = ip_tunnel_parse_protocol(skb);
+ 	return real_protocol && skb->protocol == real_protocol;
+ }
+ 
+--- a/drivers/net/wireguard/receive.c
++++ b/drivers/net/wireguard/receive.c
+@@ -387,7 +387,7 @@ static void wg_packet_consume_data_done(
+ 	 */
+ 	skb->ip_summed = CHECKSUM_UNNECESSARY;
+ 	skb->csum_level = ~0; /* All levels */
+-	skb->protocol = wg_examine_packet_protocol(skb);
++	skb->protocol = ip_tunnel_parse_protocol(skb);
+ 	if (skb->protocol == htons(ETH_P_IP)) {
+ 		len = ntohs(ip_hdr(skb)->tot_len);
+ 		if (unlikely(len < sizeof(struct iphdr)))