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, 38 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-receive-reset-last_under_load-to-zero.patch b/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-receive-reset-last_under_load-to-zero.patch
new file mode 100644
index 0000000000..2f3e6a3c9a
--- /dev/null
+++ b/target/linux/generic/backport-5.4/080-wireguard-0088-wireguard-receive-reset-last_under_load-to-zero.patch
@@ -0,0 +1,38 @@
+From b3969f204f6f3e1b712d4892050abf35ad178ccc Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Fri, 14 Feb 2020 23:57:21 +0100
+Subject: [PATCH 088/124] wireguard: receive: reset last_under_load to zero
+
+commit 2a8a4df36462aa85b0db87b7c5ea145ba67e34a8 upstream.
+
+This is a small optimization that prevents more expensive comparisons
+from happening when they are no longer necessary, by clearing the
+last_under_load variable whenever we wind up in a state where we were
+under load but we no longer are.
+
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+Suggested-by: Matt Dunwoodie <ncon@noconroy.net>
+Signed-off-by: David S. Miller <davem@davemloft.net>
+Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
+---
+ drivers/net/wireguard/receive.c | 7 +++++--
+ 1 file changed, 5 insertions(+), 2 deletions(-)
+
+--- a/drivers/net/wireguard/receive.c
++++ b/drivers/net/wireguard/receive.c
+@@ -118,10 +118,13 @@ static void wg_receive_handshake_packet(
+ 
+ 	under_load = skb_queue_len(&wg->incoming_handshakes) >=
+ 		     MAX_QUEUED_INCOMING_HANDSHAKES / 8;
+-	if (under_load)
++	if (under_load) {
+ 		last_under_load = ktime_get_coarse_boottime_ns();
+-	else if (last_under_load)
++	} else if (last_under_load) {
+ 		under_load = !wg_birthdate_has_expired(last_under_load, 1);
++		if (!under_load)
++			last_under_load = 0;
++	}
+ 	mac_state = wg_cookie_validate_packet(&wg->cookie_checker, skb,
+ 					      under_load);
+ 	if ((under_load && mac_state == VALID_MAC_WITH_COOKIE) ||