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, 35 insertions, 0 deletions

diff --git a/target/linux/generic/backport-5.4/080-wireguard-0093-wireguard-receive-remove-dead-code-from-default-pack.patch b/target/linux/generic/backport-5.4/080-wireguard-0093-wireguard-receive-remove-dead-code-from-default-pack.patch
new file mode 100644
index 0000000000..ed4c4a017e
--- /dev/null
+++ b/target/linux/generic/backport-5.4/080-wireguard-0093-wireguard-receive-remove-dead-code-from-default-pack.patch
@@ -0,0 +1,35 @@
+From 827489b9186ac53ed1e162c7d9b0f7b19d1a5995 Mon Sep 17 00:00:00 2001
+From: "Jason A. Donenfeld" <Jason@zx2c4.com>
+Date: Wed, 18 Mar 2020 18:30:46 -0600
+Subject: [PATCH 093/124] wireguard: receive: remove dead code from default
+ packet type case
+
+commit 2b8765c52db24c0fbcc81bac9b5e8390f2c7d3c8 upstream.
+
+The situation in which we wind up hitting the default case here
+indicates a major bug in earlier parsing code. It is not a usual thing
+that should ever happen, which means a "friendly" message for it doesn't
+make sense. Rather, replace this with a WARN_ON, just like we do earlier
+in the file for a similar situation, so that somebody sends us a bug
+report and we can fix it.
+
+Reported-by: Fabian Freyer <fabianfreyer@radicallyopensecurity.com>
+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/receive.c | 3 +--
+ 1 file changed, 1 insertion(+), 2 deletions(-)
+
+--- a/drivers/net/wireguard/receive.c
++++ b/drivers/net/wireguard/receive.c
+@@ -587,8 +587,7 @@ void wg_packet_receive(struct wg_device
+ 		wg_packet_consume_data(wg, skb);
+ 		break;
+ 	default:
+-		net_dbg_skb_ratelimited("%s: Invalid packet from %pISpfsc\n",
+-					wg->dev->name, skb);
++		WARN(1, "Non-exhaustive parsing of packet header lead to unknown packet type!\n");
+ 		goto err;
+ 	}
+ 	return;