From: "Jason A. Donenfeld" <Jason@zx2c4.com>
Date: Mon, 29 Jun 2020 19:06:22 -0600
Subject: tun: implement header_ops->parse_protocol for AF_PACKET
Patch-mainline: v5.8-rc5
Git-commit: b9815eb1d13f0dc088ee8afb6e6d0683ea551098
References: bsc#1176447

The tun driver passes up skb->protocol to userspace in the form of PI headers.
For AF_PACKET injection, we need to support its call chain of:

    packet_sendmsg -> packet_snd -> packet_parse_headers ->
      dev_parse_header_protocol -> parse_protocol

Without a valid parse_protocol, this returns zero, and the tun driver
then gives userspace bogus values that it can't deal with.

Note that this isn't the case with tap, because tap already benefits
from the shared infrastructure for ethernet headers. But with tun,
there's nothing.

Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Acked-by: Thomas Bogendoerfer <tbogendoerfer@suse.de>
---
 drivers/net/tun.c |    2 ++
 1 file changed, 2 insertions(+)

--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -62,6 +62,7 @@
 #include <net/rtnetlink.h>
 #include <net/sock.h>
 #include <net/xdp.h>
+#include <net/ip_tunnels.h>
 #include <linux/seq_file.h>
 #include <linux/uio.h>
 #include <linux/skb_array.h>
@@ -1351,6 +1352,7 @@ static void tun_net_init(struct net_devi
 	switch (tun->flags & TUN_TYPE_MASK) {
 	case IFF_TUN:
 		dev->netdev_ops = &tun_netdev_ops;
+		dev->header_ops = &ip_tunnel_header_ops;
 
 		/* Point-to-Point TUN Device */
 		dev->hard_header_len = 0;