From: Michal Kubecek <mkubecek@suse.cz>
Date: Mon, 18 Jan 2021 18:30:59 +0100
Subject: kabi: preserve struct header_ops after bsc#1176081 fix
Patch-mainline: Never, kabi workaround
References: bsc#1176081

Backport of mainline commit e78b2915517e ("net: Introduce parse_protocol
header_ops callback") adds ->parse_protocol() callback into struct
header_ops which would break kabi.

As this callback is only used in dev_parse_header_protocol() and only set
in eth_header_ops - the latter until mainline commit 2606aff91685 ("net:
ip_tunnel: add header_ops for layer 3 devices") - replace the call in
dev_parse_header_protocol() with an explicit test of dev->header_ops
against &eth_header_ops so that we can drop the callback from struct
header_ops.

Duplicating the eth_header_ops and eth_header_parse_protocol declaration in
include/linux/netdevice.h is a bit unclean but including
<linux/etherdevice.h> could result in spurious "became defined" kabi
errors.

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
---
 include/linux/netdevice.h | 11 +++++++----
 net/ethernet/eth.c        |  2 +-
 2 files changed, 8 insertions(+), 5 deletions(-)

--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -262,6 +262,9 @@ struct hh_cache {
 #define LL_RESERVED_SPACE_EXTRA(dev,extra) \
 	((((dev)->hard_header_len+(dev)->needed_headroom+(extra))&~(HH_DATA_MOD - 1)) + HH_DATA_MOD)
 
+extern const struct header_ops eth_header_ops;
+__be16 eth_header_parse_protocol(const struct sk_buff *skb);
+
 struct header_ops {
 	int	(*create) (struct sk_buff *skb, struct net_device *dev,
 			   unsigned short type, const void *daddr,
@@ -272,7 +275,6 @@ struct header_ops {
 				const struct net_device *dev,
 				const unsigned char *haddr);
 	bool	(*validate)(const char *ll_header, unsigned int len);
-	__be16	(*parse_protocol)(const struct sk_buff *skb);
 };
 
 /* These flag bits are private to the generic network queueing
@@ -2730,9 +2732,10 @@ static inline __be16 dev_parse_header_protocol(const struct sk_buff *skb)
 {
 	const struct net_device *dev = skb->dev;
 
-	if (!dev->header_ops || !dev->header_ops->parse_protocol)
-		return 0;
-	return dev->header_ops->parse_protocol(skb);
+	if (dev->header_ops == &eth_header_ops)
+		return eth_header_parse_protocol(skb);
+
+	return 0;
 }
 
 /* ll_header must have at least hard_header_len allocated */
--- a/net/ethernet/eth.c
+++ b/net/ethernet/eth.c
@@ -355,8 +355,8 @@ const struct header_ops eth_header_ops ____cacheline_aligned = {
 	.parse		= eth_header_parse,
 	.cache		= eth_header_cache,
 	.cache_update	= eth_header_cache_update,
-	.parse_protocol	= eth_header_parse_protocol,
 };
+EXPORT_SYMBOL(eth_header_ops);
 
 /**
  * ether_setup - setup Ethernet network device