From: Daniel Borkmann <daniel@iogearbox.net>
Date: Sun, 2 Jul 2017 02:13:25 +0200
Subject: bpf, net: add skb_mac_header_len helper
Git-commit: 0daf4349406074fc03e4889ba5e97e6fb5311bab
Patch-mainline: v4.13-rc1
References: networking-stable-18_09_24, bsc#1109837

Add a small skb_mac_header_len() helper similarly as the
skb_network_header_len() we have and replace open coded
places in BPF's bpf_skb_change_proto() helper. Will also
be used in upcoming work.

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 include/linux/skbuff.h |    5 +++++
 net/core/filter.c      |    4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2204,6 +2204,11 @@ static inline int skb_mac_offset(const s
 	return skb_mac_header(skb) - skb->data;
 }
 
+static inline u32 skb_mac_header_len(const struct sk_buff *skb)
+{
+	return skb->network_header - skb->mac_header;
+}
+
 static inline int skb_mac_header_was_set(const struct sk_buff *skb)
 {
 	return skb->mac_header != (typeof(skb->mac_header))~0U;
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2011,7 +2011,7 @@ static int bpf_skb_net_hdr_pop(struct sk
 static int bpf_skb_proto_4_to_6(struct sk_buff *skb)
 {
 	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
-	u32 off = skb->network_header - skb->mac_header;
+	u32 off = skb_mac_header_len(skb);
 	int ret;
 
 	ret = skb_cow(skb, len_diff);
@@ -2047,7 +2047,7 @@ static int bpf_skb_proto_4_to_6(struct s
 static int bpf_skb_proto_6_to_4(struct sk_buff *skb)
 {
 	const u32 len_diff = sizeof(struct ipv6hdr) - sizeof(struct iphdr);
-	u32 off = skb->network_header - skb->mac_header;
+	u32 off = skb_mac_header_len(skb);
 	int ret;
 
 	ret = skb_unclone(skb, GFP_ATOMIC);