netdev - [PATCH net-next] gre: change gre_parse_header to return the header length

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Message-Id: <3627136025fbd767d70e2ce563aa5e37373c880a.1462280197.git.jbenc@redhat.com>
Date:	Tue,  3 May 2016 15:00:21 +0200
From:	Jiri Benc <jbenc@...hat.com>
To:	netdev@...r.kernel.org
Cc:	Tom Herbert <tom@...bertland.com>,
	David Miller <davem@...emloft.net>
Subject: [PATCH net-next] gre: change gre_parse_header to return the header length

It's easier for gre_parse_header to return the header length instead of
filing it into a parameter. That way, the callers that don't care about the
header length can just check whether the returned value is lower than zero.

In gre_err, the tunnel header must not be pulled. See commit b7f8fe251e46
("gre: do not pull header in ICMP error processing") for details.

This patch reduces the conflict between the mentioned commit and commit
95f5c64c3c13 ("gre: Move utility functions to common headers").

Signed-off-by: Jiri Benc <jbenc@...hat.com>
---
To resolve the conflict between net and net-next, please apply this patch to
net-next and then pull net into net-next. At the conflicting places, take
the hunks from net-next (including the large code removal at the beginning
of ip_gre.c).

The only exception is a call to gre_build_header/build_header in
gre_fb_xmit; in there, also take the hunk from net-next but change
"htons(ETH_P_TEB)" to "proto".

Alternatively, this patch can be used during merge for the conflict
resolution instead of committing it on its own.
---
 include/net/gre.h    | 2 +-
 net/ipv4/gre_demux.c | 6 +++---
 net/ipv4/ip_gre.c    | 9 +++------
 net/ipv6/ip6_gre.c   | 3 ++-
 4 files changed, 9 insertions(+), 11 deletions(-)

diff --git a/include/net/gre.h b/include/net/gre.h
index 29e37322c06e..a14093c70eab 100644
--- a/include/net/gre.h
+++ b/include/net/gre.h
@@ -26,7 +26,7 @@ int gre_del_protocol(const struct gre_protocol *proto, u8 version);
 struct net_device *gretap_fb_dev_create(struct net *net, const char *name,
 				       u8 name_assign_type);
 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
-		     bool *csum_err, int *hdr_len);
+		     bool *csum_err);
 
 static inline int gre_calc_hlen(__be16 o_flags)
 {
diff --git a/net/ipv4/gre_demux.c b/net/ipv4/gre_demux.c
index 371674801e84..a41e73ab1369 100644
--- a/net/ipv4/gre_demux.c
+++ b/net/ipv4/gre_demux.c
@@ -60,8 +60,9 @@ int gre_del_protocol(const struct gre_protocol *proto, u8 version)
 }
 EXPORT_SYMBOL_GPL(gre_del_protocol);
 
+/* Fills in tpi and returns header length to be pulled. */
 int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
-		     bool *csum_err, int *ret_hdr_len)
+		     bool *csum_err)
 {
 	const struct gre_base_hdr *greh;
 	__be32 *options;
@@ -119,8 +120,7 @@ int gre_parse_header(struct sk_buff *skb, struct tnl_ptk_info *tpi,
 				return -EINVAL;
 		}
 	}
-	*ret_hdr_len = hdr_len;
-	return 0;
+	return hdr_len;
 }
 EXPORT_SYMBOL(gre_parse_header);
 
diff --git a/net/ipv4/ip_gre.c b/net/ipv4/ip_gre.c
index 2480d79b0e37..d4ee229880bf 100644
--- a/net/ipv4/ip_gre.c
+++ b/net/ipv4/ip_gre.c
@@ -221,16 +221,12 @@ static void gre_err(struct sk_buff *skb, u32 info)
 	const int code = icmp_hdr(skb)->code;
 	struct tnl_ptk_info tpi;
 	bool csum_err = false;
-	int hdr_len;
 
-	if (gre_parse_header(skb, &tpi, &csum_err, &hdr_len)) {
+	if (gre_parse_header(skb, &tpi, &csum_err) < 0) {
 		if (!csum_err)		/* ignore csum errors. */
 			return;
 	}
 
-	if (iptunnel_pull_header(skb, hdr_len, tpi.proto, false))
-		return;
-
 	if (type == ICMP_DEST_UNREACH && code == ICMP_FRAG_NEEDED) {
 		ipv4_update_pmtu(skb, dev_net(skb->dev), info,
 				 skb->dev->ifindex, 0, IPPROTO_GRE, 0);
@@ -314,7 +310,8 @@ static int gre_rcv(struct sk_buff *skb)
 	}
 #endif
 
-	if (gre_parse_header(skb, &tpi, &csum_err, &hdr_len) < 0)
+	hdr_len = gre_parse_header(skb, &tpi, &csum_err);
+	if (hdr_len < 0)
 		goto drop;
 
 	if (iptunnel_pull_header(skb, hdr_len, tpi.proto, false))
diff --git a/net/ipv6/ip6_gre.c b/net/ipv6/ip6_gre.c
index 10127741a60d..47b671a46dc4 100644
--- a/net/ipv6/ip6_gre.c
+++ b/net/ipv6/ip6_gre.c
@@ -468,7 +468,8 @@ static int gre_rcv(struct sk_buff *skb)
 	bool csum_err = false;
 	int hdr_len;
 
-	if (gre_parse_header(skb, &tpi, &csum_err, &hdr_len) < 0)
+	hdr_len = gre_parse_header(skb, &tpi, &csum_err);
+	if (hdr_len < 0)
 		goto drop;
 
 	if (iptunnel_pull_header(skb, hdr_len, tpi.proto, false))
-- 
1.8.3.1