linux-kernel - [PATCH 4.4 040/137] udp6: fix UDP/IPv6 encap resubmit path

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Date:	Mon, 18 Apr 2016 11:28:22 +0900
From:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:	linux-kernel@...r.kernel.org
Cc:	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	stable@...r.kernel.org, Bill Sommerfeld <wsommerfeld@...gle.com>,
	"David S. Miller" <davem@...emloft.net>
Subject: [PATCH 4.4 040/137] udp6: fix UDP/IPv6 encap resubmit path

4.4-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Bill Sommerfeld <wsommerfeld@...gle.com>

[ Upstream commit 59dca1d8a6725a121dae6c452de0b2611d5865dc ]

IPv4 interprets a negative return value from a protocol handler as a
request to redispatch to a new protocol.  In contrast, IPv6 interprets a
negative value as an error, and interprets a positive value as a request
for redispatch.

UDP for IPv6 was unaware of this difference.  Change __udp6_lib_rcv() to
return a positive value for redispatch.  Note that the socket's
encap_rcv hook still needs to return a negative value to request
dispatch, and in the case of IPv6 packets, adjust IP6CB(skb)->nhoff to
identify the byte containing the next protocol.

Signed-off-by: Bill Sommerfeld <wsommerfeld@...gle.com>
Signed-off-by: David S. Miller <davem@...emloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 net/ipv6/udp.c |    6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -916,11 +916,9 @@ int __udp6_lib_rcv(struct sk_buff *skb,
 		ret = udpv6_queue_rcv_skb(sk, skb);
 		sock_put(sk);

-		/* a return value > 0 means to resubmit the input, but
-		 * it wants the return to be -protocol, or 0
-		 */
+		/* a return value > 0 means to resubmit the input */
 		if (ret > 0)
-			return -ret;
+			return ret;

 		return 0;
 	}