udp6: fix UDP/IPv6 encap resubmit path

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@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 4 deletions

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 22e28a44e3c8..422dd014aa2c 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -962,11 +962,9 @@ int __udp6_lib_rcv(struct sk_buff *skb, struct udp_table *udptable,
                 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;
         }