[PATCH] udp6: fix UDP/IPv6 encap resubmit path

[PATCH] udp6: fix UDP/IPv6 encap resubmit path

[Bill Sommerfeld]

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>
---
 net/ipv6/udp.c | 6 ++----
 1 file changed, 2 insertions(+), 4 deletions(-)

diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
index 0711f8f..fd25e44 100644
--- a/net/ipv6/udp.c
+++ b/net/ipv6/udp.c
@@ -922,11 +922,9 @@ 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;
 	}
-- 
2.7.0.rc3.207.g0ac5344

Re: [PATCH] udp6: fix UDP/IPv6 encap resubmit path

[Josh Hunt]

On 03/04/2016 04:47 PM, Bill Sommerfeld wrote:
> 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>
> ---
>   net/ipv6/udp.c | 6 ++----
>   1 file changed, 2 insertions(+), 4 deletions(-)
>
> diff --git a/net/ipv6/udp.c b/net/ipv6/udp.c
> index 0711f8f..fd25e44 100644
> --- a/net/ipv6/udp.c
> +++ b/net/ipv6/udp.c
> @@ -922,11 +922,9 @@ 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;
>   	}
>

This looks good to me. Thanks Bill!

Josh

Re: [PATCH] udp6: fix UDP/IPv6 encap resubmit path

[David Miller]

From: Bill Sommerfeld <wsommerfeld@google.com>
Date: Fri,  4 Mar 2016 14:47:21 -0800

> 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>

Applied and queued up for -stable, thanks.