2016-03-04 22:47:30

by Bill Sommerfeld

Subject: [PATCH] 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 <[email protected]>
---
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

2016-03-07 19:35:11

by Josh Hunt

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

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 <[email protected]>
> ---
> 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

2016-03-07 20:24:05

by David Miller

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

From: Bill Sommerfeld <[email protected]>
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 <[email protected]>

Applied and queued up for -stable, thanks.