Subject: Re: [RESEND PATCH net-next-2.6 3/3] ipv6 sit: Set relay to 0.0.0.0 directly if relay_prefixlen == 0.

From: Eric Dumazet <[email-masked]>
Date: Mon, 12 Oct 2009 09:32:41 +0200

YOSHIFUJI Hideaki a écrit :
> ipv6 sit: Set relay to 0.0.0.0 directly if relay_prefixlen == 0.
> 
> Do not use bit-shift if relay_prefixlen == 0;
> relay_prefix << 32 does not result in 0.
> 
> Signed-off-by: YOSHIFUJI Hideaki <[email-masked]>
> ---
>  net/ipv6/sit.c |    9 ++++++---
>  1 files changed, 6 insertions(+), 3 deletions(-)
> 
> diff --git a/net/ipv6/sit.c b/net/ipv6/sit.c
> index 193d0c6..510d31f 100644
> --- a/net/ipv6/sit.c
> +++ b/net/ipv6/sit.c
> @@ -1014,9 +1014,12 @@ ipip6_tunnel_ioctl (struct net_device *dev, struct ifreq *ifr, int cmd)
>  					 ip6rd.prefixlen);
>  			if (!ipv6_addr_equal(&prefix, &ip6rd.prefix))
>  				goto done;
> -			relay_prefix = ip6rd.relay_prefix &
> -				       htonl(0xffffffffUL <<
> -					     (32 - ip6rd.relay_prefixlen));
> +			if (ip6rd.relay_prefixlen)
> +				relay_prefix = ip6rd.relay_prefix &
> +					       htonl(0xffffffffUL <<
> +						     (32 - ip6rd.relay_prefixlen));
> +			else
> +				relay_prefix = 0;
>  			if (relay_prefix != ip6rd.relay_prefix)
>  				goto done;
>  

Sorry I dont get it

u32 val = any_value ;
u32 relay_prefix = val & htonl(0xffffffffUL << 32) should give 0

If not, something is broken and should be fixed.