Re: git: fb8ef16bab0d - main - IPv4: correct limit on loopback_prefix

> The branch main has been updated by karels:
> 
> URL: https://cgit.FreeBSD.org/src/commit/?id=fb8ef16bab0d23e185deed5a6b2e44e72ad53d43
> 
> commit fb8ef16bab0d23e185deed5a6b2e44e72ad53d43
> Author:     Mike Karels <karels@FreeBSD.org>
> AuthorDate: 2022-07-21 13:10:15 +0000
> Commit:     Mike Karels <karels@FreeBSD.org>
> CommitDate: 2022-07-21 14:38:17 +0000
> 
>     IPv4: correct limit on loopback_prefix
>     
>     Commit efe58855f3ea allowed the net.inet.ip.loopback_prefix value
>     to be 32.  However, with a 32-bit mask, 127.0.0.1 is not included
>     in the reserved loopback range, which should not be allowed.
>     Change the max prefix length to 31.

Hummm... 127.0.0.1/32 specifices exactly and ONLY 127.0.0.1, and
this should be fine.  Looking at the mask calculated below with
loopback_prefix=32 this should yeild a mask of 0xffffffff, which
appears to be exactly what is correct.  What DOES become an issue
when /32 is used is that the loopback ROUTE 127.0.0.0/32 is wrong
now, but then with a /32 you dont need a network route, as you
should have a host route to exactly 127.0.0.1.

Can you be more descriptive on what problem arrose with /32?

> ---
>  sys/netinet/in.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/sys/netinet/in.c b/sys/netinet/in.c
> index c3880c4ba983..1c44623bdec1 100644
> --- a/sys/netinet/in.c
> +++ b/sys/netinet/in.c
> @@ -297,7 +297,7 @@ sysctl_loopback_prefixlen(SYSCTL_HANDLER_ARGS)
>  	error = sysctl_handle_int(oidp, &preflen, 0, req);
>  	if (error || !req->newptr)
>  		return (error);
> -	if (preflen < 8 || preflen > 32)
> +	if (preflen < 8 || preflen > 31)
>  		return (EINVAL);
>  	V_in_loopback_mask = 0xffffffff << (32 - preflen);
>  	return (0);
> 

-- 
Rod Grimes                                                 rgrimes@freebsd.org