Re: [RFC 04/12] conf: Apply -n/--netmask to most recently added address

[David Gibson <david@gibson.dropbear.id.au>]

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On Sun, Dec 14, 2025 at 08:54:33PM -0500, Jon Maloy wrote:
> We allow for multiple -n/--netmask options, and update the handling so
> that each given prefix length is applied to the most recently added
> address instead of always to addrs[0].
> 
> This allows per-address prefix configuration, such as:
> 
>     -a 10.0.0.1 -n 24 -a 10.0.0.2 -n 16
> 
> If no address has been added yet, -n still applies to addrs[0] for
> backwards compatibility.

Huh.  I'd forgotten until looking at this series that we had the -n
option.  We probably do need this change, but in general I think we'd
be better off deprecating -n, in favour of allowing a prefix len as
part of the -a option, e.g.

	-a 10.0.0.1/24 -a 10.0.0.2/16

That could be a smaller change preliminary to this series.

> 
> Signed-off-by: Jon Maloy <jmaloy@redhat.com>
> ---
>  conf.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/conf.c b/conf.c
> index e9f217b..0a4a28a 100644
> --- a/conf.c
> +++ b/conf.c
> @@ -1528,6 +1528,7 @@ void conf(struct ctx *c, int argc, char **argv)
>  	size_t logsize = 0;
>  	char *runas = NULL;
>  	long fd_tap_opt;
> +	int prefix, idx;
>  	int name, ret;
>  	uid_t uid;
>  	gid_t gid;
> @@ -1872,10 +1873,14 @@ void conf(struct ctx *c, int argc, char **argv)
>  			die("Invalid address: %s", optarg);
>  			break;
>  		case 'n':
> -			c->ip4.addrs[0].prefix_len = conf_ip4_prefix(optarg);
> -			if (c->ip4.addrs[0].prefix_len < 0)
> +			prefix = conf_ip4_prefix(optarg);
> +
> +			if (prefix < 0)
>  				die("Invalid netmask: %s", optarg);
>  
> +			/* Apply to most recent address, or addrs[0] if none yet */
> +			idx = c->ip4.addr_count ? c->ip4.addr_count - 1 : 0;
> +			c->ip4.addrs[idx].prefix_len = prefix;
>  			break;
>  		case 'M':
>  			parse_mac(c->our_tap_mac, optarg);
> -- 
> 2.51.1
> 

-- 
David Gibson (he or they)	| I'll have my music baroque, and my code
david AT gibson.dropbear.id.au	| minimalist, thank you, not the other way
				| around.
http://www.ozlabs.org/~dgibson

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