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

[Jon Maloy <jmaloy@redhat.com>]

On 2025-12-15 04:54, David Gibson wrote:
> 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.

Excellent idea. I really wasn't happy this semantics, either.
I'll send a separate patch.
/j
> 
>>
>> 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
>>
>