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

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 --- 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