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

[Jon Maloy <jmaloy@redhat.com>]

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.

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