conf: Use "-D none" and "-S none" instead of missing empty option arguments

Both the -D (--dns) and -S (--search) options take an optional argument.
If the argument is omitted the option is disabled entirely.  However,
handling the optional argument requires some ugly special case handling if
it's the last option on the command line, and has potential ambiguity with
non-option arguments used with pasta.  It can also make it more confusing
to read command lines.

Simplify the logic here by replacing the non-argument versions with an
explicit "-D none" or "-S none".

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>
[sbrivio: Reworked logic to exclude redundant/conflicting options]
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>

1 files changed, 32 insertions, 24 deletions

diff --git a/conf.c b/conf.c
index 4eb9e3d..7c4930a 100644
--- a/conf.c
+++ b/conf.c
@@ -1022,8 +1022,8 @@ void conf(struct ctx *c, int argc, char **argv)
 		{"mac-addr",	required_argument,	NULL,		'M' },
 		{"gateway",	required_argument,	NULL,		'g' },
 		{"interface",	required_argument,	NULL,		'i' },
-		{"dns",		optional_argument,	NULL,		'D' },
-		{"search",	optional_argument,	NULL,		'S' },
+		{"dns",		required_argument,	NULL,		'D' },
+		{"search",	required_argument,	NULL,		'S' },
 		{"no-tcp",	no_argument,		&c->no_tcp,	1 },
 		{"no-udp",	no_argument,		&c->no_udp,	1 },
 		{"no-icmp",	no_argument,		&c->no_icmp,	1 },
@@ -1077,16 +1077,6 @@ void conf(struct ctx *c, int argc, char **argv)
 
 		name = getopt_long(argc, argv, optstring, options, NULL);
 
-		if ((name == 'D' || name == 'S') && !optarg &&
-		    optind < argc && *argv[optind] && *argv[optind] != '-') {
-			if (c->mode == MODE_PASTA) {
-				if (conf_ns_opt(c, nsdir, userns, argv[optind]))
-					optarg = argv[optind++];
-			} else {
-				optarg = argv[optind++];
-			}
-		}
-
 		switch (name) {
 		case -1:
 		case 0:
@@ -1397,17 +1387,26 @@ void conf(struct ctx *c, int argc, char **argv)
 			}
 			break;
 		case 'D':
-			if (c->no_dns ||
-			    (!optarg && (dns4 - c->ip4.dns || dns6 - c->ip6.dns))) {
-				err("Empty and non-empty DNS options given");
-				usage(argv[0]);
-			}
+			if (!strcmp(optarg, "none")) {
+				if (c->no_dns) {
+					err("Redundant DNS options");
+					usage(argv[0]);
+				}
+
+				if (dns4 - c->ip4.dns || dns6 - c->ip6.dns) {
+					err("Conflicting DNS options");
+					usage(argv[0]);
+				}
 
-			if (!optarg) {
 				c->no_dns = 1;
 				break;
 			}
 
+			if (c->no_dns) {
+				err("Conflicting DNS options");
+				usage(argv[0]);
+			}
+
 			if (dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) &&
 			    inet_pton(AF_INET, optarg, dns4)) {
 				dns4++;
@@ -1424,17 +1423,26 @@ void conf(struct ctx *c, int argc, char **argv)
 			usage(argv[0]);
 			break;
 		case 'S':
-			if (c->no_dns_search ||
-			    (!optarg && dnss != c->dns_search)) {
-				err("Empty and non-empty DNS search given");
-				usage(argv[0]);
-			}
+			if (!strcmp(optarg, "none")) {
+				if (c->no_dns_search) {
+					err("Redundant DNS search options");
+					usage(argv[0]);
+				}
+
+				if (dnss != c->dns_search) {
+					err("Conflicting DNS search options");
+					usage(argv[0]);
+				}
 
-			if (!optarg) {
 				c->no_dns_search = 1;
 				break;
 			}
 
+			if (c->no_dns_search) {
+				err("Conflicting DNS search options");
+				usage(argv[0]);
+			}
+
 			if (dnss - c->dns_search < ARRAY_SIZE(c->dns_search)) {
 				ret = snprintf(dnss->n, sizeof(*c->dns_search),
 					       "%s", optarg);