conf, udp: Drop mostly duplicated dns_send arrays, rename related fields

Given that we use just the first valid DNS resolver address
configured, or read from resolv.conf(5) on the host, to forward DNS
queries to, in case --dns-forward is used, we don't need to duplicate
dns[] to dns_send[]:

- rename dns_send[] back to dns[]: those are the resolvers we
  advertise to the guest/container

- for forwarding purposes, instead of dns[], use a single field (for
  each protocol version): dns_host

- and rename dns_fwd to dns_match, so that it's clear this is the
  address we are matching DNS queries against, to decide if they need
  to be forwarded

Suggested-by: David Gibson <david@gibson.dropbear.id.au>
Signed-off-by: Stefano Brivio <sbrivio@redhat.com>
Reviewed-by: David Gibson <david@gibson.dropbear.id.au>

1 files changed, 33 insertions, 43 deletions

diff --git a/conf.c b/conf.c
index 1adcf83..a995eb7 100644
--- a/conf.c
+++ b/conf.c
@@ -355,11 +355,9 @@ overlap:
  */
 static void get_dns(struct ctx *c)
 {
-	struct in6_addr *dns6_send = &c->ip6.dns_send[0];
-	struct in_addr *dns4_send = &c->ip4.dns_send[0];
+	struct in6_addr *dns6 = &c->ip6.dns[0], dns6_tmp;
+	struct in_addr *dns4 = &c->ip4.dns[0], dns4_tmp;
 	int dns4_set, dns6_set, dnss_set, dns_set, fd;
-	struct in6_addr *dns6 = &c->ip6.dns[0];
-	struct in_addr *dns4 = &c->ip4.dns[0];
 	struct fqdn *s = c->dns_search;
 	struct lineread resolvconf;
 	int line_len;
@@ -388,49 +386,44 @@ static void get_dns(struct ctx *c)
 				*end = 0;
 
 			if (!dns4_set &&
-			    dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) - 1 &&
-			    inet_pton(AF_INET, p + 1, dns4)) {
+			    dns4 - &c->ip4.dns[0] < ARRAY_SIZE(c->ip4.dns) - 1
+			    && inet_pton(AF_INET, p + 1, &dns4_tmp)) {
 				/* Guest or container can only access local
 				 * addresses via local redirect
 				 */
-				if (IN4_IS_ADDR_LOOPBACK(dns4)) {
+				if (IN4_IS_ADDR_LOOPBACK(&dns4_tmp)) {
 					if (!c->no_map_gw) {
-						*dns4_send = c->ip4.gw;
-						dns4_send++;
+						*dns4 = c->ip4.gw;
+						dns4++;
 					}
 				} else {
-					*dns4_send = *dns4;
-					dns4_send++;
+					*dns4 = dns4_tmp;
+					dns4++;
 				}
 
-				dns4++;
-
-				dns4->s_addr = htonl(INADDR_ANY);
-				dns4_send->s_addr = htonl(INADDR_ANY);
+				if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_host))
+					c->ip4.dns_host = dns4_tmp;
 			}
 
 			if (!dns6_set &&
-			    dns6 - &c->ip6.dns[0] < ARRAY_SIZE(c->ip6.dns) - 1 &&
-			    inet_pton(AF_INET6, p + 1, dns6)) {
+			    dns6 - &c->ip6.dns[0] < ARRAY_SIZE(c->ip6.dns) - 1
+			    && inet_pton(AF_INET6, p + 1, &dns6_tmp)) {
 				/* Guest or container can only access local
 				 * addresses via local redirect
 				 */
-				if (IN6_IS_ADDR_LOOPBACK(dns6)) {
+				if (IN6_IS_ADDR_LOOPBACK(&dns6_tmp)) {
 					if (!c->no_map_gw) {
-						memcpy(dns6_send, &c->ip6.gw,
-						       sizeof(*dns6_send));
-						dns6_send++;
+						memcpy(dns6, &c->ip6.gw,
+						       sizeof(*dns6));
+						dns6++;
 					}
 				} else {
-					memcpy(dns6_send, dns6,
-					       sizeof(*dns6_send));
-					dns6_send++;
+					memcpy(dns6, &dns6_tmp, sizeof(*dns6));
+					dns6++;
 				}
 
-				dns6++;
-
-				memset(dns6, 0, sizeof(*dns6));
-				memset(dns6_send, 0, sizeof(*dns6_send));
+				if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_host))
+					c->ip6.dns_host = dns6_tmp;
 			}
 		} else if (!dnss_set && strstr(line, "search ") == line &&
 			   s == c->dns_search) {
@@ -897,12 +890,10 @@ static void conf_print(const struct ctx *c)
 			     inet_ntop(AF_INET, &c->ip4.gw,   buf4, sizeof(buf4)));
 		}
 
-		for (i = 0; !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_send[i]);
-		     i++) {
+		for (i = 0; !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns[i]); i++) {
 			if (!i)
 				info("DNS:");
-			inet_ntop(AF_INET, &c->ip4.dns_send[i], buf4,
-				  sizeof(buf4));
+			inet_ntop(AF_INET, &c->ip4.dns[i], buf4, sizeof(buf4));
 			info("    %s", buf4);
 		}
 
@@ -933,8 +924,7 @@ static void conf_print(const struct ctx *c)
 		     inet_ntop(AF_INET6, &c->ip6.addr_ll, buf6, sizeof(buf6)));
 
 dns6:
-		for (i = 0; !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_send[i]);
-		     i++) {
+		for (i = 0; !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns[i]); i++) {
 			if (!i)
 				info("DNS:");
 			inet_ntop(AF_INET6, &c->ip6.dns[i], buf6, sizeof(buf6));
@@ -1230,17 +1220,17 @@ void conf(struct ctx *c, int argc, char **argv)
 			c->no_dhcp_dns_search = 1;
 			break;
 		case 9:
-			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_fwd)	&&
-			    inet_pton(AF_INET6, optarg, &c->ip6.dns_fwd) &&
-			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_fwd)	&&
-			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.dns_fwd))
+			if (IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_match)     &&
+			    inet_pton(AF_INET6, optarg, &c->ip6.dns_match) &&
+			    !IN6_IS_ADDR_UNSPECIFIED(&c->ip6.dns_match)    &&
+			    !IN6_IS_ADDR_LOOPBACK(&c->ip6.dns_match))
 				break;
 
-			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_fwd)	&&
-			    inet_pton(AF_INET, optarg, &c->ip4.dns_fwd)	&&
-			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_fwd)	&&
-			    !IN4_IS_ADDR_BROADCAST(&c->ip4.dns_fwd)	&&
-			    !IN4_IS_ADDR_LOOPBACK(&c->ip4.dns_fwd))
+			if (IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_match)    &&
+			    inet_pton(AF_INET, optarg, &c->ip4.dns_match) &&
+			    !IN4_IS_ADDR_UNSPECIFIED(&c->ip4.dns_match)   &&
+			    !IN4_IS_ADDR_BROADCAST(&c->ip4.dns_match)     &&
+			    !IN4_IS_ADDR_LOOPBACK(&c->ip4.dns_match))
 				break;
 
 			err("Invalid DNS forwarding address: %s", optarg);