router: make announcing DNS info configurable (FS#2020)

Make announcing options Recursive DNS server and DNS search list
configurable via the ra_dns config option.
This allows to disable sending RA based DNS info if such info is
already provided by DHCPv6.

Signed-off-by: Hans Dedecker <dedeckeh@gmail.com>

3 files changed, 31 insertions, 15 deletions

diff --git a/src/config.c b/src/config.c
index 9ffe1ac..29d7181 100644
--- a/src/config.c
+++ b/src/config.c
@@ -58,6 +58,7 @@ enum {
 	IFACE_ATTR_RA_RETRANSTIME,
 	IFACE_ATTR_RA_HOPLIMIT,
 	IFACE_ATTR_RA_MTU,
+	IFACE_ATTR_RA_DNS,
 	IFACE_ATTR_PD_MANAGER,
 	IFACE_ATTR_PD_CER,
 	IFACE_ATTR_NDPROXY_ROUTING,
@@ -103,6 +104,7 @@ static const struct blobmsg_policy iface_attrs[IFACE_ATTR_MAX] = {
 	[IFACE_ATTR_RA_RETRANSTIME] = { .name = "ra_retranstime", .type = BLOBMSG_TYPE_INT32 },
 	[IFACE_ATTR_RA_HOPLIMIT] = { .name = "ra_hoplimit", .type = BLOBMSG_TYPE_INT32 },
 	[IFACE_ATTR_RA_MTU] = { .name = "ra_mtu", .type = BLOBMSG_TYPE_INT32 },
+	[IFACE_ATTR_RA_DNS] = { .name = "ra_dns", .type = BLOBMSG_TYPE_BOOL },
 	[IFACE_ATTR_NDPROXY_ROUTING] = { .name = "ndproxy_routing", .type = BLOBMSG_TYPE_BOOL },
 	[IFACE_ATTR_NDPROXY_SLAVE] = { .name = "ndproxy_slave", .type = BLOBMSG_TYPE_BOOL },
 	[IFACE_ATTR_PREFIX_FILTER] = { .name = "prefix_filter", .type = BLOBMSG_TYPE_STRING },
@@ -218,6 +220,7 @@ static void set_interface_defaults(struct interface *iface)
 	iface->ra_maxinterval = 600;
 	iface->ra_mininterval = iface->ra_maxinterval/3;
 	iface->ra_lifetime = -1;
+	iface->ra_dns = true;
 }
 
 static void clean_interface(struct interface *iface)
@@ -704,6 +707,9 @@ int config_parse_interface(void *data, size_t len, const char *name, bool overwr
 	if ((c = tb[IFACE_ATTR_RA_USELEASETIME]))
 		iface->ra_useleasetime = blobmsg_get_bool(c);
 
+	if ((c = tb[IFACE_ATTR_RA_DNS]))
+		iface->ra_dns = blobmsg_get_bool(c);
+
 	if ((c = tb[IFACE_ATTR_RA_PREFERENCE])) {
 		const char *prio = blobmsg_get_string(c);
 
diff --git a/src/odhcpd.h b/src/odhcpd.h
index 80dbb40..10f26b1 100644
--- a/src/odhcpd.h
+++ b/src/odhcpd.h
@@ -193,6 +193,7 @@ struct interface {
 	bool ra_not_onlink;
 	bool ra_advrouter;
 	bool ra_useleasetime;
+	bool ra_dns;
 	bool no_dynamic_dhcp;
 	uint8_t pio_filter_length;
 	struct in6_addr pio_filter_addr;
diff --git a/src/router.c b/src/router.c
index f45ecab..f8a83a6 100644
--- a/src/router.c
+++ b/src/router.c
@@ -428,12 +428,14 @@ static uint64_t send_router_advert(struct interface *iface, const struct in6_add
 	struct in6_addr dns_pref, *dns_addr = NULL;
 	size_t dns_cnt = 0;
 
-	if (iface->dns_cnt > 0) {
-		dns_addr = iface->dns;
-		dns_cnt = iface->dns_cnt;
-	} else if (!odhcpd_get_interface_dns_addr(iface, &dns_pref)) {
-		dns_addr = &dns_pref;
-		dns_cnt = 1;
+	if (iface->ra_dns) {
+		if (iface->dns_cnt > 0) {
+			dns_addr = iface->dns;
+			dns_cnt = iface->dns_cnt;
+		} else if (!odhcpd_get_interface_dns_addr(iface, &dns_pref)) {
+			dns_addr = &dns_pref;
+			dns_cnt = 1;
+		}
 	}
 
 	/* Construct Prefix Information options */
@@ -541,15 +543,22 @@ static uint64_t send_router_advert(struct interface *iface, const struct in6_add
 	} dns = {ND_OPT_RECURSIVE_DNS, (1 + (2 * dns_cnt)), 0, 0, 0};
 
 	/* DNS Search options */
-	uint8_t search_buf[256], *search_domain = iface->search;
-	size_t search_len = iface->search_len, search_padded = 0;
-
-	if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
-		int len = dn_comp(_res.dnsrch[0], search_buf,
-				sizeof(search_buf), NULL, NULL);
-		if (len > 0) {
-			search_domain = search_buf;
-			search_len = len;
+	uint8_t *search_domain = NULL;
+	size_t search_len = 0, search_padded = 0;
+
+	if (iface->ra_dns) {
+		search_len = iface->search_len;
+		search_domain = iface->search;
+
+		if (!search_domain && !res_init() && _res.dnsrch[0] && _res.dnsrch[0][0]) {
+			uint8_t search_buf[256];
+
+			int len = dn_comp(_res.dnsrch[0], search_buf,
+					sizeof(search_buf), NULL, NULL);
+			if (len > 0) {
+				search_domain = search_buf;
+				search_len = len;
+			}
 		}
 	}