interface-ip: DNS name server sorting support in resolv.conf.auto

Interface name servers when being written to resolv.conf.auto are sorted
based on the following parameters:
-Primary sorting key is interface dns_metric; name servers having lowest
interface dns_metric are listed first
-Secondary sorting key is interface metric; in case of equal interface
dns_metric name servers having lowest interface metric are listed first
-Finally alphabetical order of the interface names in case of equal
interface dns_metric and metric

In case the resolver queries the multiple servers in the order
listed; sorting is usefull in the following scenarios :
-Name resolving over a main and backup interface
-Assign priority to IPv6 name servers over IPv4 or vice versa

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

1 files changed, 1 insertions, 0 deletions

diff --git a/ubus.c b/ubus.c
index 2b8bb90..4d43b57 100644
--- a/ubus.c
+++ b/ubus.c
@@ -687,6 +687,7 @@ netifd_dump_status(struct interface *iface)
 		if (iface->ip6table)
 			blobmsg_add_u32(&b, "ip6table", iface->ip6table);
 		blobmsg_add_u32(&b, "metric", iface->metric);
+		blobmsg_add_u32(&b, "dns_metric", iface->dns_metric);
 		blobmsg_add_u8(&b, "delegation", !iface->proto_ip.no_delegation);
 		a = blobmsg_open_array(&b, "ipv4-address");
 		interface_ip_dump_address_list(&iface->config_ip, false, true);