[nrf fromtree] net: ppp: Bind DNS to device ppp network interface

Make sure received DNS server information is bound to the
ppp network interface.

Signed-off-by: Jukka Rissanen <[email protected]>
(cherry picked from commit 8704b3a)
Signed-off-by: Robert Lubos <[email protected]>

Author: jukkar

subsys/net/l2/ppp/ipcp.c

@@ -362,6 +362,8 @@ static void ipcp_set_dns_servers(struct ppp_fsm *fsm)
 		(struct sockaddr *) &dns2,
 		NULL
 	};
+	int ifindex = net_if_get_by_iface(ctx->iface);
+	int interfaces[2] = { ifindex, ifindex };
 	int ret;
 
 	if (!dns1.sin_addr.s_addr) {
@@ -373,7 +375,8 @@ static void ipcp_set_dns_servers(struct ppp_fsm *fsm)
 	}
 
 	dnsctx = dns_resolve_get_default();
-	ret = dns_resolve_reconfigure(dnsctx, NULL, dns_servers);
+	ret = dns_resolve_reconfigure_with_interfaces(dnsctx, NULL, dns_servers,
+						      interfaces);
 	if (ret < 0) {
 		NET_ERR("Could not set DNS servers");
 		return;