net: shell: dns: Print DNS server with network interface

If network interface is specified in the DNS server, then send
the queries to the server via the network interface. Print this
information in the server list.

Signed-off-by: Jukka Rissanen <[email protected]>

Author: jukkar

subsys/net/lib/shell/dns.c

@@ -8,6 +8,7 @@
 #include <zephyr/logging/log.h>
 LOG_MODULE_DECLARE(net_shell);
 
+#include <zephyr/net/socket.h>
 #include <zephyr/net/dns_resolve.h>
 
 #include "net_shell_private.h"
@@ -59,29 +60,55 @@ static void dns_result_cb(enum dns_resolve_status status,
 	PR_WARNING("dns: Unhandled status %d received\n", status);
 }
 
+static const char *printable_iface(const char *iface_name,
+				   const char *found,
+				   const char *not_found)
+{
+	if (iface_name[0] != '\0') {
+		return found;
+	}
+
+	return not_found;
+}
+
 static void print_dns_info(const struct shell *sh,
 			   struct dns_resolve_context *ctx)
 {
-	int i;
+	int i, ret;
 
 	PR("DNS servers:\n");
 
 	for (i = 0; i < CONFIG_DNS_RESOLVER_MAX_SERVERS +
 		     DNS_MAX_MCAST_SERVERS; i++) {
+		char iface_name[IFNAMSIZ] = { 0 };
+
+		if (ctx->servers[i].if_index > 0) {
+			ret = net_if_get_name(
+				net_if_get_by_index(ctx->servers[i].if_index),
+				iface_name, sizeof(iface_name));
+			if (ret < 0) {
+				snprintk(iface_name, sizeof(iface_name), "%d",
+					 ctx->servers[i].if_index);
+			}
+		}
+
 		if (ctx->servers[i].dns_server.sa_family == AF_INET) {
-			PR("\t%s:%u\n",
+			PR("\t%s:%u%s%s\n",
 			   net_sprint_ipv4_addr(
 				   &net_sin(&ctx->servers[i].dns_server)->
 				   sin_addr),
-			   ntohs(net_sin(
-				 &ctx->servers[i].dns_server)->sin_port));
+			   ntohs(net_sin(&ctx->servers[i].dns_server)->sin_port),
+			   printable_iface(iface_name, " via ", ""),
+			   printable_iface(iface_name, iface_name, ""));
+
 		} else if (ctx->servers[i].dns_server.sa_family == AF_INET6) {
-			PR("\t[%s]:%u\n",
+			PR("\t[%s]:%u%s%s\n",
 			   net_sprint_ipv6_addr(
 				   &net_sin6(&ctx->servers[i].dns_server)->
 				   sin6_addr),
-			   ntohs(net_sin6(
-				 &ctx->servers[i].dns_server)->sin6_port));
+			   ntohs(net_sin6(&ctx->servers[i].dns_server)->sin6_port),
+			   printable_iface(iface_name, " via ", ""),
+			   printable_iface(iface_name, iface_name, ""));
 		}
 	}