From 0341d6bf0c20a8f0dc592dfefa4d78d372a66ffa Mon Sep 17 00:00:00 2001
From: Jukka Rissanen <jukka.rissanen@nordicsemi.no>
Date: Thu, 27 Feb 2025 18:01:33 +0200
Subject: [PATCH] net: shell: iface: Allow user to set the default interface

It is useful in testing to allow user to change the default
network interface by "net iface default <index>".
Also print out the default interface for "net iface" and
"net iface default" commands.

Signed-off-by: Jukka Rissanen <jukka.rissanen@nordicsemi.no>
---
 subsys/net/lib/shell/iface.c | 43 +++++++++++++++++++++++++++++++++++-
 1 file changed, 42 insertions(+), 1 deletion(-)

diff --git a/subsys/net/lib/shell/iface.c b/subsys/net/lib/shell/iface.c
index 6f19a743689..c3efdebe3a9 100644
--- a/subsys/net/lib/shell/iface.c
+++ b/subsys/net/lib/shell/iface.c
@@ -724,8 +724,10 @@ static int cmd_net_iface(const struct shell *sh, size_t argc, char *argv[])
 	}
 
 #if defined(CONFIG_NET_HOSTNAME_ENABLE)
-	PR("Hostname: %s\n\n", net_hostname_get());
+	PR("Hostname: %s\n", net_hostname_get());
 #endif
+	PR("Default interface: %d\n\n",
+	   net_if_get_by_iface(net_if_get_default()));
 
 	user_data.sh = sh;
 	user_data.user_data = iface;
@@ -735,6 +737,42 @@ static int cmd_net_iface(const struct shell *sh, size_t argc, char *argv[])
 	return 0;
 }
 
+static int cmd_net_default_iface(const struct shell *sh, size_t argc, char *argv[])
+{
+	struct net_if *iface = NULL;
+	int idx;
+
+	if (argc < 2) {
+		iface = net_if_get_default();
+		if (!iface) {
+			PR_WARNING("No default interface\n");
+			return -ENOEXEC;
+		}
+
+		idx = net_if_get_by_iface(iface);
+		PR("Default interface: %d\n", idx);
+	} else {
+		int new_idx;
+
+		idx = get_iface_idx(sh, argv[1]);
+		if (idx < 0) {
+			return -ENOEXEC;
+		}
+
+		net_if_set_default(net_if_get_by_index(idx));
+
+		new_idx = net_if_get_by_iface(net_if_get_default());
+		if (new_idx != idx) {
+			PR_WARNING("Failed to set default interface to %d\n", idx);
+			return -ENOEXEC;
+		}
+
+		PR("Default interface: %d\n", new_idx);
+	}
+
+	return 0;
+}
+
 #if defined(CONFIG_NET_SHELL_DYN_CMD_COMPLETION)
 
 #include "iface_dynamic.h"
@@ -756,6 +794,9 @@ SHELL_STATIC_SUBCMD_SET_CREATE(net_cmd_iface,
 	SHELL_CMD(set_mac, IFACE_DYN_CMD,
 		  "'net iface set_mac <index> <MAC>' sets MAC address for the network interface.",
 		  cmd_net_set_mac),
+	SHELL_CMD(default, IFACE_DYN_CMD,
+		  "'net iface default [<index>]' displays or sets the default network interface.",
+		  cmd_net_default_iface),
 	SHELL_SUBCMD_SET_END
 );