mwan3: prefer default route source address

Prefer the source address from the interface default route before falling
back to the interface address from netifd.

This fixes diagnostics and tracking in setups where the route-selected
source address differs from the interface address.

Fixes: #29055
Signed-off-by: Dharmik Parmar <dharmikparmar2004@yahoo.com>

Author: dhrm1k

net/mwan3/Makefile

@@ -9,7 +9,7 @@ include $(TOPDIR)/rules.mk
 
 PKG_NAME:=mwan3
 PKG_VERSION:=2.12.1
-PKG_RELEASE:=1
+PKG_RELEASE:=2
 
 PKG_MAINTAINER:=Florian Eckert <fe@dev.tdt.de>
 PKG_LICENSE:=GPL-2.0

net/mwan3/files/lib/mwan3/common.sh

@@ -72,7 +72,12 @@ mwan3_get_src_ip()
 		IP="$IP6"
 	fi
 
-	$addr_cmd _src_ip "$true_iface"
+	network_get_device device $true_iface
+	if [ -n "$device" ]; then
+		_src_ip=$($IP route show default dev "$device" 2>/dev/null |
+			sed -ne 's/.* src \([^ ]*\).*/\1/;T;p;q')
+	fi
+	[ -z "$_src_ip" ] && $addr_cmd _src_ip "$true_iface"
 	if [ -z "$_src_ip" ]; then
 		if [ "$family" = "ipv6" ]; then
 			# on IPv6-PD interfaces (like PPPoE interfaces) we don't
@@ -98,7 +103,6 @@ mwan3_get_src_ip()
 			fi
 		fi
 		if [ -z "$_src_ip" ]; then
-			network_get_device device $true_iface
 			_src_ip=$($IP address ls dev $device 2>/dev/null | sed -ne "$sed_str")
 		fi
 		if [ -n "$_src_ip" ]; then