From 3a4e9a165a3942445d60ad1488943f57640d39ce Mon Sep 17 00:00:00 2001
From: Kroese <kroese@users.noreply.github.com>
Date: Thu, 28 Dec 2023 20:05:43 +0100
Subject: [PATCH] feat: Detect default interface (#276)

---
 src/network.sh | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/src/network.sh b/src/network.sh
index 53b6a1c..c8701b2 100644
--- a/src/network.sh
+++ b/src/network.sh
@@ -7,8 +7,8 @@ set -Eeuo pipefail
 : ${CONTROL_PORTS:=''}
 : ${MAC:='82:cf:d0:5e:57:66'}
 
+: ${VM_NET_DEV:=''}
 : ${VM_NET_TAP:='qemu'}
-: ${VM_NET_DEV:='eth0'}
 : ${VM_NET_MAC:="$MAC"}
 : ${VM_NET_HOST:='QEMU'}
 
@@ -211,6 +211,12 @@ fi
 update-alternatives --set iptables /usr/sbin/iptables-legacy > /dev/null
 update-alternatives --set ip6tables /usr/sbin/ip6tables-legacy > /dev/null
 
+if [ -z "$VM_NET_DEV" ]; then
+  # Automaticly detect the default network interface
+  VM_NET_DEV=$(awk '$2 == 00000000 { print $1 }' /proc/net/route)
+  [ -z "$VM_NET_DEV" ] && VM_NET_DEV="eth0"
+fi
+
 if [ ! -d "/sys/class/net/$VM_NET_DEV" ]; then
   error "Network interface $VM_NET_DEV does not exist inside the container!"
   error "$ADD_ERR -e \"VM_NET_DEV=NAME\" to specify another interface name." && exit 27