Fix issue of gateway interface detection in the case of VPN usage

[Lab-8916100448256]

Problem

The gateway interface is detected with the following code :
new_gateway_interface=$(ip route get 1.2.3.4 | awk '{ print $5; }')
This code works as expected in some cases because ip route get 1.2.3.4 returns a line where the interface name is in the 5th field, like in this first example :

root@clic:~
# -> ip route get 1.2.3.4 
1.2.3.4 via 192.168.1.254 dev end0 src 192.168.1.35 uid 0 

But in some other cases, for example when a wireguard VPN is used to make the server reachable from the internet, the network interface name is in the 3rd field, like in this second example :

root@lab12:~# ip route get 1.2.3.4
1.2.3.4 dev vpn_iloth table 51820 src 5.6.7.8 uid 0 

(note that in the above example the actual public IP address of the VPN was replaced by 5.6.7.8 to anonymize it)

Solution

replace the gateway interface detection code with the following :
new_gateway_interface=$(ip route get 1.2.3.4 | awk '$2 ~ /^dev$/ { print $3; } $4 ~ /^dev$/ { print $5; }')
I have tested that this is working in both cases described above. But I'm no awk expert. There might be a better way to do this that would find the interface name in any other position in the result of ip route get 1.2.3.4

PR Status

• Code finished and ready to be reviewed/tested
• The fix/enhancement were manually tested (if applicable)

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