There’s a quick way to test the offline behaviour of programs on Linux.
shell unshare -c -n bash Run bash in a new network namespace Then only loopback is available. shell $ ip addr 1: lo: <LOOPBACK> mtu 65536 qdisc noop state DOWN group default qlen 1000 link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00 List network namespaces with lsns.
shell $ lsns -t net NS TYPE NPROCS PID USER NETNSID COMMAND 999 net 2 111 user 3 systemd 888 net 1 222 user unassigned └─bash