Previously, IPv4 shared method will automatically enable the IPv4
global forwarding, all the per-interface level IPv4 forwarding settings
may be changed to match the global setting. Also, all the per-inteface
level forwarding settings can not be restored when deactivating the
shared connection. This is problematic as it may disrupt custom
configurations and lead to inconsistent forwarding behavior across
different network interfaces.
To address this, the implementation now ensures that the original
per-interface forwarding settings are preserved. Upon activating a
shared connection, instead of enabling IPv4 global forwarding
automatically, the per-interface forwarding is enabled on all other
connections unless a connection explicitly has the forwarding set to
"no" in its configuration. Upon deactivating all shared connection,
per-interface forwarding settings are restored to sysctl's default
value. Furthermore, deactivating any connection explicitly sets the
forwarding to sysctl's default value ensuring that network forwarding
behavior remains consistent.
2ad5fbf025