Add an option to pass the pppd linkname

[randomstuff]

This is a convenient way to apply connection-specific hooks in /etc/pppd/*.d:

#!/bin/sh
[ "$LINKNAME" = myvpn ] || exit 0
...

According to the documentation:

For the ip-down and auth-down scripts, pppd also sets the following variables giving statistics for the connection:

[...]

LINKNAME : The logical name of the link, set with the linkname option

Currently, an alternative solution is to use the -pppd-ipparam= flag.