[3G] ppp-2.4.5

environment variable:
[ipv6]
LLLOCAL
LLREMOTE

BUNDLE
PEERNAME
ORIG_UID
PPPLOGNAME
PPPD_PID
IPLOCAL
IPREMOTE
DNS1
DNS2
USEPEERDNS
OLDIPLOCAL
OLDIPREMOTE
MACREMOTE
UID
DEVICE
SPEED
IFNAME
LINKNAME
CONNECT_TIME
BYTES_SENT
BYTES_RCVD

ip-pre-up:

* Pppd will now run /etc/ppp/ip-pre-up, if it exists, after creating
  the ppp interface and configuring its IP addresses but before
  bringing it up.  This can be used, for example, for adding firewall
  rules for the interface.