We've set up to pptp/pppd 2.4.3 to authenticate against a radius
server (vasco vacman).

PPTPCLIENT <--- pptp/ppp ----> PPPD <--- radius ---> VASCO-VACMAN
Radius server

This worked fine until the new version of the radius server, which
strictly checks if the nas-ip-address attribute is valid, and rejects
access if no valid ip adress is specified.

There seems to be a bug in the radius.so plugin because it transmits
the nas-ip-address attribute as one byte, 0x01. It should be 4 bytes,
and the radius server also logs this:

[2008/10/20|09:57:15][05524][INFO ][adt_record] > Audit: {Source
Location:, Request ID:110, Client Location:,
Password Protocol:MS-CHAP2, Action:Process, Input Details:User-
Name:abcdefg, NAS-IP-Address:0x01, MS-CHAP-Challenge:0x....., MS-CHAP2-
Response:0x......, Authenticator:0x....}
[2008/10/20|09:57:15][05524][MINOR][DPPIProtocolHandler::doAuth] >
Invalid NAS IPv4 address

You can also see that the attribute is wrong in the tcpdump:
I already tried with the newest pppd version (newest radius plugin),
but still it sends out 0x01 as nas-ip-address.

Anyone also experienced problems with pppd radius client or knows a
Stijn Gruwier