Jakub Adam authored Jun 29, 2016 and Olivier Crête committed Oct 26, 2016

In order to preserve compatibility with clients which use custom CRC
lookup table from [MS-ICE2], whenever a connectivity check request or
reply is sent, an additional message is sent along. These two messages
differ only in FINGERPRINT attribute - one uses regular CRC lookup table
for calculation, the other uses the modified table.

When a message is received and FINGERPRINT doesn't pass validation using
regular CRC table, the receiver also tries to verify using the modified
table.

[MS-ICE2] 3.1.4.8.2 describes this procedure.

The commit fixes compatibility with older MSOC and Lync clients.

Differential Revision: https://phabricator.freedesktop.org/D1138