Previously the server code was relaxed to allow packets with zero

Previously the server code was relaxed to allow packets with zero
length client ids to be processed.  Under some situations use of
zero length client ids can cause the server to go into an infinite
loop.  As such ids are not valid according to RFC 2132 section 9.14
the server no longer accepts them.  Client ids with a length of 1
are also invalid but the server still accepts them in order to
minimize disruption.  The restriction will likely be tightened in
the future to disallow ids with a length of 1.
Thanks to Markus Hietava of Codenomicon CROSS project for the
finding this issue and CERT-FI for vulnerability coordination.
[ISC-Bugs #29851]
CVE: CVE-2012-3571