In setting up Kamailio with MSILO, I've noticed that some sip clients (I'm 
using CSipSimple), upon un-REGISTER-ing do not send an Allow header, but do 
send an "Expires: 0" header as well as a Contact header.

However as the Contact header doesn't contain "expires=0", it appears as 
though the MSILO skips over checking the Expires header.

As such, I've had to add the following workaround to my route[REGISTRAR] block 
or else these clients trigger the m_dump.

# Ensure we aren't unregistering
# Right now, CSipSimple doesn't send an Allow header with an un-REGISTER,
# so Kamailio skips to checking the Contact header for expires, and appears
# to ignore the fact that an Expires: 0 header is present.
	if($hdr(Expires) != 0)
		m_dump();

Looking through the msilo  check_message_support function, it appears that it 
never checks for the Expires header if there is no Allow header and the 
Contact header does not specify an expire setting.

I do believe that we're missing the check for the Expires header, regardless 
of whether or not there is an Allow header, or a Contact header with expires=0

-A