There was an embarrasing bug here added in r28874. In the second of
three calls to get_srcaddr, the interface was being indexed by an index
variable that, in this place, was actually an index into the routes
table. This would in general produce a nonsensical source address or
out-of-bounds access.
The symptom of this problem was the following error messages:
get_srcaddr: can't connect socket: The requested address is not valid in its context.
Failed to convert source address to presentation format!?! Error: Unknown error
The first showed that get_srcaddr failed, and the second was caused by
the bogus source address.
http://seclists.org/nmap-dev/2012/q3/859http://seclists.org/nmap-dev/2012/q4/59