Philip Withnall authored Jan 16, 2014 and Olivier Crête committed Jan 31, 2014

stun_message_validate_buffer_length() is already fast, but requires the
entire message to be in a single monolithic buffer. For introducing
vectored I/O, this becomes impossible to guarantee.

Rather than rewriting the STUN code to natively support vectors of
buffers (which would be a huge undertaking, and would probably slow
the code down considerably), implement a fast check of whether a message
is likely to be a STUN packet which *does* support vectored I/O. This
can then be used to determine whether to compact the vector of buffers
to a single monolithic one in order to validate the message more
thoroughly.