In general case m_pullup() does not really guarantee any data alignment.
Instead of depenting on side effects caused by data being always copied
out of mbuf cluster (which is probably a bug by itself), always allocate
aligned BHS buffer and read data there directly from socket.
While there, reuse new icl_conn_receive_buf() function to read digests.
The code could probably be even more optimized to aggregate those reads,
but until that done, this is still easier then the way it was before.