/* * Send on a socket. * If send must go all at once and message is larger than * send buffering, then hard error. * Lock against other senders. * If must go all at once and not enough room now, then * inform user that this would block and do nothing. * Otherwise, if nonblocking, send as much as possible. * The data to be sent is described by "uio" if nonzero, * otherwise by the mbuf chain "top" (which must be null * if uio is not). Data provided in mbuf chain must be small * enough to send all at once. * * Returns nonzero on error, timeout or signal; callers * must check for short counts if EINTR/ERESTART are returned. * Data and control buffers are freed on return. */