implement sendto()/recvfrom() equivalents.

elsewhere as well.

download

this saves around 70us per received packet (which is around 50% of the
overall packet processing time).

other protocol won't work at the moment.

exception rather than the rule; we may as well keep things clean for other
protocols.

will enable us to cascade async operations, which is necessary in order to
properly support DNS.  (For example, an HTTP request may have to redirect
to a new location and will have to perform a new DNS lookup, so we can't
just rely on doing the name lookup at the time of parsing the initial
URL).

Anything other than HTTP is probably broken right now; I'll fix the others
up asap.

order so we can just use buffer->fill.

may be called during the RX data processor, before the RX engine
transitions back to idle.  It doesn't really matter if the RX engine
isn't idle when iscsi_done() is called, because it will just pick up
where it left off on the next call.  (The same is not true for the TX
engine, so keep the TX engine assertion.)

reopen connection.  (The TCP API will soon change to render this step
unnecessary.)

TargetAddress from the login response, because we still need the old
address while we close the connection!

phase.  In iscsi_issue(), detect this state and immediately refuse the
operation.  This avoids trying multiple logins when scsi.c tries
several times to read the drive capacity.

reconnection mechanism.  This avoids the problems of trying to reuse
the TCP connection structure before the old connection has cleanly exited.

Remove the now-totally-obsolete sockaddr_in field from tcp.h.

Added CHAP authentication

negotiation phases, to allow inclusion of CHAP authentication.

against NULL.