Text requests and responses can span multiple PDUs. In that case,
the sender sets the Continue bit in non-final PDUs and the Final
bit in the last PDU. The receiver responds to non-final PDUs with
an empty text PDU.
To support this, add a more abstract API in libiscsi which accepts
and receives key sets rather than PDUs. These routines internally
send or receive one or more PDUs. Use these new functions to replace
the handling of TextRequest and TextResponse PDUs in discovery sessions
in both ctld and iscsid.
Note that there is not currently a use case for large Text requests
and those are still always sent as a single PDU. However, discovery
sessions can return a text response listing targets that spans
multiple PDUs, so the new API supports sending and receiving multi-PDU
responses.
Reported by: Jithesh Arakkan @ Chelsio
Sponsored by: Chelsio Communications