tree c8e650d72b8451f7d4ab93cd92eaed6549e84ae5
parent 3ab26a6fd01ba211ba5dea0d86d53897b9e8430c
author David Howells <dhowells@redhat.com> 1496835603 +0100
committer David Howells <dhowells@redhat.com> 1496852146 +0100

rxrpc: Provide a cmsg to specify the amount of Tx data for a call

Provide a control message that can be specified on the first sendmsg() of a
client call or the first sendmsg() of a service response to indicate the
total length of the data to be transmitted for that call.

Currently, because the length of the payload of an encrypted DATA packet is
encrypted in front of the data, the packet cannot be encrypted until we
know how much data it will hold.

By specifying the length at the beginning of the transmit phase, each DATA
packet length can be set before we start loading data from userspace (where
several sendmsg() calls may contribute to a particular packet).

An error will be returned if too little or too much data is presented in
the Tx phase.

Signed-off-by: David Howells <dhowells@redhat.com>