s3:smbd: add infrastructure to wait for TCP acks

This will be the core of the logic that allows
us to retry break notifications.

When we start the "pending break cycle" we ask for
the current retransmission timemout (rto) on the TCP connection
and remember how many unacked bytes are in the kernel's
send queue. Each time we send bytes into the kernel
we add them to the unacked bytes.
We use a timer using the rto interval in order
to check the amount of unacked bytes again.
The provides send_queu_entry.ack.req will be completed
with tevent_req_done() when everything is completely acked,
tevent_req_nterror(NT_STATUS_IO_TIMEOUT) when
send_queu_entry.ack.timeout is expired or
tevent_req_nterror(connection_error) when the connection
gets disconnected.

It works with support from the FreeBSD and Linux kernels.
For other platforms we just have a fixed rto of 1 second.
And pretend all bytes are acked when we recheck after 1 second.
So only a connection error could trigger tevent_req_nterror(),
but there's no timeout. A follow up commit will most likely
disable support for multi-channel if we don't have kernel support.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=11897

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Reviewed-by: Günther Deschner <gd@samba.org>

0 files changed, 0 insertions, 0 deletions