ipcpd: Use capacity queue estimation for mb-ecn

The mb-ecn algorithm was using rbuff queue depths in packets to mark,
but sockets in the poa component report capacity in bytes. The tx
rings are now adaptive to block on queuing delay instead of when full
to prevent buffer bloat, controllable via fccntl (FLOWSTXQDLY and
FLOWGTXQDLY).

Signed-off-by: Dimitri Staessens <dimitri@ouroboros.rocks>
Signed-off-by: Sander Vrijders <sander@ouroboros.rocks>

1 files changed, 12 insertions, 1 deletions

diff --git a/doc/man/fccntl.3 b/doc/man/fccntl.3
index 767342b9..61022837 100644
--- a/doc/man/fccntl.3
+++ b/doc/man/fccntl.3
@@ -76,6 +76,16 @@ buffer. Takes a \fBsize_t \fIqlen\fR * as third argument.
 \fBFLOWGTXQLEN\fR   - get the current number of packets in the transmit
 buffer. Takes a \fBsize_t \fIqlen\fR * as third argument.
 
+\fBFLOWSTXQDLY\fR   - set the target queueing delay for the transmit
+occupancy limiter. Takes a \fBstruct timespec * \fItimeo\fR as third
+argument. A zero delay leaves the ring unlimited, bounded only by its
+slot count. The build-time default is applied when the flow is
+created.
+
+\fBFLOWGTXQDLY\fR   - retrieve the current target queueing delay for
+the transmit occupancy limiter. Takes a \fBstruct timespec * \fItimeo\fR
+as third argument.
+
 \fBFRCTSFLAGS\fR    - set the current flow flags. Takes an \fBuint16_t
 \fIflags\fR as third argument. Supported flags are:
 
@@ -106,7 +116,8 @@ An invalid argument was passed.
 .B -EPERM
 Operation not permitted. This is returned when requesting the value of
 a timeout (FLOWGSNDTIMEO or FLOWGRCVTIMEO) when no such timeout was
-set.
+set, or when FLOWSTXQDLY/FLOWGTXQDLY is used on a flow with no
+transmit occupancy ring.
 
 .B -EBADF
 Invalid flow descriptor passed.