sctp: introduce stream scheduler foundations

This patch introduces the hooks necessary to do stream scheduling, as
per RFC Draft ndata.  It also introduces the first scheduler, which is
what we do today but now factored out: first come first served (FCFS).

With stream scheduling now we have to track which chunk was enqueued on
which stream and be able to select another other than the in front of
the main outqueue. So we introduce a list on sctp_stream_out_ext
structure for this purpose.

We reuse sctp_chunk->transmitted_list space for the list above, as the
chunk cannot belong to the two lists at the same time. By using the
union in there, we can have distinct names for these moments.

sctp_sched_ops are the operations expected to be implemented by each
scheduler. The dequeueing is a bit particular to this implementation but
it is to match how we dequeue packets today. We first dequeue and then
check if it fits the packet and if not, we requeue it at head. Thus why
we don't have a peek operation but have dequeue_done instead, which is
called once the chunk can be safely considered as transmitted.

The check removed from sctp_outq_flush is now performed by
sctp_stream_outq_migrate, which is only called during assoc setup.
(sctp_sendmsg() also checks for it)

The only operation that is foreseen but not yet added here is a way to
signalize that a new packet is starting or that the packet is done, for
round robin scheduler per packet, but is intentionally left to the
patch that actually implements it.

Support for I-DATA chunks, also described in this RFC, with user message
interleaving is straightforward as it just requires the schedulers to
probe for the feature and ignore datamsg boundaries when dequeueing.

See-also: https://tools.ietf.org/html/draft-ietf-tsvwg-sctp-ndata-13
Tested-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: Marcelo Ricardo Leitner <marcelo.leitner@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 81 insertions, 7 deletions

diff --git a/net/sctp/stream.c b/net/sctp/stream.c
index 055ca25bbc91..5ea33a2c453b 100644
--- a/net/sctp/stream.c
+++ b/net/sctp/stream.c
@@ -32,8 +32,61 @@
  *    Xin Long <lucien.xin@gmail.com>
  */
 
+#include <linux/list.h>
 #include <net/sctp/sctp.h>
 #include <net/sctp/sm.h>
+#include <net/sctp/stream_sched.h>
+
+/* Migrates chunks from stream queues to new stream queues if needed,
+ * but not across associations. Also, removes those chunks to streams
+ * higher than the new max.
+ */
+static void sctp_stream_outq_migrate(struct sctp_stream *stream,
+                                     struct sctp_stream *new, __u16 outcnt)
+{
+        struct sctp_association *asoc;
+        struct sctp_chunk *ch, *temp;
+        struct sctp_outq *outq;
+        int i;
+
+        asoc = container_of(stream, struct sctp_association, stream);
+        outq = &asoc->outqueue;
+
+        list_for_each_entry_safe(ch, temp, &outq->out_chunk_list, list) {
+                __u16 sid = sctp_chunk_stream_no(ch);
+
+                if (sid < outcnt)
+                        continue;
+
+                sctp_sched_dequeue_common(outq, ch);
+                /* No need to call dequeue_done here because
+                 * the chunks are not scheduled by now.
+                 */
+
+                /* Mark as failed send. */
+                sctp_chunk_fail(ch, SCTP_ERROR_INV_STRM);
+                if (asoc->peer.prsctp_capable &&
+                    SCTP_PR_PRIO_ENABLED(ch->sinfo.sinfo_flags))
+                        asoc->sent_cnt_removable--;
+
+                sctp_chunk_free(ch);
+        }
+
+        if (new) {
+                /* Here we actually move the old ext stuff into the new
+                 * buffer, because we want to keep it. Then
+                 * sctp_stream_update will swap ->out pointers.
+                 */
+                for (i = 0; i < outcnt; i++) {
+                        kfree(new->out[i].ext);
+                        new->out[i].ext = stream->out[i].ext;
+                        stream->out[i].ext = NULL;
+                }
+        }
+
+        for (i = outcnt; i < stream->outcnt; i++)
+                kfree(stream->out[i].ext);
+}
 
 static int sctp_stream_alloc_out(struct sctp_stream *stream, __u16 outcnt,
                                  gfp_t gfp)
@@ -87,7 +140,8 @@ static int sctp_stream_alloc_in(struct sctp_stream *stream, __u16 incnt,
 int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
                      gfp_t gfp)
 {
-        int i;
+        struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+        int i, ret = 0;
 
         gfp |= __GFP_NOWARN;
 
@@ -97,6 +151,11 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
         if (outcnt == stream->outcnt)
                 goto in;
 
+        /* Filter out chunks queued on streams that won't exist anymore */
+        sched->unsched_all(stream);
+        sctp_stream_outq_migrate(stream, NULL, outcnt);
+        sched->sched_all(stream);
+
         i = sctp_stream_alloc_out(stream, outcnt, gfp);
         if (i)
                 return i;
@@ -105,20 +164,27 @@ int sctp_stream_init(struct sctp_stream *stream, __u16 outcnt, __u16 incnt,
         for (i = 0; i < stream->outcnt; i++)
                 stream->out[i].state = SCTP_STREAM_OPEN;
 
+        sched->init(stream);
+
 in:
         if (!incnt)
-                return 0;
+                goto out;
 
         i = sctp_stream_alloc_in(stream, incnt, gfp);
         if (i) {
-                kfree(stream->out);
-                stream->out = NULL;
-                return -ENOMEM;
+                ret = -ENOMEM;
+                goto free;
         }
 
         stream->incnt = incnt;
+        goto out;
 
-        return 0;
+free:
+        sched->free(stream);
+        kfree(stream->out);
+        stream->out = NULL;
+out:
+        return ret;
 }
 
 int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
@@ -130,13 +196,15 @@ int sctp_stream_init_ext(struct sctp_stream *stream, __u16 sid)
                 return -ENOMEM;
         stream->out[sid].ext = soute;
 
-        return 0;
+        return sctp_sched_init_sid(stream, sid, GFP_KERNEL);
 }
 
 void sctp_stream_free(struct sctp_stream *stream)
 {
+        struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
         int i;
 
+        sched->free(stream);
         for (i = 0; i < stream->outcnt; i++)
                 kfree(stream->out[i].ext);
         kfree(stream->out);
@@ -156,6 +224,10 @@ void sctp_stream_clear(struct sctp_stream *stream)
 
 void sctp_stream_update(struct sctp_stream *stream, struct sctp_stream *new)
 {
+        struct sctp_sched_ops *sched = sctp_sched_ops_from_stream(stream);
+
+        sched->unsched_all(stream);
+        sctp_stream_outq_migrate(stream, new, new->outcnt);
         sctp_stream_free(stream);
 
         stream->out = new->out;
@@ -163,6 +235,8 @@ void sctp_stream_update(struct sctp_stream *stream, struct sctp_stream *new)
         stream->outcnt = new->outcnt;
         stream->incnt  = new->incnt;
 
+        sched->sched_all(stream);
+
         new->out = NULL;
         new->in  = NULL;
 }