sctp: implement prsctp PRIO policy

prsctp PRIO policy is a policy to abandon lower priority chunks when
asoc doesn't have enough snd buffer, so that the current chunk with
higher priority can be queued successfully.

Similar to TTL/RTX policy, we will set the priority of the chunk to
prsctp_param with sinfo->sinfo_timetolive in sctp_set_prsctp_policy().
So if PRIO policy is enabled, msg->expire_at won't work.

asoc->sent_cnt_removable will record how many chunks can be checked to
remove. If priority policy is enabled, when the chunk is queued into
the out_queue, we will increase sent_cnt_removable. When the chunk is
moved to abandon_queue or dequeue and free, we will decrease
sent_cnt_removable.

In sctp_sendmsg, we will check if there is enough snd buffer for current
msg and if sent_cnt_removable is not 0. Then try to abandon chunks in
sctp_prune_prsctp when sendmsg from the retransmit/transmited queue, and
free chunks from out_queue in right order until the abandon+free size >
msg_len - sctp_wfree. For the abandon size, we have to wait until it
sends FORWARD TSN, receives the sack and the chunks are really freed.

Signed-off-by: Xin Long <lucien.xin@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 1 deletions

diff --git a/net/sctp/sm_make_chunk.c b/net/sctp/sm_make_chunk.c
index cfde934..1c96f47 100644
--- a/net/sctp/sm_make_chunk.c
+++ b/net/sctp/sm_make_chunk.c
@@ -720,7 +720,8 @@ static void sctp_set_prsctp_policy(struct sctp_chunk *chunk,
 	if (SCTP_PR_TTL_ENABLED(sinfo->sinfo_flags))
 		chunk->prsctp_param =
 			jiffies + msecs_to_jiffies(sinfo->sinfo_timetolive);
-	else if (SCTP_PR_RTX_ENABLED(sinfo->sinfo_flags))
+	else if (SCTP_PR_RTX_ENABLED(sinfo->sinfo_flags) ||
+		 SCTP_PR_PRIO_ENABLED(sinfo->sinfo_flags))
 		chunk->prsctp_param = sinfo->sinfo_timetolive;
 }