From a5cd7dcbd94c0ebb2c9a43a8b545656b2463692f Mon Sep 17 00:00:00 2001
From: Jon Shallow <supjps-libcoap@jpshallow.com>
Date: Wed, 25 Jul 2018 22:09:57 +0100
Subject: [PATCH] net.c,coap_session.c: Flush out session->sendqueue when PDU
 is delayed

Delayed PDUs (found by the limiting of 1 CON request outstanding) are
added to session->sendqueue by coap_session_delay_pdu().
The session->sendqueue is only flushed out when a session becomes established
by calling coap_session_connected().

This fix now calls coap_session_connected() whenever the current CON count
is decremented.

Additionally, CON tracking now only tracks UDP & DTLS sessions.

coap_session_connected() is updated to not sent out more than one CON
request.
---
 src/coap_session.c | 11 +++++++++--
 src/net.c          | 18 ++++++++++++++----
 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/src/coap_session.c b/src/coap_session.c
index b5ca7c5d..340a36fc 100644
--- a/src/coap_session.c
+++ b/src/coap_session.c
@@ -304,7 +304,8 @@ void coap_session_send_csm(coap_session_t *session) {
 }
 
 void coap_session_connected(coap_session_t *session) {
-  debug("*** %s: session connected\n", coap_session_str(session));
+  if (session->state != COAP_SESSION_STATE_ESTABLISHED)
+    coap_log(LOG_DEBUG, "*** %s: session connected\n", coap_session_str(session));
 
   session->state = COAP_SESSION_STATE_ESTABLISHED;
   session->partial_write = 0;
@@ -322,7 +323,13 @@ void coap_session_connected(coap_session_t *session) {
     coap_queue_t *q = session->sendqueue;
     session->sendqueue = q->next;
     q->next = NULL;
-    debug("** %s tid=%d: transmitted after delay\n", coap_session_str(session), (int)q->pdu->tid);
+    if (q->pdu->type == COAP_MESSAGE_CON && COAP_PROTO_NOT_RELIABLE(session->proto)) {
+      if (session->con_active >= COAP_DEFAULT_NSTART)
+        break;
+      session->con_active++;
+    }
+    coap_log(LOG_DEBUG, "**  %s: tid=%d: transmitted after delay\n",
+             coap_session_str(session), (int)q->pdu->tid);
     bytes_written = coap_session_send_pdu(session, q->pdu);
     if (q->pdu->type == COAP_MESSAGE_CON && COAP_PROTO_NOT_RELIABLE(session->proto)) {
       if (coap_wait_ack(session->context, session, q) >= 0)
diff --git a/src/net.c b/src/net.c
index 8632b901..0ed70f5e 100644
--- a/src/net.c
+++ b/src/net.c
@@ -648,8 +648,9 @@ coap_send_pdu(coap_session_t *session, coap_pdu_t *pdu, coap_queue_t *node) {
     assert(session->endpoint != NULL);
     sock = &session->endpoint->sock;
   }
-  if (pdu->type == COAP_MESSAGE_CON)
+  if (pdu->type == COAP_MESSAGE_CON && COAP_PROTO_NOT_RELIABLE(session->proto))
     session->con_active++;
+
   bytes_written = coap_socket_send_pdu(sock, session, pdu);
   if (LOG_DEBUG <= coap_get_log_level()) {
     coap_show_pdu(pdu);
@@ -713,8 +714,9 @@ coap_send_pdu(coap_session_t *session, coap_pdu_t *pdu, coap_queue_t *node) {
     (session->sock.flags & COAP_SOCKET_WANT_WRITE))
     return coap_session_delay_pdu(session, pdu, node);
 
-  if (pdu->type == COAP_MESSAGE_CON)
+  if (pdu->type == COAP_MESSAGE_CON && COAP_PROTO_NOT_RELIABLE(session->proto))
     session->con_active++;
+
   bytes_written = coap_session_send_pdu(session, pdu);
 
 #endif /* WITH_LWIP */
@@ -2100,8 +2102,12 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
       /* find transaction in sendqueue to stop retransmission */
       coap_remove_from_queue(&context->sendqueue, session, pdu->tid, &sent);
 
-      if (session->con_active)
+      if (session->con_active) {
         session->con_active--;
+        if (session->state == COAP_SESSION_STATE_ESTABLISHED)
+          /* Flush out any entries on session->sendqueue */
+          coap_session_connected(session);
+      }
       if (pdu->code == 0)
         goto cleanup;
 
@@ -2122,8 +2128,12 @@ coap_dispatch(coap_context_t *context, coap_session_t *session,
 
       coap_log(LOG_ALERT, "got RST for message %d\n", pdu->tid);
 
-      if (session->con_active)
+      if (session->con_active) {
         session->con_active--;
+        if (session->state == COAP_SESSION_STATE_ESTABLISHED)
+          /* Flush out any entries on session->sendqueue */
+          coap_session_connected(session);
+      }
 
       /* find transaction in sendqueue to stop retransmission */
       coap_remove_from_queue(&context->sendqueue, session, pdu->tid, &sent);