CCBC-1672: Fix protocol violation

Protocol violation by sending garbage in front of the operations for
new connections. In most of the cases, this bytes getting rejected
by the server with connection termination, and libcouchbase
successfully reconnects the pipeline after that rendering the issue
invisible for the user. But in rare cases the "garbage" might be
actual packet header, and the server does not detect problem as
everything is passing protocol checks.

To fix the issue, the mcreq_wipe_packet have to check pending list of
the pipeline and remove everything related to the current detached
packet.

Change-Id: Ib20a1c11057cf9a1ea66bbb349bcda9976f35c0f
Reviewed-on: https://review.couchbase.org/c/libcouchbase/+/232491
Reviewed-by: Michael Reiche <michael.reiche@couchbase.com>
Tested-by: Build Bot <build@couchbase.com>

Author: avsej

src/mc/mcreq.c

@@ -366,6 +366,9 @@ void mcreq_wipe_packet(mc_PIPELINE *pipeline, mc_PACKET *packet)
 {
     if (!(packet->flags & MCREQ_F_KEY_NOCOPY)) {
         if ((packet->flags & MCREQ_F_DETACHED)) {
+            if (pipeline) {
+                netbuf_cleanup_packet(&pipeline->nbmgr, packet);
+            }
             free(SPAN_BUFFER(&packet->kh_span));
         } else {
             netbuf_mblock_release(&pipeline->nbmgr, &packet->kh_span);

src/netbuf/netbuf.c

@@ -729,6 +729,20 @@ void netbuf_init(nb_MGR *mgr, const nb_SETTINGS *user_settings)
     mblock_init(bufpool);
 }
 
+void netbuf_cleanup_packet(nb_MGR *mgr, const void *packet)
+{
+    sllist_iterator iter;
+
+    SLLIST_ITERFOR(&mgr->sendq.pending, &iter)
+    {
+        nb_SNDQELEM *e = SLLIST_ITEM(iter.cur, nb_SNDQELEM, slnode);
+        if (e->parent == packet) {
+            sllist_iter_remove(&mgr->sendq.pending, &iter);
+            mblock_release_ptr(&mgr->sendq.elempool, (char *)e, sizeof(*e));
+        }
+    }
+}
+
 void netbuf_cleanup(nb_MGR *mgr)
 {
     sllist_iterator iter;

src/netbuf/netbuf.h

@@ -341,6 +341,7 @@ void netbuf_init(nb_MGR *mgr, const nb_SETTINGS *settings);
  * @param mgr the manager for which to release resources
  */
 void netbuf_cleanup(nb_MGR *mgr);
+void netbuf_cleanup_packet(nb_MGR *mgr, const void *packet);
 
 /**
  * Populates the settings structure with the default settings. This structure