Add initial XEP-0198 support (EJAB-532)

Implement partial support for XEP-0198: Stream Management.  After
successful negotiation of this feature, the server requests an ACK for
each stanza transmitted to the client and responds to ACK requests
issued by the client.  On session termination, the server re-routes any
unacknowledged stanzas.  The length of the pending queue can be limited
by setting the "max_ack_queue" option to some integer value (default:
500).  XEP-0198 support can be disabled entirely by setting the
"stream_management" option to false (default: true).

So far, stream management is implemented only for c2s connections, and
the optional stream resumption feature also described in XEP-0198 is not
(yet) supported.

This addition was originally based on a patch provided by Magnus Henoch
and updated by Grzegorz Grasza.  Their code implements an early draft of
XEP-0198 for some previous version of ejabberd.  It has since been
rewritten almost entirely.

1 files changed, 14 insertions, 2 deletions

diff --git a/doc/guide.tex b/doc/guide.tex
index 5d5bf2fdc..59f39e256 100644
--- a/doc/guide.tex
+++ b/doc/guide.tex
@@ -870,9 +870,10 @@ The available modules, their purpose and the options allowed by each one are:
   \titem{\texttt{ejabberd\_c2s}}
     Handles c2s connections.\\
     Options: \texttt{access}, \texttt{certfile}, \texttt{ciphers},
-    \texttt{max\_fsm\_queue},
+    \texttt{max\_ack\_queue}, \texttt{max\_fsm\_queue},
     \texttt{max\_stanza\_size}, \texttt{shaper},
-    \texttt{starttls}, \texttt{starttls\_required}, \texttt{tls},
+    \texttt{starttls}, \texttt{starttls\_required},
+    \texttt{stream\_management}, \texttt{tls},
     \texttt{zlib}, \texttt{tls\_compression}
   \titem{\texttt{ejabberd\_s2s\_in}}
     Handles incoming s2s connections.\\
@@ -962,6 +963,13 @@ This is a detailed description of each option allowed by the listening modules:
     \term{http\_poll\_timeout}. The default value is five minutes.
     The option can be defined in \term{ejabberd.yml}, expressing the time
     in seconds: \verb|{http_poll_timeout, 300}.|
+  \titem{max\_ack\_queue: Size}
+    This option specifies the maximum number of unacknowledged stanzas
+    queued for possible retransmission if \term{stream\_management} is
+    enabled. When the limit is reached, the first stanza is dropped from
+    the queue before adding the next one. This option can be specified
+    for \term{ejabberd\_c2s} listeners. The allowed values are positive
+    integers and \term{infinity}. Default value: \term{500}.
   \titem{max\_fsm\_queue: Size}
     This option specifies the maximum number of elements in the queue of the FSM
     (Finite State Machine).
@@ -1022,6 +1030,10 @@ request_handlers:
     No unencrypted connections will be allowed.
     You should also set the \option{certfile} option.
     You can define a certificate file for a specific domain using the global option \option{domain\_certfile}.
+  \titem{stream\_management: true|false}
+    Setting this option to \term{false} disables ejabberd's support for
+    \ind{protocols!XEP-0198: Stream Management}. It can be specified for
+    \term{ejabberd\_c2s} listeners. The default value is \term{true}.
   \titem{timeout: Integer} \ind{options!timeout}
     Timeout of the connections, expressed in milliseconds.
     Default: 5000