stanzastream: actually count stanzas in stream management

Looks like a horrible oversight. And this will need tests, but I'm short
on time right now.

Fixes #170.

tokio-xmpp/ChangeLog

@@ -8,6 +8,8 @@ Version NEXT:
       - Gate `AsRawFd` behind `ktls` feature to make Windows build work again.
       - Implicitly use the `Client`'s bound JID on empty `to` in tokio-xmpp's
         `IqResponseTracker`.
+      - Actually count inbound stream management stanzas (!657) instead of
+        always sending h='0' in our `<a/>`.
 
 Version 5.0.0:
 2025-10-28 pep <pep@bouah.net>

tokio-xmpp/src/event.rs

@@ -21,6 +21,9 @@ pub(crate) fn make_id() -> String {
 }
 
 /// A stanza sent/received over the stream.
+// WARNING: do not add variants to this enum! Adding variants which refer
+// to anything but IQ, Message or Presence stanzas will cause the
+// stream management counters to be off.
 #[derive(FromXml, AsXml, Debug, PartialEq)]
 #[xml()]
 pub enum Stanza {

tokio-xmpp/src/stanzastream/connected.rs

@@ -543,6 +543,9 @@ impl ConnectedState {
                 match item {
                     // Easy case, we got some data.
                     Ok(XmppStreamElement::Stanza(data)) => {
+                        if let Some(sm_state) = sm_state.as_mut() {
+                            sm_state.received();
+                        }
                         Poll::Ready(Some(ConnectedEvent::Worker(WorkerEvent::Stanza(data))))
                     }
 

tokio-xmpp/src/stanzastream/stream_management.rs

@@ -214,6 +214,11 @@ impl SmState {
         self.inbound_ctr
     }
 
+    /// Increase the inbound counter.
+    pub fn received(&mut self) {
+        self.inbound_ctr = self.inbound_ctr.wrapping_add(1);
+    }
+
     /// Get the info necessary for resumption.
     ///
     /// Returns the stream ID and the current inbound counter if resumption is