MINOR: listener: pause_listener() becomes suspend_listener()

We are simply renaming pause_listener() to suspend_listener() to prevent
confusion around listener pausing.

A suspended listener can be in two differents valid states:
 - LI_PAUSED: the listener is effectively paused, it will unpause on
   resume_listener()
 - LI_ASSIGNED (not bound): the listener does not support the LI_PAUSED
   state, so it was unbound to satisfy the suspend request, it will
   correcly re-bind on resume_listener()

Besides that, we add the LI_F_SUSPENDED flag to mark suspended listeners in
suspend_listener() and unmark them in resume_listener().

We're also adding li_suspend proxy variable to track the number of currently
suspended listeners:
That is, the number of listeners that were suspended through suspend_listener()
and that are either in LI_PAUSED or LI_ASSIGNED state.

Counter is increased on successful suspend in suspend_listener() and it is
decreased on successful resume in resume_listener()

--
Backport notes:

-> 2.4 only, as "MINOR: proxy/listener: support for additional PAUSED state"
was not backported:

Replace this:

    |                /* PROXY_LOCK is require
    |                proxy_cond_resume(px);

By this:

    |                ha_warning("Resumed %s %s.\n", proxy_cap_str(px->cap), px->id);
    |                send_log(px, LOG_WARNING, "Resumed %s %s.\n", proxy_cap_str(px->cap), px->id);

-> 2.6 and 2.7 only, as "MINOR: listener: make sure we don't pause/resume" was
custom patched:

Replace this:

    |@@ -253,6 +253,7 @@ struct listener {
    |
    | /* listener flags (16 bits) */
    | #define LI_F_FINALIZED           0x0001  /* listener made it to the READY||LIMITED||FULL state at least once, may be suspended/resumed safely */
    |+#define LI_F_SUSPENDED           0x0002  /* listener has been suspended using suspend_listener(), it is either is LI_PAUSED or LI_ASSIGNED state */
    |
    | /* Descriptor for a "bind" keyword. The ->parse() function returns 0 in case of
    |  * success, or a combination of ERR_* flags if an error is encountered. The

By this:

    |@@ -222,6 +222,7 @@ struct li_per_thread {
    |
    | #define LI_F_QUIC_LISTENER       0x00000001  /* listener uses proto quic */
    | #define LI_F_FINALIZED           0x00000002  /* listener made it to the READY||LIMITED||FULL state at least once, may be suspended/resumed safely */
    |+#define LI_F_SUSPENDED           0x00000004  /* listener has been suspended using suspend_listener(), it is either is LI_PAUSED or LI_ASSIGNED state */
    |
    | /* The listener will be directly referenced by the fdtab[] which holds its
    |  * socket. The listener provides the protocol-specific accept() function to

include/haproxy/listener-t.h

@@ -253,6 +253,7 @@ struct listener {
 
 /* listener flags (16 bits) */
 #define LI_F_FINALIZED           0x0001  /* listener made it to the READY||LIMITED||FULL state at least once, may be suspended/resumed safely */
+#define LI_F_SUSPENDED           0x0002  /* listener has been suspended using suspend_listener(), it is either is LI_PAUSED or LI_ASSIGNED state */
 
 /* Descriptor for a "bind" keyword. The ->parse() function returns 0 in case of
  * success, or a combination of ERR_* flags if an error is encountered. The

include/haproxy/listener.h

@@ -43,11 +43,13 @@ void listener_set_state(struct listener *l, enum li_state st);
  * involves SHUT_WR && listen && SHUT_RD. In case of success, the FD's polling
  * is disabled. It normally returns non-zero, unless an error is reported.
  * It will need to operate under the proxy's lock and the listener's lock.
+ * suspend() may totally stop a listener if it doesn't support the PAUSED
+ * state, in which case state will be set to ASSIGNED.
  * The caller is responsible for indicating in lpx, lli whether the respective
  * locks are already held (non-zero) or not (zero) so that the function pick
  * the missing ones, in this order.
  */
-int pause_listener(struct listener *l, int lpx, int lli);
+int suspend_listener(struct listener *l, int lpx, int lli);
 
 /* This function tries to resume a temporarily disabled listener.
  * The resulting state will either be LI_READY or LI_FULL. 0 is returned

include/haproxy/proxy-t.h

@@ -403,6 +403,7 @@ struct proxy {
 	unsigned int li_paused;                 /* total number of listeners paused (LI_PAUSED) */
 	unsigned int li_bound;                  /* total number of listeners ready (LI_LISTEN)  */
 	unsigned int li_ready;                  /* total number of listeners ready (>=LI_READY) */
+	unsigned int li_suspended;		/* total number of listeners suspended (could be paused or unbound) */
 
 	/* warning: these structs are huge, keep them at the bottom */
 	struct sockaddr_storage dispatch_addr;	/* the default address to connect to */

src/listener.c

@@ -480,14 +480,14 @@ int default_resume_listener(struct listener *l)
  * closes upon SHUT_WR and refuses to rebind. So a common validation path
  * involves SHUT_WR && listen && SHUT_RD. In case of success, the FD's polling
  * is disabled. It normally returns non-zero, unless an error is reported.
- * pause() may totally stop a listener if it doesn't support the PAUSED state,
- * in which case state will be set to ASSIGNED.
+ * suspend() may totally stop a listener if it doesn't support the PAUSED
+ * state, in which case state will be set to ASSIGNED.
  * It will need to operate under the proxy's lock and the listener's lock.
  * The caller is responsible for indicating in lpx, lli whether the respective
  * locks are already held (non-zero) or not (zero) so that the function pick
  * the missing ones, in this order.
  */
-int pause_listener(struct listener *l, int lpx, int lli)
+int suspend_listener(struct listener *l, int lpx, int lli)
 {
 	struct proxy *px = l->bind_conf->frontend;
 	int ret = 1;
@@ -518,6 +518,10 @@ int pause_listener(struct listener *l, int lpx, int lli)
 	 */
 	listener_set_state(l, ((ret) ? LI_PAUSED : LI_ASSIGNED));
 
+	if (px && !(l->flags & LI_F_SUSPENDED))
+		px->li_suspended++;
+	l->flags |= LI_F_SUSPENDED;
+
 	/* at this point, everything is under control, no error should be
 	 * returned to calling function
 	 */
@@ -545,7 +549,7 @@ int pause_listener(struct listener *l, int lpx, int lli)
  * or LI_FULL. 0 is returned in case of failure to resume (eg: dead socket).
  * Listeners bound to a different process are not woken up unless we're in
  * foreground mode, and are ignored. If the listener was only in the assigned
- * state, it's totally rebound. This can happen if a pause() has completely
+ * state, it's totally rebound. This can happen if a suspend() has completely
  * stopped it. If the resume fails, 0 is returned and an error might be
  * displayed.
  * It will need to operate under the proxy's lock and the listener's lock.
@@ -590,6 +594,10 @@ int resume_listener(struct listener *l, int lpx, int lli)
 	listener_set_state(l, LI_READY);
 
   done:
+	if (px && (l->flags & LI_F_SUSPENDED))
+		px->li_suspended--;
+	l->flags &= ~LI_F_SUSPENDED;
+
 	if (was_paused && !px->li_paused) {
 		/* PROXY_LOCK is required */
 		proxy_cond_resume(px);
@@ -1275,7 +1283,7 @@ void listener_accept(struct listener *l)
 	 * Let's put it to pause in this case.
 	 */
 	if (l->rx.proto && l->rx.proto->rx_listening(&l->rx) == 0) {
-		pause_listener(l, 0, 0);
+		suspend_listener(l, 0, 0);
 		goto end;
 	}
 

src/protocol.c

@@ -174,10 +174,10 @@ void protocol_stop_now(void)
 	HA_SPIN_UNLOCK(PROTO_LOCK, &proto_lock);
 }
 
-/* pauses all listeners of all registered protocols. This is typically
+/* suspends all listeners of all registered protocols. This is typically
  * used on SIG_TTOU to release all listening sockets for the time needed to
- * try to bind a new process. The listeners enter LI_PAUSED. It returns
- * ERR_NONE, with ERR_FATAL on failure.
+ * try to bind a new process. The listeners enter LI_PAUSED or LI_ASSIGNED.
+ * It returns ERR_NONE, with ERR_FATAL on failure.
  */
 int protocol_pause_all(void)
 {
@@ -189,7 +189,7 @@ int protocol_pause_all(void)
 	HA_SPIN_LOCK(PROTO_LOCK, &proto_lock);
 	list_for_each_entry(proto, &protocols, list) {
 		list_for_each_entry(listener, &proto->receivers, rx.proto_list)
-			if (!pause_listener(listener, 0, 0))
+			if (!suspend_listener(listener, 0, 0))
 				err |= ERR_FATAL;
 	}
 	HA_SPIN_UNLOCK(PROTO_LOCK, &proto_lock);

src/proxy.c

@@ -2286,7 +2286,7 @@ int pause_proxy(struct proxy *p)
 		goto end;
 
 	list_for_each_entry(l, &p->conf.listeners, by_fe)
-		pause_listener(l, 1, 0);
+		suspend_listener(l, 1, 0);
 
 	if (p->li_ready) {
 		ha_warning("%s %s failed to enter pause mode.\n", proxy_cap_str(p->cap), p->id);