fixes #961 surprising pipe event order

include/nng/nng.h

@@ -271,6 +271,7 @@ uint32_t nng_sockaddr_port(const nng_sockaddr *sa);
 // Only one callback can be set on a given socket, and there is no way
 // to retrieve the old value.
 typedef enum {
+	NNG_PIPE_EV_NONE,     // Used internally, must be first, never posted
 	NNG_PIPE_EV_ADD_PRE,  // Called just before pipe added to socket
 	NNG_PIPE_EV_ADD_POST, // Called just after pipe added to socket
 	NNG_PIPE_EV_REM_POST, // Called just after pipe removed from socket

src/core/pipe.c

@@ -256,13 +256,13 @@ pipe_create(nni_pipe **pp, nni_sock *sock, nni_sp_tran *tran, nni_dialer *d,
 		return (NNG_ENOMEM);
 	}
 
-	p->p_size      = sz;
-	p->p_proto_ops = *pops;
-	p->p_tran_ops  = *tops;
-	p->p_sock      = sock;
-	p->p_cbs       = false;
-	p->p_dialer    = d;
-	p->p_listener  = l;
+	p->p_size       = sz;
+	p->p_proto_ops  = *pops;
+	p->p_tran_ops   = *tops;
+	p->p_sock       = sock;
+	p->p_dialer     = d;
+	p->p_listener   = l;
+	p->p_last_event = NNG_PIPE_EV_NONE;
 
 	// Two references - one for our caller, and
 	// one to be dropped when the pipe is closed.

src/core/socket.c

@@ -104,6 +104,7 @@ struct nni_socket {
 
 	nni_mtx          s_pipe_cbs_mtx;
 	nni_sock_pipe_cb s_pipe_cbs[NNG_PIPE_EV_NUM];
+	bool             s_want_evs;
 
 #ifdef NNG_ENABLE_STATS
 	nni_stat_item st_root;      // socket scope
@@ -1013,10 +1014,16 @@ nni_sock_flags(nni_sock *sock)
 void
 nni_sock_set_pipe_cb(nni_sock *s, int ev, nng_pipe_cb cb, void *arg)
 {
-	if ((ev >= 0) && (ev < NNG_PIPE_EV_NUM)) {
+	if ((ev > NNG_PIPE_EV_NONE) && (ev < NNG_PIPE_EV_NUM)) {
 		nni_mtx_lock(&s->s_pipe_cbs_mtx);
 		s->s_pipe_cbs[ev].cb_fn  = cb;
 		s->s_pipe_cbs[ev].cb_arg = arg;
+		s->s_want_evs            = false;
+		for (ev = NNG_PIPE_EV_NONE; ev < NNG_PIPE_EV_NUM; ev++) {
+			if (s->s_pipe_cbs[ev].cb_fn != NULL) {
+				s->s_want_evs = true;
+			}
+		}
 		nni_mtx_unlock(&s->s_pipe_cbs_mtx);
 	}
 }
@@ -1538,25 +1545,39 @@ nni_pipe_start(nni_pipe *p)
 void
 nni_pipe_run_cb(nni_pipe *p, nng_pipe_ev ev)
 {
-	nni_sock   *s = p->p_sock;
-	nng_pipe_cb cb;
-	void       *arg;
+	nni_sock      *s = p->p_sock;
+	nng_pipe_cb    cb;
+	void          *arg;
+	bool           wantevs;
+	static nni_mtx serialize = NNI_MTX_INITIALIZER;
 
 	nni_mtx_lock(&s->s_pipe_cbs_mtx);
-	if (ev == NNG_PIPE_EV_ADD_PRE) {
-		p->p_cbs = true;
-	} else if (!p->p_cbs) {
-		nni_mtx_unlock(&s->s_pipe_cbs_mtx);
-		return;
-	}
-	cb  = s->s_pipe_cbs[ev].cb_fn;
-	arg = s->s_pipe_cbs[ev].cb_arg;
+	cb      = s->s_pipe_cbs[ev].cb_fn;
+	arg     = s->s_pipe_cbs[ev].cb_arg;
+	wantevs = s->s_want_evs;
 	nni_mtx_unlock(&s->s_pipe_cbs_mtx);
 
-	if (cb != NULL) {
+	if (wantevs) {
+		nni_mtx_lock(&serialize);
+		// this pipe never got an event before, so don't start now
+		if (p->p_last_event == NNG_PIPE_EV_NONE &&
+		    ev != NNG_PIPE_EV_ADD_PRE) {
+			nni_mtx_unlock(&serialize);
+			return;
+		}
+		if (p->p_last_event >= ev) {
+			// this pipe event already was notified, or a "later"
+			// one was, so don't go backwards.
+			nni_mtx_unlock(&serialize);
+			return;
+		}
+		p->p_last_event = ev;
 		nng_pipe pid;
 		pid.id = p->p_id;
-		cb(pid, ev, arg);
+		if (cb != NULL) {
+			cb(pid, ev, arg);
+		}
+		nni_mtx_unlock(&serialize);
 	}
 }
 

src/core/sockimpl.h

@@ -1,5 +1,5 @@
 //
-// Copyright 2023 Staysail Systems, Inc. <[email protected]>
+// Copyright 2024 Staysail Systems, Inc. <[email protected]>
 // Copyright 2018 Capitar IT Group BV <[email protected]>
 //
 // This software is supplied under the terms of the MIT License, a
@@ -104,9 +104,9 @@ struct nni_pipe {
 	nni_listener      *p_listener;
 	nni_atomic_bool    p_closed;
 	nni_atomic_flag    p_stop;
-	bool               p_cbs;
 	nni_reap_node      p_reap;
 	nni_refcnt         p_refcnt;
+	nng_pipe_ev        p_last_event;
 
 #ifdef NNG_ENABLE_STATS
 	nni_stat_item st_root;
@@ -125,15 +125,13 @@ extern int  nni_sock_add_listener(nni_sock *, nni_listener *);
 extern void nni_sock_remove_listener(nni_listener *);
 extern void nni_sock_remove_dialer(nni_dialer *);
 
-extern void nni_dialer_add_pipe(nni_dialer *, void *);
 extern void nni_dialer_shutdown(nni_dialer *);
 extern void nni_dialer_reap(nni_dialer *);
 extern void nni_dialer_destroy(nni_dialer *);
 extern void nni_dialer_timer_start(nni_dialer *);
 extern void nni_dialer_stop(nni_dialer *);
 
 extern void nni_listener_start_pipe(nni_listener *, nni_pipe *);
-extern void nni_listener_add_pipe(nni_listener *, void *);
 extern void nni_listener_shutdown(nni_listener *);
 extern void nni_listener_reap(nni_listener *);
 extern void nni_listener_destroy(nni_listener *);