POSIX poller: add support for select, and for choosing the poller

Some platforms or configurations may not have more modern options
like kqueue or epoll, or may be constrained by policy.

src/platform/posix/CMakeLists.txt

@@ -60,6 +60,8 @@ if (NNG_PLATFORM_POSIX)
     nng_check_sym(port_create port.h NNG_HAVE_PORT_CREATE)
     nng_check_sym(epoll_create sys/epoll.h NNG_HAVE_EPOLL)
     nng_check_sym(epoll_create1 sys/epoll.h NNG_HAVE_EPOLL_CREATE1)
+    nng_check_sym(poll poll.h NNG_HAVE_POLL)
+    nng_check_sym(select sys/select.h NNG_HAVE_SELECT)
     nng_check_sym(getpeereid unistd.h NNG_HAVE_GETPEEREID)
     nng_check_sym(SO_PEERCRED sys/socket.h NNG_HAVE_SOPEERCRED)
     nng_check_struct_member(sockpeercred uid sys/socket.h NNG_HAVE_SOCKPEERCRED)
@@ -101,14 +103,48 @@ if (NNG_PLATFORM_POSIX)
             posix_udp.c
     )
 
-    if (NNG_HAVE_PORT_CREATE)
-        nng_sources(posix_pollq_port.c)
+    set(NNG_POLLQ_POLLER "auto" CACHE STRING "Poller used for multiplexing I/O")
+    set_property(CACHE NNG_POLLQ_POLLER PROPERTY STRINGS auto ports kqueue epoll poll select)
+    mark_as_advanced(NNG_POLLQ_POLLER)
+    if (NNG_POLLQ_POLLER STREQUAL "ports")
+        nng_defines(NNG_POLLQ_PORTS)
+    elseif (NNG_POLLQ_POLLER STREQUAL "kqueue")
+        nng_defines(NNG_POLLQ_KQUEUE)
+    elseif (NNG_POLLQ_POLLER STREQUAL "epoll")
+        nng_defines(NNG_POLLQ_EPOLL)
+    elseif (NNG_POLLQ_POLLER STREQUAL "poll")
+        nng_defines(NNG_POLLQ_POLL)
+    elseif (NNG_POLLQ_POLLER STREQUAL "select")
+        set(NNG_POLLQ_SELECT ON)
+    elseif (NNG_HAVE_PORT_CREATE)
+        set(NNG_POLLQ_PORTS ON)
     elseif (NNG_HAVE_KQUEUE)
-        nng_sources(posix_pollq_kqueue.c)
+        set(NNG_POLLQ_KQUEUE ON)
     elseif (NNG_HAVE_EPOLL AND NNG_HAVE_EVENTFD)
+        set(NNG_POLLQ_EPOLL ON)
+    elseif (NNG_HAVE_POLL)
+        set(NNG_POLLQ_POLL ON)
+    elseif (NNG_HAVE_SELECT)
+        set(NNG_POLLQ_SELECT TRUE)
+    endif()
+
+    if (NNG_POLLQ_PORTS)
+        message(STATUS "Using port events for multiplexing I/O.")
+        nng_sources(posix_pollq_port.c)
+    elseif (NNG_POLLQ_KQUEUE)
+        message(STATUS "Using kqueue for multiplexing I/O.")
+        nng_sources(posix_pollq_kqueue.c)
+    elseif (NNG_POLLQ_EPOLL)
+        message(DEBUG "Using epoll for multiplexing I/O.")
         nng_sources(posix_pollq_epoll.c)
-    else ()
+    elseif (NNG_POLLQ_POLL)
+        message(STATUS "Using poll for multiplexing I/O.")
         nng_sources(posix_pollq_poll.c)
+    elseif (NNG_POLLQ_SELECT)
+        message(STATUS "Using select for multiplexing I/O.")
+        nng_sources(posix_pollq_select.c)
+    else()
+        message(FATAL_ERROR "No suitable poller found for multiplexing I/O.")
     endif ()
 
     if (NNG_HAVE_ARC4RANDOM)

src/platform/posix/posix_ipcconn.c

@@ -264,7 +264,7 @@ ipc_send(void *arg, nni_aio *aio)
 		// means we didn't finish the job, so arm the poller to
 		// complete us.
 		if (nni_list_first(&c->writeq) == aio) {
-			nni_posix_pfd_arm(c->pfd, POLLOUT);
+			nni_posix_pfd_arm(c->pfd, NNI_POLL_OUT);
 		}
 	}
 	nni_mtx_unlock(&c->mtx);
@@ -298,7 +298,7 @@ ipc_recv(void *arg, nni_aio *aio)
 		// means we didn't finish the job, so arm the poller to
 		// complete us.
 		if (nni_list_first(&c->readq) == aio) {
-			nni_posix_pfd_arm(c->pfd, POLLIN);
+			nni_posix_pfd_arm(c->pfd, NNI_POLL_IN);
 		}
 	}
 	nni_mtx_unlock(&c->mtx);

src/platform/posix/posix_pollq.h

@@ -32,11 +32,20 @@ extern int  nni_posix_pfd_fd(nni_posix_pfd *);
 extern void nni_posix_pfd_close(nni_posix_pfd *);
 extern void nni_posix_pfd_set_cb(nni_posix_pfd *, nni_posix_pfd_cb, void *);
 
+#ifdef POLLIN
 #define NNI_POLL_IN ((unsigned) POLLIN)
 #define NNI_POLL_OUT ((unsigned) POLLOUT)
 #define NNI_POLL_HUP ((unsigned) POLLHUP)
 #define NNI_POLL_ERR ((unsigned) POLLERR)
 #define NNI_POLL_INVAL ((unsigned) POLLNVAL)
+#else
+// maybe using select
+#define NNI_POLL_IN (0x0001)
+#define NNI_POLL_OUT (0x0010)
+#define NNI_POLL_HUP (0x0004)
+#define NNI_POLL_ERR (0x0008)
+#define NNI_POLL_INVAL (0x0020)
+#endif // POLLIN
 
 #endif // NNG_PLATFORM_POSIX
 

src/platform/posix/posix_pollq_kqueue.c

@@ -198,10 +198,10 @@ nni_posix_pfd_arm(nni_posix_pfd *pf, unsigned events)
 		return (0);
 	}
 
-	if (events & POLLIN) {
+	if (events & NNI_POLL_IN) {
 		EV_SET(&ev[nev++], pf->fd, EVFILT_READ, flags, 0, 0, pf);
 	}
-	if (events & POLLOUT) {
+	if (events & NNI_POLL_OUT) {
 		EV_SET(&ev[nev++], pf->fd, EVFILT_WRITE, flags, 0, 0, pf);
 	}
 	while (kevent(pq->kq, ev, nev, NULL, 0, NULL) != 0) {
@@ -254,10 +254,10 @@ nni_posix_poll_thr(void *arg)
 
 			switch (ev->filter) {
 			case EVFILT_READ:
-				revents = POLLIN;
+				revents = NNI_POLL_IN;
 				break;
 			case EVFILT_WRITE:
-				revents = POLLOUT;
+				revents = NNI_POLL_OUT;
 				break;
 			}
 			if (ev->udata == NULL) {
@@ -267,7 +267,7 @@ nni_posix_poll_thr(void *arg)
 			}
 			pf = (void *) ev->udata;
 			if (ev->flags & EV_ERROR) {
-				revents |= POLLHUP;
+				revents |= NNI_POLL_HUP;
 			}
 
 			nni_mtx_lock(&pf->mtx);