Create nng_socket_pair

include/nng/supplemental/util/platform.h

@@ -104,6 +104,13 @@ NNG_DECL void nng_cv_wake1(nng_cv *);
 // nng_random returns a "strong" (cryptographic sense) random number.
 NNG_DECL uint32_t nng_random(void);
 
+// nng_socket_pair is used to create a bound pair of file descriptors
+// typically using the socketpair() call.  The descriptors are backed
+// by reliable, bidirectional, byte streams.  This will return NNG_ENOTSUP
+// if the platform lacks support for this.  The argument is a pointer
+// to an array of file descriptors (or HANDLES or similar).
+NNG_DECL int nng_socket_pair(int *);
+
 #ifdef __cplusplus
 }
 #endif

src/core/platform.h

@@ -386,9 +386,9 @@ extern int nni_ipc_listener_alloc(nng_stream_listener **, const nng_url *);
 typedef struct nni_plat_udp nni_plat_udp;
 
 // nni_plat_udp_open initializes a UDP socket, binding to the local
-// address specified specified in the AIO.  The remote address is
+// address specified in the AIO.  The remote address is
 // not used.  The resulting nni_plat_udp structure is returned in the
-// the aio's a_pipe.
+// aio's a_pipe.
 extern int nni_plat_udp_open(nni_plat_udp **, nni_sockaddr *);
 
 // nni_plat_udp_close closes the underlying UDP socket.
@@ -434,6 +434,19 @@ extern void nni_plat_pipe_close(int, int);
 
 extern int nni_plat_udp_sockname(nni_plat_udp *, nni_sockaddr *);
 
+// nni_socket_pair is used to create a socket pair using socketpair()
+// on POSIX systems.  (Windows might provide a similar solution, using
+// AF_UNIX at some point, in which case the arguments will actually be
+// an array of HANDLEs.)  If not supported, this returns NNG_ENOTSUP.
+//
+// This API can only create a pair of open file descriptors, suitable for use
+// with the fdconn transport, each bound to the other.  The transport must be
+// a bidirectional reliable byte stream.  This should be suitable for use
+// in APIs to transport file descriptors, or across a fork/exec boundary (so
+// that child processes may use these with fdconn to inherit a socket that is
+// connected to the parent.)
+extern int nni_socket_pair(int *);
+
 //
 // File/Store Support
 //

src/platform/posix/CMakeLists.txt

@@ -1,5 +1,5 @@
 #
-# Copyright 2020 Staysail Systems, Inc. <[email protected]>
+# Copyright 2023 Staysail Systems, Inc. <[email protected]>
 #
 # This software is supplied under the terms of the MIT License, a
 # copy of which should be located in the distribution where this
@@ -61,6 +61,7 @@ if (NNG_PLATFORM_POSIX)
     nng_check_sym(LOCAL_PEERPID sys/un.h NNG_HAVE_LOCALPEERPID)
     nng_check_sym(getpeerucred ucred.h NNG_HAVE_GETPEERUCRED)
     nng_check_sym(atomic_flag_test_and_set stdatomic.h NNG_HAVE_STDATOMIC)
+    nng_check_sym(socketpair sys/socket.h NNG_HAVE_SOCKETPAIR)
 
     nng_sources(
             posix_impl.h
@@ -82,6 +83,7 @@ if (NNG_PLATFORM_POSIX)
             posix_pipe.c
             posix_resolv_gai.c
             posix_sockaddr.c
+            posix_socketpair.c
             posix_tcpconn.c
             posix_tcpdial.c
             posix_tcplisten.c

src/platform/posix/posix_socketpair.c

@@ -0,0 +1,37 @@
+//
+// Copyright 2023 Staysail Systems, Inc. <[email protected]>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+#include "core/nng_impl.h"
+
+#ifdef NNG_HAVE_SOCKETPAIR
+// This provides an implementation of socketpair(), which is supposed
+// to be present on XPG6 and newer.  This trivial implementation
+// only supports SOCK_STREAM over AF_UNIX.  Which is sufficient for
+// most purposes.  The fds array should point to an int[2].
+#include <errno.h>
+#include <sys/socket.h>
+
+int
+nni_socket_pair(int *fds)
+{
+	int rv;
+	rv = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
+	if (rv != 0) {
+		return (nni_plat_errno(errno));
+	}
+
+	return (0);
+}
+#else
+int
+nni_socket_pair(int *fds)
+{
+	return (NNG_ENOTSUP);
+}
+#endif

src/platform/windows/CMakeLists.txt

@@ -39,6 +39,7 @@ if (NNG_PLATFORM_WINDOWS)
             win_rand.c
             win_resolv.c
             win_sockaddr.c
+            win_socketpair.c
             win_tcp.c
             win_tcpconn.c
             win_tcpdial.c

src/platform/windows/win_socketpair.c

@@ -0,0 +1,37 @@
+//
+// Copyright 2023 Staysail Systems, Inc. <[email protected]>
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+#include "core/nng_impl.h"
+
+
+#ifdef NNG_HAVE_SOCKETPAIR_TODO
+// TODO: Windows lacks socketpair.  We can emulate it with an explcit
+// implementation based on AF_UNIX.
+
+#include <errno.h>
+#include <sys/socket.h>
+
+int
+nni_socket_pair(int *fds)
+{
+	int rv;
+	rv = socketpair(PF_UNIX, SOCK_STREAM, 0, fds);
+	if (rv != 0) {
+		return (nni_plat_errno(errno));
+	}
+
+	return (0);
+}
+#else
+int
+nni_socket_pair(int *fds)
+{
+	return (NNG_ENOTSUP);
+}
+#endif

src/sp/transport/fdconn/fdc_test.c

@@ -23,27 +23,6 @@ test_fdc_connect_fail(void)
 	NUTS_CLOSE(s);
 }
 
-void
-test_tcp_local_address_connect(void)
-{
-
-	nng_socket s1;
-	nng_socket s2;
-	char       addr[NNG_MAXADDRLEN];
-	uint16_t   port;
-
-	NUTS_OPEN(s1);
-	NUTS_OPEN(s2);
-	port = nuts_next_port();
-	(void) snprintf(addr, sizeof(addr), "tcp://127.0.0.1:%u", port);
-	NUTS_PASS(nng_listen(s1, addr, NULL, 0));
-	(void) snprintf(
-	    addr, sizeof(addr), "tcp://127.0.0.1;127.0.0.1:%u", port);
-	NUTS_PASS(nng_dial(s2, addr, NULL, 0));
-	NUTS_CLOSE(s2);
-	NUTS_CLOSE(s1);
-}
-
 void
 test_fdc_malformed_address(void)
 {
@@ -64,15 +43,14 @@ test_fdc_listen(void)
 	NUTS_CLOSE(s1);
 }
 
-#include <sys/socket.h>
 void
 test_fdc_accept(void)
 {
 	nng_socket s1, s2;
 	nng_listener l;
 	int fds[2];
 
-	NUTS_PASS(socketpair(PF_UNIX, SOCK_STREAM, 0, fds));
+	NUTS_PASS(nng_socket_pair(fds));
 	// make sure we won't have to deal with SIGPIPE - EPIPE is better
 	signal(SIGPIPE, SIG_IGN);
 	NUTS_OPEN(s1);
@@ -93,7 +71,7 @@ test_fdc_exchange(void)
 	nng_listener l1, l2;
 	int fds[2];
 
-	NUTS_PASS(socketpair(PF_UNIX, SOCK_STREAM, 0, fds));
+	NUTS_PASS(nng_socket_pair(fds));
 	// make sure we won't have to deal with SIGPIPE - EPIPE is better
 	signal(SIGPIPE, SIG_IGN);
 	NUTS_OPEN(s1);
@@ -127,7 +105,7 @@ test_fdc_recv_max(void)
 	size_t       sz;
 	int fds[2];
 
-	NUTS_PASS(socketpair(PF_UNIX, SOCK_STREAM, 0, fds));
+	NUTS_PASS(nng_socket_pair(fds));
 
 	NUTS_OPEN(s0);
 	NUTS_PASS(nng_socket_set_ms(s0, NNG_OPT_RECVTIMEO, 100));
@@ -157,11 +135,12 @@ NUTS_TESTS = {
 
 	{ "fdc connect fail", test_fdc_connect_fail },
 	{ "fdc malformed address", test_fdc_malformed_address },
+#ifdef NNG_HAVE_SOCKETPAIR
 	{ "fdc listen", test_fdc_listen },
 	{ "fdc accept", test_fdc_accept },
 	{ "fdc exchange", test_fdc_exchange },
 	{ "fdc recv max", test_fdc_recv_max },
+#endif
 
-	// { "fdc recv max", test_tcp_recv_max },
 	{ NULL, NULL },
 };

src/supplemental/util/platform.c

@@ -164,3 +164,9 @@ nng_random(void)
 	(void) nni_init();
 	return (nni_random());
 }
+
+int
+nng_socket_pair(int *fds)
+{
+	return (nni_socket_pair(fds));
+}