fixes #608 Add TCP support to specify local network interface

This also fixes a leaked TCP connection on a failure path, which we
noticed while working this change.

7 files changed, 215 insertions, 28 deletions

diff --git a/src/core/platform.h b/src/core/platform.h
index 70f4e9ef..48f1e1a7 100644
--- a/src/core/platform.h
+++ b/src/core/platform.h
@@ -265,6 +265,15 @@ extern void nni_tcp_dialer_fini(nni_tcp_dialer *);
 // connection will be aborted.
 extern void nni_tcp_dialer_close(nni_tcp_dialer *);
 
+// nni_tcp_dialer_set_src_addr sets the source address to use for outgoing
+// connections.  Only the IP (or IPv6) address may be specified; the port
+// must be zero.  This must be called before calling nni_tcp_dialer_dial.
+// The source address must be associated with one of the addresses on the
+// local system -- this is not checked until bind() is called just prior to
+// the connect() call.  Likewise the address family must be the same as the
+// address used when dialing, or errors will occur.
+extern int nni_tcp_dialer_set_src_addr(nni_tcp_dialer *, const nng_sockaddr *);
+
 // nni_tcp_dialer_dial attempts to create an outgoing connection,
 // asynchronously, to the address specified. On success, the first (and only)
 // output will be an nni_tcp_conn * associated with the remote server.
diff --git a/src/platform/posix/posix_tcp.h b/src/platform/posix/posix_tcp.h
index aefce7f7..633a63b5 100644
--- a/src/platform/posix/posix_tcp.h
+++ b/src/platform/posix/posix_tcp.h
@@ -25,9 +25,11 @@ struct nni_tcp_conn {
 };
 
 struct nni_tcp_dialer {
-	nni_list connq; // pending connections
-	bool     closed;
-	nni_mtx  mtx;
+	nni_list                connq; // pending connections
+	bool                    closed;
+	struct sockaddr_storage src;
+	size_t                  srclen;
+	nni_mtx                 mtx;
 };
 
 struct nni_tcp_listener {
diff --git a/src/platform/posix/posix_tcpdial.c b/src/platform/posix/posix_tcpdial.c
index ab3f3545..918ee9ba 100644
--- a/src/platform/posix/posix_tcpdial.c
+++ b/src/platform/posix/posix_tcpdial.c
@@ -149,6 +149,46 @@ tcp_dialer_cb(nni_posix_pfd *pfd, int ev, void *arg)
 	nni_aio_finish(aio, 0, 0);
 }
 
+int
+nni_tcp_dialer_set_src_addr(nni_tcp_dialer *d, const nni_sockaddr *sa)
+{
+	struct sockaddr_storage ss;
+	struct sockaddr_in *    sin;
+	struct sockaddr_in6 *   sin6;
+	size_t                  sslen;
+
+	if ((sslen = nni_posix_nn2sockaddr(&ss, sa)) == 0) {
+		return (NNG_EADDRINVAL);
+	}
+	// Ensure we are either IPv4 or IPv6, and port is not set.  (We
+	// do not allow binding to a specific port.)
+	switch (ss.ss_family) {
+	case AF_INET:
+		sin = (void *) &ss;
+		if (sin->sin_port != 0) {
+			return (NNG_EADDRINVAL);
+		}
+		break;
+	case AF_INET6:
+		sin6 = (void *) &ss;
+		if (sin6->sin6_port != 0) {
+			return (NNG_EADDRINVAL);
+		}
+		break;
+	default:
+		return (NNG_EADDRINVAL);
+	}
+	nni_mtx_lock(&d->mtx);
+	if (d->closed) {
+		nni_mtx_unlock(&d->mtx);
+		return (NNG_ECLOSED);
+	}
+	d->src    = ss;
+	d->srclen = sslen;
+	nni_mtx_unlock(&d->mtx);
+	return (0);
+}
+
 // We don't give local address binding support.  Outbound dialers always
 // get an ephemeral port.
 void
@@ -196,6 +236,12 @@ nni_tcp_dialer_dial(nni_tcp_dialer *d, const nni_sockaddr *sa, nni_aio *aio)
 		rv = NNG_ECLOSED;
 		goto error;
 	}
+	if (d->srclen != 0) {
+		if ((rv = bind(fd, (void *) &d->src, d->srclen)) != 0) {
+			rv = nni_plat_errno(errno);
+			goto error;
+		}
+	}
 	if ((rv = nni_aio_schedule(aio, tcp_dialer_cancel, d)) != 0) {
 		goto error;
 	}
diff --git a/src/platform/windows/win_tcp.h b/src/platform/windows/win_tcp.h
index 7025af81..9c7a4d0e 100644
--- a/src/platform/windows/win_tcp.h
+++ b/src/platform/windows/win_tcp.h
@@ -39,11 +39,13 @@ struct nni_tcp_conn {
 };
 
 struct nni_tcp_dialer {
-	LPFN_CONNECTEX connectex; // looked up name via ioctl
-	nni_list       aios;      // in flight connections
-	bool           closed;
-	nni_mtx        mtx;
-	nni_reap_item  reap;
+	LPFN_CONNECTEX   connectex; // looked up name via ioctl
+	nni_list         aios;      // in flight connections
+	bool             closed;
+	SOCKADDR_STORAGE src;
+	size_t           srclen;
+	nni_mtx          mtx;
+	nni_reap_item    reap;
 };
 
 struct nni_tcp_listener {
diff --git a/src/platform/windows/win_tcpdial.c b/src/platform/windows/win_tcpdial.c
index 99308ceb..1225b560 100644
--- a/src/platform/windows/win_tcpdial.c
+++ b/src/platform/windows/win_tcpdial.c
@@ -145,6 +145,46 @@ tcp_dial_cb(nni_win_io *io, int rv, size_t cnt)
 	}
 }
 
+int
+nni_tcp_dialer_set_src_addr(nni_tcp_dialer *d, const nni_sockaddr *sa)
+{
+	SOCKADDR_STORAGE     ss;
+	struct sockaddr_in * sin;
+	struct sockaddr_in6 *sin6;
+	size_t               sslen;
+
+	if ((sslen = nni_win_nn2sockaddr(&ss, sa)) == 0) {
+		return (NNG_EADDRINVAL);
+	}
+	// Ensure we are either IPv4 or IPv6, and port is not set.  (We
+	// do not allow binding to a specific port.)
+	switch (ss.ss_family) {
+	case AF_INET:
+		sin = (void *) &ss;
+		if (sin->sin_port != 0) {
+			return (NNG_EADDRINVAL);
+		}
+		break;
+	case AF_INET6:
+		sin6 = (void *) &ss;
+		if (sin6->sin6_port != 0) {
+			return (NNG_EADDRINVAL);
+		}
+		break;
+	default:
+		return (NNG_EADDRINVAL);
+	}
+	nni_mtx_lock(&d->mtx);
+	if (d->closed) {
+		nni_mtx_unlock(&d->mtx);
+		return (NNG_ECLOSED);
+	}
+	d->src    = ss;
+	d->srclen = sslen;
+	nni_mtx_unlock(&d->mtx);
+	return (0);
+}
+
 void
 nni_tcp_dialer_dial(nni_tcp_dialer *d, const nni_sockaddr *sa, nni_aio *aio)
 {
@@ -176,19 +216,7 @@ nni_tcp_dialer_dial(nni_tcp_dialer *d, const nni_sockaddr *sa, nni_aio *aio)
 
 	c->peername = ss;
 
-	// Windows ConnectEx requires the socket to be bound
-	// first. We just bind to an ephemeral address in the
-	// same family.
-	ZeroMemory(&c->sockname, sizeof(c->sockname));
-	c->sockname.ss_family = ss.ss_family;
-	if (bind(s, (SOCKADDR *) &c->sockname, len) < 0) {
-		rv = nni_win_error(GetLastError());
-		nni_tcp_conn_fini(c);
-		nni_aio_finish_error(aio, rv);
-		return;
-	}
 	if ((rv = nni_win_io_init(&c->conn_io, tcp_dial_cb, c)) != 0) {
-		nni_tcp_conn_fini(c);
 		nni_aio_finish_error(aio, rv);
 		return;
 	}
@@ -196,13 +224,34 @@ nni_tcp_dialer_dial(nni_tcp_dialer *d, const nni_sockaddr *sa, nni_aio *aio)
 	nni_mtx_lock(&d->mtx);
 	if (d->closed) {
 		nni_mtx_unlock(&d->mtx);
+		nni_tcp_conn_fini(c);
 		nni_aio_finish_error(aio, NNG_ECLOSED);
 		return;
 	}
+
+	// Windows ConnectEx requires the socket to be bound
+	// first. We just bind to an ephemeral address in the
+	// same family, unless a different default was requested.
+	if (d->srclen != 0) {
+		len = (int) d->srclen;
+		memcpy(&c->sockname, &d->src, len);
+	} else {
+		ZeroMemory(&c->sockname, sizeof(c->sockname));
+		c->sockname.ss_family = ss.ss_family;
+	}
+	if (bind(s, (SOCKADDR *) &c->sockname, len) != 0) {
+		rv = nni_win_error(GetLastError());
+		nni_mtx_unlock(&d->mtx);
+		nni_tcp_conn_fini(c);
+		nni_aio_finish_error(aio, rv);
+		return;
+	}
+
 	c->dialer = d;
 	nni_aio_set_prov_extra(aio, 0, c);
 	if ((rv = nni_aio_schedule(aio, tcp_dial_cancel, d)) != 0) {
 		nni_mtx_unlock(&d->mtx);
+		nni_tcp_conn_fini(c);
 		nni_aio_finish_error(aio, rv);
 		return;
 	}
diff --git a/src/transport/tcp/tcp.c b/src/transport/tcp/tcp.c
index 3a4e018e..017b4ccf 100644
--- a/src/transport/tcp/tcp.c
+++ b/src/transport/tcp/tcp.c
@@ -61,6 +61,8 @@ struct tcptran_ep {
 	bool              keepalive;
 	bool              fini;
 	nni_url *         url;
+	const char *      host; // for dialers
+	nng_sockaddr      src;
 	nng_sockaddr      sa;
 	nng_sockaddr      bsa;
 	nni_list          pipes;
@@ -750,9 +752,11 @@ tcptran_ep_close(void *arg)
 static int
 tcptran_ep_init_dialer(void **dp, nni_url *url, nni_sock *sock)
 {
-	tcptran_ep *ep;
-	int         rv;
-	uint16_t    af;
+	tcptran_ep * ep;
+	int          rv;
+	uint16_t     af;
+	char *       host;
+	nng_sockaddr srcsa;
 
 	if (strcmp(url->u_scheme, "tcp") == 0) {
 		af = NNG_AF_UNSPEC;
@@ -785,11 +789,52 @@ tcptran_ep_init_dialer(void **dp, nni_url *url, nni_sock *sock)
 	ep->keepalive = false;
 	ep->url       = url;
 
-	if ((rv = nni_tcp_dialer_init(&ep->dialer)) != 0) {
+	// Detect an embedded local interface name in the hostname.  This
+	// syntax is only valid with dialers.
+	if ((host = strchr(url->u_hostname, ';')) != NULL) {
+		size_t   len;
+		char *   src = NULL;
+		nni_aio *aio;
+		len = (uintptr_t) host - (uintptr_t) url->u_hostname;
+		host++;
+		if ((len < 2) || (strlen(host) == 0)) {
+			tcptran_ep_fini(ep);
+			return (NNG_EADDRINVAL);
+		}
+		if ((src = nni_alloc(len + 1)) == NULL) {
+			tcptran_ep_fini(ep);
+			return (NNG_ENOMEM);
+		}
+		memcpy(src, url->u_hostname, len);
+		src[len] = 0;
+
+		if ((rv = nni_aio_init(&aio, NULL, NULL)) != 0) {
+			tcptran_ep_fini(ep);
+			nni_strfree(src);
+			return (rv);
+		}
+		nni_aio_set_input(aio, 0, &srcsa);
+		nni_tcp_resolv(src, 0, af, 1, aio);
+		nni_aio_wait(aio);
+		rv = nni_aio_result(aio);
+		nni_aio_fini(aio);
+		nni_strfree(src);
+		ep->host = host;
+	} else {
+		srcsa.s_family = NNG_AF_UNSPEC;
+		ep->host       = url->u_hostname;
+		rv             = 0;
+	}
+
+	if ((rv != 0) || ((rv = nni_tcp_dialer_init(&ep->dialer)) != 0)) {
+		tcptran_ep_fini(ep);
+		return (rv);
+	}
+	if ((srcsa.s_family != NNG_AF_UNSPEC) &&
+	    ((rv = nni_tcp_dialer_set_src_addr(ep->dialer, &srcsa)) != 0)) {
 		tcptran_ep_fini(ep);
 		return (rv);
 	}
-
 	*dp = ep;
 	return (0);
 }
@@ -897,8 +942,7 @@ tcptran_ep_connect(void *arg, nni_aio *aio)
 	p->useraio = aio;
 	// Start the name resolution before we try connecting.
 	nni_aio_set_input(p->rslvaio, 0, &p->sa);
-	nni_tcp_resolv(
-	    ep->url->u_hostname, ep->url->u_port, ep->af, 0, p->rslvaio);
+	nni_tcp_resolv(ep->host, ep->url->u_port, ep->af, 0, p->rslvaio);
 	nni_mtx_unlock(&ep->mtx);
 }
 
diff --git a/tests/tcp.c b/tests/tcp.c
index 0018fce7..d13cc83d 100644
--- a/tests/tcp.c
+++ b/tests/tcp.c
@@ -59,7 +59,6 @@ check_props_v4(nng_msg *msg)
 }
 
 TestMain("TCP Transport", {
-
 	trantest_test_extended("tcp://127.0.0.1:%u", check_props_v4);
 
 	Convey("We cannot connect to wild cards", {
@@ -109,6 +108,42 @@ TestMain("TCP Transport", {
 		nng_strfree(addr);
 	});
 
+	Convey("We can use local interface to connet", {
+		nng_socket s1;
+		nng_socket s2;
+		char       addr[NNG_MAXADDRLEN];
+
+		So(nng_pair_open(&s1) == 0);
+		So(nng_pair_open(&s2) == 0);
+		Reset({
+			nng_close(s2);
+			nng_close(s1);
+		});
+		trantest_next_address(addr, "tcp://127.0.0.1:%u");
+		So(nng_listen(s1, addr, NULL, 0) == 0);
+		// reset port back one
+		trantest_prev_address(addr, "tcp://127.0.0.1;127.0.0.1:%u");
+		So(nng_dial(s2, addr, NULL, 0) == 0);
+	});
+
+	Convey("Botched local interfaces fail resonably", {
+		nng_socket s1;
+
+		So(nng_pair_open(&s1) == 0);
+		Reset({ nng_close(s1); });
+		So(nng_dial(s1, "tcp://1x.2;127.0.0.1:80", NULL, 0) ==
+		    NNG_EADDRINVAL);
+	});
+
+	Convey("Can't specify address that isn't ours", {
+		nng_socket s1;
+
+		So(nng_pair_open(&s1) == 0);
+		Reset({ nng_close(s1); });
+		So(nng_dial(s1, "tcp://8.8.8.8;127.0.0.1:80", NULL, 0) ==
+		    NNG_EADDRINVAL);
+	});
+
 	Convey("Malformed TCP addresses do not panic", {
 		nng_socket s1;