fixes #1746 Create a new socket:// transport for socketpair() based connections

This transport only listens, and creates connections when
the application calls setopt on the lister with NNG_OPT_SOCKET_FD,
to pass a file descriptor.  The FD is turned into an nng_stream,
and utilized for SP.  The protocol over the descriptor is identical
to the TCP protocol (not the IPC protocol).

The options for peer information are borrowed from the IPC transport,
as they may be useful for these purposes.

This includes a test suite and full documentation.

1 files changed, 122 insertions, 0 deletions

diff --git a/src/platform/posix/posix_peerid.c b/src/platform/posix/posix_peerid.c
new file mode 100644
index 00000000..e0020150
--- /dev/null
+++ b/src/platform/posix/posix_peerid.c
@@ -0,0 +1,122 @@
+//
+// Copyright 2023 Staysail Systems, Inc. <info@staysail.tech>
+// Copyright 2018 Capitar IT Group BV <info@capitar.com>
+// Copyright 2019 Devolutions <info@devolutions.net>
+//
+// 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"
+
+#include <errno.h>
+#include <fcntl.h>
+#include <poll.h>
+#include <stdbool.h>
+#include <string.h>
+#include <sys/socket.h>
+#include <sys/uio.h>
+#include <sys/un.h>
+
+#if defined(NNG_HAVE_GETPEERUCRED)
+#include <ucred.h>
+#elif defined(NNG_HAVE_LOCALPEERCRED) || defined(NNG_HAVE_SOCKPEERCRED)
+#include <sys/ucred.h>
+#endif
+#if defined(NNG_HAVE_GETPEEREID)
+#include <sys/types.h>
+#include <unistd.h>
+#endif
+
+#ifndef MSG_NOSIGNAL
+#define MSG_NOSIGNAL 0
+#endif
+
+#ifndef SOL_LOCAL
+#define SOL_LOCAL 0
+#endif
+
+
+int
+nni_posix_peerid(int fd, uint64_t *euid, uint64_t *egid, uint64_t *prid,
+    uint64_t *znid)
+{
+#if defined(NNG_HAVE_GETPEEREID) && !defined(NNG_HAVE_LOCALPEERCRED)
+	uid_t uid;
+	gid_t gid;
+
+	if (getpeereid(fd, &uid, &gid) != 0) {
+		return (nni_plat_errno(errno));
+	}
+	*euid = uid;
+	*egid = gid;
+	*prid = (uint64_t) -1;
+	*znid = (uint64_t) -1;
+	return (0);
+#elif defined(NNG_HAVE_GETPEERUCRED)
+	ucred_t *ucp = NULL;
+	if (getpeerucred(fd, &ucp) != 0) {
+		return (nni_plat_errno(errno));
+	}
+	*euid = ucred_geteuid(ucp);
+	*egid = ucred_getegid(ucp);
+	*prid = ucred_getpid(ucp);
+	*znid = ucred_getzoneid(ucp);
+	ucred_free(ucp);
+	return (0);
+#elif defined(NNG_HAVE_SOCKPEERCRED)
+	struct sockpeercred uc;
+	socklen_t           len = sizeof(uc);
+	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &uc, &len) != 0) {
+		return (nni_plat_errno(errno));
+	}
+	*euid = uc.uid;
+	*egid = uc.gid;
+	*prid = uc.pid;
+	*znid = (uint64_t) -1;
+	return (0);
+#elif defined(NNG_HAVE_SOPEERCRED)
+	struct ucred uc;
+	socklen_t    len = sizeof(uc);
+	if (getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &uc, &len) != 0) {
+		return (nni_plat_errno(errno));
+	}
+	*euid = uc.uid;
+	*egid = uc.gid;
+	*prid = uc.pid;
+	*znid = (uint64_t) -1;
+	return (0);
+#elif defined(NNG_HAVE_LOCALPEERCRED)
+	struct xucred xu;
+	socklen_t     len = sizeof(xu);
+	if (getsockopt(fd, SOL_LOCAL, LOCAL_PEERCRED, &xu, &len) != 0) {
+		return (nni_plat_errno(errno));
+	}
+	*euid = xu.cr_uid;
+	*egid = xu.cr_gid;
+	*prid = (uint64_t) -1;
+	*znid = (uint64_t) -1;
+#if defined(NNG_HAVE_LOCALPEERPID) // documented on macOS since 10.8
+	{
+		pid_t pid;
+		if (getsockopt(fd, SOL_LOCAL, LOCAL_PEERPID, &pid, &len) ==
+		    0) {
+			*prid = (uint64_t) pid;
+		}
+	}
+#endif // NNG_HAVE_LOCALPEERPID
+	return (0);
+#else
+	if (fd < 0) {
+		return (NNG_ECLOSED);
+	}
+	NNI_ARG_UNUSED(euid);
+	NNI_ARG_UNUSED(egid);
+	NNI_ARG_UNUSED(prid);
+	NNI_ARG_UNUSED(znid);
+	return (NNG_ENOTSUP);
+#endif
+}
+