Adding upstream version 15.5.upstream/15.5

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 1976 insertions, 0 deletions

diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
new file mode 100644
index 0000000..75392a8
--- /dev/null
+++ b/src/backend/libpq/pqcomm.c
@@ -0,0 +1,1976 @@
+/*-------------------------------------------------------------------------
+ *
+ * pqcomm.c
+ *	  Communication functions between the Frontend and the Backend
+ *
+ * These routines handle the low-level details of communication between
+ * frontend and backend.  They just shove data across the communication
+ * channel, and are ignorant of the semantics of the data.
+ *
+ * To emit an outgoing message, use the routines in pqformat.c to construct
+ * the message in a buffer and then emit it in one call to pq_putmessage.
+ * There are no functions to send raw bytes or partial messages; this
+ * ensures that the channel will not be clogged by an incomplete message if
+ * execution is aborted by ereport(ERROR) partway through the message.
+ *
+ * At one time, libpq was shared between frontend and backend, but now
+ * the backend's "backend/libpq" is quite separate from "interfaces/libpq".
+ * All that remains is similarities of names to trap the unwary...
+ *
+ * Portions Copyright (c) 1996-2022, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *	src/backend/libpq/pqcomm.c
+ *
+ *-------------------------------------------------------------------------
+ */
+
+/*------------------------
+ * INTERFACE ROUTINES
+ *
+ * setup/teardown:
+ *		StreamServerPort	- Open postmaster's server port
+ *		StreamConnection	- Create new connection with client
+ *		StreamClose			- Close a client/backend connection
+ *		TouchSocketFiles	- Protect socket files against /tmp cleaners
+ *		pq_init			- initialize libpq at backend startup
+ *		socket_comm_reset	- reset libpq during error recovery
+ *		socket_close		- shutdown libpq at backend exit
+ *
+ * low-level I/O:
+ *		pq_getbytes		- get a known number of bytes from connection
+ *		pq_getmessage	- get a message with length word from connection
+ *		pq_getbyte		- get next byte from connection
+ *		pq_peekbyte		- peek at next byte from connection
+ *		pq_flush		- flush pending output
+ *		pq_flush_if_writable - flush pending output if writable without blocking
+ *		pq_getbyte_if_available - get a byte if available without blocking
+ *
+ * message-level I/O
+ *		pq_putmessage	- send a normal message (suppressed in COPY OUT mode)
+ *		pq_putmessage_noblock - buffer a normal message (suppressed in COPY OUT)
+ *
+ *------------------------
+ */
+#include "postgres.h"
+
+#ifdef HAVE_POLL_H
+#include <poll.h>
+#endif
+#include <signal.h>
+#include <fcntl.h>
+#include <grp.h>
+#include <unistd.h>
+#include <sys/file.h>
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <sys/time.h>
+#include <netdb.h>
+#include <netinet/in.h>
+#ifdef HAVE_NETINET_TCP_H
+#include <netinet/tcp.h>
+#endif
+#include <utime.h>
+#ifdef _MSC_VER					/* mstcpip.h is missing on mingw */
+#include <mstcpip.h>
+#endif
+
+#include "common/ip.h"
+#include "libpq/libpq.h"
+#include "miscadmin.h"
+#include "port/pg_bswap.h"
+#include "storage/ipc.h"
+#include "utils/guc.h"
+#include "utils/memutils.h"
+
+/*
+ * Cope with the various platform-specific ways to spell TCP keepalive socket
+ * options.  This doesn't cover Windows, which as usual does its own thing.
+ */
+#if defined(TCP_KEEPIDLE)
+/* TCP_KEEPIDLE is the name of this option on Linux and *BSD */
+#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPIDLE
+#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPIDLE"
+#elif defined(TCP_KEEPALIVE_THRESHOLD)
+/* TCP_KEEPALIVE_THRESHOLD is the name of this option on Solaris >= 11 */
+#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPALIVE_THRESHOLD
+#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPALIVE_THRESHOLD"
+#elif defined(TCP_KEEPALIVE) && defined(__darwin__)
+/* TCP_KEEPALIVE is the name of this option on macOS */
+/* Caution: Solaris has this symbol but it means something different */
+#define PG_TCP_KEEPALIVE_IDLE TCP_KEEPALIVE
+#define PG_TCP_KEEPALIVE_IDLE_STR "TCP_KEEPALIVE"
+#endif
+
+/*
+ * Configuration options
+ */
+int			Unix_socket_permissions;
+char	   *Unix_socket_group;
+
+/* Where the Unix socket files are (list of palloc'd strings) */
+static List *sock_paths = NIL;
+
+/*
+ * Buffers for low-level I/O.
+ *
+ * The receive buffer is fixed size. Send buffer is usually 8k, but can be
+ * enlarged by pq_putmessage_noblock() if the message doesn't fit otherwise.
+ */
+
+#define PQ_SEND_BUFFER_SIZE 8192
+#define PQ_RECV_BUFFER_SIZE 8192
+
+static char *PqSendBuffer;
+static int	PqSendBufferSize;	/* Size send buffer */
+static int	PqSendPointer;		/* Next index to store a byte in PqSendBuffer */
+static int	PqSendStart;		/* Next index to send a byte in PqSendBuffer */
+
+static char PqRecvBuffer[PQ_RECV_BUFFER_SIZE];
+static int	PqRecvPointer;		/* Next index to read a byte from PqRecvBuffer */
+static int	PqRecvLength;		/* End of data available in PqRecvBuffer */
+
+/*
+ * Message status
+ */
+static bool PqCommBusy;			/* busy sending data to the client */
+static bool PqCommReadingMsg;	/* in the middle of reading a message */
+
+
+/* Internal functions */
+static void socket_comm_reset(void);
+static void socket_close(int code, Datum arg);
+static void socket_set_nonblocking(bool nonblocking);
+static int	socket_flush(void);
+static int	socket_flush_if_writable(void);
+static bool socket_is_send_pending(void);
+static int	socket_putmessage(char msgtype, const char *s, size_t len);
+static void socket_putmessage_noblock(char msgtype, const char *s, size_t len);
+static int	internal_putbytes(const char *s, size_t len);
+static int	internal_flush(void);
+
+#ifdef HAVE_UNIX_SOCKETS
+static int	Lock_AF_UNIX(const char *unixSocketDir, const char *unixSocketPath);
+static int	Setup_AF_UNIX(const char *sock_path);
+#endif							/* HAVE_UNIX_SOCKETS */
+
+static const PQcommMethods PqCommSocketMethods = {
+	socket_comm_reset,
+	socket_flush,
+	socket_flush_if_writable,
+	socket_is_send_pending,
+	socket_putmessage,
+	socket_putmessage_noblock
+};
+
+const PQcommMethods *PqCommMethods = &PqCommSocketMethods;
+
+WaitEventSet *FeBeWaitSet;
+
+
+/* --------------------------------
+ *		pq_init - initialize libpq at backend startup
+ * --------------------------------
+ */
+void
+pq_init(void)
+{
+	int			socket_pos PG_USED_FOR_ASSERTS_ONLY;
+	int			latch_pos PG_USED_FOR_ASSERTS_ONLY;
+
+	/* initialize state variables */
+	PqSendBufferSize = PQ_SEND_BUFFER_SIZE;
+	PqSendBuffer = MemoryContextAlloc(TopMemoryContext, PqSendBufferSize);
+	PqSendPointer = PqSendStart = PqRecvPointer = PqRecvLength = 0;
+	PqCommBusy = false;
+	PqCommReadingMsg = false;
+
+	/* set up process-exit hook to close the socket */
+	on_proc_exit(socket_close, 0);
+
+	/*
+	 * In backends (as soon as forked) we operate the underlying socket in
+	 * nonblocking mode and use latches to implement blocking semantics if
+	 * needed. That allows us to provide safely interruptible reads and
+	 * writes.
+	 *
+	 * Use COMMERROR on failure, because ERROR would try to send the error to
+	 * the client, which might require changing the mode again, leading to
+	 * infinite recursion.
+	 */
+#ifndef WIN32
+	if (!pg_set_noblock(MyProcPort->sock))
+		ereport(COMMERROR,
+				(errmsg("could not set socket to nonblocking mode: %m")));
+#endif
+
+	FeBeWaitSet = CreateWaitEventSet(TopMemoryContext, FeBeWaitSetNEvents);
+	socket_pos = AddWaitEventToSet(FeBeWaitSet, WL_SOCKET_WRITEABLE,
+								   MyProcPort->sock, NULL, NULL);
+	latch_pos = AddWaitEventToSet(FeBeWaitSet, WL_LATCH_SET, PGINVALID_SOCKET,
+								  MyLatch, NULL);
+	AddWaitEventToSet(FeBeWaitSet, WL_POSTMASTER_DEATH, PGINVALID_SOCKET,
+					  NULL, NULL);
+
+	/*
+	 * The event positions match the order we added them, but let's sanity
+	 * check them to be sure.
+	 */
+	Assert(socket_pos == FeBeWaitSetSocketPos);
+	Assert(latch_pos == FeBeWaitSetLatchPos);
+}
+
+/* --------------------------------
+ *		socket_comm_reset - reset libpq during error recovery
+ *
+ * This is called from error recovery at the outer idle loop.  It's
+ * just to get us out of trouble if we somehow manage to elog() from
+ * inside a pqcomm.c routine (which ideally will never happen, but...)
+ * --------------------------------
+ */
+static void
+socket_comm_reset(void)
+{
+	/* Do not throw away pending data, but do reset the busy flag */
+	PqCommBusy = false;
+}
+
+/* --------------------------------
+ *		socket_close - shutdown libpq at backend exit
+ *
+ * This is the one pg_on_exit_callback in place during BackendInitialize().
+ * That function's unusual signal handling constrains that this callback be
+ * safe to run at any instant.
+ * --------------------------------
+ */
+static void
+socket_close(int code, Datum arg)
+{
+	/* Nothing to do in a standalone backend, where MyProcPort is NULL. */
+	if (MyProcPort != NULL)
+	{
+#ifdef ENABLE_GSS
+		/*
+		 * Shutdown GSSAPI layer.  This section does nothing when interrupting
+		 * BackendInitialize(), because pg_GSS_recvauth() makes first use of
+		 * "ctx" and "cred".
+		 *
+		 * Note that we don't bother to free MyProcPort->gss, since we're
+		 * about to exit anyway.
+		 */
+		if (MyProcPort->gss)
+		{
+			OM_uint32	min_s;
+
+			if (MyProcPort->gss->ctx != GSS_C_NO_CONTEXT)
+				gss_delete_sec_context(&min_s, &MyProcPort->gss->ctx, NULL);
+
+			if (MyProcPort->gss->cred != GSS_C_NO_CREDENTIAL)
+				gss_release_cred(&min_s, &MyProcPort->gss->cred);
+		}
+#endif							/* ENABLE_GSS */
+
+		/*
+		 * Cleanly shut down SSL layer.  Nowhere else does a postmaster child
+		 * call this, so this is safe when interrupting BackendInitialize().
+		 */
+		secure_close(MyProcPort);
+
+		/*
+		 * Formerly we did an explicit close() here, but it seems better to
+		 * leave the socket open until the process dies.  This allows clients
+		 * to perform a "synchronous close" if they care --- wait till the
+		 * transport layer reports connection closure, and you can be sure the
+		 * backend has exited.
+		 *
+		 * We do set sock to PGINVALID_SOCKET to prevent any further I/O,
+		 * though.
+		 */
+		MyProcPort->sock = PGINVALID_SOCKET;
+	}
+}
+
+
+
+/*
+ * Streams -- wrapper around Unix socket system calls
+ *
+ *
+ *		Stream functions are used for vanilla TCP connection protocol.
+ */
+
+
+/*
+ * StreamServerPort -- open a "listening" port to accept connections.
+ *
+ * family should be AF_UNIX or AF_UNSPEC; portNumber is the port number.
+ * For AF_UNIX ports, hostName should be NULL and unixSocketDir must be
+ * specified.  For TCP ports, hostName is either NULL for all interfaces or
+ * the interface to listen on, and unixSocketDir is ignored (can be NULL).
+ *
+ * Successfully opened sockets are added to the ListenSocket[] array (of
+ * length MaxListen), at the first position that isn't PGINVALID_SOCKET.
+ *
+ * RETURNS: STATUS_OK or STATUS_ERROR
+ */
+
+int
+StreamServerPort(int family, const char *hostName, unsigned short portNumber,
+				 const char *unixSocketDir,
+				 pgsocket ListenSocket[], int MaxListen)
+{
+	pgsocket	fd;
+	int			err;
+	int			maxconn;
+	int			ret;
+	char		portNumberStr[32];
+	const char *familyDesc;
+	char		familyDescBuf[64];
+	const char *addrDesc;
+	char		addrBuf[NI_MAXHOST];
+	char	   *service;
+	struct addrinfo *addrs = NULL,
+			   *addr;
+	struct addrinfo hint;
+	int			listen_index = 0;
+	int			added = 0;
+
+#ifdef HAVE_UNIX_SOCKETS
+	char		unixSocketPath[MAXPGPATH];
+#endif
+#if !defined(WIN32) || defined(IPV6_V6ONLY)
+	int			one = 1;
+#endif
+
+	/* Initialize hint structure */
+	MemSet(&hint, 0, sizeof(hint));
+	hint.ai_family = family;
+	hint.ai_flags = AI_PASSIVE;
+	hint.ai_socktype = SOCK_STREAM;
+
+#ifdef HAVE_UNIX_SOCKETS
+	if (family == AF_UNIX)
+	{
+		/*
+		 * Create unixSocketPath from portNumber and unixSocketDir and lock
+		 * that file path
+		 */
+		UNIXSOCK_PATH(unixSocketPath, portNumber, unixSocketDir);
+		if (strlen(unixSocketPath) >= UNIXSOCK_PATH_BUFLEN)
+		{
+			ereport(LOG,
+					(errmsg("Unix-domain socket path \"%s\" is too long (maximum %d bytes)",
+							unixSocketPath,
+							(int) (UNIXSOCK_PATH_BUFLEN - 1))));
+			return STATUS_ERROR;
+		}
+		if (Lock_AF_UNIX(unixSocketDir, unixSocketPath) != STATUS_OK)
+			return STATUS_ERROR;
+		service = unixSocketPath;
+	}
+	else
+#endif							/* HAVE_UNIX_SOCKETS */
+	{
+		snprintf(portNumberStr, sizeof(portNumberStr), "%d", portNumber);
+		service = portNumberStr;
+	}
+
+	ret = pg_getaddrinfo_all(hostName, service, &hint, &addrs);
+	if (ret || !addrs)
+	{
+		if (hostName)
+			ereport(LOG,
+					(errmsg("could not translate host name \"%s\", service \"%s\" to address: %s",
+							hostName, service, gai_strerror(ret))));
+		else
+			ereport(LOG,
+					(errmsg("could not translate service \"%s\" to address: %s",
+							service, gai_strerror(ret))));
+		if (addrs)
+			pg_freeaddrinfo_all(hint.ai_family, addrs);
+		return STATUS_ERROR;
+	}
+
+	for (addr = addrs; addr; addr = addr->ai_next)
+	{
+		if (family != AF_UNIX && addr->ai_family == AF_UNIX)
+		{
+			/*
+			 * Only set up a unix domain socket when they really asked for it.
+			 * The service/port is different in that case.
+			 */
+			continue;
+		}
+
+		/* See if there is still room to add 1 more socket. */
+		for (; listen_index < MaxListen; listen_index++)
+		{
+			if (ListenSocket[listen_index] == PGINVALID_SOCKET)
+				break;
+		}
+		if (listen_index >= MaxListen)
+		{
+			ereport(LOG,
+					(errmsg("could not bind to all requested addresses: MAXLISTEN (%d) exceeded",
+							MaxListen)));
+			break;
+		}
+
+		/* set up address family name for log messages */
+		switch (addr->ai_family)
+		{
+			case AF_INET:
+				familyDesc = _("IPv4");
+				break;
+#ifdef HAVE_IPV6
+			case AF_INET6:
+				familyDesc = _("IPv6");
+				break;
+#endif
+#ifdef HAVE_UNIX_SOCKETS
+			case AF_UNIX:
+				familyDesc = _("Unix");
+				break;
+#endif
+			default:
+				snprintf(familyDescBuf, sizeof(familyDescBuf),
+						 _("unrecognized address family %d"),
+						 addr->ai_family);
+				familyDesc = familyDescBuf;
+				break;
+		}
+
+		/* set up text form of address for log messages */
+#ifdef HAVE_UNIX_SOCKETS
+		if (addr->ai_family == AF_UNIX)
+			addrDesc = unixSocketPath;
+		else
+#endif
+		{
+			pg_getnameinfo_all((const struct sockaddr_storage *) addr->ai_addr,
+							   addr->ai_addrlen,
+							   addrBuf, sizeof(addrBuf),
+							   NULL, 0,
+							   NI_NUMERICHOST);
+			addrDesc = addrBuf;
+		}
+
+		if ((fd = socket(addr->ai_family, SOCK_STREAM, 0)) == PGINVALID_SOCKET)
+		{
+			ereport(LOG,
+					(errcode_for_socket_access(),
+			/* translator: first %s is IPv4, IPv6, or Unix */
+					 errmsg("could not create %s socket for address \"%s\": %m",
+							familyDesc, addrDesc)));
+			continue;
+		}
+
+#ifndef WIN32
+
+		/*
+		 * Without the SO_REUSEADDR flag, a new postmaster can't be started
+		 * right away after a stop or crash, giving "address already in use"
+		 * error on TCP ports.
+		 *
+		 * On win32, however, this behavior only happens if the
+		 * SO_EXCLUSIVEADDRUSE is set. With SO_REUSEADDR, win32 allows
+		 * multiple servers to listen on the same address, resulting in
+		 * unpredictable behavior. With no flags at all, win32 behaves as Unix
+		 * with SO_REUSEADDR.
+		 */
+		if (addr->ai_family != AF_UNIX)
+		{
+			if ((setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
+							(char *) &one, sizeof(one))) == -1)
+			{
+				ereport(LOG,
+						(errcode_for_socket_access(),
+				/* translator: third %s is IPv4, IPv6, or Unix */
+						 errmsg("%s(%s) failed for %s address \"%s\": %m",
+								"setsockopt", "SO_REUSEADDR",
+								familyDesc, addrDesc)));
+				closesocket(fd);
+				continue;
+			}
+		}
+#endif
+
+#ifdef IPV6_V6ONLY
+		if (addr->ai_family == AF_INET6)
+		{
+			if (setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY,
+						   (char *) &one, sizeof(one)) == -1)
+			{
+				ereport(LOG,
+						(errcode_for_socket_access(),
+				/* translator: third %s is IPv4, IPv6, or Unix */
+						 errmsg("%s(%s) failed for %s address \"%s\": %m",
+								"setsockopt", "IPV6_V6ONLY",
+								familyDesc, addrDesc)));
+				closesocket(fd);
+				continue;
+			}
+		}
+#endif
+
+		/*
+		 * Note: This might fail on some OS's, like Linux older than
+		 * 2.4.21-pre3, that don't have the IPV6_V6ONLY socket option, and map
+		 * ipv4 addresses to ipv6.  It will show ::ffff:ipv4 for all ipv4
+		 * connections.
+		 */
+		err = bind(fd, addr->ai_addr, addr->ai_addrlen);
+		if (err < 0)
+		{
+			int			saved_errno = errno;
+
+			ereport(LOG,
+					(errcode_for_socket_access(),
+			/* translator: first %s is IPv4, IPv6, or Unix */
+					 errmsg("could not bind %s address \"%s\": %m",
+							familyDesc, addrDesc),
+					 saved_errno == EADDRINUSE ?
+					 (addr->ai_family == AF_UNIX ?
+					  errhint("Is another postmaster already running on port %d?",
+							  (int) portNumber) :
+					  errhint("Is another postmaster already running on port %d?"
+							  " If not, wait a few seconds and retry.",
+							  (int) portNumber)) : 0));
+			closesocket(fd);
+			continue;
+		}
+
+#ifdef HAVE_UNIX_SOCKETS
+		if (addr->ai_family == AF_UNIX)
+		{
+			if (Setup_AF_UNIX(service) != STATUS_OK)
+			{
+				closesocket(fd);
+				break;
+			}
+		}
+#endif
+
+		/*
+		 * Select appropriate accept-queue length limit.  PG_SOMAXCONN is only
+		 * intended to provide a clamp on the request on platforms where an
+		 * overly large request provokes a kernel error (are there any?).
+		 */
+		maxconn = MaxBackends * 2;
+		if (maxconn > PG_SOMAXCONN)
+			maxconn = PG_SOMAXCONN;
+
+		err = listen(fd, maxconn);
+		if (err < 0)
+		{
+			ereport(LOG,
+					(errcode_for_socket_access(),
+			/* translator: first %s is IPv4, IPv6, or Unix */
+					 errmsg("could not listen on %s address \"%s\": %m",
+							familyDesc, addrDesc)));
+			closesocket(fd);
+			continue;
+		}
+
+#ifdef HAVE_UNIX_SOCKETS
+		if (addr->ai_family == AF_UNIX)
+			ereport(LOG,
+					(errmsg("listening on Unix socket \"%s\"",
+							addrDesc)));
+		else
+#endif
+			ereport(LOG,
+			/* translator: first %s is IPv4 or IPv6 */
+					(errmsg("listening on %s address \"%s\", port %d",
+							familyDesc, addrDesc, (int) portNumber)));
+
+		ListenSocket[listen_index] = fd;
+		added++;
+	}
+
+	pg_freeaddrinfo_all(hint.ai_family, addrs);
+
+	if (!added)
+		return STATUS_ERROR;
+
+	return STATUS_OK;
+}
+
+
+#ifdef HAVE_UNIX_SOCKETS
+
+/*
+ * Lock_AF_UNIX -- configure unix socket file path
+ */
+static int
+Lock_AF_UNIX(const char *unixSocketDir, const char *unixSocketPath)
+{
+	/* no lock file for abstract sockets */
+	if (unixSocketPath[0] == '@')
+		return STATUS_OK;
+
+	/*
+	 * Grab an interlock file associated with the socket file.
+	 *
+	 * Note: there are two reasons for using a socket lock file, rather than
+	 * trying to interlock directly on the socket itself.  First, it's a lot
+	 * more portable, and second, it lets us remove any pre-existing socket
+	 * file without race conditions.
+	 */
+	CreateSocketLockFile(unixSocketPath, true, unixSocketDir);
+
+	/*
+	 * Once we have the interlock, we can safely delete any pre-existing
+	 * socket file to avoid failure at bind() time.
+	 */
+	(void) unlink(unixSocketPath);
+
+	/*
+	 * Remember socket file pathnames for later maintenance.
+	 */
+	sock_paths = lappend(sock_paths, pstrdup(unixSocketPath));
+
+	return STATUS_OK;
+}
+
+
+/*
+ * Setup_AF_UNIX -- configure unix socket permissions
+ */
+static int
+Setup_AF_UNIX(const char *sock_path)
+{
+	/* no file system permissions for abstract sockets */
+	if (sock_path[0] == '@')
+		return STATUS_OK;
+
+	/*
+	 * Fix socket ownership/permission if requested.  Note we must do this
+	 * before we listen() to avoid a window where unwanted connections could
+	 * get accepted.
+	 */
+	Assert(Unix_socket_group);
+	if (Unix_socket_group[0] != '\0')
+	{
+#ifdef WIN32
+		elog(WARNING, "configuration item unix_socket_group is not supported on this platform");
+#else
+		char	   *endptr;
+		unsigned long val;
+		gid_t		gid;
+
+		val = strtoul(Unix_socket_group, &endptr, 10);
+		if (*endptr == '\0')
+		{						/* numeric group id */
+			gid = val;
+		}
+		else
+		{						/* convert group name to id */
+			struct group *gr;
+
+			gr = getgrnam(Unix_socket_group);
+			if (!gr)
+			{
+				ereport(LOG,
+						(errmsg("group \"%s\" does not exist",
+								Unix_socket_group)));
+				return STATUS_ERROR;
+			}
+			gid = gr->gr_gid;
+		}
+		if (chown(sock_path, -1, gid) == -1)
+		{
+			ereport(LOG,
+					(errcode_for_file_access(),
+					 errmsg("could not set group of file \"%s\": %m",
+							sock_path)));
+			return STATUS_ERROR;
+		}
+#endif
+	}
+
+	if (chmod(sock_path, Unix_socket_permissions) == -1)
+	{
+		ereport(LOG,
+				(errcode_for_file_access(),
+				 errmsg("could not set permissions of file \"%s\": %m",
+						sock_path)));
+		return STATUS_ERROR;
+	}
+	return STATUS_OK;
+}
+#endif							/* HAVE_UNIX_SOCKETS */
+
+
+/*
+ * StreamConnection -- create a new connection with client using
+ *		server port.  Set port->sock to the FD of the new connection.
+ *
+ * ASSUME: that this doesn't need to be non-blocking because
+ *		the Postmaster uses select() to tell when the socket is ready for
+ *		accept().
+ *
+ * RETURNS: STATUS_OK or STATUS_ERROR
+ */
+int
+StreamConnection(pgsocket server_fd, Port *port)
+{
+	/* accept connection and fill in the client (remote) address */
+	port->raddr.salen = sizeof(port->raddr.addr);
+	if ((port->sock = accept(server_fd,
+							 (struct sockaddr *) &port->raddr.addr,
+							 &port->raddr.salen)) == PGINVALID_SOCKET)
+	{
+		ereport(LOG,
+				(errcode_for_socket_access(),
+				 errmsg("could not accept new connection: %m")));
+
+		/*
+		 * If accept() fails then postmaster.c will still see the server
+		 * socket as read-ready, and will immediately try again.  To avoid
+		 * uselessly sucking lots of CPU, delay a bit before trying again.
+		 * (The most likely reason for failure is being out of kernel file
+		 * table slots; we can do little except hope some will get freed up.)
+		 */
+		pg_usleep(100000L);		/* wait 0.1 sec */
+		return STATUS_ERROR;
+	}
+
+	/* fill in the server (local) address */
+	port->laddr.salen = sizeof(port->laddr.addr);
+	if (getsockname(port->sock,
+					(struct sockaddr *) &port->laddr.addr,
+					&port->laddr.salen) < 0)
+	{
+		ereport(LOG,
+				(errmsg("%s() failed: %m", "getsockname")));
+		return STATUS_ERROR;
+	}
+
+	/* select NODELAY and KEEPALIVE options if it's a TCP connection */
+	if (port->laddr.addr.ss_family != AF_UNIX)
+	{
+		int			on;
+#ifdef WIN32
+		int			oldopt;
+		int			optlen;
+		int			newopt;
+#endif
+
+#ifdef	TCP_NODELAY
+		on = 1;
+		if (setsockopt(port->sock, IPPROTO_TCP, TCP_NODELAY,
+					   (char *) &on, sizeof(on)) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "setsockopt", "TCP_NODELAY")));
+			return STATUS_ERROR;
+		}
+#endif
+		on = 1;
+		if (setsockopt(port->sock, SOL_SOCKET, SO_KEEPALIVE,
+					   (char *) &on, sizeof(on)) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "setsockopt", "SO_KEEPALIVE")));
+			return STATUS_ERROR;
+		}
+
+#ifdef WIN32
+
+		/*
+		 * This is a Win32 socket optimization.  The OS send buffer should be
+		 * large enough to send the whole Postgres send buffer in one go, or
+		 * performance suffers.  The Postgres send buffer can be enlarged if a
+		 * very large message needs to be sent, but we won't attempt to
+		 * enlarge the OS buffer if that happens, so somewhat arbitrarily
+		 * ensure that the OS buffer is at least PQ_SEND_BUFFER_SIZE * 4.
+		 * (That's 32kB with the current default).
+		 *
+		 * The default OS buffer size used to be 8kB in earlier Windows
+		 * versions, but was raised to 64kB in Windows 2012.  So it shouldn't
+		 * be necessary to change it in later versions anymore.  Changing it
+		 * unnecessarily can even reduce performance, because setting
+		 * SO_SNDBUF in the application disables the "dynamic send buffering"
+		 * feature that was introduced in Windows 7.  So before fiddling with
+		 * SO_SNDBUF, check if the current buffer size is already large enough
+		 * and only increase it if necessary.
+		 *
+		 * See https://support.microsoft.com/kb/823764/EN-US/ and
+		 * https://msdn.microsoft.com/en-us/library/bb736549%28v=vs.85%29.aspx
+		 */
+		optlen = sizeof(oldopt);
+		if (getsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &oldopt,
+					   &optlen) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "getsockopt", "SO_SNDBUF")));
+			return STATUS_ERROR;
+		}
+		newopt = PQ_SEND_BUFFER_SIZE * 4;
+		if (oldopt < newopt)
+		{
+			if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &newopt,
+						   sizeof(newopt)) < 0)
+			{
+				ereport(LOG,
+						(errmsg("%s(%s) failed: %m", "setsockopt", "SO_SNDBUF")));
+				return STATUS_ERROR;
+			}
+		}
+#endif
+
+		/*
+		 * Also apply the current keepalive parameters.  If we fail to set a
+		 * parameter, don't error out, because these aren't universally
+		 * supported.  (Note: you might think we need to reset the GUC
+		 * variables to 0 in such a case, but it's not necessary because the
+		 * show hooks for these variables report the truth anyway.)
+		 */
+		(void) pq_setkeepalivesidle(tcp_keepalives_idle, port);
+		(void) pq_setkeepalivesinterval(tcp_keepalives_interval, port);
+		(void) pq_setkeepalivescount(tcp_keepalives_count, port);
+		(void) pq_settcpusertimeout(tcp_user_timeout, port);
+	}
+
+	return STATUS_OK;
+}
+
+/*
+ * StreamClose -- close a client/backend connection
+ *
+ * NOTE: this is NOT used to terminate a session; it is just used to release
+ * the file descriptor in a process that should no longer have the socket
+ * open.  (For example, the postmaster calls this after passing ownership
+ * of the connection to a child process.)  It is expected that someone else
+ * still has the socket open.  So, we only want to close the descriptor,
+ * we do NOT want to send anything to the far end.
+ */
+void
+StreamClose(pgsocket sock)
+{
+	closesocket(sock);
+}
+
+/*
+ * TouchSocketFiles -- mark socket files as recently accessed
+ *
+ * This routine should be called every so often to ensure that the socket
+ * files have a recent mod date (ordinary operations on sockets usually won't
+ * change the mod date).  That saves them from being removed by
+ * overenthusiastic /tmp-directory-cleaner daemons.  (Another reason we should
+ * never have put the socket file in /tmp...)
+ */
+void
+TouchSocketFiles(void)
+{
+	ListCell   *l;
+
+	/* Loop through all created sockets... */
+	foreach(l, sock_paths)
+	{
+		char	   *sock_path = (char *) lfirst(l);
+
+		/* Ignore errors; there's no point in complaining */
+		(void) utime(sock_path, NULL);
+	}
+}
+
+/*
+ * RemoveSocketFiles -- unlink socket files at postmaster shutdown
+ */
+void
+RemoveSocketFiles(void)
+{
+	ListCell   *l;
+
+	/* Loop through all created sockets... */
+	foreach(l, sock_paths)
+	{
+		char	   *sock_path = (char *) lfirst(l);
+
+		/* Ignore any error. */
+		(void) unlink(sock_path);
+	}
+	/* Since we're about to exit, no need to reclaim storage */
+	sock_paths = NIL;
+}
+
+
+/* --------------------------------
+ * Low-level I/O routines begin here.
+ *
+ * These routines communicate with a frontend client across a connection
+ * already established by the preceding routines.
+ * --------------------------------
+ */
+
+/* --------------------------------
+ *			  socket_set_nonblocking - set socket blocking/non-blocking
+ *
+ * Sets the socket non-blocking if nonblocking is true, or sets it
+ * blocking otherwise.
+ * --------------------------------
+ */
+static void
+socket_set_nonblocking(bool nonblocking)
+{
+	if (MyProcPort == NULL)
+		ereport(ERROR,
+				(errcode(ERRCODE_CONNECTION_DOES_NOT_EXIST),
+				 errmsg("there is no client connection")));
+
+	MyProcPort->noblock = nonblocking;
+}
+
+/* --------------------------------
+ *		pq_recvbuf - load some bytes into the input buffer
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+static int
+pq_recvbuf(void)
+{
+	if (PqRecvPointer > 0)
+	{
+		if (PqRecvLength > PqRecvPointer)
+		{
+			/* still some unread data, left-justify it in the buffer */
+			memmove(PqRecvBuffer, PqRecvBuffer + PqRecvPointer,
+					PqRecvLength - PqRecvPointer);
+			PqRecvLength -= PqRecvPointer;
+			PqRecvPointer = 0;
+		}
+		else
+			PqRecvLength = PqRecvPointer = 0;
+	}
+
+	/* Ensure that we're in blocking mode */
+	socket_set_nonblocking(false);
+
+	/* Can fill buffer from PqRecvLength and upwards */
+	for (;;)
+	{
+		int			r;
+
+		r = secure_read(MyProcPort, PqRecvBuffer + PqRecvLength,
+						PQ_RECV_BUFFER_SIZE - PqRecvLength);
+
+		if (r < 0)
+		{
+			if (errno == EINTR)
+				continue;		/* Ok if interrupted */
+
+			/*
+			 * Careful: an ereport() that tries to write to the client would
+			 * cause recursion to here, leading to stack overflow and core
+			 * dump!  This message must go *only* to the postmaster log.
+			 */
+			ereport(COMMERROR,
+					(errcode_for_socket_access(),
+					 errmsg("could not receive data from client: %m")));
+			return EOF;
+		}
+		if (r == 0)
+		{
+			/*
+			 * EOF detected.  We used to write a log message here, but it's
+			 * better to expect the ultimate caller to do that.
+			 */
+			return EOF;
+		}
+		/* r contains number of bytes read, so just incr length */
+		PqRecvLength += r;
+		return 0;
+	}
+}
+
+/* --------------------------------
+ *		pq_getbyte	- get a single byte from connection, or return EOF
+ * --------------------------------
+ */
+int
+pq_getbyte(void)
+{
+	Assert(PqCommReadingMsg);
+
+	while (PqRecvPointer >= PqRecvLength)
+	{
+		if (pq_recvbuf())		/* If nothing in buffer, then recv some */
+			return EOF;			/* Failed to recv data */
+	}
+	return (unsigned char) PqRecvBuffer[PqRecvPointer++];
+}
+
+/* --------------------------------
+ *		pq_peekbyte		- peek at next byte from connection
+ *
+ *	 Same as pq_getbyte() except we don't advance the pointer.
+ * --------------------------------
+ */
+int
+pq_peekbyte(void)
+{
+	Assert(PqCommReadingMsg);
+
+	while (PqRecvPointer >= PqRecvLength)
+	{
+		if (pq_recvbuf())		/* If nothing in buffer, then recv some */
+			return EOF;			/* Failed to recv data */
+	}
+	return (unsigned char) PqRecvBuffer[PqRecvPointer];
+}
+
+/* --------------------------------
+ *		pq_getbyte_if_available - get a single byte from connection,
+ *			if available
+ *
+ * The received byte is stored in *c. Returns 1 if a byte was read,
+ * 0 if no data was available, or EOF if trouble.
+ * --------------------------------
+ */
+int
+pq_getbyte_if_available(unsigned char *c)
+{
+	int			r;
+
+	Assert(PqCommReadingMsg);
+
+	if (PqRecvPointer < PqRecvLength)
+	{
+		*c = PqRecvBuffer[PqRecvPointer++];
+		return 1;
+	}
+
+	/* Put the socket into non-blocking mode */
+	socket_set_nonblocking(true);
+
+	r = secure_read(MyProcPort, c, 1);
+	if (r < 0)
+	{
+		/*
+		 * Ok if no data available without blocking or interrupted (though
+		 * EINTR really shouldn't happen with a non-blocking socket). Report
+		 * other errors.
+		 */
+		if (errno == EAGAIN || errno == EWOULDBLOCK || errno == EINTR)
+			r = 0;
+		else
+		{
+			/*
+			 * Careful: an ereport() that tries to write to the client would
+			 * cause recursion to here, leading to stack overflow and core
+			 * dump!  This message must go *only* to the postmaster log.
+			 */
+			ereport(COMMERROR,
+					(errcode_for_socket_access(),
+					 errmsg("could not receive data from client: %m")));
+			r = EOF;
+		}
+	}
+	else if (r == 0)
+	{
+		/* EOF detected */
+		r = EOF;
+	}
+
+	return r;
+}
+
+/* --------------------------------
+ *		pq_getbytes		- get a known number of bytes from connection
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+int
+pq_getbytes(char *s, size_t len)
+{
+	size_t		amount;
+
+	Assert(PqCommReadingMsg);
+
+	while (len > 0)
+	{
+		while (PqRecvPointer >= PqRecvLength)
+		{
+			if (pq_recvbuf())	/* If nothing in buffer, then recv some */
+				return EOF;		/* Failed to recv data */
+		}
+		amount = PqRecvLength - PqRecvPointer;
+		if (amount > len)
+			amount = len;
+		memcpy(s, PqRecvBuffer + PqRecvPointer, amount);
+		PqRecvPointer += amount;
+		s += amount;
+		len -= amount;
+	}
+	return 0;
+}
+
+/* --------------------------------
+ *		pq_discardbytes		- throw away a known number of bytes
+ *
+ *		same as pq_getbytes except we do not copy the data to anyplace.
+ *		this is used for resynchronizing after read errors.
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+static int
+pq_discardbytes(size_t len)
+{
+	size_t		amount;
+
+	Assert(PqCommReadingMsg);
+
+	while (len > 0)
+	{
+		while (PqRecvPointer >= PqRecvLength)
+		{
+			if (pq_recvbuf())	/* If nothing in buffer, then recv some */
+				return EOF;		/* Failed to recv data */
+		}
+		amount = PqRecvLength - PqRecvPointer;
+		if (amount > len)
+			amount = len;
+		PqRecvPointer += amount;
+		len -= amount;
+	}
+	return 0;
+}
+
+/* --------------------------------
+ *		pq_buffer_has_data		- is any buffered data available to read?
+ *
+ * This will *not* attempt to read more data.
+ * --------------------------------
+ */
+bool
+pq_buffer_has_data(void)
+{
+	return (PqRecvPointer < PqRecvLength);
+}
+
+
+/* --------------------------------
+ *		pq_startmsgread - begin reading a message from the client.
+ *
+ *		This must be called before any of the pq_get* functions.
+ * --------------------------------
+ */
+void
+pq_startmsgread(void)
+{
+	/*
+	 * There shouldn't be a read active already, but let's check just to be
+	 * sure.
+	 */
+	if (PqCommReadingMsg)
+		ereport(FATAL,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("terminating connection because protocol synchronization was lost")));
+
+	PqCommReadingMsg = true;
+}
+
+
+/* --------------------------------
+ *		pq_endmsgread	- finish reading message.
+ *
+ *		This must be called after reading a message with pq_getbytes()
+ *		and friends, to indicate that we have read the whole message.
+ *		pq_getmessage() does this implicitly.
+ * --------------------------------
+ */
+void
+pq_endmsgread(void)
+{
+	Assert(PqCommReadingMsg);
+
+	PqCommReadingMsg = false;
+}
+
+/* --------------------------------
+ *		pq_is_reading_msg - are we currently reading a message?
+ *
+ * This is used in error recovery at the outer idle loop to detect if we have
+ * lost protocol sync, and need to terminate the connection. pq_startmsgread()
+ * will check for that too, but it's nicer to detect it earlier.
+ * --------------------------------
+ */
+bool
+pq_is_reading_msg(void)
+{
+	return PqCommReadingMsg;
+}
+
+/* --------------------------------
+ *		pq_getmessage	- get a message with length word from connection
+ *
+ *		The return value is placed in an expansible StringInfo, which has
+ *		already been initialized by the caller.
+ *		Only the message body is placed in the StringInfo; the length word
+ *		is removed.  Also, s->cursor is initialized to zero for convenience
+ *		in scanning the message contents.
+ *
+ *		maxlen is the upper limit on the length of the
+ *		message we are willing to accept.  We abort the connection (by
+ *		returning EOF) if client tries to send more than that.
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+int
+pq_getmessage(StringInfo s, int maxlen)
+{
+	int32		len;
+
+	Assert(PqCommReadingMsg);
+
+	resetStringInfo(s);
+
+	/* Read message length word */
+	if (pq_getbytes((char *) &len, 4) == EOF)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("unexpected EOF within message length word")));
+		return EOF;
+	}
+
+	len = pg_ntoh32(len);
+
+	if (len < 4 || len > maxlen)
+	{
+		ereport(COMMERROR,
+				(errcode(ERRCODE_PROTOCOL_VIOLATION),
+				 errmsg("invalid message length")));
+		return EOF;
+	}
+
+	len -= 4;					/* discount length itself */
+
+	if (len > 0)
+	{
+		/*
+		 * Allocate space for message.  If we run out of room (ridiculously
+		 * large message), we will elog(ERROR), but we want to discard the
+		 * message body so as not to lose communication sync.
+		 */
+		PG_TRY();
+		{
+			enlargeStringInfo(s, len);
+		}
+		PG_CATCH();
+		{
+			if (pq_discardbytes(len) == EOF)
+				ereport(COMMERROR,
+						(errcode(ERRCODE_PROTOCOL_VIOLATION),
+						 errmsg("incomplete message from client")));
+
+			/* we discarded the rest of the message so we're back in sync. */
+			PqCommReadingMsg = false;
+			PG_RE_THROW();
+		}
+		PG_END_TRY();
+
+		/* And grab the message */
+		if (pq_getbytes(s->data, len) == EOF)
+		{
+			ereport(COMMERROR,
+					(errcode(ERRCODE_PROTOCOL_VIOLATION),
+					 errmsg("incomplete message from client")));
+			return EOF;
+		}
+		s->len = len;
+		/* Place a trailing null per StringInfo convention */
+		s->data[len] = '\0';
+	}
+
+	/* finished reading the message. */
+	PqCommReadingMsg = false;
+
+	return 0;
+}
+
+
+static int
+internal_putbytes(const char *s, size_t len)
+{
+	size_t		amount;
+
+	while (len > 0)
+	{
+		/* If buffer is full, then flush it out */
+		if (PqSendPointer >= PqSendBufferSize)
+		{
+			socket_set_nonblocking(false);
+			if (internal_flush())
+				return EOF;
+		}
+		amount = PqSendBufferSize - PqSendPointer;
+		if (amount > len)
+			amount = len;
+		memcpy(PqSendBuffer + PqSendPointer, s, amount);
+		PqSendPointer += amount;
+		s += amount;
+		len -= amount;
+	}
+	return 0;
+}
+
+/* --------------------------------
+ *		socket_flush		- flush pending output
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+static int
+socket_flush(void)
+{
+	int			res;
+
+	/* No-op if reentrant call */
+	if (PqCommBusy)
+		return 0;
+	PqCommBusy = true;
+	socket_set_nonblocking(false);
+	res = internal_flush();
+	PqCommBusy = false;
+	return res;
+}
+
+/* --------------------------------
+ *		internal_flush - flush pending output
+ *
+ * Returns 0 if OK (meaning everything was sent, or operation would block
+ * and the socket is in non-blocking mode), or EOF if trouble.
+ * --------------------------------
+ */
+static int
+internal_flush(void)
+{
+	static int	last_reported_send_errno = 0;
+
+	char	   *bufptr = PqSendBuffer + PqSendStart;
+	char	   *bufend = PqSendBuffer + PqSendPointer;
+
+	while (bufptr < bufend)
+	{
+		int			r;
+
+		r = secure_write(MyProcPort, bufptr, bufend - bufptr);
+
+		if (r <= 0)
+		{
+			if (errno == EINTR)
+				continue;		/* Ok if we were interrupted */
+
+			/*
+			 * Ok if no data writable without blocking, and the socket is in
+			 * non-blocking mode.
+			 */
+			if (errno == EAGAIN ||
+				errno == EWOULDBLOCK)
+			{
+				return 0;
+			}
+
+			/*
+			 * Careful: an ereport() that tries to write to the client would
+			 * cause recursion to here, leading to stack overflow and core
+			 * dump!  This message must go *only* to the postmaster log.
+			 *
+			 * If a client disconnects while we're in the midst of output, we
+			 * might write quite a bit of data before we get to a safe query
+			 * abort point.  So, suppress duplicate log messages.
+			 */
+			if (errno != last_reported_send_errno)
+			{
+				last_reported_send_errno = errno;
+				ereport(COMMERROR,
+						(errcode_for_socket_access(),
+						 errmsg("could not send data to client: %m")));
+			}
+
+			/*
+			 * We drop the buffered data anyway so that processing can
+			 * continue, even though we'll probably quit soon. We also set a
+			 * flag that'll cause the next CHECK_FOR_INTERRUPTS to terminate
+			 * the connection.
+			 */
+			PqSendStart = PqSendPointer = 0;
+			ClientConnectionLost = 1;
+			InterruptPending = 1;
+			return EOF;
+		}
+
+		last_reported_send_errno = 0;	/* reset after any successful send */
+		bufptr += r;
+		PqSendStart += r;
+	}
+
+	PqSendStart = PqSendPointer = 0;
+	return 0;
+}
+
+/* --------------------------------
+ *		pq_flush_if_writable - flush pending output if writable without blocking
+ *
+ * Returns 0 if OK, or EOF if trouble.
+ * --------------------------------
+ */
+static int
+socket_flush_if_writable(void)
+{
+	int			res;
+
+	/* Quick exit if nothing to do */
+	if (PqSendPointer == PqSendStart)
+		return 0;
+
+	/* No-op if reentrant call */
+	if (PqCommBusy)
+		return 0;
+
+	/* Temporarily put the socket into non-blocking mode */
+	socket_set_nonblocking(true);
+
+	PqCommBusy = true;
+	res = internal_flush();
+	PqCommBusy = false;
+	return res;
+}
+
+/* --------------------------------
+ *	socket_is_send_pending	- is there any pending data in the output buffer?
+ * --------------------------------
+ */
+static bool
+socket_is_send_pending(void)
+{
+	return (PqSendStart < PqSendPointer);
+}
+
+/* --------------------------------
+ * Message-level I/O routines begin here.
+ * --------------------------------
+ */
+
+
+/* --------------------------------
+ *		socket_putmessage - send a normal message (suppressed in COPY OUT mode)
+ *
+ *		msgtype is a message type code to place before the message body.
+ *
+ *		len is the length of the message body data at *s.  A message length
+ *		word (equal to len+4 because it counts itself too) is inserted by this
+ *		routine.
+ *
+ *		We suppress messages generated while pqcomm.c is busy.  This
+ *		avoids any possibility of messages being inserted within other
+ *		messages.  The only known trouble case arises if SIGQUIT occurs
+ *		during a pqcomm.c routine --- quickdie() will try to send a warning
+ *		message, and the most reasonable approach seems to be to drop it.
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+static int
+socket_putmessage(char msgtype, const char *s, size_t len)
+{
+	uint32		n32;
+
+	Assert(msgtype != 0);
+
+	if (PqCommBusy)
+		return 0;
+	PqCommBusy = true;
+	if (internal_putbytes(&msgtype, 1))
+		goto fail;
+
+	n32 = pg_hton32((uint32) (len + 4));
+	if (internal_putbytes((char *) &n32, 4))
+		goto fail;
+
+	if (internal_putbytes(s, len))
+		goto fail;
+	PqCommBusy = false;
+	return 0;
+
+fail:
+	PqCommBusy = false;
+	return EOF;
+}
+
+/* --------------------------------
+ *		pq_putmessage_noblock	- like pq_putmessage, but never blocks
+ *
+ *		If the output buffer is too small to hold the message, the buffer
+ *		is enlarged.
+ */
+static void
+socket_putmessage_noblock(char msgtype, const char *s, size_t len)
+{
+	int			res PG_USED_FOR_ASSERTS_ONLY;
+	int			required;
+
+	/*
+	 * Ensure we have enough space in the output buffer for the message header
+	 * as well as the message itself.
+	 */
+	required = PqSendPointer + 1 + 4 + len;
+	if (required > PqSendBufferSize)
+	{
+		PqSendBuffer = repalloc(PqSendBuffer, required);
+		PqSendBufferSize = required;
+	}
+	res = pq_putmessage(msgtype, s, len);
+	Assert(res == 0);			/* should not fail when the message fits in
+								 * buffer */
+}
+
+/* --------------------------------
+ *		pq_putmessage_v2 - send a message in protocol version 2
+ *
+ *		msgtype is a message type code to place before the message body.
+ *
+ *		We no longer support protocol version 2, but we have kept this
+ *		function so that if a client tries to connect with protocol version 2,
+ *		as a courtesy we can still send the "unsupported protocol version"
+ *		error to the client in the old format.
+ *
+ *		Like in pq_putmessage(), we suppress messages generated while
+ *		pqcomm.c is busy.
+ *
+ *		returns 0 if OK, EOF if trouble
+ * --------------------------------
+ */
+int
+pq_putmessage_v2(char msgtype, const char *s, size_t len)
+{
+	Assert(msgtype != 0);
+
+	if (PqCommBusy)
+		return 0;
+	PqCommBusy = true;
+	if (internal_putbytes(&msgtype, 1))
+		goto fail;
+
+	if (internal_putbytes(s, len))
+		goto fail;
+	PqCommBusy = false;
+	return 0;
+
+fail:
+	PqCommBusy = false;
+	return EOF;
+}
+
+/*
+ * Support for TCP Keepalive parameters
+ */
+
+/*
+ * On Windows, we need to set both idle and interval at the same time.
+ * We also cannot reset them to the default (setting to zero will
+ * actually set them to zero, not default), therefore we fallback to
+ * the out-of-the-box default instead.
+ */
+#if defined(WIN32) && defined(SIO_KEEPALIVE_VALS)
+static int
+pq_setkeepaliveswin32(Port *port, int idle, int interval)
+{
+	struct tcp_keepalive ka;
+	DWORD		retsize;
+
+	if (idle <= 0)
+		idle = 2 * 60 * 60;		/* default = 2 hours */
+	if (interval <= 0)
+		interval = 1;			/* default = 1 second */
+
+	ka.onoff = 1;
+	ka.keepalivetime = idle * 1000;
+	ka.keepaliveinterval = interval * 1000;
+
+	if (WSAIoctl(port->sock,
+				 SIO_KEEPALIVE_VALS,
+				 (LPVOID) &ka,
+				 sizeof(ka),
+				 NULL,
+				 0,
+				 &retsize,
+				 NULL,
+				 NULL)
+		!= 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) failed: error code %d",
+						"WSAIoctl", "SIO_KEEPALIVE_VALS", WSAGetLastError())));
+		return STATUS_ERROR;
+	}
+	if (port->keepalives_idle != idle)
+		port->keepalives_idle = idle;
+	if (port->keepalives_interval != interval)
+		port->keepalives_interval = interval;
+	return STATUS_OK;
+}
+#endif
+
+int
+pq_getkeepalivesidle(Port *port)
+{
+#if defined(PG_TCP_KEEPALIVE_IDLE) || defined(SIO_KEEPALIVE_VALS)
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return 0;
+
+	if (port->keepalives_idle != 0)
+		return port->keepalives_idle;
+
+	if (port->default_keepalives_idle == 0)
+	{
+#ifndef WIN32
+		socklen_t	size = sizeof(port->default_keepalives_idle);
+
+		if (getsockopt(port->sock, IPPROTO_TCP, PG_TCP_KEEPALIVE_IDLE,
+					   (char *) &port->default_keepalives_idle,
+					   &size) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "getsockopt", PG_TCP_KEEPALIVE_IDLE_STR)));
+			port->default_keepalives_idle = -1; /* don't know */
+		}
+#else							/* WIN32 */
+		/* We can't get the defaults on Windows, so return "don't know" */
+		port->default_keepalives_idle = -1;
+#endif							/* WIN32 */
+	}
+
+	return port->default_keepalives_idle;
+#else
+	return 0;
+#endif
+}
+
+int
+pq_setkeepalivesidle(int idle, Port *port)
+{
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return STATUS_OK;
+
+/* check SIO_KEEPALIVE_VALS here, not just WIN32, as some toolchains lack it */
+#if defined(PG_TCP_KEEPALIVE_IDLE) || defined(SIO_KEEPALIVE_VALS)
+	if (idle == port->keepalives_idle)
+		return STATUS_OK;
+
+#ifndef WIN32
+	if (port->default_keepalives_idle <= 0)
+	{
+		if (pq_getkeepalivesidle(port) < 0)
+		{
+			if (idle == 0)
+				return STATUS_OK;	/* default is set but unknown */
+			else
+				return STATUS_ERROR;
+		}
+	}
+
+	if (idle == 0)
+		idle = port->default_keepalives_idle;
+
+	if (setsockopt(port->sock, IPPROTO_TCP, PG_TCP_KEEPALIVE_IDLE,
+				   (char *) &idle, sizeof(idle)) < 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) failed: %m", "setsockopt", PG_TCP_KEEPALIVE_IDLE_STR)));
+		return STATUS_ERROR;
+	}
+
+	port->keepalives_idle = idle;
+#else							/* WIN32 */
+	return pq_setkeepaliveswin32(port, idle, port->keepalives_interval);
+#endif
+#else
+	if (idle != 0)
+	{
+		ereport(LOG,
+				(errmsg("setting the keepalive idle time is not supported")));
+		return STATUS_ERROR;
+	}
+#endif
+
+	return STATUS_OK;
+}
+
+int
+pq_getkeepalivesinterval(Port *port)
+{
+#if defined(TCP_KEEPINTVL) || defined(SIO_KEEPALIVE_VALS)
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return 0;
+
+	if (port->keepalives_interval != 0)
+		return port->keepalives_interval;
+
+	if (port->default_keepalives_interval == 0)
+	{
+#ifndef WIN32
+		socklen_t	size = sizeof(port->default_keepalives_interval);
+
+		if (getsockopt(port->sock, IPPROTO_TCP, TCP_KEEPINTVL,
+					   (char *) &port->default_keepalives_interval,
+					   &size) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "getsockopt", "TCP_KEEPINTVL")));
+			port->default_keepalives_interval = -1; /* don't know */
+		}
+#else
+		/* We can't get the defaults on Windows, so return "don't know" */
+		port->default_keepalives_interval = -1;
+#endif							/* WIN32 */
+	}
+
+	return port->default_keepalives_interval;
+#else
+	return 0;
+#endif
+}
+
+int
+pq_setkeepalivesinterval(int interval, Port *port)
+{
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return STATUS_OK;
+
+#if defined(TCP_KEEPINTVL) || defined(SIO_KEEPALIVE_VALS)
+	if (interval == port->keepalives_interval)
+		return STATUS_OK;
+
+#ifndef WIN32
+	if (port->default_keepalives_interval <= 0)
+	{
+		if (pq_getkeepalivesinterval(port) < 0)
+		{
+			if (interval == 0)
+				return STATUS_OK;	/* default is set but unknown */
+			else
+				return STATUS_ERROR;
+		}
+	}
+
+	if (interval == 0)
+		interval = port->default_keepalives_interval;
+
+	if (setsockopt(port->sock, IPPROTO_TCP, TCP_KEEPINTVL,
+				   (char *) &interval, sizeof(interval)) < 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) failed: %m", "setsockopt", "TCP_KEEPINTVL")));
+		return STATUS_ERROR;
+	}
+
+	port->keepalives_interval = interval;
+#else							/* WIN32 */
+	return pq_setkeepaliveswin32(port, port->keepalives_idle, interval);
+#endif
+#else
+	if (interval != 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) not supported", "setsockopt", "TCP_KEEPINTVL")));
+		return STATUS_ERROR;
+	}
+#endif
+
+	return STATUS_OK;
+}
+
+int
+pq_getkeepalivescount(Port *port)
+{
+#ifdef TCP_KEEPCNT
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return 0;
+
+	if (port->keepalives_count != 0)
+		return port->keepalives_count;
+
+	if (port->default_keepalives_count == 0)
+	{
+		socklen_t	size = sizeof(port->default_keepalives_count);
+
+		if (getsockopt(port->sock, IPPROTO_TCP, TCP_KEEPCNT,
+					   (char *) &port->default_keepalives_count,
+					   &size) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "getsockopt", "TCP_KEEPCNT")));
+			port->default_keepalives_count = -1;	/* don't know */
+		}
+	}
+
+	return port->default_keepalives_count;
+#else
+	return 0;
+#endif
+}
+
+int
+pq_setkeepalivescount(int count, Port *port)
+{
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return STATUS_OK;
+
+#ifdef TCP_KEEPCNT
+	if (count == port->keepalives_count)
+		return STATUS_OK;
+
+	if (port->default_keepalives_count <= 0)
+	{
+		if (pq_getkeepalivescount(port) < 0)
+		{
+			if (count == 0)
+				return STATUS_OK;	/* default is set but unknown */
+			else
+				return STATUS_ERROR;
+		}
+	}
+
+	if (count == 0)
+		count = port->default_keepalives_count;
+
+	if (setsockopt(port->sock, IPPROTO_TCP, TCP_KEEPCNT,
+				   (char *) &count, sizeof(count)) < 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) failed: %m", "setsockopt", "TCP_KEEPCNT")));
+		return STATUS_ERROR;
+	}
+
+	port->keepalives_count = count;
+#else
+	if (count != 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) not supported", "setsockopt", "TCP_KEEPCNT")));
+		return STATUS_ERROR;
+	}
+#endif
+
+	return STATUS_OK;
+}
+
+int
+pq_gettcpusertimeout(Port *port)
+{
+#ifdef TCP_USER_TIMEOUT
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return 0;
+
+	if (port->tcp_user_timeout != 0)
+		return port->tcp_user_timeout;
+
+	if (port->default_tcp_user_timeout == 0)
+	{
+		socklen_t	size = sizeof(port->default_tcp_user_timeout);
+
+		if (getsockopt(port->sock, IPPROTO_TCP, TCP_USER_TIMEOUT,
+					   (char *) &port->default_tcp_user_timeout,
+					   &size) < 0)
+		{
+			ereport(LOG,
+					(errmsg("%s(%s) failed: %m", "getsockopt", "TCP_USER_TIMEOUT")));
+			port->default_tcp_user_timeout = -1;	/* don't know */
+		}
+	}
+
+	return port->default_tcp_user_timeout;
+#else
+	return 0;
+#endif
+}
+
+int
+pq_settcpusertimeout(int timeout, Port *port)
+{
+	if (port == NULL || port->laddr.addr.ss_family == AF_UNIX)
+		return STATUS_OK;
+
+#ifdef TCP_USER_TIMEOUT
+	if (timeout == port->tcp_user_timeout)
+		return STATUS_OK;
+
+	if (port->default_tcp_user_timeout <= 0)
+	{
+		if (pq_gettcpusertimeout(port) < 0)
+		{
+			if (timeout == 0)
+				return STATUS_OK;	/* default is set but unknown */
+			else
+				return STATUS_ERROR;
+		}
+	}
+
+	if (timeout == 0)
+		timeout = port->default_tcp_user_timeout;
+
+	if (setsockopt(port->sock, IPPROTO_TCP, TCP_USER_TIMEOUT,
+				   (char *) &timeout, sizeof(timeout)) < 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) failed: %m", "setsockopt", "TCP_USER_TIMEOUT")));
+		return STATUS_ERROR;
+	}
+
+	port->tcp_user_timeout = timeout;
+#else
+	if (timeout != 0)
+	{
+		ereport(LOG,
+				(errmsg("%s(%s) not supported", "setsockopt", "TCP_USER_TIMEOUT")));
+		return STATUS_ERROR;
+	}
+#endif
+
+	return STATUS_OK;
+}
+
+/*
+ * Check if the client is still connected.
+ */
+bool
+pq_check_connection(void)
+{
+	WaitEvent	events[FeBeWaitSetNEvents];
+	int			rc;
+
+	/*
+	 * It's OK to modify the socket event filter without restoring, because
+	 * all FeBeWaitSet socket wait sites do the same.
+	 */
+	ModifyWaitEvent(FeBeWaitSet, FeBeWaitSetSocketPos, WL_SOCKET_CLOSED, NULL);
+
+retry:
+	rc = WaitEventSetWait(FeBeWaitSet, 0, events, lengthof(events), 0);
+	for (int i = 0; i < rc; ++i)
+	{
+		if (events[i].events & WL_SOCKET_CLOSED)
+			return false;
+		if (events[i].events & WL_LATCH_SET)
+		{
+			/*
+			 * A latch event might be preventing other events from being
+			 * reported.  Reset it and poll again.  No need to restore it
+			 * because no code should expect latches to survive across
+			 * CHECK_FOR_INTERRUPTS().
+			 */
+			ResetLatch(MyLatch);
+			goto retry;
+		}
+	}
+
+	return true;
+}