/src/postgres/src/backend/libpq/pqcomm.c

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/*-------------------------------------------------------------------------
 *
 * 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) 1996-2025, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *  src/backend/libpq/pqcomm.c
 *
 *-------------------------------------------------------------------------
 */

/*------------------------
 * INTERFACE ROUTINES
 *
 * setup/teardown:
 *    ListenServerPort  - Open postmaster's server port
 *    AcceptConnection  - Accept new connection with client
 *    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>
#include <netinet/tcp.h>
#include <utime.h>
#ifdef WIN32
#include <mstcpip.h>
#endif

#include "common/ip.h"
#include "libpq/libpq.h"
#include "miscadmin.h"
#include "port/pg_bswap.h"
#include "postmaster/postmaster.h"
#include "storage/ipc.h"
#include "utils/guc_hooks.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 size_t PqSendPointer;  /* Next index to store a byte in PqSendBuffer */
static size_t 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 inline int internal_putbytes(const void *b, size_t len);
static inline int internal_flush(void);
static pg_noinline int internal_flush_buffer(const char *buf, size_t *start,
                       size_t *end);

static int  Lock_AF_UNIX(const char *unixSocketDir, const char *unixSocketPath);
static int  Setup_AF_UNIX(const char *sock_path);

static const PQcommMethods PqCommSocketMethods = {
  .comm_reset = socket_comm_reset,
  .flush = socket_flush,
  .flush_if_writable = socket_flush_if_writable,
  .is_send_pending = socket_is_send_pending,
  .putmessage = socket_putmessage,
  .putmessage_noblock = socket_putmessage_noblock
};

const PQcommMethods *PqCommMethods = &PqCommSocketMethods;

WaitEventSet *FeBeWaitSet;


/* --------------------------------
 *    pq_init - initialize libpq at backend startup
 * --------------------------------
 */
Port *
pq_init(ClientSocket *client_sock)
{
  Port     *port;
  int     socket_pos PG_USED_FOR_ASSERTS_ONLY;
  int     latch_pos PG_USED_FOR_ASSERTS_ONLY;

  /* allocate the Port struct and copy the ClientSocket contents to it */
  port = palloc0(sizeof(Port));
  port->sock = client_sock->sock;
  memcpy(&port->raddr.addr, &client_sock->raddr.addr, client_sock->raddr.salen);
  port->raddr.salen = client_sock->raddr.salen;

  /* 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(FATAL,
        (errmsg("%s() failed: %m", "getsockname")));
  }

  /* 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(FATAL,
          (errmsg("%s(%s) failed: %m", "setsockopt", "TCP_NODELAY")));
    }
#endif
    on = 1;
    if (setsockopt(port->sock, SOL_SOCKET, SO_KEEPALIVE,
             (char *) &on, sizeof(on)) < 0)
    {
      ereport(FATAL,
          (errmsg("%s(%s) failed: %m", "setsockopt", "SO_KEEPALIVE")));
    }

#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(FATAL,
          (errmsg("%s(%s) failed: %m", "getsockopt", "SO_SNDBUF")));
    }
    newopt = PQ_SEND_BUFFER_SIZE * 4;
    if (oldopt < newopt)
    {
      if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &newopt,
               sizeof(newopt)) < 0)
      {
        ereport(FATAL,
            (errmsg("%s(%s) failed: %m", "setsockopt", "SO_SNDBUF")));
      }
    }
#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);
  }

  /* 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.
   */
#ifndef WIN32
  if (!pg_set_noblock(port->sock))
    ereport(FATAL,
        (errmsg("could not set socket to nonblocking mode: %m")));
#endif

#ifndef WIN32

  /* Don't give the socket to any subprograms we execute. */
  if (fcntl(port->sock, F_SETFD, FD_CLOEXEC) < 0)
    elog(FATAL, "fcntl(F_SETFD) failed on socket: %m");
#endif

  FeBeWaitSet = CreateWaitEventSet(NULL, FeBeWaitSetNEvents);
  socket_pos = AddWaitEventToSet(FeBeWaitSet, WL_SOCKET_WRITEABLE,
                   port->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);

  return port;
}

/* --------------------------------
 *    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;
  }
}



/* --------------------------------
 * Postmaster functions to handle sockets.
 * --------------------------------
 */

/*
 * ListenServerPort -- 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 appended to the ListenSockets[] array.  On
 * entry, *NumListenSockets holds the number of elements currently in the
 * array, and it is updated to reflect the opened sockets.  MaxListen is the
 * allocated size of the array.
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */
int
ListenServerPort(int family, const char *hostName, unsigned short portNumber,
         const char *unixSocketDir,
         pgsocket ListenSockets[], int *NumListenSockets, 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     added = 0;
  char    unixSocketPath[MAXPGPATH];
#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;

  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
  {
    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. */
    if (*NumListenSockets == 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;
      case AF_INET6:
        familyDesc = _("IPv6");
        break;
      case AF_UNIX:
        familyDesc = _("Unix");
        break;
      default:
        snprintf(familyDescBuf, sizeof(familyDescBuf),
             _("unrecognized address family %d"),
             addr->ai_family);
        familyDesc = familyDescBuf;
        break;
    }

    /* set up text form of address for log messages */
    if (addr->ai_family == AF_UNIX)
      addrDesc = unixSocketPath;
    else
    {
      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
    /* Don't give the listen socket to any subprograms we execute. */
    if (fcntl(fd, F_SETFD, FD_CLOEXEC) < 0)
      elog(FATAL, "fcntl(F_SETFD) failed on socket: %m");

    /*
     * 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 or IPv6 */
             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 IPv6 */
             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;
    }

    if (addr->ai_family == AF_UNIX)
    {
      if (Setup_AF_UNIX(service) != STATUS_OK)
      {
        closesocket(fd);
        break;
      }
    }

    /*
     * Select appropriate accept-queue length limit.  It seems reasonable
     * to use a value similar to the maximum number of child processes
     * that the postmaster will permit.
     */
    maxconn = MaxConnections * 2;

    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;
    }

    if (addr->ai_family == AF_UNIX)
      ereport(LOG,
          (errmsg("listening on Unix socket \"%s\"",
              addrDesc)));
    else
      ereport(LOG,
      /* translator: first %s is IPv4 or IPv6 */
          (errmsg("listening on %s address \"%s\", port %d",
              familyDesc, addrDesc, (int) portNumber)));

    ListenSockets[*NumListenSockets] = fd;
    (*NumListenSockets)++;
    added++;
  }

  pg_freeaddrinfo_all(hint.ai_family, addrs);

  if (!added)
    return STATUS_ERROR;

  return STATUS_OK;
}


/*
 * 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;
}


/*
 * AcceptConnection -- accept a new connection with client using
 *    server port.  Fills *client_sock with the FD and endpoint info
 *    of the new connection.
 *
 * ASSUME: that this doesn't need to be non-blocking because
 *    the Postmaster waits for the socket to be ready to accept().
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */
int
AcceptConnection(pgsocket server_fd, ClientSocket *client_sock)
{
  /* accept connection and fill in the client (remote) address */
  client_sock->raddr.salen = sizeof(client_sock->raddr.addr);
  if ((client_sock->sock = accept(server_fd,
                  (struct sockaddr *) &client_sock->raddr.addr,
                  &client_sock->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;
  }

  return STATUS_OK;
}

/*
 * 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;

    errno = 0;

    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.
       *
       * If errno is zero, assume it's EOF and let the caller complain.
       */
      if (errno != 0)
        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);

  errno = 0;

  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.
       *
       * If errno is zero, assume it's EOF and let the caller complain.
       */
      if (errno != 0)
        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(void *b, size_t len)
{
  char     *s = b;
  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_remaining_data  - return number of bytes in receive buffer
 *
 * This will *not* attempt to read more data. And reading up to that number of
 * bytes should not cause reading any more data either.
 * --------------------------------
 */
ssize_t
pq_buffer_remaining_data(void)
{
  Assert(PqRecvLength >= PqRecvPointer);
  return (PqRecvLength - PqRecvPointer);
}


/* --------------------------------
 *    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(&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 inline int
internal_putbytes(const void *b, size_t len)
{
  const char *s = b;

  while (len > 0)
  {
    /* If buffer is full, then flush it out */
    if (PqSendPointer >= PqSendBufferSize)
    {
      socket_set_nonblocking(false);
      if (internal_flush())
        return EOF;
    }

    /*
     * If the buffer is empty and data length is larger than the buffer
     * size, send it without buffering.  Otherwise, copy as much data as
     * possible into the buffer.
     */
    if (len >= PqSendBufferSize && PqSendStart == PqSendPointer)
    {
      size_t    start = 0;

      socket_set_nonblocking(false);
      if (internal_flush_buffer(s, &start, &len))
        return EOF;
    }
    else
    {
      size_t    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 inline int
internal_flush(void)
{
  return internal_flush_buffer(PqSendBuffer, &PqSendStart, &PqSendPointer);
}

/* --------------------------------
 *    internal_flush_buffer - flush the given buffer content
 *
 * 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 pg_noinline int
internal_flush_buffer(const char *buf, size_t *start, size_t *end)
{
  static int  last_reported_send_errno = 0;

  const char *bufptr = buf + *start;
  const char *bufend = buf + *end;

  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.
       */
      *start = *end = 0;
      ClientConnectionLost = 1;
      InterruptPending = 1;
      return EOF;
    }

    last_reported_send_errno = 0; /* reset after any successful send */
    bufptr += r;
    *start += r;
  }

  *start = *end = 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(&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;
}

/*
 * GUC assign_hook for tcp_keepalives_idle
 */
void
assign_tcp_keepalives_idle(int newval, void *extra)
{
  /*
   * The kernel API provides no way to test a value without setting it; and
   * once we set it we might fail to unset it.  So there seems little point
   * in fully implementing the check-then-assign GUC API for these
   * variables.  Instead we just do the assignment on demand.
   * pq_setkeepalivesidle reports any problems via ereport(LOG).
   *
   * This approach means that the GUC value might have little to do with the
   * actual kernel value, so we use a show_hook that retrieves the kernel
   * value rather than trusting GUC's copy.
   */
  (void) pq_setkeepalivesidle(newval, MyProcPort);
}

/*
 * GUC show_hook for tcp_keepalives_idle
 */
const char *
show_tcp_keepalives_idle(void)
{
  /* See comments in assign_tcp_keepalives_idle */
  static char nbuf[16];

  snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesidle(MyProcPort));
  return nbuf;
}

/*
 * GUC assign_hook for tcp_keepalives_interval
 */
void
assign_tcp_keepalives_interval(int newval, void *extra)
{
  /* See comments in assign_tcp_keepalives_idle */
  (void) pq_setkeepalivesinterval(newval, MyProcPort);
}

/*
 * GUC show_hook for tcp_keepalives_interval
 */
const char *
show_tcp_keepalives_interval(void)
{
  /* See comments in assign_tcp_keepalives_idle */
  static char nbuf[16];

  snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivesinterval(MyProcPort));
  return nbuf;
}

/*
 * GUC assign_hook for tcp_keepalives_count
 */
void
assign_tcp_keepalives_count(int newval, void *extra)
{
  /* See comments in assign_tcp_keepalives_idle */
  (void) pq_setkeepalivescount(newval, MyProcPort);
}

/*
 * GUC show_hook for tcp_keepalives_count
 */
const char *
show_tcp_keepalives_count(void)
{
  /* See comments in assign_tcp_keepalives_idle */
  static char nbuf[16];

  snprintf(nbuf, sizeof(nbuf), "%d", pq_getkeepalivescount(MyProcPort));
  return nbuf;
}

/*
 * GUC assign_hook for tcp_user_timeout
 */
void
assign_tcp_user_timeout(int newval, void *extra)
{
  /* See comments in assign_tcp_keepalives_idle */
  (void) pq_settcpusertimeout(newval, MyProcPort);
}

/*
 * GUC show_hook for tcp_user_timeout
 */
const char *
show_tcp_user_timeout(void)
{
  /* See comments in assign_tcp_keepalives_idle */
  static char nbuf[16];

  snprintf(nbuf, sizeof(nbuf), "%d", pq_gettcpusertimeout(MyProcPort));
  return nbuf;
}

/*
 * 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;
}

Coverage Report

Created: 2025-06-15 06:31