Logo Search packages:      
Sourcecode: postgresql-8.4 version File versions  Download package

pqcomm.c

/*-------------------------------------------------------------------------
 *
 * 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 --- or would be,
 * except for major brain damage in the design of the old COPY OUT protocol.
 * Unfortunately, COPY OUT was designed to commandeer the communication
 * channel (it just transfers data without wrapping it into messages).
 * No other messages can be sent while COPY OUT is in progress; and if the
 * copy is aborted by an ereport(ERROR), we need to close out the copy so that
 * the frontend gets back into sync.  Therefore, these routines have to be
 * aware of COPY OUT state.  (New COPY-OUT is message-based and does *not*
 * set the DoingCopyOut flag.)
 *
 * NOTE: generally, it's a bad idea to emit outgoing messages directly with
 * pq_putbytes(), especially if the message would require multiple calls
 * to send.  Instead, use the routines in pqformat.c to construct the message
 * in a buffer and then emit it in one call to pq_putmessage.  This ensures
 * that the channel will not be clogged by an incomplete message if execution
 * is aborted by ereport(ERROR) partway through the message.  The only
 * non-libpq code that should call pq_putbytes directly is old-style COPY OUT.
 *
 * 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) 1996-2009, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *    $PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.199 2009/01/01 17:23:42 momjian Exp $
 *
 *-------------------------------------------------------------------------
 */

/*------------------------
 * INTERFACE ROUTINES
 *
 * setup/teardown:
 *          StreamServerPort  - Open postmaster's server port
 *          StreamConnection  - Create new connection with client
 *          StreamClose             - Close a client/backend connection
 *          TouchSocketFile         - Protect socket file against /tmp cleaners
 *          pq_init                 - initialize libpq at backend startup
 *          pq_comm_reset     - reset libpq during error recovery
 *          pq_close          - shutdown libpq at backend exit
 *
 * low-level I/O:
 *          pq_getbytes       - get a known number of bytes from connection
 *          pq_getstring      - get a null terminated string 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_putbytes       - send bytes to connection (not flushed until pq_flush)
 *          pq_flush          - flush pending output
 *
 * message-level I/O (and old-style-COPY-OUT cruft):
 *          pq_putmessage     - send a normal message (suppressed in COPY OUT mode)
 *          pq_startcopyout - inform libpq that a COPY OUT transfer is beginning
 *          pq_endcopyout     - end a COPY OUT transfer
 *
 *------------------------
 */
#include "postgres.h"

#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 <arpa/inet.h>
#ifdef HAVE_UTIME_H
#include <utime.h>
#endif

#include "libpq/ip.h"
#include "libpq/libpq.h"
#include "miscadmin.h"
#include "storage/ipc.h"
#include "utils/guc.h"

/*
 * Configuration options
 */
int               Unix_socket_permissions;
char     *Unix_socket_group;


/* Where the Unix socket file is */
static char sock_path[MAXPGPATH];


/*
 * Buffers for low-level I/O
 */

#define PQ_BUFFER_SIZE 8192

static char PqSendBuffer[PQ_BUFFER_SIZE];
static int  PqSendPointer;          /* Next index to store a byte in PqSendBuffer */

static char PqRecvBuffer[PQ_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;
static bool DoingCopyOut;


/* Internal functions */
static void pq_close(int code, Datum arg);
static int  internal_putbytes(const char *s, size_t len);
static int  internal_flush(void);

#ifdef HAVE_UNIX_SOCKETS
static int  Lock_AF_UNIX(unsigned short portNumber, char *unixSocketName);
static int  Setup_AF_UNIX(void);
#endif   /* HAVE_UNIX_SOCKETS */


/* --------------------------------
 *          pq_init - initialize libpq at backend startup
 * --------------------------------
 */
void
pq_init(void)
{
      PqSendPointer = PqRecvPointer = PqRecvLength = 0;
      PqCommBusy = false;
      DoingCopyOut = false;
      on_proc_exit(pq_close, 0);
}

/* --------------------------------
 *          pq_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...)
 * --------------------------------
 */
void
pq_comm_reset(void)
{
      /* Do not throw away pending data, but do reset the busy flag */
      PqCommBusy = false;
      /* We can abort any old-style COPY OUT, too */
      pq_endcopyout(true);
}

/* --------------------------------
 *          pq_close - shutdown libpq at backend exit
 *
 * Note: in a standalone backend MyProcPort will be null,
 * don't crash during exit...
 * --------------------------------
 */
static void
pq_close(int code, Datum arg)
{
      if (MyProcPort != NULL)
      {
#if defined(ENABLE_GSS) || defined(ENABLE_SSPI)
#ifdef ENABLE_GSS
            OM_uint32   min_s;

            /* Shutdown GSSAPI layer */
            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 */
            /* GSS and SSPI share the port->gss struct */

            free(MyProcPort->gss);
#endif   /* ENABLE_GSS || ENABLE_SSPI */

            /* Cleanly shut down SSL layer */
            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 -1 to prevent any further I/O, though.
             */
            MyProcPort->sock = -1;
      }
}



/*
 * Streams -- wrapper around Unix socket system calls
 *
 *
 *          Stream functions are used for vanilla TCP connection protocol.
 */


/* StreamDoUnlink()
 * Shutdown routine for backend connection
 * If a Unix socket is used for communication, explicitly close it.
 */
#ifdef HAVE_UNIX_SOCKETS
static void
StreamDoUnlink(int code, Datum arg)
{
      Assert(sock_path[0]);
      unlink(sock_path);
}
#endif   /* HAVE_UNIX_SOCKETS */

/*
 * StreamServerPort -- open a "listening" port to accept connections.
 *
 * Successfully opened sockets are added to the ListenSocket[] array,
 * at the first position that isn't -1.
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */

int
StreamServerPort(int family, char *hostName, unsigned short portNumber,
                         char *unixSocketName,
                         int ListenSocket[], int MaxListen)
{
      int               fd,
                        err;
      int               maxconn;
      int               ret;
      char        portNumberStr[32];
      const char *familyDesc;
      char        familyDescBuf[64];
      char     *service;
      struct addrinfo *addrs = NULL,
                     *addr;
      struct addrinfo hint;
      int               listen_index = 0;
      int               added = 0;

#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)
      {
            /* Lock_AF_UNIX will also fill in sock_path. */
            if (Lock_AF_UNIX(portNumber, unixSocketName) != STATUS_OK)
                  return STATUS_ERROR;
            service = sock_path;
      }
      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 (!IS_AF_UNIX(family) && IS_AF_UNIX(addr->ai_family))
            {
                  /*
                   * 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] == -1)
                        break;
            }
            if (listen_index >= MaxListen)
            {
                  ereport(LOG,
                              (errmsg("could not bind to all requested addresses: MAXLISTEN (%d) exceeded",
                                          MaxListen)));
                  break;
            }

            /* set up family name for possible error 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;
            }

            if ((fd = socket(addr->ai_family, SOCK_STREAM, 0)) < 0)
            {
                  ereport(LOG,
                              (errcode_for_socket_access(),
                  /* translator: %s is IPv4, IPv6, or Unix */
                               errmsg("could not create %s socket: %m",
                                          familyDesc)));
                  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_EXLUSIVEADDRUSE 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 (!IS_AF_UNIX(addr->ai_family))
            {
                  if ((setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
                                          (char *) &one, sizeof(one))) == -1)
                  {
                        ereport(LOG,
                                    (errcode_for_socket_access(),
                                     errmsg("setsockopt(SO_REUSEADDR) failed: %m")));
                        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(),
                                     errmsg("setsockopt(IPV6_V6ONLY) failed: %m")));
                        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)
            {
                  ereport(LOG,
                              (errcode_for_socket_access(),
                  /* translator: %s is IPv4, IPv6, or Unix */
                               errmsg("could not bind %s socket: %m",
                                          familyDesc),
                               (IS_AF_UNIX(addr->ai_family)) ?
                          errhint("Is another postmaster already running on port %d?"
                                      " If not, remove socket file \"%s\" and retry.",
                                      (int) portNumber, sock_path) :
                          errhint("Is another postmaster already running on port %d?"
                                      " If not, wait a few seconds and retry.",
                                      (int) portNumber)));
                  closesocket(fd);
                  continue;
            }

#ifdef HAVE_UNIX_SOCKETS
            if (addr->ai_family == AF_UNIX)
            {
                  if (Setup_AF_UNIX() != 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: %s is IPv4, IPv6, or Unix */
                               errmsg("could not listen on %s socket: %m",
                                          familyDesc)));
                  closesocket(fd);
                  continue;
            }
            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(unsigned short portNumber, char *unixSocketName)
{
      UNIXSOCK_PATH(sock_path, portNumber, unixSocketName);

      /*
       * Grab an interlock file associated with the socket file.
       */
      CreateSocketLockFile(sock_path, true);

      /*
       * Once we have the interlock, we can safely delete any pre-existing
       * socket file to avoid failure at bind() time.
       */
      unlink(sock_path);

      return STATUS_OK;
}


/*
 * Setup_AF_UNIX -- configure unix socket permissions
 */
static int
Setup_AF_UNIX(void)
{
      /* Arrange to unlink the socket file at exit */
      on_proc_exit(StreamDoUnlink, 0);

      /*
       * 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 server master
 *          socket is ready for accept().
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */
int
StreamConnection(int 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)) < 0)
      {
            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;
      }

#ifdef SCO_ACCEPT_BUG

      /*
       * UnixWare 7+ and OpenServer 5.0.4 are known to have this bug, but it
       * shouldn't hurt to catch it for all versions of those platforms.
       */
      if (port->raddr.addr.ss_family == 0)
            port->raddr.addr.ss_family = AF_UNIX;
#endif

      /* 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)
      {
            elog(LOG, "getsockname() failed: %m");
            return STATUS_ERROR;
      }

      /* select NODELAY and KEEPALIVE options if it's a TCP connection */
      if (!IS_AF_UNIX(port->laddr.addr.ss_family))
      {
            int               on;

#ifdef      TCP_NODELAY
            on = 1;
            if (setsockopt(port->sock, IPPROTO_TCP, TCP_NODELAY,
                                 (char *) &on, sizeof(on)) < 0)
            {
                  elog(LOG, "setsockopt(TCP_NODELAY) failed: %m");
                  return STATUS_ERROR;
            }
#endif
            on = 1;
            if (setsockopt(port->sock, SOL_SOCKET, SO_KEEPALIVE,
                                 (char *) &on, sizeof(on)) < 0)
            {
                  elog(LOG, "setsockopt(SO_KEEPALIVE) failed: %m");
                  return STATUS_ERROR;
            }

#ifdef WIN32

            /*
             * This is a Win32 socket optimization.  The ideal size is 32k.
             * http://support.microsoft.com/kb/823764/EN-US/
             */
            on = PQ_BUFFER_SIZE * 4;
            if (setsockopt(port->sock, SOL_SOCKET, SO_SNDBUF, (char *) &on,
                                 sizeof(on)) < 0)
            {
                  elog(LOG, "setsockopt(SO_SNDBUF) failed: %m");
                  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);
      }

      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(int sock)
{
      closesocket(sock);
}

/*
 * TouchSocketFile -- mark socket file as recently accessed
 *
 * This routine should be called every so often to ensure that the socket
 * file has a recent mod date (ordinary operations on sockets usually won't
 * change the mod date).  That saves it from being removed by
 * overenthusiastic /tmp-directory-cleaner daemons.  (Another reason we should
 * never have put the socket file in /tmp...)
 */
void
TouchSocketFile(void)
{
      /* Do nothing if we did not create a socket... */
      if (sock_path[0] != '\0')
      {
            /*
             * utime() is POSIX standard, utimes() is a common alternative. If we
             * have neither, there's no way to affect the mod or access time of
             * the socket :-(
             *
             * In either path, we ignore errors; there's no point in complaining.
             */
#ifdef HAVE_UTIME
            utime(sock_path, NULL);
#else                                     /* !HAVE_UTIME */
#ifdef HAVE_UTIMES
            utimes(sock_path, NULL);
#endif   /* HAVE_UTIMES */
#endif   /* HAVE_UTIME */
      }
}


/* --------------------------------
 * Low-level I/O routines begin here.
 *
 * These routines communicate with a frontend client across a connection
 * already established by the preceding routines.
 * --------------------------------
 */


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

      /* Can fill buffer from PqRecvLength and upwards */
      for (;;)
      {
            int               r;

            r = secure_read(MyProcPort, PqRecvBuffer + PqRecvLength,
                                    PQ_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)
{
      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)
{
      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_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;

      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;

      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_getstring      - get a null terminated string from connection
 *
 *          The return value is placed in an expansible StringInfo, which has
 *          already been initialized by the caller.
 *
 *          This is used only for dealing with old-protocol clients.  The idea
 *          is to produce a StringInfo that looks the same as we would get from
 *          pq_getmessage() with a newer client; we will then process it with
 *          pq_getmsgstring.  Therefore, no character set conversion is done here,
 *          even though this is presumably useful only for text.
 *
 *          returns 0 if OK, EOF if trouble
 * --------------------------------
 */
int
pq_getstring(StringInfo s)
{
      int               i;

      resetStringInfo(s);

      /* Read until we get the terminating '\0' */
      for (;;)
      {
            while (PqRecvPointer >= PqRecvLength)
            {
                  if (pq_recvbuf()) /* If nothing in buffer, then recv some */
                        return EOF;       /* Failed to recv data */
            }

            for (i = PqRecvPointer; i < PqRecvLength; i++)
            {
                  if (PqRecvBuffer[i] == '\0')
                  {
                        /* include the '\0' in the copy */
                        appendBinaryStringInfo(s, PqRecvBuffer + PqRecvPointer,
                                                         i - PqRecvPointer + 1);
                        PqRecvPointer = i + 1;  /* advance past \0 */
                        return 0;
                  }
            }

            /* If we're here we haven't got the \0 in the buffer yet. */
            appendBinaryStringInfo(s, PqRecvBuffer + PqRecvPointer,
                                             PqRecvLength - PqRecvPointer);
            PqRecvPointer = PqRecvLength;
      }
}


/* --------------------------------
 *          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.
 *
 *          If maxlen is not zero, it is an 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;

      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 = ntohl(len);

      if (len < 4 ||
            (maxlen > 0 && 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")));
                  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';
      }

      return 0;
}


/* --------------------------------
 *          pq_putbytes       - send bytes to connection (not flushed until pq_flush)
 *
 *          returns 0 if OK, EOF if trouble
 * --------------------------------
 */
int
pq_putbytes(const char *s, size_t len)
{
      int               res;

      /* Should only be called by old-style COPY OUT */
      Assert(DoingCopyOut);
      /* No-op if reentrant call */
      if (PqCommBusy)
            return 0;
      PqCommBusy = true;
      res = internal_putbytes(s, len);
      PqCommBusy = false;
      return res;
}

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 >= PQ_BUFFER_SIZE)
                  if (internal_flush())
                        return EOF;
            amount = PQ_BUFFER_SIZE - PqSendPointer;
            if (amount > len)
                  amount = len;
            memcpy(PqSendBuffer + PqSendPointer, s, amount);
            PqSendPointer += amount;
            s += amount;
            len -= amount;
      }
      return 0;
}

/* --------------------------------
 *          pq_flush          - flush pending output
 *
 *          returns 0 if OK, EOF if trouble
 * --------------------------------
 */
int
pq_flush(void)
{
      int               res;

      /* No-op if reentrant call */
      if (PqCommBusy)
            return 0;
      PqCommBusy = true;
      res = internal_flush();
      PqCommBusy = false;
      return res;
}

static int
internal_flush(void)
{
      static int  last_reported_send_errno = 0;

      char     *bufptr = PqSendBuffer;
      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 */

                  /*
                   * 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.
                   */
                  PqSendPointer = 0;
                  return EOF;
            }

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

      PqSendPointer = 0;
      return 0;
}


/* --------------------------------
 * Message-level I/O routines begin here.
 *
 * These routines understand about the old-style COPY OUT protocol.
 * --------------------------------
 */


/* --------------------------------
 *          pq_putmessage     - send a normal message (suppressed in COPY OUT mode)
 *
 *          If msgtype is not '\0', it is a message type code to place before
 *          the message body.  If msgtype is '\0', then the message has no type
 *          code (this is only valid in pre-3.0 protocols).
 *
 *          len is the length of the message body data at *s.  In protocol 3.0
 *          and later, a message length word (equal to len+4 because it counts
 *          itself too) is inserted by this routine.
 *
 *          All normal messages are suppressed while old-style COPY OUT is in
 *          progress.  (In practice only a few notice messages might get emitted
 *          then; dropping them is annoying, but at least they will still appear
 *          in the postmaster log.)
 *
 *          We also 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
 * --------------------------------
 */
int
pq_putmessage(char msgtype, const char *s, size_t len)
{
      if (DoingCopyOut || PqCommBusy)
            return 0;
      PqCommBusy = true;
      if (msgtype)
            if (internal_putbytes(&msgtype, 1))
                  goto fail;
      if (PG_PROTOCOL_MAJOR(FrontendProtocol) >= 3)
      {
            uint32            n32;

            n32 = htonl((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_startcopyout - inform libpq that an old-style COPY OUT transfer
 *                is beginning
 * --------------------------------
 */
void
pq_startcopyout(void)
{
      DoingCopyOut = true;
}

/* --------------------------------
 *          pq_endcopyout     - end an old-style COPY OUT transfer
 *
 *          If errorAbort is indicated, we are aborting a COPY OUT due to an error,
 *          and must send a terminator line.  Since a partial data line might have
 *          been emitted, send a couple of newlines first (the first one could
 *          get absorbed by a backslash...)  Note that old-style COPY OUT does
 *          not allow binary transfers, so a textual terminator is always correct.
 * --------------------------------
 */
void
pq_endcopyout(bool errorAbort)
{
      if (!DoingCopyOut)
            return;
      if (errorAbort)
            pq_putbytes("\n\n\\.\n", 5);
      /* in non-error case, copy.c will have emitted the terminator line */
      DoingCopyOut = false;
}


/*
 * Support for TCP Keepalive parameters
 */

int
pq_getkeepalivesidle(Port *port)
{
#ifdef TCP_KEEPIDLE
      if (port == NULL || IS_AF_UNIX(port->laddr.addr.ss_family))
            return 0;

      if (port->keepalives_idle != 0)
            return port->keepalives_idle;

      if (port->default_keepalives_idle == 0)
      {
            ACCEPT_TYPE_ARG3 size = sizeof(port->default_keepalives_idle);

            if (getsockopt(port->sock, IPPROTO_TCP, TCP_KEEPIDLE,
                                 (char *) &port->default_keepalives_idle,
                                 &size) < 0)
            {
                  elog(LOG, "getsockopt(TCP_KEEPIDLE) failed: %m");
                  port->default_keepalives_idle = -1; /* don't know */
            }
      }

      return port->default_keepalives_idle;
#else
      return 0;
#endif
}

int
pq_setkeepalivesidle(int idle, Port *port)
{
      if (port == NULL || IS_AF_UNIX(port->laddr.addr.ss_family))
            return STATUS_OK;

#ifdef TCP_KEEPIDLE
      if (idle == port->keepalives_idle)
            return STATUS_OK;

      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, TCP_KEEPIDLE,
                           (char *) &idle, sizeof(idle)) < 0)
      {
            elog(LOG, "setsockopt(TCP_KEEPIDLE) failed: %m");
            return STATUS_ERROR;
      }

      port->keepalives_idle = idle;
#else
      if (idle != 0)
      {
            elog(LOG, "setsockopt(TCP_KEEPIDLE) not supported");
            return STATUS_ERROR;
      }
#endif

      return STATUS_OK;
}

int
pq_getkeepalivesinterval(Port *port)
{
#ifdef TCP_KEEPINTVL
      if (port == NULL || IS_AF_UNIX(port->laddr.addr.ss_family))
            return 0;

      if (port->keepalives_interval != 0)
            return port->keepalives_interval;

      if (port->default_keepalives_interval == 0)
      {
            ACCEPT_TYPE_ARG3 size = sizeof(port->default_keepalives_interval);

            if (getsockopt(port->sock, IPPROTO_TCP, TCP_KEEPINTVL,
                                 (char *) &port->default_keepalives_interval,
                                 &size) < 0)
            {
                  elog(LOG, "getsockopt(TCP_KEEPINTVL) failed: %m");
                  port->default_keepalives_interval = -1;         /* don't know */
            }
      }

      return port->default_keepalives_interval;
#else
      return 0;
#endif
}

int
pq_setkeepalivesinterval(int interval, Port *port)
{
      if (port == NULL || IS_AF_UNIX(port->laddr.addr.ss_family))
            return STATUS_OK;

#ifdef TCP_KEEPINTVL
      if (interval == port->keepalives_interval)
            return STATUS_OK;

      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)
      {
            elog(LOG, "setsockopt(TCP_KEEPINTVL) failed: %m");
            return STATUS_ERROR;
      }

      port->keepalives_interval = interval;
#else
      if (interval != 0)
      {
            elog(LOG, "setsockopt(TCP_KEEPINTVL) not supported");
            return STATUS_ERROR;
      }
#endif

      return STATUS_OK;
}

int
pq_getkeepalivescount(Port *port)
{
#ifdef TCP_KEEPCNT
      if (port == NULL || IS_AF_UNIX(port->laddr.addr.ss_family))
            return 0;

      if (port->keepalives_count != 0)
            return port->keepalives_count;

      if (port->default_keepalives_count == 0)
      {
            ACCEPT_TYPE_ARG3 size = sizeof(port->default_keepalives_count);

            if (getsockopt(port->sock, IPPROTO_TCP, TCP_KEEPCNT,
                                 (char *) &port->default_keepalives_count,
                                 &size) < 0)
            {
                  elog(LOG, "getsockopt(TCP_KEEPCNT) failed: %m");
                  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 || IS_AF_UNIX(port->laddr.addr.ss_family))
            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)
      {
            elog(LOG, "setsockopt(TCP_KEEPCNT) failed: %m");
            return STATUS_ERROR;
      }

      port->keepalives_count = count;
#else
      if (count != 0)
      {
            elog(LOG, "setsockopt(TCP_KEEPCNT) not supported");
            return STATUS_ERROR;
      }
#endif

      return STATUS_OK;
}

Generated by  Doxygen 1.6.0   Back to index