pqcomm.c

关系型数据库 Postgresql 6.5.2

/*-------------------------------------------------------------------------
 *
 * 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 COPY OUT protocol.
 * Unfortunately, COPY OUT is 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 elog(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.
 *
 * 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 helps
 * ensure that the channel will not be clogged by an incomplete message
 * if execution is aborted by elog(ERROR) partway through the message.
 * The only non-libpq code that should call pq_putbytes directly is 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...
 *
 * Copyright (c) 1994, Regents of the University of California
 *
 *	$Id: pqcomm.c,v 1.73.2.1 1999/09/08 23:00:51 tgl Exp $
 *
 *-------------------------------------------------------------------------
 */

/*------------------------
 * INTERFACE ROUTINES
 *
 * setup/teardown:
 *		StreamServerPort	- Open postmaster's server port
 *		StreamConnection	- Create new connection with client
 *		StreamClose			- Close a client/backend connection
 *		pq_getport		- return the PGPORT setting
 *		pq_init			- initialize libpq at backend startup
 *		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_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 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 <stdio.h>
#if defined(HAVE_STRING_H)
#include <string.h>
#else
#include <strings.h>
#endif
#include <signal.h>
#include <errno.h>
#include <fcntl.h>
#include <unistd.h>				/* for ttyname() */
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <arpa/inet.h>
#include <sys/file.h>

#include "libpq/libpq.h"		/* where my declarations go */
#include "miscadmin.h"
#include "libpq/pqsignal.h"
#include "libpq/auth.h"
#include "storage/ipc.h"
#include "utils/trace.h"

#ifndef SOMAXCONN
#define SOMAXCONN 5				/* from Linux listen(2) man page */
#endif	 /* SOMAXCONN */

extern FILE *debug_port;		/* in util.c */

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

#define PQ_BUFFER_SIZE 8192

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

static unsigned 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 DoingCopyOut;


/* --------------------------------
 *		pq_init - initialize libpq at backend startup
 * --------------------------------
 */
void
pq_init(void)
{
	PqSendPointer = PqRecvPointer = PqRecvLength = 0;
	DoingCopyOut = false;
	if (getenv("LIBPQ_DEBUG"))
		debug_port = stderr;
}

/* --------------------------------
 *		pq_getport - return the PGPORT setting
 * --------------------------------
 */
int
pq_getport(void)
{
	char	   *envport = getenv("PGPORT");

	if (envport)
		return atoi(envport);
	return atoi(DEF_PGPORT);
}

/* --------------------------------
 *		pq_close - shutdown libpq at backend exit
 * --------------------------------
 */
void
pq_close(void)
{
	close(MyProcPort->sock);
}



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

static char sock_path[MAXPGPATH + 1] = "";

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

/*
 * StreamServerPort -- open a sock stream "listening" port.
 *
 * This initializes the Postmaster's connection-accepting port.
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */

int
StreamServerPort(char *hostName, unsigned short portName, int *fdP)
{
	SockAddr	saddr;
	int			fd,
				err,
				family;
	size_t		len;
	int			one = 1;

#ifdef HAVE_FCNTL_SETLK
	int			lock_fd;

#endif

	family = ((hostName != NULL) ? AF_INET : AF_UNIX);

	if ((fd = socket(family, SOCK_STREAM, 0)) < 0)
	{
		snprintf(PQerrormsg, ERROR_MSG_LENGTH,
				 "FATAL: StreamServerPort: socket() failed: %s\n",
				 strerror(errno));
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return STATUS_ERROR;
	}

#ifdef ONLY_REUSE_INET_SOCKETS
	if (family == AF_INET)
	{
#endif

		if ((setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, (char *) &one,
						sizeof(one))) == -1)
		{
			snprintf(PQerrormsg, ERROR_MSG_LENGTH,
					 "FATAL: StreamServerPort: setsockopt(SO_REUSEADDR) failed: %s\n",
					 strerror(errno));
			fputs(PQerrormsg, stderr);
			pqdebug("%s", PQerrormsg);
			return STATUS_ERROR;
		}

#ifdef ONLY_REUSE_INET_SOCKETS
	}
#endif

	MemSet((char *) &saddr, 0, sizeof(saddr));
	saddr.sa.sa_family = family;
	if (family == AF_UNIX)
	{
		len = UNIXSOCK_PATH(saddr.un, portName);
		strcpy(sock_path, saddr.un.sun_path);

		/*
		 * If the socket exists but nobody has an advisory lock on it we
		 * can safely delete the file.
		 */
#ifdef HAVE_FCNTL_SETLK
#ifndef __CYGWIN32__
		if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK, 0666)) >= 0)
#else
		if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK | O_BINARY, 0666)) >= 0)
#endif
		{
			struct flock lck;

			lck.l_whence = SEEK_SET;
			lck.l_start = lck.l_len = 0;
			lck.l_type = F_WRLCK;
			if (fcntl(lock_fd, F_SETLK, &lck) == 0)
			{
				TPRINTF(TRACE_VERBOSE, "flock on %s, deleting", sock_path);
				unlink(sock_path);
			}
			else
				TPRINTF(TRACE_VERBOSE, "flock failed for %s", sock_path);
			close(lock_fd);
		}
#endif	 /* HAVE_FCNTL_SETLK */
	}
	else
	{
		saddr.in.sin_addr.s_addr = htonl(INADDR_ANY);
		saddr.in.sin_port = htons(portName);
		len = sizeof(struct sockaddr_in);
	}
	err = bind(fd, &saddr.sa, len);
	if (err < 0)
	{
		snprintf(PQerrormsg, ERROR_MSG_LENGTH,
				 "FATAL: StreamServerPort: bind() failed: %s\n",
				 strerror(errno));
		strcat(PQerrormsg,
			   "\tIs another postmaster already running on that port?\n");
		if (family == AF_UNIX)
		{
			snprintf(PQerrormsg + strlen(PQerrormsg),
					 ERROR_MSG_LENGTH - strlen(PQerrormsg),
					 "\tIf not, remove socket node (%s) and retry.\n",
					 sock_path);
		}
		else
			strcat(PQerrormsg, "\tIf not, wait a few seconds and retry.\n");
		fputs(PQerrormsg, stderr);
		pqdebug("%s", PQerrormsg);
		return STATUS_ERROR;
	}

	if (family == AF_UNIX)
	{
		on_proc_exit(StreamDoUnlink, NULL);

		/*
		 * Open the socket file and get an advisory lock on it. The
		 * lock_fd is left open to keep the lock.
		 */
#ifdef HAVE_FCNTL_SETLK
#ifndef __CYGWIN32__
		if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK, 0666)) >= 0)
#else
		if ((lock_fd = open(sock_path, O_WRONLY | O_NONBLOCK | O_BINARY, 0666)) >= 0)
#endif
		{
			struct flock lck;

			lck.l_whence = SEEK_SET;
			lck.l_start = lck.l_len = 0;
			lck.l_type = F_WRLCK;
			if (fcntl(lock_fd, F_SETLK, &lck) != 0)
				TPRINTF(TRACE_VERBOSE, "flock error for %s", sock_path);
		}
#endif	 /* HAVE_FCNTL_SETLK */
	}

	listen(fd, SOMAXCONN);

	/*
	 * MS: I took this code from Dillon's version.  It makes the listening
	 * port non-blocking.  That is not necessary (and may tickle kernel
	 * bugs).
	 *
	 * fcntl(fd, F_SETFD, 1); fcntl(fd, F_SETFL, FNDELAY);
	 */

	*fdP = fd;
	if (family == AF_UNIX)
		chmod(sock_path, 0777);
	return STATUS_OK;
}

/*
 * StreamConnection -- create a new connection with client using
 *		server port.
 *
 * 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().
 *
 * NB: this can NOT call elog() because it is invoked in the postmaster,
 * not in standard backend context.  If we get an error, the best we can do
 * is log it to stderr.
 *
 * RETURNS: STATUS_OK or STATUS_ERROR
 */
int
StreamConnection(int server_fd, Port *port)
{
	SOCKET_SIZE_TYPE addrlen;

	/* accept connection (and fill in the client (remote) address) */
	addrlen = sizeof(port->raddr);
	if ((port->sock = accept(server_fd,