pqcomm.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

/*-------------------------------------------------------------------------
 *
 * 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) 1996-2005, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *	$PostgreSQL: pgsql/src/backend/libpq/pqcomm.c,v 1.182.2.1 2006/01/24 16:38:50 tgl 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 <errno.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/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)
	{
		/* 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			one = 1;
	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;

	/* 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;
		}

		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;
			}
		}

#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