pqcomm.c

PostgreSQL 8.1.4的源码 适用于Linux下的开源数据库系统

 */
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.
 *
 * 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")));
		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;
		}

		/*
		 * 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;

	/* Reset string to empty */
	s->len = 0;
	s->data[0] = '\0';
	s->cursor = 0;

	/* 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;

	/* Reset message buffer to empty */
	s->len = 0;
	s->data[0] = '\0';
	s->cursor = 0;

	/* 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