/*
* handleSyncLoss: clean up after loss of message-boundary sync
*
* There isn't really a lot we can do here except abandon the connection.
*/
static void
handleSyncLoss(PGconn *conn, char id, int msgLength)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext(
"lost synchronization with server: got message type \"%c\", length %d\n"),
id, msgLength);
/* build an error result holding the error message */
pqSaveErrorResult(conn);
conn->asyncStatus = PGASYNC_READY; /* drop out of GetResult wait loop */
pqsecure_close(conn);
closesocket(conn->sock);
conn->sock = -1;
conn->status = CONNECTION_BAD; /* No more connection to backend */
}
/* ----------
* pqReadData: read more data, if any is available
* Possible return values:
* 1: successfully loaded at least one more byte
* 0: no data is presently available, but no error detected
* -1: error detected (including EOF = connection closure);
* conn->errorMessage set
* NOTE: callers must not assume that pointers or indexes into conn->inBuffer
* remain valid across this call!
* ----------
*/
int
pqReadData(PGconn *conn)
{
int someread = 0;
int nread;
char sebuf[256];
if (conn->sock < 0)
{
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("connection not open\n"));
return -1;
}
/* Left-justify any data in the buffer to make room */
if (conn->inStart < conn->inEnd)
{
if (conn->inStart > 0)
{
memmove(conn->inBuffer, conn->inBuffer + conn->inStart,
conn->inEnd - conn->inStart);
conn->inEnd -= conn->inStart;
conn->inCursor -= conn->inStart;
conn->inStart = 0;
}
}
else
{
/* buffer is logically empty, reset it */
conn->inStart = conn->inCursor = conn->inEnd = 0;
}
/*
* If the buffer is fairly full, enlarge it. We need to be able to enlarge
* the buffer in case a single message exceeds the initial buffer size. We
* enlarge before filling the buffer entirely so as to avoid asking the
* kernel for a partial packet. The magic constant here should be large
* enough for a TCP packet or Unix pipe bufferload. 8K is the usual pipe
* buffer size, so...
*/
if (conn->inBufSize - conn->inEnd < 8192)
{
if (pqCheckInBufferSpace(conn->inEnd + (size_t) 8192, conn))
{
/*
* We don't insist that the enlarge worked, but we need some room
*/
if (conn->inBufSize - conn->inEnd < 100)
return -1; /* errorMessage already set */
}
}
/* OK, try to read some data */
retry3:
nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
conn->inBufSize - conn->inEnd);
if (nread < 0)
{
if (SOCK_ERRNO == EINTR)
goto retry3;
/* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
if (SOCK_ERRNO == EAGAIN)
return someread;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
if (SOCK_ERRNO == EWOULDBLOCK)
return someread;
#endif
/* We might get ECONNRESET here if using TCP and backend died */
#ifdef ECONNRESET
if (SOCK_ERRNO == ECONNRESET)
goto definitelyFailed;
#endif
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not receive data from server: %s\n"),
SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
return -1;
}
if (nread > 0)
{
conn->inEnd += nread;
/*
* Hack to deal with the fact that some kernels will only give us back
* 1 packet per recv() call, even if we asked for more and there is
* more available. If it looks like we are reading a long message,
* loop back to recv() again immediately, until we run out of data or
* buffer space. Without this, the block-and-restart behavior of
* libpq's higher levels leads to O(N^2) performance on long messages.
*
* Since we left-justified the data above, conn->inEnd gives the
* amount of data already read in the current message. We consider
* the message "long" once we have acquired 32k ...
*/
if (conn->inEnd > 32768 &&
(conn->inBufSize - conn->inEnd) >= 8192)
{
someread = 1;
goto retry3;
}
return 1;
}
if (someread)
return 1; /* got a zero read after successful tries */
/*
* A return value of 0 could mean just that no data is now available, or
* it could mean EOF --- that is, the server has closed the connection.
* Since we have the socket in nonblock mode, the only way to tell the
* difference is to see if select() is saying that the file is ready.
* Grumble. Fortunately, we don't expect this path to be taken much,
* since in normal practice we should not be trying to read data unless
* the file selected for reading already.
*
* In SSL mode it's even worse: SSL_read() could say WANT_READ and then
* data could arrive before we make the pqReadReady() test. So we must
* play dumb and assume there is more data, relying on the SSL layer to
* detect true EOF.
*/
#ifdef USE_SSL
if (conn->ssl)
return 0;
#endif
switch (pqReadReady(conn))
{
case 0:
/* definitely no data available */
return 0;
case 1:
/* ready for read */
break;
default:
goto definitelyFailed;
}
/*
* Still not sure that it's EOF, because some data could have just
* arrived.
*/
retry4:
nread = pqsecure_read(conn, conn->inBuffer + conn->inEnd,
conn->inBufSize - conn->inEnd);
if (nread < 0)
{
if (SOCK_ERRNO == EINTR)
goto retry4;
/* Some systems return EAGAIN/EWOULDBLOCK for no data */
#ifdef EAGAIN
if (SOCK_ERRNO == EAGAIN)
return 0;
#endif
#if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
if (SOCK_ERRNO == EWOULDBLOCK)
return 0;
#endif
/* We might get ECONNRESET here if using TCP and backend died */
#ifdef ECONNRESET
if (SOCK_ERRNO == ECONNRESET)
goto definitelyFailed;
#endif
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext("could not receive data from server: %s\n"),
SOCK_STRERROR(SOCK_ERRNO, sebuf, sizeof(sebuf)));
return -1;
}
if (nread > 0)
{
conn->inEnd += nread;
return 1;
}
/*
* OK, we are getting a zero read even though select() says ready. This
* means the connection has been closed. Cope.
*/
definitelyFailed:
printfPQExpBuffer(&conn->errorMessage,
libpq_gettext(
"server closed the connection unexpectedly\n"
"\tThis probably means the server terminated abnormally\n"
"\tbefore or while processing the request.\n"));
conn->status = CONNECTION_BAD; /* No more connection to backend */
pqsecure_close(conn);
closesocket(conn->sock);
conn->sock = -1;
return -1;
}
