From: Heikki Linnakangas <heikki.linnakangas@iki.fi>
Date: Thu, 12 Feb 2015 16:58:01 +0000 (+0200)
Subject: WIP: Do the same block-raw-read dance in backend.
X-Git-Url: http://git.postgresql.org/gitweb/static/gitweb.js?a=commitdiff_plain;h=63eb36c44bd95776ecf2d7dfc68928a245b96d33;p=users%2Fheikki%2Fpostgres.git

WIP: Do the same block-raw-read dance in backend.

This is more complicated than in the client, because the callers of
secure_write() will not automatically do a read, if the write fails.
Need to expose pq_recvbuf() and call it from secure_write(), which is
modularity violation.
---

diff --git a/src/backend/libpq/be-secure.c b/src/backend/libpq/be-secure.c
index a8d14d5d8a..f37ec8ea06 100644
--- a/src/backend/libpq/be-secure.c
+++ b/src/backend/libpq/be-secure.c
@@ -108,6 +108,9 @@ int			ssl_renegotiation_limit;
 /* are we in the middle of a renegotiation? */
 static bool in_ssl_renegotiation = false;
 
+/* kill-switch to have my_sock_read pretend there's no data */
+static bool my_block_raw_read = false;
+
 static SSL_CTX *SSL_context = NULL;
 static bool ssl_loaded_verify_locations = false;
 #endif
@@ -367,7 +370,9 @@ secure_write(Port *port, void *ptr, size_t len)
 
 wloop:
 		errno = 0;
+		my_block_raw_read = true;
 		n = SSL_write(port->ssl, ptr, len);
+		my_block_raw_read = false;
 		err = SSL_get_error(port->ssl, n);
 		switch (err)
 		{
@@ -382,6 +387,15 @@ wloop:
 									FD_READ | FD_CLOSE : FD_WRITE | FD_CLOSE,
 											INFINITE);
 #endif
+				if (err == SSL_ERROR_WANT_READ)
+				{
+					if (pq_recvbuf(false) != 0)
+					{
+						errno = ECONNRESET;
+						n = -1;
+						break;
+					}
+				}
 				goto wloop;
 			case SSL_ERROR_SYSCALL:
 				/* leave it to caller to ereport the value of errno */
@@ -466,19 +480,28 @@ my_sock_read(BIO *h, char *buf, int size)
 {
 	int			res = 0;
 
-	prepare_for_client_read();
+	if (buf == NULL)
+		return 0;	/* XXX: can this happen? */
 
-	if (buf != NULL)
+	/* If the kill-switch is set, pretend that there is no data. */
+	if (my_block_raw_read)
 	{
-		res = recv(h->num, buf, size, 0);
 		BIO_clear_retry_flags(h);
-		if (res <= 0)
+		BIO_set_retry_read(h);
+		errno = EWOULDBLOCK;
+		return -1;
+	}
+
+	prepare_for_client_read();
+
+	res = recv(h->num, buf, size, 0);
+	BIO_clear_retry_flags(h);
+	if (res <= 0)
+	{
+		/* If we were interrupted, tell caller to retry */
+		if (errno == EINTR)
 		{
-			/* If we were interrupted, tell caller to retry */
-			if (errno == EINTR)
-			{
-				BIO_set_retry_read(h);
-			}
+			BIO_set_retry_read(h);
 		}
 	}
 
diff --git a/src/backend/libpq/pqcomm.c b/src/backend/libpq/pqcomm.c
index c08c5d73ba..88c34b09ab 100644
--- a/src/backend/libpq/pqcomm.c
+++ b/src/backend/libpq/pqcomm.c
@@ -825,11 +825,11 @@ pq_set_nonblocking(bool nonblocking)
 /* --------------------------------
  *		pq_recvbuf - load some bytes into the input buffer
  *
- *		returns 0 if OK, EOF if trouble
+ *		returns 0 if OK, EOF if	trouble
  * --------------------------------
  */
-static int
-pq_recvbuf(void)
+int
+pq_recvbuf(bool block)
 {
 	if (PqRecvPointer > 0)
 	{
@@ -845,8 +845,8 @@ pq_recvbuf(void)
 			PqRecvLength = PqRecvPointer = 0;
 	}
 
-	/* Ensure that we're in blocking mode */
-	pq_set_nonblocking(false);
+	/* Ensure that we're in blocking mode (or not) */
+	pq_set_nonblocking(!block);
 
 	/* Can fill buffer from PqRecvLength and upwards */
 	for (;;)
@@ -861,6 +861,12 @@ pq_recvbuf(void)
 			if (errno == EINTR)
 				continue;		/* Ok if interrupted */
 
+			if (!block)
+			{
+				if (errno == EWOULDBLOCK || errno == EAGAIN)
+					return 0;
+			}
+
 			/*
 			 * Careful: an ereport() that tries to write to the client would
 			 * cause recursion to here, leading to stack overflow and core
@@ -896,7 +902,7 @@ pq_getbyte(void)
 
 	while (PqRecvPointer >= PqRecvLength)
 	{
-		if (pq_recvbuf())		/* If nothing in buffer, then recv some */
+		if (pq_recvbuf(true))		/* If nothing in buffer, then recv some */
 			return EOF;			/* Failed to recv data */
 	}
 	return (unsigned char) PqRecvBuffer[PqRecvPointer++];
@@ -913,7 +919,7 @@ pq_peekbyte(void)
 {
 	while (PqRecvPointer >= PqRecvLength)
 	{
-		if (pq_recvbuf())		/* If nothing in buffer, then recv some */
+		if (pq_recvbuf(true))	/* If nothing in buffer, then recv some */
 			return EOF;			/* Failed to recv data */
 	}
 	return (unsigned char) PqRecvBuffer[PqRecvPointer];
@@ -992,7 +998,7 @@ pq_getbytes(char *s, size_t len)
 	{
 		while (PqRecvPointer >= PqRecvLength)
 		{
-			if (pq_recvbuf())	/* If nothing in buffer, then recv some */
+			if (pq_recvbuf(true))	/* If nothing in buffer, then recv some */
 				return EOF;		/* Failed to recv data */
 		}
 		amount = PqRecvLength - PqRecvPointer;
@@ -1026,7 +1032,7 @@ pq_discardbytes(size_t len)
 	{
 		while (PqRecvPointer >= PqRecvLength)
 		{
-			if (pq_recvbuf())	/* If nothing in buffer, then recv some */
+			if (pq_recvbuf(true))	/* If nothing in buffer, then recv some */
 				return EOF;		/* Failed to recv data */
 		}
 		amount = PqRecvLength - PqRecvPointer;
@@ -1067,7 +1073,7 @@ pq_getstring(StringInfo s)
 	{
 		while (PqRecvPointer >= PqRecvLength)
 		{
-			if (pq_recvbuf())	/* If nothing in buffer, then recv some */
+			if (pq_recvbuf(true))	/* If nothing in buffer, then recv some */
 				return EOF;		/* Failed to recv data */
 		}
 
diff --git a/src/include/libpq/libpq.h b/src/include/libpq/libpq.h
index 9d216facae..3b08fad11b 100644
--- a/src/include/libpq/libpq.h
+++ b/src/include/libpq/libpq.h
@@ -1,3 +1,4 @@
+
 /*-------------------------------------------------------------------------
  *
  * libpq.h
@@ -69,6 +70,7 @@ extern int	pq_putmessage(char msgtype, const char *s, size_t len);
 extern void pq_putmessage_noblock(char msgtype, const char *s, size_t len);
 extern void pq_startcopyout(void);
 extern void pq_endcopyout(bool errorAbort);
+extern int	pq_recvbuf(bool block);
 
 /*
  * prototypes for functions in be-secure.c