Recognize network-failure errnos as indicating hard connection loss.

Up to now, only ECONNRESET (and EPIPE, in most but not quite all places)
received special treatment in our error handling logic.  This patch
changes things so that related error codes such as ECONNABORTED are
also recognized as indicating that the connection's dead and unlikely
to come back.

We continue to think, however, that only ECONNRESET and EPIPE should be
reported as probable server crashes; the other cases indicate network
connectivity problems but prove little about the server's state.  Thus,
there's no change in the error message texts that are output for such
cases.  The key practical effect is that errcode_for_socket_access()
will report ERRCODE_CONNECTION_FAILURE rather than
ERRCODE_INTERNAL_ERROR for a network failure.  It's expected that this
will fix buildfarm member lorikeet's failures since commit 32a9c0bd,
as that seems to be due to not treating ECONNABORTED equivalently to
ECONNRESET.

The set of errnos treated this way now includes ECONNABORTED, EHOSTDOWN,
EHOSTUNREACH, ENETDOWN, ENETRESET, and ENETUNREACH.  Several of these
were second-class citizens in terms of their handling in places like
get_errno_symbol(), so upgrade the infrastructure where necessary.

As committed, this patch assumes that all these symbols are defined
everywhere.  POSIX specifies all of them except EHOSTDOWN, but that
seems to exist on all platforms of interest; we'll see what the
buildfarm says about that.

Probably this should be back-patched, but let's see what the buildfarm
thinks of it first.

Fujii Masao and Tom Lane

Discussion: https://postgr.es/m/2621622.1602184554@sss.pgh.pa.us

src/backend/port/win32/socket.c

@@ -120,13 +120,21 @@ TranslateSocketError(void)
 		case WSAEADDRNOTAVAIL:
 			errno = EADDRNOTAVAIL;
 			break;
-		case WSAEHOSTUNREACH:
 		case WSAEHOSTDOWN:
+			errno = EHOSTDOWN;
+			break;
+		case WSAEHOSTUNREACH:
 		case WSAHOST_NOT_FOUND:
+			errno = EHOSTUNREACH;
+			break;
 		case WSAENETDOWN:
+			errno = ENETDOWN;
+			break;
 		case WSAENETUNREACH:
+			errno = ENETUNREACH;
+			break;
 		case WSAENETRESET:
-			errno = EHOSTUNREACH;
+			errno = ENETRESET;
 			break;
 		case WSAENOTCONN:
 		case WSAESHUTDOWN:

src/backend/utils/error/elog.c

@@ -711,10 +711,7 @@ errcode_for_socket_access(void)
 	switch (edata->saved_errno)
 	{
 			/* Loss of connection */
-		case EPIPE:
-#ifdef ECONNRESET
-		case ECONNRESET:
-#endif
+		case ALL_CONNECTION_FAILURE_ERRNOS:
 			edata->sqlerrcode = ERRCODE_CONNECTION_FAILURE;
 			break;
 

src/bin/pg_dump/parallel.c

@@ -1825,10 +1825,15 @@ piperead(int s, char *buf, int len)
 {
 	int			ret = recv(s, buf, len, 0);
 
-	if (ret < 0 && WSAGetLastError() == WSAECONNRESET)
+	if (ret < 0)
 	{
-		/* EOF on the pipe! */
+		switch (TranslateSocketError())
+		{
+			case ALL_CONNECTION_FAILURE_ERRNOS:
+				/* Treat connection loss as EOF on the pipe */
 				ret = 0;
+				break;
+		}
 	}
 	return ret;
 }

src/include/port.h

@@ -99,6 +99,28 @@ extern void pgfnames_cleanup(char **filenames);
 )
 #endif
 
+/*
+ * This macro provides a centralized list of all errnos that identify
+ * hard failure of a previously-established network connection.
+ * The macro is intended to be used in a switch statement, in the form
+ * "case ALL_CONNECTION_FAILURE_ERRNOS:".
+ *
+ * Note: this groups EPIPE and ECONNRESET, which we take to indicate a
+ * probable server crash, with other errors that indicate loss of network
+ * connectivity without proving much about the server's state.  Places that
+ * are actually reporting errors typically single out EPIPE and ECONNRESET,
+ * while allowing the network failures to be reported generically.
+ */
+#define ALL_CONNECTION_FAILURE_ERRNOS \
+	EPIPE: \
+	case ECONNRESET: \
+	case ECONNABORTED: \
+	case EHOSTDOWN: \
+	case EHOSTUNREACH: \
+	case ENETDOWN: \
+	case ENETRESET: \
+	case ENETUNREACH
+
 /* Portable locale initialization (in exec.c) */
 extern void set_pglocale_pgservice(const char *argv0, const char *app);
 

src/include/port/win32_port.h

@@ -369,8 +369,16 @@ extern int	_pgstat64(const char *name, struct stat *buf);
 #define EADDRINUSE WSAEADDRINUSE
 #undef EADDRNOTAVAIL
 #define EADDRNOTAVAIL WSAEADDRNOTAVAIL
+#undef EHOSTDOWN
+#define EHOSTDOWN WSAEHOSTDOWN
 #undef EHOSTUNREACH
 #define EHOSTUNREACH WSAEHOSTUNREACH
+#undef ENETDOWN
+#define ENETDOWN WSAENETDOWN
+#undef ENETRESET
+#define ENETRESET WSAENETRESET
+#undef ENETUNREACH
+#define ENETUNREACH WSAENETUNREACH
 #undef ENOTCONN
 #define ENOTCONN WSAENOTCONN
 

src/interfaces/libpq/fe-misc.c

@@ -668,25 +668,30 @@ retry3:
 						  conn->inBufSize - conn->inEnd);
 	if (nread < 0)
 	{
-		if (SOCK_ERRNO == EINTR)
+		switch (SOCK_ERRNO)
+		{
+			case EINTR:
 				goto retry3;
+
 				/* Some systems return EAGAIN/EWOULDBLOCK for no data */
 #ifdef EAGAIN
-		if (SOCK_ERRNO == EAGAIN)
+			case EAGAIN:
 				return someread;
 #endif
 #if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
-		if (SOCK_ERRNO == EWOULDBLOCK)
+			case EWOULDBLOCK:
 				return someread;
 #endif
-		/* We might get ECONNRESET here if using TCP and backend died */
-#ifdef ECONNRESET
-		if (SOCK_ERRNO == ECONNRESET)
+
+				/* We might get ECONNRESET etc here if connection failed */
+			case ALL_CONNECTION_FAILURE_ERRNOS:
 				goto definitelyFailed;
-#endif
+
+			default:
 				/* pqsecure_read set the error message for us */
 				return -1;
 		}
+	}
 	if (nread > 0)
 	{
 		conn->inEnd += nread;
@@ -758,25 +763,30 @@ retry4:
 						  conn->inBufSize - conn->inEnd);
 	if (nread < 0)
 	{
-		if (SOCK_ERRNO == EINTR)
+		switch (SOCK_ERRNO)
+		{
+			case EINTR:
 				goto retry4;
+
 				/* Some systems return EAGAIN/EWOULDBLOCK for no data */
 #ifdef EAGAIN
-		if (SOCK_ERRNO == EAGAIN)
+			case EAGAIN:
 				return 0;
 #endif
 #if defined(EWOULDBLOCK) && (!defined(EAGAIN) || (EWOULDBLOCK != EAGAIN))
-		if (SOCK_ERRNO == EWOULDBLOCK)
+			case EWOULDBLOCK:
 				return 0;
 #endif
-		/* We might get ECONNRESET here if using TCP and backend died */
-#ifdef ECONNRESET
-		if (SOCK_ERRNO == ECONNRESET)
+
+				/* We might get ECONNRESET etc here if connection failed */
+			case ALL_CONNECTION_FAILURE_ERRNOS:
 				goto definitelyFailed;
-#endif
+
+			default:
 				/* pqsecure_read set the error message for us */
 				return -1;
 		}
+	}
 	if (nread > 0)
 	{
 		conn->inEnd += nread;

src/interfaces/libpq/fe-secure.c

@@ -261,14 +261,13 @@ pqsecure_raw_read(PGconn *conn, void *ptr, size_t len)
 				/* no error message, caller is expected to retry */
 				break;
 
-#ifdef ECONNRESET
+			case EPIPE:
 			case ECONNRESET:
 				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"));
 				break;
-#endif
 
 			default:
 				printfPQExpBuffer(&conn->errorMessage,
@@ -374,11 +373,9 @@ retry_masked:
 				/* Set flag for EPIPE */
 				REMEMBER_EPIPE(spinfo, true);
 
-#ifdef ECONNRESET
 				/* FALL THRU */
 
 			case ECONNRESET:
-#endif
 				printfPQExpBuffer(&conn->errorMessage,
 								  libpq_gettext("server closed the connection unexpectedly\n"
 												"\tThis probably means the server terminated abnormally\n"

src/interfaces/libpq/win32.h

@@ -14,17 +14,6 @@
 #define write(a,b,c) _write(a,b,c)
 
 #undef EAGAIN					/* doesn't apply on sockets */
-#undef EINTR
-#define EINTR WSAEINTR
-#ifndef EWOULDBLOCK
-#define EWOULDBLOCK WSAEWOULDBLOCK
-#endif
-#ifndef ECONNRESET
-#define ECONNRESET WSAECONNRESET
-#endif
-#ifndef EINPROGRESS
-#define EINPROGRESS WSAEINPROGRESS
-#endif
 
 /*
  * support for handling Windows Socket errors

src/port/strerror.c

@@ -146,16 +146,12 @@ get_errno_symbol(int errnum)
 			return "EBUSY";
 		case ECHILD:
 			return "ECHILD";
-#ifdef ECONNABORTED
 		case ECONNABORTED:
 			return "ECONNABORTED";
-#endif
 		case ECONNREFUSED:
 			return "ECONNREFUSED";
-#ifdef ECONNRESET
 		case ECONNRESET:
 			return "ECONNRESET";
-#endif
 		case EDEADLK:
 			return "EDEADLK";
 		case EDOM:
@@ -166,10 +162,10 @@ get_errno_symbol(int errnum)
 			return "EFAULT";
 		case EFBIG:
 			return "EFBIG";
-#ifdef EHOSTUNREACH
+		case EHOSTDOWN:
+			return "EHOSTDOWN";
 		case EHOSTUNREACH:
 			return "EHOSTUNREACH";
-#endif
 		case EIDRM:
 			return "EIDRM";
 		case EINPROGRESS:
@@ -198,6 +194,12 @@ get_errno_symbol(int errnum)
 			return "EMSGSIZE";
 		case ENAMETOOLONG:
 			return "ENAMETOOLONG";
+		case ENETDOWN:
+			return "ENETDOWN";
+		case ENETRESET:
+			return "ENETRESET";
+		case ENETUNREACH:
+			return "ENETUNREACH";
 		case ENFILE:
 			return "ENFILE";
 		case ENOBUFS: