v4-0004-Use-newer-client-socket-options-where-available.patch

From fdae48117c9bc0d7d25eed09ec57710fda6c28ed Mon Sep 17 00:00:00 2001
From: Thomas Munro <thomas.munro@gmail.com>
Date: Mon, 6 Feb 2023 14:54:03 +1300
Subject: [PATCH v4 4/5] Use newer client socket options where available.

As a recent commit did for the server side, we can now also try to set
client sockets to nonblocking and close-on-exit atomically when creating
the socket.  This uses flags expected in the next POSIX revision, but
already widely available on common platforms.

This saves a couple of fcntl() calls, and plugs a tiny window for
resource leaks in multi-threaded programs that might fork-and-exec while
another thread would otherwise have to run socket() and then fcntl().

Discussion: https://postgr.es/m/CA%2BhUKGKb6FsAdQWcRL35KJsftv%2B9zXqQbzwkfRf1i0J2e57%2BhQ%40mail.gmail.com
---
 src/interfaces/libpq/fe-connect.c | 23 ++++++++++++++++++++++-
 1 file changed, 22 insertions(+), 1 deletion(-)

diff --git a/src/interfaces/libpq/fe-connect.c b/src/interfaces/libpq/fe-connect.c
index 50b5df3490..953abc640f 100644
--- a/src/interfaces/libpq/fe-connect.c
+++ b/src/interfaces/libpq/fe-connect.c
@@ -2464,6 +2464,7 @@ keep_going:						/* We will come back to here until there is
 				{
 					struct addrinfo *addr_cur = conn->addr_cur;
 					char		host_addr[NI_MAXHOST];
+					int			sock_type;
 
 					/*
 					 * Advance to next possible host, if we've tried all of
@@ -2494,7 +2495,23 @@ keep_going:						/* We will come back to here until there is
 						conn->connip = strdup(host_addr);
 
 					/* Try to create the socket */
-					conn->sock = socket(addr_cur->ai_family, SOCK_STREAM, 0);
+					sock_type = SOCK_STREAM;
+#ifdef SOCK_CLOEXEC
+					/*
+					 * Atomically mark close-on-exec, if possible on this
+					 * platform, for the benefit of multi-threaded programs.
+					 * Otherwise see below.
+					 */
+					sock_type |= SOCK_CLOEXEC;
+#endif
+#ifdef SOCK_NONBLOCK
+					/*
+					 * We might as well skip a system call for nonblocking
+					 * mode too, if we can.
+					 */
+					sock_type |= SOCK_NONBLOCK;
+#endif
+					conn->sock = socket(addr_cur->ai_family, sock_type, 0);
 					if (conn->sock == PGINVALID_SOCKET)
 					{
 						int			errorno = SOCK_ERRNO;
@@ -2540,6 +2557,7 @@ keep_going:						/* We will come back to here until there is
 							goto keep_going;
 						}
 					}
+#ifndef SOCK_NONBLOCK
 					if (!pg_set_noblock(conn->sock))
 					{
 						libpq_append_conn_error(conn, "could not set socket to nonblocking mode: %s",
@@ -2547,7 +2565,9 @@ keep_going:						/* We will come back to here until there is
 						conn->try_next_addr = true;
 						goto keep_going;
 					}
+#endif
 
+#ifndef SOCK_CLOEXEC
 #ifdef F_SETFD
 					if (fcntl(conn->sock, F_SETFD, FD_CLOEXEC) == -1)
 					{
@@ -2557,6 +2577,7 @@ keep_going:						/* We will come back to here until there is
 						goto keep_going;
 					}
 #endif							/* F_SETFD */
+#endif
 
 					if (addr_cur->ai_family != AF_UNIX)
 					{
-- 
2.39.1