From 63c53e21fed731bdc98846ba20227a39203c72dc Mon Sep 17 00:00:00 2001
From: Nicolas Boichat <drinkcat@google.com>
Date: Mon, 26 Jul 2021 18:57:17 +0800
Subject: [PATCH] base: Add SOCK_CLOEXEC when creating/accepting sockets

Prevents any forked process (e.g. diod) from holding on the sockets
if gem5 crashes.

This flag is only supported on Linux, so we stub it out on other
platforms.

Test: ls -l /proc/$DIOD_PID/fd shows a lot less fds.
Change-Id: I6bc195ed3bd638ab28ff7690f43afce030fa28c7
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/48623
Reviewed-by: Gabe Black <gabe.black@gmail.com>
Maintainer: Gabe Black <gabe.black@gmail.com>
Tested-by: kokoro <noreply+kokoro@google.com>
---
 src/base/socket.cc | 26 ++++++++++++++++++++++++--
 src/base/socket.hh | 10 ++++++++++
 2 files changed, 34 insertions(+), 2 deletions(-)

diff --git a/src/base/socket.cc b/src/base/socket.cc
index fa61ea4cfc..f0aeb01992 100644
--- a/src/base/socket.cc
+++ b/src/base/socket.cc
@@ -81,6 +81,28 @@ ListenSocket::loopbackOnly()
     bindToLoopback = true;
 }
 
+// Wrappers to stub out SOCK_CLOEXEC/accept4 availability
+
+int
+ListenSocket::socketCloexec(int domain, int type, int protocol)
+{
+#ifdef SOCK_CLOEXEC
+    type |= SOCK_CLOEXEC;
+#endif
+    return ::socket(domain, type, protocol);
+}
+
+int
+ListenSocket::acceptCloexec(int sockfd, struct sockaddr *addr,
+                             socklen_t *addrlen)
+{
+#if defined(_GNU_SOURCE) && defined(SOCK_CLOEXEC)
+    return ::accept4(sockfd, addr, addrlen, SOCK_CLOEXEC);
+#else
+    return ::accept(sockfd, addr, addrlen);
+#endif
+}
+
 ////////////////////////////////////////////////////////////////////////
 //
 //
@@ -104,7 +126,7 @@ ListenSocket::listen(int port, bool reuse)
 
     // only create socket if not already created by a previous call
     if (fd == -1) {
-        fd = ::socket(PF_INET, SOCK_STREAM, 0);
+        fd = socketCloexec(PF_INET, SOCK_STREAM | SOCK_CLOEXEC, 0);
         if (fd < 0)
             panic("Can't create socket:%s !", strerror(errno));
     }
@@ -150,7 +172,7 @@ ListenSocket::accept(bool nodelay)
 {
     struct sockaddr_in sockaddr;
     socklen_t slen = sizeof (sockaddr);
-    int sfd = ::accept(fd, (struct sockaddr *)&sockaddr, &slen);
+    int sfd = acceptCloexec(fd, (struct sockaddr *)&sockaddr, &slen);
     if (sfd != -1 && nodelay) {
         int i = 1;
         if (::setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (char *)&i,
diff --git a/src/base/socket.hh b/src/base/socket.hh
index b9b257c10b..4ed6185152 100644
--- a/src/base/socket.hh
+++ b/src/base/socket.hh
@@ -29,6 +29,9 @@
 #ifndef __SOCKET_HH__
 #define __SOCKET_HH__
 
+#include <sys/socket.h>
+#include <sys/types.h>
+
 namespace gem5
 {
 
@@ -59,6 +62,13 @@ class ListenSocket
      */
     static void cleanup();
 
+  private:
+    /* Create a socket, adding SOCK_CLOEXEC if available. */
+    static int socketCloexec(int domain, int type, int protocol);
+    /* Accept a connection, adding SOCK_CLOEXEC if available. */
+    static int acceptCloexec(int sockfd, struct sockaddr *addr,
+                              socklen_t *addrlen);
+
 
   public:
     /**