Guard socket file descriptor in UDPSocketLibevent

net/udp/udp_socket_libevent.cc

Index: net/udp/udp_socket_libevent.cc
diff --git a/net/udp/udp_socket_libevent.cc b/net/udp/udp_socket_libevent.cc
index a6c1b72b50ac651c8a711c568c042e0d9ddcd504..c7f288d2c68a7f6758515834505f0d24e6240e21 100644
--- a/net/udp/udp_socket_libevent.cc
+++ b/net/udp/udp_socket_libevent.cc
@@ -6,8 +6,8 @@
 
 #include <errno.h>
 #include <fcntl.h>
-#include <netdb.h>
 #include <net/if.h>
+#include <netdb.h>
 #include <netinet/in.h>
 #include <sys/ioctl.h>
 #include <sys/socket.h>
@@ -56,6 +56,25 @@ int GetIPv4AddressFromIndex(int socket, uint32 index, uint32* address){
   return OK;
 }
 
+// On OSX the file descriptor is guarded to detect the cause of
+// crbug.com/461246. sys/guarded.h is not included in the SDK, so the API needs
+// to be defined here.

[Mark Mentovai, 2015/04/02 14:37:06]

Drive the point home by saying in the comment that this is temporary and will be
removed.

[Sergey Ulanov, 2015/04/02 18:05:42]

Added TODO to remove it.

+
+typedef uint64_t guardid_t;
+
+int guarded_close_np(int fd, const guardid_t *guard) {
+  return syscall(442, fd, guard);

[Mark Mentovai, 2015/04/02 14:37:06]

This is only available in 10.9 and 10.10. It’ll be ENOSYS elsewhere. The
majority of users are on 10.9 and 10.10, so this shouldn’t be a problem.

I recommend calling through the syscall wrappers in libSystem instead of making
the syscall() like this. You can dlsym() for "guarded_close_np" and
"change_fdguard_np". If it returns nullptr for either of those, you’ll know that
the kernel doesn’t provide file descriptor guards, and you can fall back to
using close() instead of guarded_close_np().

[Sergey Ulanov, 2015/04/02 18:05:42]

Done.

+}
+int change_fdguard_np(int fd, const guardid_t *guard, u_int flags,
+    const guardid_t *nguard, u_int nflags, int *fdflagsp) {
+  return syscall(444, fd, guard, flags, nguard, nflags, fdflagsp);
+}
+
+const unsigned int GUARD_CLOSE = 1u<<0;
+const unsigned int GUARD_DUP = 1u<<1;
+
+const guardid_t kSocketFdGuard = 0xD712BC0BC9A4EAD4;
+
 #endif  // OS_MACOSX
 
 }  // namespace
@@ -98,6 +117,10 @@ int UDPSocketLibevent::Open(AddressFamily address_family) {
   socket_ = CreatePlatformSocket(addr_family_, SOCK_DGRAM, 0);
   if (socket_ == kInvalidSocket)
     return MapSystemError(errno);
+#if defined(OS_MACOSX)
+  PCHECK(change_fdguard_np(socket_, NULL, 0, &kSocketFdGuard,
+                           GUARD_CLOSE | GUARD_DUP, NULL) == 0);
+#endif  // OS_MACOSX
   if (SetNonBlocking(socket_)) {
     const int err = MapSystemError(errno);
     Close();
@@ -127,7 +150,11 @@ void UDPSocketLibevent::Close() {
   ok = write_socket_watcher_.StopWatchingFileDescriptor();
   DCHECK(ok);
 
+#if defined(OS_MACOSX)
+  PCHECK(IGNORE_EINTR(guarded_close_np(socket_, &kSocketFdGuard)) == 0);
+#else
   PCHECK(IGNORE_EINTR(close(socket_)) == 0);
+#endif  // OS_MACOSX
 
   socket_ = kInvalidSocket;
   addr_family_ = 0;