Ensure native library isn't actually loaded, and no IO on net thread

net/udp/udp_socket_posix.cc

Index: net/udp/udp_socket_posix.cc
diff --git a/net/udp/udp_socket_posix.cc b/net/udp/udp_socket_posix.cc
index 401158289a7a730886f59ad5035f132b82114275..20c2a991f38a354a29126f483734d0d025a8a324 100644
--- a/net/udp/udp_socket_posix.cc
+++ b/net/udp/udp_socket_posix.cc
@@ -4,6 +4,7 @@
 
 #include "net/udp/udp_socket_posix.h"
 
+#include <dlfcn.h>

[xunjieli, 2016/06/29 13:35:09]

Should this header be in the #if defined(OS_ANDROID) ?

[pauljensen, 2016/06/29 13:45:49]

Done.

 #include <errno.h>
 #include <fcntl.h>
 #include <net/if.h>
@@ -35,6 +36,8 @@
 #include "base/android/build_info.h"
 #include "base/native_library.h"
 #include "base/strings/utf_string_conversions.h"
+// This was added in Lollipop to dlfcn.h
+#define RTLD_NOLOAD 4
 #endif
 
 namespace net {
@@ -351,11 +354,11 @@ int UDPSocketPosix::BindToNetwork(
   // shouldn't matter.
   if (!setNetworkForSocket) {
     // Android's netd client library should always be loaded in our address
-    // space as it shims libc functions like connect().
+    // space as it shims socket() which was used to create |socket_|.
     base::FilePath file(base::GetNativeLibraryName("netd_client"));
-    base::NativeLibrary lib = base::LoadNativeLibrary(file, nullptr);
-    setNetworkForSocket = reinterpret_cast<SetNetworkForSocket>(
-        base::GetFunctionPointerFromNativeLibrary(lib, "setNetworkForSocket"));
+    void* dl = dlopen(file.value().c_str(), RTLD_NOW | RTLD_NOLOAD);

[xunjieli, 2016/06/29 13:35:09]

Could add a brief comment on the flags (RTLD_NOW | RTLD_NOLOAD)? I checked the
documentation, but am not quite sure why these two are chosen.

[pauljensen, 2016/06/29 13:45:50]

Done.

+    setNetworkForSocket =
+        reinterpret_cast<SetNetworkForSocket>(dlsym(dl, "setNetworkForSocket"));
   }
   if (!setNetworkForSocket)
     return ERR_NOT_IMPLEMENTED;