Introduce netd_client, a dynamic library that talks to netd.

This library is dynamically loaded and used by bionic, to replace selected
standard socket syscalls with versions that talk to netd.

Implement connect() by requesting that the socket be marked with the netId of
the default network and then calling through to the actual syscall.

There are two escape hatches:

+ If the fwmark server is unavailable, it isn't an error; we proceed with the
  syscall. This might help at boot time (when the server isn't ready yet) and if
  we get rid of the fwmarkd socket entirely in future platform versions.

+ If the ANDROID_NO_USE_FWMARK_CLIENT environment variable is set, we don't
  attempt to use the fwmark server (even if it's available). This allows apps to
  sidestep unforseen issues in production at runtime.

(cherry picked from commit 0581cb455ef924f128a5c6d46bc70868b5099eec)

Change-Id: Ib6198e19dbc306521a26fcecfdf6e8424d163fc9

1 files changed, 29 insertions, 0 deletions

diff --git a/include/netd_client/FwmarkCommands.h b/include/netd_client/FwmarkCommands.h
new file mode 100644
index 000000000..0d22f02e0
--- /dev/null
+++ b/include/netd_client/FwmarkCommands.h
@@ -0,0 +1,29 @@
+/*
+ * Copyright (C) 2014 The Android Open Source Project
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef NETD_CLIENT_FWMARK_COMMANDS_H
+#define NETD_CLIENT_FWMARK_COMMANDS_H
+
+#include <stdint.h>
+
+// Commands sent from clients to the fwmark server to mark sockets (i.e., set their SO_MARK).
+const uint8_t FWMARK_COMMAND_ON_CREATE        = 0;
+const uint8_t FWMARK_COMMAND_ON_CONNECT       = 1;
+const uint8_t FWMARK_COMMAND_ON_ACCEPT        = 2;
+const uint8_t FWMARK_COMMAND_SELECT_NETWORK   = 3;
+const uint8_t FWMARK_COMMAND_PROTECT_FROM_VPN = 4;
+
+#endif  // NETD_CLIENT_FWMARK_COMMANDS_H