Add some netdutils socket option helpers

Test: as follows
    - built
Bug: 64133961
Bug: 34953048
Change-Id: I9a381d76a7595499decd39249109077164d94041
diff --git a/libnetdutils/include/netdutils/SocketOption.h b/libnetdutils/include/netdutils/SocketOption.h
new file mode 100644
index 0000000..3b0aab7
--- /dev/null
+++ b/libnetdutils/include/netdutils/SocketOption.h
@@ -0,0 +1,60 @@
+/*
+ * Copyright (C) 2018 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 NETDUTILS_SOCKETOPTION_H
+#define NETDUTILS_SOCKETOPTION_H
+
+#include <netinet/in.h>
+#include <sys/socket.h>
+#include <string>
+
+#include "netdutils/Fd.h"
+#include "netdutils/Status.h"
+
+namespace android {
+namespace netdutils {
+
+// Turn on simple "boolean" socket options.
+//
+// This is simple wrapper for options that are enabled via code of the form:
+//
+//     int on = 1;
+//     setsockopt(..., &on, sizeof(on));
+Status enableSockopt(Fd sock, int level, int optname);
+
+// Turn on TCP keepalives, and set keepalive parameters for this socket.
+//
+// A parameter value of zero does not set that parameter.
+//
+// Typical system defaults are:
+//
+//     idleTime (in seconds)
+//     $ cat /proc/sys/net/ipv4/tcp_keepalive_time
+//     7200
+//
+//     numProbes
+//     $ cat /proc/sys/net/ipv4/tcp_keepalive_probes
+//     9
+//
+//     probeInterval (in seconds)
+//     $ cat /proc/sys/net/ipv4/tcp_keepalive_intvl
+//     75
+Status enableTcpKeepAlives(Fd sock, unsigned idleTime, unsigned numProbes, unsigned probeInterval);
+
+}  // namespace netdutils
+}  // namespace android
+
+#endif /* NETDUTILS_SOCKETOPTION_H */