libcutils: add socket_get_local_port().

Tests that require a local server currently hardcode a test value,
which can run into conflicts depending on what's currently running on
the machine.

This CL adds socket_get_local_port(), which lets us pass 0 so the
system picks an open port and we can query which port it chose.

Bug: http://b/26236380
Change-Id: I01d1558884e7636081d9a357db6faa86929934f6

1 files changed, 47 insertions, 0 deletions

diff --git a/libcutils/sockets.cpp b/libcutils/sockets.cpp
new file mode 100644
index 000000000..d9ab14611
--- /dev/null
+++ b/libcutils/sockets.cpp
@@ -0,0 +1,47 @@
+/*
+ * Copyright (C) 2016 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+// This file contains socket implementation that can be shared between
+// platforms as long as the correct headers are included.
+
+#include <cutils/sockets.h>
+
+#if !defined(_WIN32)
+#include <netinet/in.h>
+#endif
+
+int socket_get_local_port(cutils_socket_t sock) {
+    sockaddr_storage addr;
+    socklen_t addr_size = sizeof(addr);
+
+    if (getsockname(sock, reinterpret_cast<sockaddr*>(&addr), &addr_size) == 0) {
+        // sockaddr_in and sockaddr_in6 always overlap the port field.
+        return ntohs(reinterpret_cast<sockaddr_in*>(&addr)->sin_port);
+    }
+    return -1;
+}