First part of an RPC mechanism for container <-> host communication

Mostly based on the protobuf based implementation from Mir.

android/service/local_socket_connection.cpp

@@ -0,0 +1,77 @@
+/*
+ * Copyright (C) 2016 Simon Fels <morphis@gravedo.de>
+ *
+ * This program is free software: you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 3, as published
+ * by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranties of
+ * MERCHANTABILITY, SATISFACTORY QUALITY, or FITNESS FOR A PARTICULAR
+ * PURPOSE.  See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along
+ * with this program.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "android/service/local_socket_connection.h"
+
+#include <sys/types.h>
+#include <sys/socket.h>
+#include <sys/un.h>
+#include <unistd.h>
+#include <errno.h>
+
+namespace {
+bool socket_error_is_transient(int error_code) {
+    return (error_code == EINTR);
+}
+}
+
+namespace anbox {
+namespace android {
+LocalSocketConnection::LocalSocketConnection(const std::string &path) :
+    fd_(Fd::invalid) {
+
+    struct sockaddr_un socket_address;
+    memset(&socket_address, 0, sizeof(socket_address));
+
+    socket_address.sun_family = AF_UNIX;
+    memcpy(socket_address.sun_path, path.data(), path.size());
+
+    fd_ = Fd{socket(AF_UNIX, SOCK_STREAM, 0)};
+    if (connect(fd_, reinterpret_cast<sockaddr*>(&socket_address), sizeof(socket_address)) < 0)
+        throw std::runtime_error("Failed to connect to server socket");
+}
+
+LocalSocketConnection::~LocalSocketConnection() {
+    if (fd_ > 0)
+        ::close(fd_);
+}
+
+ssize_t LocalSocketConnection::read_all(std::uint8_t *buffer, const size_t &size) {
+    ssize_t bytes_read = ::recv(fd_, reinterpret_cast<void*>(buffer), size, 0);
+    return bytes_read;
+}
+
+void LocalSocketConnection::send(char const* data, size_t length) {
+    size_t bytes_written{0};
+
+    while(bytes_written < length) {
+        ssize_t const result = ::send(fd_,
+                                      data + bytes_written,
+                                      length - bytes_written,
+                                      MSG_NOSIGNAL);
+        if (result < 0) {
+            if (socket_error_is_transient(errno))
+                continue;
+            else
+                throw std::runtime_error("Failed to send message to server");
+        }
+
+        bytes_written += result;
+    }
+}
+} // namespace android
+} // namespace anbox