Default implementation for CAN bus HAL

This implementation supports SocketCAN interfaces.

Bug: 135918744
Test: VTS (separate new change)
Change-Id: I12b93e37fa64e341bee2c64eaf130b39977fcef5
diff --git a/automotive/can/1.0/default/libnetdevice/NetlinkRequest.cpp b/automotive/can/1.0/default/libnetdevice/NetlinkRequest.cpp
new file mode 100644
index 0000000..9845bc7
--- /dev/null
+++ b/automotive/can/1.0/default/libnetdevice/NetlinkRequest.cpp
@@ -0,0 +1,58 @@
+/*
+ * Copyright (C) 2019 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.
+ */
+
+#include "NetlinkRequest.h"
+
+#include <android-base/logging.h>
+
+namespace android {
+namespace netdevice {
+namespace impl {
+
+static struct rtattr* nlmsg_tail(struct nlmsghdr* n) {
+    return reinterpret_cast<struct rtattr*>(  //
+            reinterpret_cast<uintptr_t>(n) + NLMSG_ALIGN(n->nlmsg_len));
+}
+
+struct rtattr* addattr_l(struct nlmsghdr* n, size_t maxLen, rtattrtype_t type, const void* data,
+                         size_t dataLen) {
+    size_t newLen = NLMSG_ALIGN(n->nlmsg_len) + RTA_SPACE(dataLen);
+    if (newLen > maxLen) {
+        LOG(ERROR) << "addattr_l failed - exceeded maxLen: " << newLen << " > " << maxLen;
+        return nullptr;
+    }
+
+    auto attr = nlmsg_tail(n);
+    attr->rta_len = RTA_SPACE(dataLen);
+    attr->rta_type = type;
+    if (dataLen > 0) memcpy(RTA_DATA(attr), data, dataLen);
+
+    n->nlmsg_len = newLen;
+    return attr;
+}
+
+struct rtattr* addattr_nest(struct nlmsghdr* n, size_t maxLen, rtattrtype_t type) {
+    return addattr_l(n, maxLen, type, nullptr, 0);
+}
+
+void addattr_nest_end(struct nlmsghdr* n, struct rtattr* nest) {
+    size_t nestLen = reinterpret_cast<uintptr_t>(nlmsg_tail(n)) - reinterpret_cast<uintptr_t>(nest);
+    nest->rta_len = nestLen;
+}
+
+}  // namespace impl
+}  // namespace netdevice
+}  // namespace android