1 /* 2 * Copyright (C) 2020 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #pragma once 18 19 #include <libnl++/Attributes.h> 20 #include <libnl++/Buffer.h> 21 22 #include <set> 23 24 namespace android::nl { 25 26 /** 27 * In-place Netlink message parser. 28 * 29 * This is a C++-style, memory safe(r) implementation of linux/netlink.h macros accessing Netlink 30 * message contents. The class doesn't own the underlying data, so the instance is valid as long as 31 * the source buffer is allocated and unmodified. 32 * 33 * WARNING: this class is NOT thread-safe (it's safe to be used in multithreaded application, but 34 * a single instance can only be used by a single thread - the one owning the underlying buffer). 35 */ 36 template <typename T> 37 class Message { 38 public: 39 /** 40 * Validate buffer contents as a message carrying T data and create instance of parsed message. 41 * 42 * \param buf Buffer containing the message. 43 * \return Parsed message or nullopt, if the buffer data is invalid. 44 */ parse(Buffer<nlmsghdr> buf)45 static std::optional<Message<T>> parse(Buffer<nlmsghdr> buf) { 46 const auto& [nlOk, nlHeader] = buf.getFirst(); 47 if (!nlOk) return std::nullopt; 48 49 const auto& [dataOk, dataHeader] = buf.data<T>().getFirst(); 50 if (!dataOk) return std::nullopt; 51 52 const auto attributes = buf.data<nlattr>(sizeof(T)); 53 54 return Message<T>(nlHeader, dataHeader, attributes); 55 } 56 57 /** 58 * Validate buffer contents as a message of a given type and create instance of parsed message. 59 * 60 * \param buf Buffer containing the message. 61 * \param msgtypes Acceptable message types (within a specific Netlink protocol) 62 * \return Parsed message or nullopt, if the buffer data is invalid or message type 63 * doesn't match. 64 */ parse(Buffer<nlmsghdr> buf,const std::set<nlmsgtype_t> & msgtypes)65 static std::optional<Message<T>> parse(Buffer<nlmsghdr> buf, 66 const std::set<nlmsgtype_t>& msgtypes) { 67 const auto& [nlOk, nlHeader] = buf.getFirst(); // we're doing it twice, but it's fine 68 if (!nlOk) return std::nullopt; 69 70 if (msgtypes.count(nlHeader.nlmsg_type) == 0) return std::nullopt; 71 72 return parse(buf); 73 } 74 75 /** 76 * Netlink message header. 77 * 78 * This is a generic Netlink header containing information such as message flags. 79 */ 80 const nlmsghdr& header; 81 82 /** 83 * Netlink message data. 84 * 85 * This is a payload specific to a given message type. 86 */ 87 const T& data; 88 89 /** 90 * Netlink message attributes. 91 */ 92 const Attributes attributes; 93 94 const T* operator->() const { return &data; } 95 96 private: Message(const nlmsghdr & nlHeader,const T & dataHeader,Attributes attributes)97 Message(const nlmsghdr& nlHeader, const T& dataHeader, Attributes attributes) 98 : header(nlHeader), data(dataHeader), attributes(attributes) {} 99 }; 100 101 } // namespace android::nl 102