1 /* 2 * Copyright (C) 2022 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 <linux/netlink.h> 20 #include <sys/socket.h> 21 22 #include <cerrno> 23 #include <memory> 24 #include <optional> 25 #include <string> 26 27 #include "UniqueFd.h" 28 #include "log.h" 29 30 namespace android { 31 32 class UEvent { 33 public: 34 static auto CreateInstance() -> std::unique_ptr<UEvent> { 35 auto fd = UniqueFd( 36 socket(PF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, NETLINK_KOBJECT_UEVENT)); 37 38 if (!fd) { 39 ALOGE("Failed to open uevent socket: errno=%i", errno); 40 return {}; 41 } 42 43 struct sockaddr_nl addr {}; 44 addr.nl_family = AF_NETLINK; 45 addr.nl_pid = 0; 46 addr.nl_groups = UINT32_MAX; 47 48 // NOLINTNEXTLINE(cppcoreguidelines-pro-type-cstyle-cast) 49 int ret = bind(fd.Get(), (struct sockaddr *)&addr, sizeof(addr)); 50 if (ret != 0) { 51 ALOGE("Failed to bind uevent socket: errno=%i", errno); 52 return {}; 53 } 54 55 return std::unique_ptr<UEvent>(new UEvent(fd)); 56 } 57 58 auto ReadNext() -> std::optional<std::string> { 59 constexpr int kUEventBufferSize = 1024; 60 char buffer[kUEventBufferSize]; 61 ssize_t ret = 0; 62 ret = read(fd_.Get(), &buffer, sizeof(buffer)); 63 if (ret == 0) 64 return {}; 65 66 if (ret < 0) { 67 ALOGE("Got error reading uevent %zd", ret); 68 return {}; 69 } 70 71 for (int i = 0; i < ret - 1; i++) { 72 if (buffer[i] == '\0') { 73 buffer[i] = '\n'; 74 } 75 } 76 77 return std::string(buffer); 78 } 79 80 private: UEvent(UniqueFd & fd)81 explicit UEvent(UniqueFd &fd) : fd_(std::move(fd)){}; 82 UniqueFd fd_; 83 }; 84 85 } // namespace android 86