/*
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* Copyright (C) 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#ifndef NETLINK_LISTENER_H
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#define NETLINK_LISTENER_H
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#include <functional>
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#include <map>
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#include <mutex>
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#include <thread>
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#include <android-base/thread_annotations.h>
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#include <netdutils/Netlink.h>
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#include <netdutils/Slice.h>
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#include <netdutils/Status.h>
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#include <netdutils/UniqueFd.h>
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namespace android {
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namespace net {
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class NetlinkListenerInterface {
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public:
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using DispatchFn = std::function<void(const nlmsghdr& nlmsg, const netdutils::Slice msg)>;
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using SkErrorHandler = std::function<void(const int fd, const int err)>;
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virtual ~NetlinkListenerInterface() = default;
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// Send message to the kernel using the underlying netlink socket
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virtual netdutils::Status send(const netdutils::Slice msg) = 0;
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// Deliver future messages with nlmsghdr.nlmsg_type == type to fn.
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//
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// Threadsafe.
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// All dispatch functions invoked on a single service thread.
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// subscribe() and join() must not be called from the stack of fn().
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virtual netdutils::Status subscribe(uint16_t type, const DispatchFn& fn) = 0;
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// Halt delivery of future messages with nlmsghdr.nlmsg_type == type.
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// Threadsafe.
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virtual netdutils::Status unsubscribe(uint16_t type) = 0;
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virtual void registerSkErrorHandler(const SkErrorHandler& handler) = 0;
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};
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// NetlinkListener manages a netlink socket and associated blocking
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// service thread.
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//
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// This class is written in a generic way to allow multiple different
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// netlink subsystems to share this common infrastructure. If multiple
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// subsystems share the same message delivery requirements (drops ok,
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// no drops) they may share a single listener by calling subscribe()
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// with multiple types.
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//
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// This class is suitable for moderate performance message
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// processing. In particular it avoids extra copies of received
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// message data and allows client code to control which message
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// attributes are processed.
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//
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// Note that NetlinkListener is capable of processing multiple batched
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// netlink messages in a single system call. This is useful to
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// netfilter extensions that allow batching of events like NFLOG.
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class NetlinkListener : public NetlinkListenerInterface {
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public:
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NetlinkListener(netdutils::UniqueFd event, netdutils::UniqueFd sock, const std::string& name);
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~NetlinkListener() override;
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netdutils::Status send(const netdutils::Slice msg) override;
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netdutils::Status subscribe(uint16_t type, const DispatchFn& fn) override EXCLUDES(mMutex);
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netdutils::Status unsubscribe(uint16_t type) override EXCLUDES(mMutex);
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void registerSkErrorHandler(const SkErrorHandler& handler) override;
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private:
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netdutils::Status run();
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const netdutils::UniqueFd mEvent;
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const netdutils::UniqueFd mSock;
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const std::string mThreadName;
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std::mutex mMutex;
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std::map<uint16_t, DispatchFn> mDispatchMap GUARDED_BY(mMutex);
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std::thread mWorker;
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SkErrorHandler mErrorHandler;
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};
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} // namespace net
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} // namespace android
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#endif /* NETLINK_LISTENER_H */
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