libbpf_android/include/bpf/BpfMap.h - platform/system/bpf - Git at Google

 /*
  * Copyright (C) 2018 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.
  */

 #ifndef BPF_BPFMAP_H
 #define BPF_BPFMAP_H

 #include <linux/bpf.h>

 #include <android-base/stringprintf.h>
 #include <android-base/unique_fd.h>
 #include <utils/Log.h>
 #include "bpf/BpfUtils.h"
 #include "netdutils/Status.h"
 #include "netdutils/StatusOr.h"

 namespace android {
 namespace bpf {

 // This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
 // data structure that stores data in <Key, Value> pairs. It can be read/write
 // from userspace by passing syscalls with the map file descriptor. This class
 // is used to generalize the procedure of interacting with eBPF maps and hide
 // the implementation detail from other process. Besides the basic syscalls
 // wrapper, it also provides some useful helper functions as well as an iterator
 // nested class to iterate the map more easily.
 //
 // NOTE: A kernel eBPF map may be accessed by both kernel and userspace
 // processes at the same time. Or if the map is pinned as a virtual file, it can
 // be obtained by multiple eBPF map class object and accessed concurrently.
 // Though the map class object and the underlying kernel map are thread safe, it
 // is not safe to iterate over a map while another thread or process is deleting
 // from it. In this case the iteration can return duplicate entries.
 template <class Key, class Value>
 class BpfMap {
   public:
     BpfMap<Key, Value>() : mMapFd(-1){};
     explicit BpfMap<Key, Value>(int fd) : mMapFd(fd){};
     BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags) {
         int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
         if (map_fd < 0) {
             mMapFd.reset(-1);
         } else {
             mMapFd.reset(map_fd);
         }
     }

     netdutils::StatusOr<Key> getFirstKey() const {
         Key firstKey;
         if (getFirstMapKey(mMapFd, &firstKey)) {
             return netdutils::statusFromErrno(
                 errno, base::StringPrintf("Get firstKey map %d failed", mMapFd.get()));
         }
         return firstKey;
     }

     netdutils::StatusOr<Key> getNextKey(const Key& key) const {
         Key nextKey;
         if (getNextMapKey(mMapFd, const_cast<Key*>(&key), &nextKey)) {
             return netdutils::statusFromErrno(
                 errno, base::StringPrintf("Get next key of map %d failed", mMapFd.get()));
         }
         return nextKey;
     }

     netdutils::Status writeValue(const Key& key, const Value& value, uint64_t flags) {
         if (writeToMapEntry(mMapFd, const_cast<Key*>(&key), const_cast<Value*>(&value), flags)) {
             return netdutils::statusFromErrno(
                 errno, base::StringPrintf("write to map %d failed", mMapFd.get()));
         }
         return netdutils::status::ok;
     }

     netdutils::StatusOr<Value> readValue(const Key key) const {
         Value value;
         if (findMapEntry(mMapFd, const_cast<Key*>(&key), &value)) {
             return netdutils::statusFromErrno(
                 errno, base::StringPrintf("read value of map %d failed", mMapFd.get()));
         }
         return value;
     }

     netdutils::Status deleteValue(const Key& key) {
         if (deleteMapEntry(mMapFd, const_cast<Key*>(&key))) {
             return netdutils::statusFromErrno(
                 errno, base::StringPrintf("delete entry from map %d failed", mMapFd.get()));
         }
         return netdutils::status::ok;
     }

     // Function that tries to get map from a pinned path.
     netdutils::Status init(const char* path);

     // Iterate through the map and handle each key retrieved based on the filter
     // without modification of map content.
     netdutils::Status iterate(
         const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>&
             filter) const;

     // Iterate through the map and get each <key, value> pair, handle each <key,
     // value> pair based on the filter without modification of map content.
     netdutils::Status iterateWithValue(
         const std::function<netdutils::Status(const Key& key, const Value& value,
                                               const BpfMap<Key, Value>& map)>& filter) const;

     // Iterate through the map and handle each key retrieved based on the filter
     netdutils::Status iterate(
         const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter);

     // Iterate through the map and get each <key, value> pair, handle each <key,
     // value> pair based on the filter.
     netdutils::Status iterateWithValue(
         const std::function<netdutils::Status(const Key& key, const Value& value,
                                               BpfMap<Key, Value>& map)>& filter);

     const base::unique_fd& getMap() const { return mMapFd; };

     // Move constructor
     void operator=(BpfMap<Key, Value>&& other) noexcept {
         mMapFd = std::move(other.mMapFd);
         other.reset();
     }

     void reset(int fd = -1) {
         mMapFd.reset(fd);
     }

     bool isValid() const { return mMapFd != -1; }

     // It is only safe to call this method if it is guaranteed that nothing will concurrently
     // iterate over the map in any process.
     netdutils::Status clear() {
         const auto deleteAllEntries = [](const Key& key, BpfMap<Key, Value>& map) {
             netdutils::Status res = map.deleteValue(key);
             if (!isOk(res) && (res.code() != ENOENT)) {
                 ALOGE("Failed to delete data %s\n", strerror(res.code()));
             }
             return netdutils::status::ok;
         };
         RETURN_IF_NOT_OK(iterate(deleteAllEntries));
         return netdutils::status::ok;
     }

     netdutils::StatusOr<bool> isEmpty() const {
         auto key = this->getFirstKey();
         // Return error code ENOENT means the map is empty
         if (!isOk(key) && key.status().code() == ENOENT) return true;
         RETURN_IF_NOT_OK(key);
         return false;
     }

   private:
     base::unique_fd mMapFd;
 };

 template <class Key, class Value>
 netdutils::Status BpfMap<Key, Value>::init(const char* path) {
     mMapFd = base::unique_fd(mapRetrieve(path, 0));
     if (mMapFd == -1) {
         reset();
         return netdutils::statusFromErrno(
                 errno,
                 base::StringPrintf("pinned map not accessible or does not exist: (%s)\n", path));
     }
     return netdutils::status::ok;
 }

 template <class Key, class Value>
 netdutils::Status BpfMap<Key, Value>::iterate(
     const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>& filter)
     const {
     netdutils::StatusOr<Key> curKey = getFirstKey();
     while (isOk(curKey)) {
         const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
         RETURN_IF_NOT_OK(filter(curKey.value(), *this));
         curKey = nextKey;
     }
     return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
 }

 template <class Key, class Value>
 netdutils::Status BpfMap<Key, Value>::iterateWithValue(
     const std::function<netdutils::Status(const Key& key, const Value& value,
                                           const BpfMap<Key, Value>& map)>& filter) const {
     netdutils::StatusOr<Key> curKey = getFirstKey();
     while (isOk(curKey)) {
         const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
         Value curValue;
         ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
         RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
         curKey = nextKey;
     }
     return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
 }

 template <class Key, class Value>
 netdutils::Status BpfMap<Key, Value>::iterate(
     const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter) {
     netdutils::StatusOr<Key> curKey = getFirstKey();
     while (isOk(curKey)) {
         const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
         RETURN_IF_NOT_OK(filter(curKey.value(), *this));
         curKey = nextKey;
     }
     return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
 }

 template <class Key, class Value>
 netdutils::Status BpfMap<Key, Value>::iterateWithValue(
     const std::function<netdutils::Status(const Key& key, const Value& value,
                                           BpfMap<Key, Value>& map)>& filter) {
     netdutils::StatusOr<Key> curKey = getFirstKey();
     while (isOk(curKey)) {
         const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
         Value curValue;
         ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
         RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
         curKey = nextKey;
     }
     return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
 }

 }  // namespace bpf
 }  // namespace android

 #endif
	/*
	* Copyright (C) 2018 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.
	*/

	#ifndef BPF_BPFMAP_H
	#define BPF_BPFMAP_H

	#include <linux/bpf.h>

	#include <android-base/stringprintf.h>
	#include <android-base/unique_fd.h>
	#include <utils/Log.h>
	#include "bpf/BpfUtils.h"
	#include "netdutils/Status.h"
	#include "netdutils/StatusOr.h"

	namespace android {
	namespace bpf {

	// This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
	// data structure that stores data in <Key, Value> pairs. It can be read/write
	// from userspace by passing syscalls with the map file descriptor. This class
	// is used to generalize the procedure of interacting with eBPF maps and hide
	// the implementation detail from other process. Besides the basic syscalls
	// wrapper, it also provides some useful helper functions as well as an iterator
	// nested class to iterate the map more easily.
	//
	// NOTE: A kernel eBPF map may be accessed by both kernel and userspace
	// processes at the same time. Or if the map is pinned as a virtual file, it can
	// be obtained by multiple eBPF map class object and accessed concurrently.
	// Though the map class object and the underlying kernel map are thread safe, it
	// is not safe to iterate over a map while another thread or process is deleting
	// from it. In this case the iteration can return duplicate entries.
	template <class Key, class Value>
	class BpfMap {
	public:
	BpfMap<Key, Value>() : mMapFd(-1){};
	explicit BpfMap<Key, Value>(int fd) : mMapFd(fd){};
	BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags) {
	int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
	if (map_fd < 0) {
	mMapFd.reset(-1);
	} else {
	mMapFd.reset(map_fd);
	}
	}

	netdutils::StatusOr<Key> getFirstKey() const {
	Key firstKey;
	if (getFirstMapKey(mMapFd, &firstKey)) {
	return netdutils::statusFromErrno(
	errno, base::StringPrintf("Get firstKey map %d failed", mMapFd.get()));
	}
	return firstKey;
	}

	netdutils::StatusOr<Key> getNextKey(const Key& key) const {
	Key nextKey;
	if (getNextMapKey(mMapFd, const_cast<Key*>(&key), &nextKey)) {
	return netdutils::statusFromErrno(
	errno, base::StringPrintf("Get next key of map %d failed", mMapFd.get()));
	}
	return nextKey;
	}

	netdutils::Status writeValue(const Key& key, const Value& value, uint64_t flags) {
	if (writeToMapEntry(mMapFd, const_cast<Key>(&key), const_cast<Value>(&value), flags)) {
	return netdutils::statusFromErrno(
	errno, base::StringPrintf("write to map %d failed", mMapFd.get()));
	}
	return netdutils::status::ok;
	}

	netdutils::StatusOr<Value> readValue(const Key key) const {
	Value value;
	if (findMapEntry(mMapFd, const_cast<Key*>(&key), &value)) {
	return netdutils::statusFromErrno(
	errno, base::StringPrintf("read value of map %d failed", mMapFd.get()));
	}
	return value;
	}

	netdutils::Status deleteValue(const Key& key) {
	if (deleteMapEntry(mMapFd, const_cast<Key*>(&key))) {
	return netdutils::statusFromErrno(
	errno, base::StringPrintf("delete entry from map %d failed", mMapFd.get()));
	}
	return netdutils::status::ok;
	}

	// Function that tries to get map from a pinned path.
	netdutils::Status init(const char* path);

	// Iterate through the map and handle each key retrieved based on the filter
	// without modification of map content.
	netdutils::Status iterate(
	const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>&
	filter) const;

	// Iterate through the map and get each <key, value> pair, handle each <key,
	// value> pair based on the filter without modification of map content.
	netdutils::Status iterateWithValue(
	const std::function<netdutils::Status(const Key& key, const Value& value,
	const BpfMap<Key, Value>& map)>& filter) const;

	// Iterate through the map and handle each key retrieved based on the filter
	netdutils::Status iterate(
	const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter);

	// Iterate through the map and get each <key, value> pair, handle each <key,
	// value> pair based on the filter.
	netdutils::Status iterateWithValue(
	const std::function<netdutils::Status(const Key& key, const Value& value,
	BpfMap<Key, Value>& map)>& filter);

	const base::unique_fd& getMap() const { return mMapFd; };

	// Move constructor
	void operator=(BpfMap<Key, Value>&& other) noexcept {
	mMapFd = std::move(other.mMapFd);
	other.reset();
	}

	void reset(int fd = -1) {
	mMapFd.reset(fd);
	}

	bool isValid() const { return mMapFd != -1; }

	// It is only safe to call this method if it is guaranteed that nothing will concurrently
	// iterate over the map in any process.
	netdutils::Status clear() {
	const auto deleteAllEntries = [](const Key& key, BpfMap<Key, Value>& map) {
	netdutils::Status res = map.deleteValue(key);
	if (!isOk(res) && (res.code() != ENOENT)) {
	ALOGE("Failed to delete data %s\n", strerror(res.code()));
	}
	return netdutils::status::ok;
	};
	RETURN_IF_NOT_OK(iterate(deleteAllEntries));
	return netdutils::status::ok;
	}

	netdutils::StatusOr<bool> isEmpty() const {
	auto key = this->getFirstKey();
	// Return error code ENOENT means the map is empty
	if (!isOk(key) && key.status().code() == ENOENT) return true;
	RETURN_IF_NOT_OK(key);
	return false;
	}

	private:
	base::unique_fd mMapFd;
	};

	template <class Key, class Value>
	netdutils::Status BpfMap<Key, Value>::init(const char* path) {
	mMapFd = base::unique_fd(mapRetrieve(path, 0));
	if (mMapFd == -1) {
	reset();
	return netdutils::statusFromErrno(
	errno,
	base::StringPrintf("pinned map not accessible or does not exist: (%s)\n", path));
	}
	return netdutils::status::ok;
	}

	template <class Key, class Value>
	netdutils::Status BpfMap<Key, Value>::iterate(
	const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>& filter)
	const {
	netdutils::StatusOr<Key> curKey = getFirstKey();
	while (isOk(curKey)) {
	const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
	RETURN_IF_NOT_OK(filter(curKey.value(), *this));
	curKey = nextKey;
	}
	return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
	}

	template <class Key, class Value>
	netdutils::Status BpfMap<Key, Value>::iterateWithValue(
	const std::function<netdutils::Status(const Key& key, const Value& value,
	const BpfMap<Key, Value>& map)>& filter) const {
	netdutils::StatusOr<Key> curKey = getFirstKey();
	while (isOk(curKey)) {
	const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
	Value curValue;
	ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
	RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
	curKey = nextKey;
	}
	return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
	}

	template <class Key, class Value>
	netdutils::Status BpfMap<Key, Value>::iterate(
	const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter) {
	netdutils::StatusOr<Key> curKey = getFirstKey();
	while (isOk(curKey)) {
	const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
	RETURN_IF_NOT_OK(filter(curKey.value(), *this));
	curKey = nextKey;
	}
	return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
	}

	template <class Key, class Value>
	netdutils::Status BpfMap<Key, Value>::iterateWithValue(
	const std::function<netdutils::Status(const Key& key, const Value& value,
	BpfMap<Key, Value>& map)>& filter) {
	netdutils::StatusOr<Key> curKey = getFirstKey();
	while (isOk(curKey)) {
	const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
	Value curValue;
	ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
	RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
	curKey = nextKey;
	}
	return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
	}

	} // namespace bpf
	} // namespace android

	#endif