1 /*
2 * Copyright (C) 2018 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 #ifndef BPF_BPFMAP_H
18 #define BPF_BPFMAP_H
19
20 #include <linux/bpf.h>
21
22 #include <android-base/stringprintf.h>
23 #include <android-base/unique_fd.h>
24 #include <utils/Log.h>
25 #include "bpf/BpfUtils.h"
26 #include "netdutils/Status.h"
27 #include "netdutils/StatusOr.h"
28
29 namespace android {
30 namespace bpf {
31
32 // This is a class wrapper for eBPF maps. The eBPF map is a special in-kernel
33 // data structure that stores data in <Key, Value> pairs. It can be read/write
34 // from userspace by passing syscalls with the map file descriptor. This class
35 // is used to generalize the procedure of interacting with eBPF maps and hide
36 // the implementation detail from other process. Besides the basic syscalls
37 // wrapper, it also provides some useful helper functions as well as an iterator
38 // nested class to iterate the map more easily.
39 //
40 // NOTE: A kernel eBPF map may be accessed by both kernel and userspace
41 // processes at the same time. Or if the map is pinned as a virtual file, it can
42 // be obtained by multiple eBPF map class object and accessed concurrently.
43 // Though the map class object and the underlying kernel map are thread safe, it
44 // is not safe to iterate over a map while another thread or process is deleting
45 // from it. In this case the iteration can return duplicate entries.
46 template <class Key, class Value>
47 class BpfMap {
48 public:
49 BpfMap<Key, Value>() : mMapFd(-1){};
mMapFd(fd)50 explicit BpfMap<Key, Value>(int fd) : mMapFd(fd){};
51 BpfMap<Key, Value>(bpf_map_type map_type, uint32_t max_entries, uint32_t map_flags) {
52 int map_fd = createMap(map_type, sizeof(Key), sizeof(Value), max_entries, map_flags);
53 if (map_fd < 0) {
54 mMapFd.reset(-1);
55 } else {
56 mMapFd.reset(map_fd);
57 }
58 }
59
getFirstKey()60 netdutils::StatusOr<Key> getFirstKey() const {
61 Key firstKey;
62 if (getFirstMapKey(mMapFd, &firstKey)) {
63 return netdutils::statusFromErrno(
64 errno, base::StringPrintf("Get firstKey map %d failed", mMapFd.get()));
65 }
66 return firstKey;
67 }
68
getNextKey(const Key & key)69 netdutils::StatusOr<Key> getNextKey(const Key& key) const {
70 Key nextKey;
71 if (getNextMapKey(mMapFd, const_cast<Key*>(&key), &nextKey)) {
72 return netdutils::statusFromErrno(
73 errno, base::StringPrintf("Get next key of map %d failed", mMapFd.get()));
74 }
75 return nextKey;
76 }
77
writeValue(const Key & key,const Value & value,uint64_t flags)78 netdutils::Status writeValue(const Key& key, const Value& value, uint64_t flags) {
79 if (writeToMapEntry(mMapFd, const_cast<Key*>(&key), const_cast<Value*>(&value), flags)) {
80 return netdutils::statusFromErrno(
81 errno, base::StringPrintf("write to map %d failed", mMapFd.get()));
82 }
83 return netdutils::status::ok;
84 }
85
readValue(const Key key)86 netdutils::StatusOr<Value> readValue(const Key key) const {
87 Value value;
88 if (findMapEntry(mMapFd, const_cast<Key*>(&key), &value)) {
89 return netdutils::statusFromErrno(
90 errno, base::StringPrintf("read value of map %d failed", mMapFd.get()));
91 }
92 return value;
93 }
94
deleteValue(const Key & key)95 netdutils::Status deleteValue(const Key& key) {
96 if (deleteMapEntry(mMapFd, const_cast<Key*>(&key))) {
97 return netdutils::statusFromErrno(
98 errno, base::StringPrintf("delete entry from map %d failed", mMapFd.get()));
99 }
100 return netdutils::status::ok;
101 }
102
103 // Function that tries to get map from a pinned path.
104 netdutils::Status init(const char* path);
105
106 // Iterate through the map and handle each key retrieved based on the filter
107 // without modification of map content.
108 netdutils::Status iterate(
109 const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>&
110 filter) const;
111
112 // Iterate through the map and get each <key, value> pair, handle each <key,
113 // value> pair based on the filter without modification of map content.
114 netdutils::Status iterateWithValue(
115 const std::function<netdutils::Status(const Key& key, const Value& value,
116 const BpfMap<Key, Value>& map)>& filter) const;
117
118 // Iterate through the map and handle each key retrieved based on the filter
119 netdutils::Status iterate(
120 const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter);
121
122 // Iterate through the map and get each <key, value> pair, handle each <key,
123 // value> pair based on the filter.
124 netdutils::Status iterateWithValue(
125 const std::function<netdutils::Status(const Key& key, const Value& value,
126 BpfMap<Key, Value>& map)>& filter);
127
getMap()128 const base::unique_fd& getMap() const { return mMapFd; };
129
130 // Move constructor
131 void operator=(BpfMap<Key, Value>&& other) noexcept {
132 mMapFd = std::move(other.mMapFd);
133 other.reset();
134 }
135
136 void reset(int fd = -1) {
137 mMapFd.reset(fd);
138 }
139
isValid()140 bool isValid() const { return mMapFd != -1; }
141
142 // It is only safe to call this method if it is guaranteed that nothing will concurrently
143 // iterate over the map in any process.
clear()144 netdutils::Status clear() {
145 const auto deleteAllEntries = [](const Key& key, BpfMap<Key, Value>& map) {
146 netdutils::Status res = map.deleteValue(key);
147 if (!isOk(res) && (res.code() != ENOENT)) {
148 ALOGE("Failed to delete data %s\n", strerror(res.code()));
149 }
150 return netdutils::status::ok;
151 };
152 RETURN_IF_NOT_OK(iterate(deleteAllEntries));
153 return netdutils::status::ok;
154 }
155
isEmpty()156 netdutils::StatusOr<bool> isEmpty() const {
157 auto key = this->getFirstKey();
158 // Return error code ENOENT means the map is empty
159 if (!isOk(key) && key.status().code() == ENOENT) return true;
160 RETURN_IF_NOT_OK(key);
161 return false;
162 }
163
164 private:
165 base::unique_fd mMapFd;
166 };
167
168 template <class Key, class Value>
init(const char * path)169 netdutils::Status BpfMap<Key, Value>::init(const char* path) {
170 mMapFd = base::unique_fd(mapRetrieve(path, 0));
171 if (mMapFd == -1) {
172 reset();
173 return netdutils::statusFromErrno(
174 errno,
175 base::StringPrintf("pinned map not accessible or does not exist: (%s)\n", path));
176 }
177 return netdutils::status::ok;
178 }
179
180 template <class Key, class Value>
iterate(const std::function<netdutils::Status (const Key & key,const BpfMap<Key,Value> & map)> & filter)181 netdutils::Status BpfMap<Key, Value>::iterate(
182 const std::function<netdutils::Status(const Key& key, const BpfMap<Key, Value>& map)>& filter)
183 const {
184 netdutils::StatusOr<Key> curKey = getFirstKey();
185 while (isOk(curKey)) {
186 const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
187 RETURN_IF_NOT_OK(filter(curKey.value(), *this));
188 curKey = nextKey;
189 }
190 return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
191 }
192
193 template <class Key, class Value>
iterateWithValue(const std::function<netdutils::Status (const Key & key,const Value & value,const BpfMap<Key,Value> & map)> & filter)194 netdutils::Status BpfMap<Key, Value>::iterateWithValue(
195 const std::function<netdutils::Status(const Key& key, const Value& value,
196 const BpfMap<Key, Value>& map)>& filter) const {
197 netdutils::StatusOr<Key> curKey = getFirstKey();
198 while (isOk(curKey)) {
199 const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
200 Value curValue;
201 ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
202 RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
203 curKey = nextKey;
204 }
205 return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
206 }
207
208 template <class Key, class Value>
iterate(const std::function<netdutils::Status (const Key & key,BpfMap<Key,Value> & map)> & filter)209 netdutils::Status BpfMap<Key, Value>::iterate(
210 const std::function<netdutils::Status(const Key& key, BpfMap<Key, Value>& map)>& filter) {
211 netdutils::StatusOr<Key> curKey = getFirstKey();
212 while (isOk(curKey)) {
213 const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
214 RETURN_IF_NOT_OK(filter(curKey.value(), *this));
215 curKey = nextKey;
216 }
217 return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
218 }
219
220 template <class Key, class Value>
iterateWithValue(const std::function<netdutils::Status (const Key & key,const Value & value,BpfMap<Key,Value> & map)> & filter)221 netdutils::Status BpfMap<Key, Value>::iterateWithValue(
222 const std::function<netdutils::Status(const Key& key, const Value& value,
223 BpfMap<Key, Value>& map)>& filter) {
224 netdutils::StatusOr<Key> curKey = getFirstKey();
225 while (isOk(curKey)) {
226 const netdutils::StatusOr<Key>& nextKey = getNextKey(curKey.value());
227 Value curValue;
228 ASSIGN_OR_RETURN(curValue, this->readValue(curKey.value()));
229 RETURN_IF_NOT_OK(filter(curKey.value(), curValue, *this));
230 curKey = nextKey;
231 }
232 return curKey.status().code() == ENOENT ? netdutils::status::ok : curKey.status();
233 }
234
235 } // namespace bpf
236 } // namespace android
237
238 #endif
239