1 /*
2 * Copyright (C) 2017 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 #define LOG_TAG "NetlinkListener"
18
19 #include <sstream>
20 #include <vector>
21
22 #include <linux/netfilter/nfnetlink.h>
23
24 #include <cutils/log.h>
25 #include <netdutils/Misc.h>
26 #include <netdutils/Syscalls.h>
27
28 #include "NetlinkListener.h"
29
30 namespace android {
31 namespace net {
32
33 using netdutils::Fd;
34 using netdutils::Slice;
35 using netdutils::Status;
36 using netdutils::UniqueFd;
37 using netdutils::findWithDefault;
38 using netdutils::forEachNetlinkMessage;
39 using netdutils::makeSlice;
40 using netdutils::sSyscalls;
41 using netdutils::status::ok;
42 using netdutils::statusFromErrno;
43
44 namespace {
45
46 constexpr int kNetlinkMsgErrorType = (NFNL_SUBSYS_NONE << 8) | NLMSG_ERROR;
47
48 constexpr sockaddr_nl kKernelAddr = {
49 .nl_family = AF_NETLINK, .nl_pad = 0, .nl_pid = 0, .nl_groups = 0,
50 };
51
__anonfd0bf43c0202(const nlmsghdr& nlmsg, const Slice) 52 const NetlinkListener::DispatchFn kDefaultDispatchFn = [](const nlmsghdr& nlmsg, const Slice) {
53 std::stringstream ss;
54 ss << nlmsg;
55 ALOGE("unhandled netlink message: %s", ss.str().c_str());
56 };
57
58 } // namespace
59
NetlinkListener(UniqueFd event,UniqueFd sock)60 NetlinkListener::NetlinkListener(UniqueFd event, UniqueFd sock)
61 : mEvent(std::move(event)), mSock(std::move(sock)), mWorker([this]() { run(); }) {
__anonfd0bf43c0402(const nlmsghdr& nlmsg, const Slice msg) 62 const auto rxErrorHandler = [](const nlmsghdr& nlmsg, const Slice msg) {
63 std::stringstream ss;
64 ss << nlmsg << " " << msg << " " << netdutils::toHex(msg, 32);
65 ALOGE("unhandled netlink message: %s", ss.str().c_str());
66 };
67 expectOk(NetlinkListener::subscribe(kNetlinkMsgErrorType, rxErrorHandler));
68 }
69
~NetlinkListener()70 NetlinkListener::~NetlinkListener() {
71 const auto& sys = sSyscalls.get();
72 const uint64_t data = 1;
73 // eventfd should never enter an error state unexpectedly
74 expectOk(sys.write(mEvent, makeSlice(data)).status());
75 mWorker.join();
76 }
77
send(const Slice msg)78 Status NetlinkListener::send(const Slice msg) {
79 const auto& sys = sSyscalls.get();
80 ASSIGN_OR_RETURN(auto sent, sys.sendto(mSock, msg, 0, kKernelAddr));
81 if (sent != msg.size()) {
82 return statusFromErrno(EMSGSIZE, "unexpect message size");
83 }
84 return ok;
85 }
86
subscribe(uint16_t type,const DispatchFn & fn)87 Status NetlinkListener::subscribe(uint16_t type, const DispatchFn& fn) {
88 std::lock_guard<std::mutex> guard(mMutex);
89 mDispatchMap[type] = fn;
90 return ok;
91 }
92
unsubscribe(uint16_t type)93 Status NetlinkListener::unsubscribe(uint16_t type) {
94 std::lock_guard<std::mutex> guard(mMutex);
95 mDispatchMap.erase(type);
96 return ok;
97 }
98
run()99 Status NetlinkListener::run() {
100 std::vector<char> rxbuf(4096);
101
102 const auto rxHandler = [this](const nlmsghdr& nlmsg, const Slice& buf) {
103 std::lock_guard<std::mutex> guard(mMutex);
104 const auto& fn = findWithDefault(mDispatchMap, nlmsg.nlmsg_type, kDefaultDispatchFn);
105 fn(nlmsg, buf);
106 };
107
108 const auto& sys = sSyscalls.get();
109 const std::array<Fd, 2> fds{{{mEvent}, {mSock}}};
110 const int events = POLLIN | POLLRDHUP | POLLERR | POLLHUP;
111 const double timeout = 3600;
112 while (true) {
113 ASSIGN_OR_RETURN(auto revents, sys.ppoll(fds, events, timeout));
114 // After mEvent becomes readable, we should stop servicing mSock and return
115 if (revents[0] & POLLIN) {
116 break;
117 }
118 if (revents[1] & POLLIN) {
119 auto rx = sys.recvfrom(mSock, makeSlice(rxbuf), 0);
120 if (rx.status().code() == ENOBUFS) {
121 // Ignore ENOBUFS - the socket is still usable
122 // TODO: Users other than NFLOG may need to know about this
123 continue;
124 }
125 forEachNetlinkMessage(rx.value(), rxHandler);
126 }
127 }
128 return ok;
129 }
130
131 } // namespace net
132 } // namespace android
133