NetdClient.cpp revision efbe05d203f2f1cc3c24ddc111be159a1ff1f292 
1/*
2 * Copyright (C) 2014 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#include "NetdClient.h"
18
19#include "FwmarkClient.h"
20#include "FwmarkCommand.h"
21#include "resolv_netid.h"
22
23#include <sys/socket.h>
24#include <unistd.h>
25
26namespace {
27
28int closeFdAndRestoreErrno(int fd) {
29    int error = errno;
30    close(fd);
31    errno = error;
32    return -1;
33}
34
35typedef int (*ConnectFunctionType)(int, const sockaddr*, socklen_t);
36typedef int (*AcceptFunctionType)(int, sockaddr*, socklen_t*);
37typedef unsigned (*NetIdForResolvFunctionType)(unsigned);
38
39// These variables are only modified at startup (when libc.so is loaded) and never afterwards, so
40// it's okay that they are read later at runtime without a lock.
41ConnectFunctionType libcConnect = 0;
42AcceptFunctionType libcAccept = 0;
43
44int netdClientConnect(int sockfd, const sockaddr* addr, socklen_t addrlen) {
45    if (FwmarkClient::shouldSetFwmark(sockfd, addr)) {
46        FwmarkCommand command = {FwmarkCommand::ON_CONNECT, 0};
47        if (!FwmarkClient().send(&command, sizeof(command), sockfd)) {
48            return -1;
49        }
50    }
51    return libcConnect(sockfd, addr, addrlen);
52}
53
54int netdClientAccept(int sockfd, sockaddr* addr, socklen_t* addrlen) {
55    int acceptedSocket = libcAccept(sockfd, addr, addrlen);
56    if (acceptedSocket == -1) {
57        return -1;
58    }
59    sockaddr socketAddress;
60    if (!addr) {
61        socklen_t socketAddressLen = sizeof(socketAddress);
62        if (getsockname(acceptedSocket, &socketAddress, &socketAddressLen) == -1) {
63            return closeFdAndRestoreErrno(acceptedSocket);
64        }
65        addr = &socketAddress;
66    }
67    if (FwmarkClient::shouldSetFwmark(acceptedSocket, addr)) {
68        FwmarkCommand command = {FwmarkCommand::ON_ACCEPT, 0};
69        if (!FwmarkClient().send(&command, sizeof(command), acceptedSocket)) {
70            return closeFdAndRestoreErrno(acceptedSocket);
71        }
72    }
73    return acceptedSocket;
74}
75
76// TODO: Convert to C++11 std::atomic<unsigned>.
77volatile sig_atomic_t netIdForProcess = NETID_UNSET;
78volatile sig_atomic_t netIdForResolv = NETID_UNSET;
79
80unsigned getNetworkForResolv(unsigned netId) {
81    if (netId != NETID_UNSET) {
82        return netId;
83    }
84    netId = netIdForProcess;
85    if (netId != NETID_UNSET) {
86        return netId;
87    }
88    return netIdForResolv;
89}
90
91bool setNetworkForTarget(unsigned netId, volatile sig_atomic_t* target) {
92    if (netId == NETID_UNSET) {
93        *target = netId;
94        return true;
95    }
96    // Verify that we are allowed to use |netId|, by creating a socket and trying to have it marked
97    // with the netId. Don't create an AF_INET socket, because then the creation itself might cause
98    // another check with the fwmark server (see netdClientSocket()), which would be wasteful.
99    int socketFd = socket(AF_UNIX, SOCK_DGRAM, 0);
100    if (socketFd < 0) {
101        return false;
102    }
103    bool status = setNetworkForSocket(netId, socketFd);
104    closeFdAndRestoreErrno(socketFd);
105    if (status) {
106        *target = netId;
107    }
108    return status;
109}
110
111}  // namespace
112
113extern "C" void netdClientInitConnect(ConnectFunctionType* function) {
114    if (function && *function) {
115        libcConnect = *function;
116        *function = netdClientConnect;
117    }
118}
119
120extern "C" void netdClientInitAccept(AcceptFunctionType* function) {
121    if (function && *function) {
122        libcAccept = *function;
123        *function = netdClientAccept;
124    }
125}
126
127extern "C" void netdClientInitNetIdForResolv(NetIdForResolvFunctionType* function) {
128    if (function) {
129        *function = getNetworkForResolv;
130    }
131}
132
133extern "C" unsigned getNetworkForProcess() {
134    return netIdForProcess;
135}
136
137extern "C" bool setNetworkForSocket(unsigned netId, int socketFd) {
138    if (socketFd < 0) {
139        errno = EBADF;
140        return false;
141    }
142    FwmarkCommand command = {FwmarkCommand::SELECT_NETWORK, netId};
143    return FwmarkClient().send(&command, sizeof(command), socketFd);
144}
145
146extern "C" bool setNetworkForProcess(unsigned netId) {
147    return setNetworkForTarget(netId, &netIdForProcess);
148}
149
150extern "C" bool setNetworkForResolv(unsigned netId) {
151    return setNetworkForTarget(netId, &netIdForResolv);
152}
153