1 /*
2 * Copyright 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 * tun_interface.cpp - creates tun interfaces for testing purposes
17 */
18
19 #include <fcntl.h>
20 #include <netdb.h>
21 #include <stdlib.h>
22 #include <unistd.h>
23 #include <linux/if.h>
24 #include <linux/if_tun.h>
25 #include <net/if.h>
26 #include <netinet/in.h>
27 #include <sys/ioctl.h>
28 #include <sys/socket.h>
29 #include <sys/stat.h>
30 #include <sys/types.h>
31
32 #include <android-base/stringprintf.h>
33 #include <android-base/strings.h>
34 #include <netutils/ifc.h>
35
36 #include "tun_interface.h"
37
38 #define TUN_DEV "/dev/tun"
39
40 using android::base::StringPrintf;
41
42 namespace android {
43 namespace net {
44
init()45 int TunInterface::init() {
46 // Generate a random ULA address pair.
47 arc4random_buf(&mSrcAddr, sizeof(mSrcAddr));
48 mSrcAddr.s6_addr[0] = 0xfd;
49 memcpy(&mDstAddr, &mSrcAddr, sizeof(mDstAddr));
50 mDstAddr.s6_addr[15] ^= 1;
51
52 // Convert the addresses to strings because that's what ifc_add_address takes.
53 char srcStr[INET6_ADDRSTRLEN], dstStr[INET6_ADDRSTRLEN];
54 sockaddr_in6 src6 = { .sin6_family = AF_INET6, .sin6_addr = mSrcAddr, };
55 sockaddr_in6 dst6 = { .sin6_family = AF_INET6, .sin6_addr = mDstAddr, };
56 int flags = NI_NUMERICHOST;
57 if (getnameinfo((sockaddr *) &src6, sizeof(src6), srcStr, sizeof(srcStr), NULL, 0, flags) ||
58 getnameinfo((sockaddr *) &dst6, sizeof(dst6), dstStr, sizeof(dstStr), NULL, 0, flags)) {
59 return -EINVAL;
60 }
61
62 // Create a tun interface with a name based on our PID and some randomness.
63 // iptables will only accept interfaces whose name is up to IFNAMSIZ - 1 bytes long.
64 mIfName = StringPrintf("netd%u_%u", getpid(), arc4random());
65 if (mIfName.size() >= IFNAMSIZ) {
66 mIfName.resize(IFNAMSIZ - 1);
67 }
68 struct ifreq ifr = {
69 .ifr_ifru = { .ifru_flags = IFF_TUN },
70 };
71 strlcpy(ifr.ifr_name, mIfName.c_str(), sizeof(ifr.ifr_name));
72
73 mFd = open(TUN_DEV, O_RDWR | O_NONBLOCK | O_CLOEXEC);
74 if (mFd == -1) return -errno;
75
76 int ret = ioctl(mFd, TUNSETIFF, &ifr, sizeof(ifr));
77 if (ret == -1) {
78 ret = -errno;
79 close(mFd);
80 return ret;
81 }
82
83 if (ifc_add_address(ifr.ifr_name, srcStr, 64) ||
84 ifc_add_address(ifr.ifr_name, dstStr, 64)) {
85 ret = -errno;
86 close(mFd);
87 return ret;
88 }
89
90 mIfIndex = if_nametoindex(ifr.ifr_name);
91
92 return 0;
93 }
94
destroy()95 void TunInterface::destroy() {
96 if (mFd != -1) {
97 close(mFd);
98 mFd = -1;
99 }
100 }
101
102 } // namespace net
103 } // namespace android
104