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 <sys/ioctl.h>
24#include <sys/socket.h>
25#include <sys/stat.h>
26#include <sys/types.h>
27#include <linux/if.h>
28#include <linux/if_tun.h>
29
30#include <android-base/stringprintf.h>
31#include <android-base/strings.h>
32#include <netutils/ifc.h>
33
34#include "tun_interface.h"
35
36#define TUN_DEV "/dev/tun"
37
38using android::base::StringPrintf;
39
40namespace android {
41namespace net {
42
43int TunInterface::init() {
44    // Generate a random ULA address pair.
45    arc4random_buf(&mSrcAddr, sizeof(mSrcAddr));
46    mSrcAddr.s6_addr[0] = 0xfd;
47    memcpy(&mDstAddr, &mSrcAddr, sizeof(mDstAddr));
48    mDstAddr.s6_addr[15] ^= 1;
49
50    // Convert the addresses to strings because that's what ifc_add_address takes.
51    char srcStr[INET6_ADDRSTRLEN], dstStr[INET6_ADDRSTRLEN];
52    sockaddr_in6 src6 = { .sin6_family = AF_INET6, .sin6_addr = mSrcAddr, };
53    sockaddr_in6 dst6 = { .sin6_family = AF_INET6, .sin6_addr = mDstAddr, };
54    int flags = NI_NUMERICHOST;
55    if (getnameinfo((sockaddr *) &src6, sizeof(src6), srcStr, sizeof(srcStr), NULL, 0, flags) ||
56        getnameinfo((sockaddr *) &dst6, sizeof(dst6), dstStr, sizeof(dstStr), NULL, 0, flags)) {
57        return -EINVAL;
58    }
59
60    // Create a tun interface with a name based on our PID.
61    mIfName = StringPrintf("netdtest%u", getpid());
62    struct ifreq ifr = {
63        .ifr_ifru = { .ifru_flags = IFF_TUN },
64    };
65    snprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "%s", mIfName.c_str());
66
67    mFd = open(TUN_DEV, O_RDWR | O_NONBLOCK | O_CLOEXEC);
68    if (mFd == -1) return -errno;
69
70    int ret = ioctl(mFd, TUNSETIFF, &ifr, sizeof(ifr));
71    if (ret == -1) {
72        ret = -errno;
73        close(mFd);
74        return ret;
75    }
76
77    if (ifc_add_address(ifr.ifr_name, srcStr, 64) ||
78        ifc_add_address(ifr.ifr_name, dstStr, 64)) {
79        ret = -errno;
80        close(mFd);
81        return ret;
82    }
83
84    return 0;
85}
86
87void TunInterface::destroy() {
88    if (mFd != -1) {
89        close(mFd);
90        mFd = -1;
91    }
92}
93
94}  // namespace net
95}  // namespace android
96