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      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 
     38 using android::base::StringPrintf;
     39 
     40 namespace android {
     41 namespace net {
     42 
     43 int 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 
     87 void TunInterface::destroy() {
     88     if (mFd != -1) {
     89         close(mFd);
     90         mFd = -1;
     91     }
     92 }
     93 
     94 }  // namespace net
     95 }  // namespace android
     96