/*
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* Copyright 2017 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*
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* tun_interface.cpp - creates tun interfaces for testing purposes
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*/
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#include <string>
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#include <fcntl.h>
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#include <linux/if.h>
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#include <linux/if_tun.h>
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#include <linux/netlink.h>
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#include <linux/rtnetlink.h>
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#include <net/if.h>
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#include <netdb.h>
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#include <netinet/in.h>
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#include <stdlib.h>
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#include <sys/ioctl.h>
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#include <sys/socket.h>
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#include <sys/stat.h>
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#include <sys/types.h>
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#include <unistd.h>
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#include <android-base/stringprintf.h>
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#include <android-base/strings.h>
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#include <android-base/unique_fd.h>
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#include <netutils/ifc.h>
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#include "tun_interface.h"
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#define TUN_DEV "/dev/tun"
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using android::base::StringPrintf;
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using android::base::unique_fd;
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namespace android {
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namespace net {
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int TunInterface::init(const std::string& ifName) {
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// Generate a random ULA address pair.
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arc4random_buf(&mSrcAddr, sizeof(mSrcAddr));
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mSrcAddr.s6_addr[0] = 0xfd;
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memcpy(&mDstAddr, &mSrcAddr, sizeof(mDstAddr));
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mDstAddr.s6_addr[15] ^= 1;
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// Convert the addresses to strings because that's what ifc_add_address takes.
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char srcStr[INET6_ADDRSTRLEN], dstStr[INET6_ADDRSTRLEN];
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sockaddr_in6 src6 = { .sin6_family = AF_INET6, .sin6_addr = mSrcAddr, };
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sockaddr_in6 dst6 = { .sin6_family = AF_INET6, .sin6_addr = mDstAddr, };
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int flags = NI_NUMERICHOST;
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if (getnameinfo((sockaddr *) &src6, sizeof(src6), srcStr, sizeof(srcStr), nullptr, 0, flags) ||
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getnameinfo((sockaddr *) &dst6, sizeof(dst6), dstStr, sizeof(dstStr), nullptr, 0, flags)) {
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return -EINVAL;
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}
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// Create a tun interface with a name based on a random number.
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// In order to fit the size of interface alert name , resize ifname to 9
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// Alert name format in netd: ("%sAlert", ifname)
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// Limitation in kernel: char name[15] in struct xt_quota_mtinfo2
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// Note that this form of alert doesn't actually appear to be used for interface alerts.
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// It can only be created by BandwidthController::setInterfaceAlert, but that appears to have no
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// actual callers in the framework, because mActiveAlerts is always empty.
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// TODO: remove setInterfaceAlert and use a longer interface name.
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mIfName = ifName;
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if (mIfName.empty()) {
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mIfName = StringPrintf("netd%x", arc4random());
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}
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mIfName.resize(9);
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struct ifreq ifr = {
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.ifr_ifru = { .ifru_flags = IFF_TUN },
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};
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strlcpy(ifr.ifr_name, mIfName.c_str(), sizeof(ifr.ifr_name));
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mFd = open(TUN_DEV, O_RDWR | O_NONBLOCK | O_CLOEXEC);
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if (mFd == -1) return -errno;
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int ret = ioctl(mFd, TUNSETIFF, &ifr, sizeof(ifr));
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if (ret == -1) {
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ret = -errno;
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close(mFd);
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return ret;
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}
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mIfIndex = if_nametoindex(ifr.ifr_name);
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if (addAddress(srcStr, 64) || addAddress(dstStr, 64)) {
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ret = -errno;
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close(mFd);
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return ret;
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}
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if (int ret = ifc_enable(ifr.ifr_name)) {
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return ret;
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}
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return 0;
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}
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void TunInterface::destroy() {
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if (mFd != -1) {
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ifc_disable(mIfName.c_str());
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close(mFd);
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mFd = -1;
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}
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}
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int TunInterface::addAddress(const std::string& addr, int prefixlen) {
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// Wait for an RTM_NEWADDR indicating that the address has been created.
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// This is because IPv6 addresses, even addresses that are optimistic or created with
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// IFA_F_NODAD, are not immediately usable when the netlink ACK returns.
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// This is not generally necessary in device code because the framework hears about IP addresses
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// asynchronously via netlink, but it is necessary to ensure tests aren't flaky.
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unique_fd s(socket(AF_NETLINK, SOCK_DGRAM | SOCK_CLOEXEC, 0));
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if (s == -1) return -errno;
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sockaddr_nl groups = {.nl_family = AF_NETLINK,
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.nl_groups = RTMGRP_IPV4_IFADDR | RTMGRP_IPV6_IFADDR};
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if (bind(s, reinterpret_cast<sockaddr*>(&groups), sizeof(groups)) == -1) return -errno;
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sockaddr_nl kernel = {.nl_family = AF_NETLINK};
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if (connect(s, reinterpret_cast<sockaddr*>(&kernel), sizeof(kernel)) == -1) return -errno;
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// Wait up to 200ms for address to arrive.
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timeval timeout = {.tv_usec = 200 * 1000};
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if (setsockopt(s, SOL_SOCKET, SO_RCVTIMEO, &timeout, sizeof(timeout)) == -1) return -errno;
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if (ifc_add_address(mIfName.c_str(), addr.c_str(), prefixlen)) return -errno;
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int family;
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size_t addrlen;
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union {
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in_addr ip4;
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in6_addr ip6;
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} ip;
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if (addr.find(':') != std::string::npos) {
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family = AF_INET6;
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inet_pton(AF_INET6, addr.c_str(), &ip.ip6);
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addrlen = sizeof(ip.ip6);
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} else {
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family = AF_INET;
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inet_pton(AF_INET, addr.c_str(), &ip.ip4);
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addrlen = sizeof(ip.ip4);
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}
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while (1) {
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char buf[4096];
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ssize_t len = recv(s, buf, sizeof(buf), 0);
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if (len == -1) break;
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if (len < static_cast<ssize_t>(NLMSG_SPACE(sizeof(ifaddrmsg)))) continue;
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nlmsghdr* nlmsg = reinterpret_cast<nlmsghdr*>(buf);
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if (nlmsg->nlmsg_type != RTM_NEWADDR) continue;
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ifaddrmsg* ifaddr = reinterpret_cast<ifaddrmsg*>(NLMSG_DATA(nlmsg));
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if (ifaddr->ifa_family != family) continue;
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if (ifaddr->ifa_prefixlen != prefixlen) continue;
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if (ifaddr->ifa_index != static_cast<uint32_t>(mIfIndex)) continue;
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int ifalen = IFA_PAYLOAD(nlmsg);
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for (rtattr* rta = IFA_RTA(ifaddr); RTA_OK(rta, ifalen); rta = RTA_NEXT(rta, ifalen)) {
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if (rta->rta_type != IFA_LOCAL && rta->rta_type != IFA_ADDRESS) continue;
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if (RTA_PAYLOAD(rta) != addrlen) continue;
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if (!memcmp(RTA_DATA(rta), &ip, addrlen)) {
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return 0;
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}
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}
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}
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return -errno;
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}
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} // namespace net
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} // namespace android
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