ZeroTierOne/osdep/BSDEthernetTap.cpp

/*
 * Copyright (c)2019 ZeroTier, Inc.
 *
 * Use of this software is governed by the Business Source License included
 * in the LICENSE.TXT file in the project's root directory.
 *
 * Change Date: 2026-01-01
 *
 * On the date above, in accordance with the Business Source License, use
 * of this software will be governed by version 2.0 of the Apache License.
 */
/****/

#include "BSDEthernetTap.hpp"

#include "../node/Constants.hpp"
#include "../node/Mutex.hpp"
#include "../node/Utils.hpp"
#include "OSUtils.hpp"

#include <algorithm>
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <map>
#include <net/if.h>
#include <net/if_arp.h>
#include <net/if_dl.h>
#include <net/if_media.h>
#include <net/route.h>
#include <netinet/in.h>
#include <pthread_np.h>
#include <sched.h>
#include <set>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/cdefs.h>
#include <sys/ioctl.h>
#include <sys/param.h>
#include <sys/select.h>
#include <sys/socket.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utility>

#define ZT_BASE32_CHARS "0123456789abcdefghijklmnopqrstuv"
#define ZT_TAP_BUF_SIZE (1024 * 16)

// ff:ff:ff:ff:ff:ff with no ADI
static const ZeroTier::MulticastGroup _blindWildcardMulticastGroup(ZeroTier::MAC(0xff), 0);

namespace ZeroTier {

BSDEthernetTap::BSDEthernetTap(
    const char* homePath,
    unsigned int concurrency,
    bool pinning,
    const MAC& mac,
    unsigned int mtu,
    unsigned int metric,
    uint64_t nwid,
    const char* friendlyName,
    void (*handler)(void*, void*, uint64_t, const MAC&, const MAC&, unsigned int, unsigned int, const void*, unsigned int),
    void* arg)
    : _handler(handler)
    , _concurrency(concurrency)
    , _pinning(pinning)
    , _arg(arg)
    , _nwid(nwid)
    , _mtu(mtu)
    , _metric(metric)
    , _fd(0)
    , _enabled(true)
    , _lastIfAddrsUpdate(0)
{
    static Mutex globalTapCreateLock;
    char devpath[64], ethaddr[64], mtustr[32], metstr[32], tmpdevname[32];

    Mutex::Lock _gl(globalTapCreateLock);

#ifdef __FreeBSD__
    /* FreeBSD allows long interface names and interface renaming */

    _dev = "zt";
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 60) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 55) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 50) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 45) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 40) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 35) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 30) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 25) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 20) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 15) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 10) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)((nwid >> 5) & 0x1f)]);
    _dev.push_back(ZT_BASE32_CHARS[(unsigned long)(nwid & 0x1f)]);

    std::vector<std::string> devFiles(OSUtils::listDirectory("/dev"));
    for (int i = 9993; i < (9993 + 128); ++i) {
        OSUtils::ztsnprintf(tmpdevname, sizeof(tmpdevname), "tap%d", i);
        OSUtils::ztsnprintf(devpath, sizeof(devpath), "/dev/%s", tmpdevname);
        if (std::find(devFiles.begin(), devFiles.end(), std::string(tmpdevname)) == devFiles.end()) {
            long cpid = (long)vfork();
            if (cpid == 0) {
#ifdef ZT_TRACE
                fprintf(stderr, "DEBUG: ifconfig %s create" ZT_EOL_S, tmpdevname);
#endif
                ::execl("/sbin/ifconfig", "/sbin/ifconfig", tmpdevname, "create", (const char*)0);
                ::_exit(-1);
            }
            else if (cpid > 0) {
                int exitcode = -1;
                ::waitpid(cpid, &exitcode, 0);
            }
            else
                throw std::runtime_error("fork() failed");

            struct stat stattmp;
            if (! stat(devpath, &stattmp)) {
                cpid = (long)vfork();
                if (cpid == 0) {
#ifdef ZT_TRACE
                    fprintf(stderr, "DEBUG: ifconfig %s name %s" ZT_EOL_S, tmpdevname, _dev.c_str());
#endif
                    ::execl("/sbin/ifconfig", "/sbin/ifconfig", tmpdevname, "name", _dev.c_str(), (const char*)0);
                    ::_exit(-1);
                }
                else if (cpid > 0) {
                    int exitcode = -1;
                    ::waitpid(cpid, &exitcode, 0);
                    if (exitcode)
                        throw std::runtime_error("ifconfig rename operation failed");
                }
                else
                    throw std::runtime_error("fork() failed");

                _fd = ::open(devpath, O_RDWR);
                if (_fd > 0)
                    break;
                else
                    throw std::runtime_error("unable to open created tap device");
            }
            else {
                throw std::runtime_error("cannot find /dev node for newly created tap device");
            }
        }
    }
#else
    /* Other BSDs like OpenBSD only have a limited number of tap devices that cannot be renamed */

    for (int i = 0; i < 64; ++i) {
        OSUtils::ztsnprintf(tmpdevname, sizeof(tmpdevname), "tap%d", i);
        OSUtils::ztsnprintf(devpath, sizeof(devpath), "/dev/%s", tmpdevname);
        _fd = ::open(devpath, O_RDWR);
        if (_fd > 0) {
            _dev = tmpdevname;
            break;
        }
    }
#endif

    if (_fd <= 0)
        throw std::runtime_error("unable to open TAP device or no more devices available");

    if (fcntl(_fd, F_SETFL, fcntl(_fd, F_GETFL) & ~O_NONBLOCK) == -1) {
        ::close(_fd);
        throw std::runtime_error("unable to set flags on file descriptor for TAP device");
    }

    // Configure MAC address and MTU, bring interface up
    OSUtils::ztsnprintf(ethaddr, sizeof(ethaddr), "%.2x:%.2x:%.2x:%.2x:%.2x:%.2x", (int)mac[0], (int)mac[1], (int)mac[2], (int)mac[3], (int)mac[4], (int)mac[5]);
    OSUtils::ztsnprintf(mtustr, sizeof(mtustr), "%u", _mtu);
    OSUtils::ztsnprintf(metstr, sizeof(metstr), "%u", _metric);
    long cpid = (long)vfork();
    if (cpid == 0) {
#ifdef ZT_TRACE
        fprintf(stderr, "DEBUG: ifconfig %s lladdr %s mtu %s metric %s up" ZT_EOL_S, _dev.c_str(), ethaddr, mtustr, metstr);
#endif
        ::execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "lladdr", ethaddr, "mtu", mtustr, "metric", metstr, "up", (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
        if (exitcode) {
            ::close(_fd);
            throw std::runtime_error("ifconfig failure setting link-layer address and activating tap interface");
        }
    }

    // Set close-on-exec so that devices cannot persist if we fork/exec for update
    fcntl(_fd, F_SETFD, fcntl(_fd, F_GETFD) | FD_CLOEXEC);

    ::pipe(_shutdownSignalPipe);

    _thread = Thread::start(this);
}

BSDEthernetTap::~BSDEthernetTap()
{
    ::write(_shutdownSignalPipe[1], "\0", 1);   // causes thread to exit
    ::close(_fd);
    ::close(_shutdownSignalPipe[0]);
    ::close(_shutdownSignalPipe[1]);
    long cpid = (long)vfork();
    if (cpid == 0) {
#ifdef ZT_TRACE
        fprintf(stderr, "DEBUG: ifconfig %s destroy" ZT_EOL_S, _dev.c_str());
#endif
        ::execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "destroy", (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
    }
    Thread::join(_thread);
    for (std::thread& t : _rxThreads) {
        t.join();
    }
}

void BSDEthernetTap::setEnabled(bool en)
{
    _enabled = en;
}

bool BSDEthernetTap::enabled() const
{
    return _enabled;
}

static bool ___removeIp(const std::string& _dev, const InetAddress& ip)
{
    long cpid = (long)vfork();
    if (cpid == 0) {
        char ipbuf[64];
#ifdef ZT_TRACE
        fprintf(stderr, "DEBUG: ifconfig %s inet %s -alias" ZT_EOL_S, _dev.c_str(), ip.toIpString(ipbuf));
#endif
        execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "inet", ip.toIpString(ipbuf), "-alias", (const char*)0);
        _exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        waitpid(cpid, &exitcode, 0);
        return (exitcode == 0);
    }
    return false;   // never reached, make compiler shut up about return value
}

bool BSDEthernetTap::addIp(const InetAddress& ip)
{
    if (! ip)
        return false;

    std::vector<InetAddress> allIps(ips());
    if (std::find(allIps.begin(), allIps.end(), ip) != allIps.end())
        return true;   // IP/netmask already assigned

    // Remove and reconfigure if address is the same but netmask is different
    for (std::vector<InetAddress>::iterator i(allIps.begin()); i != allIps.end(); ++i) {
        if ((i->ipsEqual(ip)) && (i->netmaskBits() != ip.netmaskBits())) {
            if (___removeIp(_dev, *i))
                break;
        }
    }

    long cpid = (long)vfork();
    if (cpid == 0) {
        char tmp[128];
#ifdef ZT_TRACE
        fprintf(stderr, "DEBUG: ifconfig %s %s %s alias" ZT_EOL_S, _dev.c_str(), ip.isV4() ? "inet" : "inet6", ip.toString(tmp));
#endif
        ::execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), ip.isV4() ? "inet" : "inet6", ip.toString(tmp), "alias", (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
        return (exitcode == 0);
    }
    return false;
}

bool BSDEthernetTap::removeIp(const InetAddress& ip)
{
    if (! ip)
        return false;
    std::vector<InetAddress> allIps(ips());
    if (std::find(allIps.begin(), allIps.end(), ip) != allIps.end()) {
        if (___removeIp(_dev, ip))
            return true;
    }
    return false;
}

std::vector<InetAddress> BSDEthernetTap::ips() const
{
    uint64_t now = OSUtils::now();

    if ((now - _lastIfAddrsUpdate) <= GETIFADDRS_CACHE_TIME) {
        return _ifaddrs;
    }
    _lastIfAddrsUpdate = now;

    struct ifaddrs* ifa = (struct ifaddrs*)0;
    if (getifaddrs(&ifa))
        return std::vector<InetAddress>();

    std::vector<InetAddress> r;

    struct ifaddrs* p = ifa;
    while (p) {
        if ((! strcmp(p->ifa_name, _dev.c_str())) && (p->ifa_addr) && (p->ifa_netmask) && (p->ifa_addr->sa_family == p->ifa_netmask->sa_family)) {
            switch (p->ifa_addr->sa_family) {
                case AF_INET: {
                    struct sockaddr_in* sin = (struct sockaddr_in*)p->ifa_addr;
                    struct sockaddr_in* nm = (struct sockaddr_in*)p->ifa_netmask;
                    r.push_back(InetAddress(&(sin->sin_addr.s_addr), 4, Utils::countBits((uint32_t)nm->sin_addr.s_addr)));
                } break;
                case AF_INET6: {
                    struct sockaddr_in6* sin = (struct sockaddr_in6*)p->ifa_addr;
                    struct sockaddr_in6* nm = (struct sockaddr_in6*)p->ifa_netmask;
                    uint32_t b[4];
                    memcpy(b, nm->sin6_addr.s6_addr, sizeof(b));
                    r.push_back(InetAddress(sin->sin6_addr.s6_addr, 16, Utils::countBits(b[0]) + Utils::countBits(b[1]) + Utils::countBits(b[2]) + Utils::countBits(b[3])));
                } break;
            }
        }
        p = p->ifa_next;
    }

    if (ifa)
        freeifaddrs(ifa);

    std::sort(r.begin(), r.end());
    std::unique(r.begin(), r.end());

    _ifaddrs = r;

    return r;
}

void BSDEthernetTap::put(const MAC& from, const MAC& to, unsigned int etherType, const void* data, unsigned int len)
{
    char putBuf[ZT_MAX_MTU + 64];
    if ((_fd > 0) && (len <= _mtu) && (_enabled)) {
        to.copyTo(putBuf, 6);
        from.copyTo(putBuf + 6, 6);
        *((uint16_t*)(putBuf + 12)) = htons((uint16_t)etherType);
        memcpy(putBuf + 14, data, len);
        len += 14;
        ::write(_fd, putBuf, len);
    }
}

std::string BSDEthernetTap::deviceName() const
{
    return _dev;
}

void BSDEthernetTap::setFriendlyName(const char* friendlyName)
{
}

void BSDEthernetTap::scanMulticastGroups(std::vector<MulticastGroup>& added, std::vector<MulticastGroup>& removed)
{
    std::vector<MulticastGroup> newGroups;

#ifndef __OpenBSD__
    struct ifmaddrs* ifmap = (struct ifmaddrs*)0;
    if (! getifmaddrs(&ifmap)) {
        struct ifmaddrs* p = ifmap;
        while (p) {
            if (p->ifma_addr->sa_family == AF_LINK) {
                struct sockaddr_dl* in = (struct sockaddr_dl*)p->ifma_name;
                struct sockaddr_dl* la = (struct sockaddr_dl*)p->ifma_addr;
                if ((la->sdl_alen == 6) && (in->sdl_nlen <= _dev.length()) && (! memcmp(_dev.data(), in->sdl_data, in->sdl_nlen)))
                    newGroups.push_back(MulticastGroup(MAC(la->sdl_data + la->sdl_nlen, 6), 0));
            }
            p = p->ifma_next;
        }
        freeifmaddrs(ifmap);
    }
#endif   // __OpenBSD__

    std::vector<InetAddress> allIps(ips());
    for (std::vector<InetAddress>::iterator ip(allIps.begin()); ip != allIps.end(); ++ip)
        newGroups.push_back(MulticastGroup::deriveMulticastGroupForAddressResolution(*ip));

    std::sort(newGroups.begin(), newGroups.end());
    std::unique(newGroups.begin(), newGroups.end());

    for (std::vector<MulticastGroup>::iterator m(newGroups.begin()); m != newGroups.end(); ++m) {
        if (! std::binary_search(_multicastGroups.begin(), _multicastGroups.end(), *m))
            added.push_back(*m);
    }
    for (std::vector<MulticastGroup>::iterator m(_multicastGroups.begin()); m != _multicastGroups.end(); ++m) {
        if (! std::binary_search(newGroups.begin(), newGroups.end(), *m))
            removed.push_back(*m);
    }

    _multicastGroups.swap(newGroups);
}

void BSDEthernetTap::setMtu(unsigned int mtu)
{
    if (mtu != _mtu) {
        _mtu = mtu;
        long cpid = (long)vfork();
        if (cpid == 0) {
            char tmp[64];
            OSUtils::ztsnprintf(tmp, sizeof(tmp), "%u", mtu);
#ifdef ZT_TRACE
            fprintf(stderr, "DEBUG: ifconfig %s mtu %s" ZT_EOL_S, _dev.c_str(), tmp);
#endif
            execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "mtu", tmp, (const char*)0);
            _exit(-1);
        }
        else if (cpid > 0) {
            int exitcode = -1;
            waitpid(cpid, &exitcode, 0);
        }
    }
}

void BSDEthernetTap::threadMain() throw()
{
    // Wait for a moment after startup -- wait for Network to finish
    // constructing itself.
    Thread::sleep(500);

    for (unsigned int i = 0; i < _concurrency; ++i) {
        _rxThreads.push_back(std::thread([this, i, _pinning] {
            if (_pinning) {
                int pinCore = i % _concurrency;
                fprintf(stderr, "Pinning thread %d to core %d\n", i, pinCore);
                pthread_t self = pthread_self();
                cpu_set_t cpuset;
                CPU_ZERO(&cpuset);
                CPU_SET(pinCore, &cpuset);
                // int rc = sched_setaffinity(self, sizeof(cpu_set_t), &cpuset);
                int rc = pthread_setaffinity_np(self, sizeof(cpu_set_t), &cpuset);
                if (rc != 0) {
                    fprintf(stderr, "Failed to pin thread %d to core %d: %s\n", i, pinCore, strerror(errno));
                    exit(1);
                }
            }

            uint8_t b[ZT_TAP_BUF_SIZE];
            MAC to, from;
            fd_set readfds, nullfds;
            int n, nfds, r;

            FD_ZERO(&readfds);
            FD_ZERO(&nullfds);
            nfds = (int)std::max(_shutdownSignalPipe[0], _fd) + 1;

            r = 0;

            for (;;) {
                FD_SET(_shutdownSignalPipe[0], &readfds);
                FD_SET(_fd, &readfds);
                select(nfds, &readfds, &nullfds, &nullfds, (struct timeval*)0);

                if (FD_ISSET(_shutdownSignalPipe[0], &readfds))   // writes to shutdown pipe terminate thread
                    break;

                if (FD_ISSET(_fd, &readfds)) {
                    n = (int)::read(_fd, b + r, sizeof(b) - r);
                    if (n < 0) {
                        if ((errno != EINTR) && (errno != ETIMEDOUT))
                            break;
                    }
                    else {
                        // Some tap drivers like to send the ethernet frame and the
                        // payload in two chunks, so handle that by accumulating
                        // data until we have at least a frame.
                        r += n;
                        if (r > 14) {
                            if (r > ((int)_mtu + 14))   // sanity check for weird TAP behavior on some platforms
                                r = _mtu + 14;

                            if (_enabled) {
                                to.setTo(b, 6);
                                from.setTo(b + 6, 6);
                                unsigned int etherType = ntohs(((const uint16_t*)b)[6]);
                                _handler(_arg, (void*)0, _nwid, from, to, etherType, 0, (const void*)(b + 14), r - 14);
                            }

                            r = 0;
                        }
                    }
                }
            }
        }));
    }
}

}   // namespace ZeroTier