ZeroTierOne/osdep/NetBSDEthernetTap.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 "NetBSDEthernetTap.hpp"

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

#include <algorithm>
#include <arpa/inet.h>
#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <iostream>
#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 <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/sysctl.h>
#include <sys/types.h>
#include <sys/uio.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utility>
using namespace std;
#define ZT_BASE32_CHARS "0123456789abcdefghijklmnopqrstuv"

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

namespace ZeroTier {

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

    Mutex::Lock _gl(globalTapCreateLock);

    if (mtu > 2800)
        throw std::runtime_error("max tap MTU is 2800");

    // we can create /dev/tap*
    std::vector<std::string> devFiles(OSUtils::listDirectory("/dev"));
    for (int i = 9993; i < (9993 + 128); ++i) {
        Utils::snprintf(tmpdevname, sizeof(tmpdevname), "tap%d", i);
        Utils::snprintf(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) {
                ::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");

            cpid = (long)vfork();
            if (cpid == 0) {
                string tmp;
                sprintf((char*)tmp.c_str(), "%d", i);
                string minor = tmp.c_str();
                ::execl("/sbin/mknod", "/sbin/mknod", devpath, "c", "169", minor.c_str(), (const char*)0);
                // http://ftp.netbsd.org/pub/NetBSD/NetBSD-current/src/sys/conf/majors
                // major 169 => tap
                ::_exit(-1);
            }
            else if (cpid > 0) {
                int exitcode = -1;
                ::waitpid(cpid, &exitcode, 0);
            }
            else
                throw std::runtime_error("fork() failed");

            cerr << "created device " << devpath << endl;

            _dev = tmpdevname;
            _fd = ::open(devpath, O_RDWR);
            if (! stat(devpath, &stattmp)) {
                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");
            }
        }
    }

    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
    Utils::snprintf(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]);
    Utils::snprintf(mtustr, sizeof(mtustr), "%u", _mtu);
    Utils::snprintf(metstr, sizeof(metstr), "%u", _metric);
    long cpid = (long)vfork();
    if (cpid == 0) {
        ::execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "link", 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");
        }
    }

    // ifconfig link seems to be different from address
    // https://wiki.netbsd.org/tutorials/faking_a_mac_address/
    cpid = (long)vfork();
    if (cpid == 0) {
        string cmdline = "net.link.tap." + string(_dev);
        cmdline += "=" + string(ethaddr);
        ::execl("/sbin/sysctl", "/sbin/sysctl", "-w", cmdline.c_str(), (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
        if (exitcode) {
            ::close(_fd);
            throw std::runtime_error("sysctl 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);
}

NetBSDEthernetTap::~NetBSDEthernetTap()
{
    ::write(_shutdownSignalPipe[1], "\0", 1);   // causes thread to exit
    Thread::join(_thread);
    ::close(_fd);
    ::close(_shutdownSignalPipe[0]);
    ::close(_shutdownSignalPipe[1]);

    long cpid = (long)vfork();
    if (cpid == 0) {
        ::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);
    }

    cpid = (long)vfork();
    if (cpid == 0) {
        string tmp = "/dev/";
        tmp += _dev.c_str();
        ::execl("/bin/rm", "/bin/rm", tmp.c_str(), (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
    }
    else
        throw std::runtime_error("fork() failed");
}

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

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

static bool ___removeIp(const std::string& _dev, const InetAddress& ip)
{
    long cpid = (long)vfork();
    if (cpid == 0) {
        execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), "inet", ip.toIpString().c_str(), "-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 NetBSDEthernetTap::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) {
        ::execl("/sbin/ifconfig", "/sbin/ifconfig", _dev.c_str(), ip.isV4() ? "inet" : "inet6", ip.toString().c_str(), "alias", (const char*)0);
        ::_exit(-1);
    }
    else if (cpid > 0) {
        int exitcode = -1;
        ::waitpid(cpid, &exitcode, 0);
        return (exitcode == 0);
    }
    return false;
}

bool NetBSDEthernetTap::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> NetBSDEthernetTap::ips() const
{
    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());

    return r;
}

void NetBSDEthernetTap::put(const MAC& from, const MAC& to, unsigned int etherType, const void* data, unsigned int len)
{
    char putBuf[4096];
    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 NetBSDEthernetTap::deviceName() const
{
    return _dev;
}

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

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

    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);
    }

    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);
}

/*
bool NetBSDEthernetTap::updateMulticastGroups(std::set<MulticastGroup> &groups)
{
    std::set<MulticastGroup> newGroups;
    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.insert(MulticastGroup(MAC(la->sdl_data + la->sdl_nlen,6),0));
            }
            p = p->ifma_next;
        }
        freeifmaddrs(ifmap);
    }

    {
        std::set<InetAddress> allIps(ips());
        for(std::set<InetAddress>::const_iterator i(allIps.begin());i!=allIps.end();++i)
            newGroups.insert(MulticastGroup::deriveMulticastGroupForAddressResolution(*i));
    }

    bool changed = false;

    for(std::set<MulticastGroup>::iterator mg(newGroups.begin());mg!=newGroups.end();++mg) {
        if (!groups.count(*mg)) {
            groups.insert(*mg);
            changed = true;
        }
    }
    for(std::set<MulticastGroup>::iterator mg(groups.begin());mg!=groups.end();) {
        if ((!newGroups.count(*mg))&&(*mg != _blindWildcardMulticastGroup)) {
            groups.erase(mg++);
            changed = true;
        } else ++mg;
    }

    return changed;
}
*/

void NetBSDEthernetTap::threadMain() throw()
{
    fd_set readfds, nullfds;
    MAC to, from;
    int n, nfds, r;
    char getBuf[8194];

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

    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, getBuf + r, sizeof(getBuf) - 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(getBuf, 6);
                        from.setTo(getBuf + 6, 6);
                        unsigned int etherType = ntohs(((const uint16_t*)getBuf)[6]);
                        // TODO: VLAN support
                        _handler(_arg, _nwid, from, to, etherType, 0, (const void*)(getBuf + 14), r - 14);
                    }

                    r = 0;
                }
            }
        }
    }
}

}   // namespace ZeroTier