ZeroTierOne/osdep/LinuxEthernetTap.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.
 */
/****/

#ifdef __GNUC__
#pragma GCC diagnostic ignored "-Wrestrict"
#endif

#include "../node/Constants.hpp"

#ifdef __LINUX__

#include "../node/Dictionary.hpp"
#include "../node/Mutex.hpp"
#include "../node/Utils.hpp"
#include "LinuxEthernetTap.hpp"
#include "LinuxNetLink.hpp"
#include "OSUtils.hpp"

#include <algorithm>
#include <arpa/inet.h>
#include <ctype.h>
#include <errno.h>
#include <fcntl.h>
#include <ifaddrs.h>
#include <linux/if.h>
#include <linux/if_addr.h>
#include <linux/if_ether.h>
#include <linux/if_tun.h>
#include <net/if_arp.h>
#include <netinet/in.h>
#include <signal.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <string>
#include <sys/ioctl.h>
#include <sys/select.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/utsname.h>
#include <sys/wait.h>
#include <unistd.h>
#include <utility>

#ifndef IFNAMSIZ
#define IFNAMSIZ 16
#endif

#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 {

// determine if we're running a really old linux kernel.
// Kernels in the 2.6.x series don't behave the same when bringing up
// the tap devices.
//
// Returns true if the kernel major version is < 3
bool isOldLinuxKernel()
{
    struct utsname buffer;
    char* p;
    long ver[16];
    int i = 0;
    if (uname(&buffer) != 0) {
        perror("uname");
        exit(EXIT_FAILURE);
    }

    p = buffer.release;

    while (*p) {
        if (isdigit(*p)) {
            ver[i] = strtol(p, &p, 10);
            i++;
        }
        else {
            p++;
        }
    }

    return ver[0] < 3;
}

static const char _base32_chars[32] = { 'a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z', '2', '3', '4', '5', '6', '7' };
static void _base32_5_to_8(const uint8_t* in, char* out)
{
    out[0] = _base32_chars[(in[0]) >> 3];
    out[1] = _base32_chars[(in[0] & 0x07) << 2 | (in[1] & 0xc0) >> 6];
    out[2] = _base32_chars[(in[1] & 0x3e) >> 1];
    out[3] = _base32_chars[(in[1] & 0x01) << 4 | (in[2] & 0xf0) >> 4];
    out[4] = _base32_chars[(in[2] & 0x0f) << 1 | (in[3] & 0x80) >> 7];
    out[5] = _base32_chars[(in[3] & 0x7c) >> 2];
    out[6] = _base32_chars[(in[3] & 0x03) << 3 | (in[4] & 0xe0) >> 5];
    out[7] = _base32_chars[(in[4] & 0x1f)];
}

LinuxEthernetTap::LinuxEthernetTap(
    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)
    , _arg(arg)
    , _nwid(nwid)
    , _mac(mac)
    , _homePath(homePath)
    , _mtu(mtu)
    , _fd(0)
    , _enabled(true)
    , _run(true)
    , _lastIfAddrsUpdate(0)
{
    static std::mutex s_tapCreateLock;
    char procpath[128], nwids[32];
    struct stat sbuf;

    // Create only one tap at a time globally.
    std::lock_guard<std::mutex> tapCreateLock(s_tapCreateLock);

    // Make sure Linux netlink is initialized.
    (void)LinuxNetLink::getInstance();

    OSUtils::ztsnprintf(nwids, sizeof(nwids), "%.16llx", nwid);

    _fd = ::open("/dev/net/tun", O_RDWR);
    if (_fd <= 0) {
        _fd = ::open("/dev/tun", O_RDWR);
        if (_fd <= 0)
            throw std::runtime_error(std::string("could not open TUN/TAP device: ") + strerror(errno));
    }

    struct ifreq ifr;
    memset(&ifr, 0, sizeof(ifr));

    // Restore device names from legacy devicemap, but for new devices we use a base32-based
    // canonical device name.
    std::map<std::string, std::string> globalDeviceMap;
    FILE* devmapf = fopen((_homePath + ZT_PATH_SEPARATOR_S + "devicemap").c_str(), "r");
    if (devmapf) {
        char buf[256];
        while (fgets(buf, sizeof(buf), devmapf)) {
            char* x = (char*)0;
            char* y = (char*)0;
            char* saveptr = (char*)0;
            for (char* f = Utils::stok(buf, "\r\n=", &saveptr); (f); f = Utils::stok((char*)0, "\r\n=", &saveptr)) {
                if (! x)
                    x = f;
                else if (! y)
                    y = f;
                else
                    break;
            }
            if ((x) && (y) && (x[0]) && (y[0]))
                globalDeviceMap[x] = y;
        }
        fclose(devmapf);
    }
    bool recalledDevice = false;
    std::map<std::string, std::string>::const_iterator gdmEntry = globalDeviceMap.find(nwids);
    if (gdmEntry != globalDeviceMap.end()) {
        Utils::scopy(ifr.ifr_name, sizeof(ifr.ifr_name), gdmEntry->second.c_str());
        OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
        recalledDevice = (stat(procpath, &sbuf) != 0);
    }

    if (! recalledDevice) {
#ifdef __SYNOLOGY__
        int devno = 50;
        do {
            OSUtils::ztsnprintf(ifr.ifr_name, sizeof(ifr.ifr_name), "eth%d", devno++);
            OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
        } while (stat(procpath, &sbuf) == 0);   // try zt#++ until we find one that does not exist
#else
        uint64_t trial = 0;   // incremented in the very unlikely event of a name collision with another network
        do {
            const uint64_t nwid40 = (nwid ^ (nwid >> 24)) + trial++;
            uint8_t tmp2[5];
            char tmp3[11];
            tmp2[0] = (uint8_t)((nwid40 >> 32) & 0xff);
            tmp2[1] = (uint8_t)((nwid40 >> 24) & 0xff);
            tmp2[2] = (uint8_t)((nwid40 >> 16) & 0xff);
            tmp2[3] = (uint8_t)((nwid40 >> 8) & 0xff);
            tmp2[4] = (uint8_t)(nwid40 & 0xff);
            tmp3[0] = 'z';
            tmp3[1] = 't';
            _base32_5_to_8(tmp2, tmp3 + 2);
            tmp3[10] = (char)0;
            memcpy(ifr.ifr_name, tmp3, 11);
            OSUtils::ztsnprintf(procpath, sizeof(procpath), "/proc/sys/net/ipv4/conf/%s", ifr.ifr_name);
        } while (stat(procpath, &sbuf) == 0);
#endif
    }

    ifr.ifr_flags = IFF_TAP | IFF_NO_PI;
    if (ioctl(_fd, TUNSETIFF, (void*)&ifr) < 0) {
        ::close(_fd);
        throw std::runtime_error("unable to configure TUN/TAP device for TAP operation");
    }

    ::ioctl(_fd, TUNSETPERSIST, 0);   // valgrind may generate a false alarm here
    _dev = ifr.ifr_name;
    ::fcntl(_fd, F_SETFD, fcntl(_fd, F_GETFD) | FD_CLOEXEC);

    (void)::pipe(_shutdownSignalPipe);

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

            uint8_t b[ZT_TAP_BUF_SIZE];
            fd_set readfds, nullfds;
            int n, nfds, r;
            if (i == 0) {
                struct ifreq ifr;
                memset(&ifr, 0, sizeof(ifr));
                strcpy(ifr.ifr_name, _dev.c_str());

                const int sock = socket(AF_INET, SOCK_DGRAM, 0);
                if (sock <= 0)
                    return;

                if (ioctl(sock, SIOCGIFFLAGS, (void*)&ifr) < 0) {
                    ::close(sock);
                    printf("WARNING: ioctl() failed setting up Linux tap device (bring interface up)\n");
                    return;
                }

                ifr.ifr_ifru.ifru_hwaddr.sa_family = ARPHRD_ETHER;
                _mac.copyTo(ifr.ifr_ifru.ifru_hwaddr.sa_data, 6);
                if (ioctl(sock, SIOCSIFHWADDR, (void*)&ifr) < 0) {
                    ::close(sock);
                    printf("WARNING: ioctl() failed setting up Linux tap device (set MAC)\n");
                    return;
                }

                usleep(100000);

                if (isOldLinuxKernel()) {
                    ifr.ifr_ifru.ifru_mtu = (int)_mtu;
                    if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
                        ::close(sock);
                        printf("WARNING: ioctl() failed setting up Linux tap device (set MTU)\n");
                        return;
                    }

                    usleep(100000);
                }

                ifr.ifr_flags |= IFF_MULTICAST;
                ifr.ifr_flags |= IFF_UP;
                if (ioctl(sock, SIOCSIFFLAGS, (void*)&ifr) < 0) {
                    ::close(sock);
                    printf("WARNING: ioctl() failed setting up Linux tap device (bring interface up)\n");
                    return;
                }

                usleep(100000);

                if (! isOldLinuxKernel()) {
                    ifr.ifr_ifru.ifru_hwaddr.sa_family = ARPHRD_ETHER;
                    _mac.copyTo(ifr.ifr_ifru.ifru_hwaddr.sa_data, 6);
                    if (ioctl(sock, SIOCSIFHWADDR, (void*)&ifr) < 0) {
                        ::close(sock);
                        printf("WARNING: ioctl() failed setting up Linux tap device (set MAC)\n");
                        return;
                    }

                    ifr.ifr_ifru.ifru_mtu = (int)_mtu;
                    if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
                        ::close(sock);
                        printf("WARNING: ioctl() failed setting up Linux tap device (set MTU)\n");
                        return;
                    }
                }

                fcntl(_fd, F_SETFL, O_NONBLOCK);

                ::close(sock);
            }

            if (! _run) {
                return;
            }

            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)) {
                    break;
                }
                if (FD_ISSET(_fd, &readfds)) {
                    for (;;) {
                        // read until there are no more packets, then return to outer select() loop
                        n = (int)::read(_fd, b + r, ZT_TAP_BUF_SIZE - r);
                        if (n > 0) {
                            // 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) {
                                    MAC to(b, 6), from(b + 6, 6);
                                    unsigned int etherType = Utils::ntoh(((const uint16_t*)b)[6]);
                                    _handler(_arg, nullptr, _nwid, from, to, etherType, 0, (const void*)(b + 14), (unsigned int)(r - 14));
                                }

                                r = 0;
                            }
                        }
                        else {
                            r = 0;
                            break;
                        }
                    }
                }
            }
        }));
    }
}

LinuxEthernetTap::~LinuxEthernetTap()
{
    _run = false;
    (void)::write(_shutdownSignalPipe[1], "\0", 1);
    ::close(_fd);
    ::close(_shutdownSignalPipe[0]);
    ::close(_shutdownSignalPipe[1]);
    for (std::thread& t : _rxThreads) {
        t.join();
    }
}

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

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

static bool ___removeIp(const std::string& _dev, const InetAddress& ip)
{
    LinuxNetLink::getInstance().removeAddress(ip, _dev.c_str());
    return true;
}

bool LinuxEthernetTap::addIps(std::vector<InetAddress> ips)
{
#ifdef __SYNOLOGY__
    std::string filepath = "/etc/sysconfig/network-scripts/ifcfg-" + _dev;
    std::string cfg_contents = "DEVICE=" + _dev + "\nBOOTPROTO=static";
    int ip4 = 0, ip6 = 0, ip4_tot = 0, ip6_tot = 0;

    for (int i = 0; i < (int)ips.size(); i++) {
        if (ips[i].isV4())
            ip4_tot++;
        else
            ip6_tot++;
    }
    // Assemble and write contents of ifcfg-dev file
    for (int i = 0; i < (int)ips.size(); i++) {
        if (ips[i].isV4()) {
            char iptmp[64], iptmp2[64];
            std::string numstr4 = ip4_tot > 1 ? std::to_string(ip4) : "";
            cfg_contents += "\nIPADDR" + numstr4 + "=" + ips[i].toIpString(iptmp) + "\nNETMASK" + numstr4 + "=" + ips[i].netmask().toIpString(iptmp2) + "\n";
            ip4++;
        }
        else {
            char iptmp[64], iptmp2[64];
            std::string numstr6 = ip6_tot > 1 ? std::to_string(ip6) : "";
            cfg_contents += "\nIPV6ADDR" + numstr6 + "=" + ips[i].toIpString(iptmp) + "\nNETMASK" + numstr6 + "=" + ips[i].netmask().toIpString(iptmp2) + "\n";
            ip6++;
        }
    }
    OSUtils::writeFile(filepath.c_str(), cfg_contents.c_str(), cfg_contents.length());
    // Finally, add IPs
    for (int i = 0; i < (int)ips.size(); i++) {
        LinuxNetLink::getInstance().addAddress(ips[i], _dev.c_str());
    }
    return true;
#endif   // __SYNOLOGY__
    return false;
}

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

    std::vector<InetAddress> allIps(ips());
    if (std::binary_search(allIps.begin(), allIps.end(), ip))
        return true;

    // 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))
            ___removeIp(_dev, *i);
    }

    LinuxNetLink::getInstance().addAddress(ip, _dev.c_str());

    return true;
}

bool LinuxEthernetTap::removeIp(const InetAddress& ip)
{
    if (! ip)
        return true;
    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> LinuxEthernetTap::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());
    r.erase(std::unique(r.begin(), r.end()), r.end());

    _ifaddrs = r;

    return r;
}

void LinuxEthernetTap::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;
        (void)::write(_fd, putBuf, len);
    }
}

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

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

void LinuxEthernetTap::scanMulticastGroups(std::vector<MulticastGroup>& added, std::vector<MulticastGroup>& removed)
{
    char *ptr, *ptr2;
    unsigned char mac[6];
    std::vector<MulticastGroup> newGroups;

    int fd = ::open("/proc/net/dev_mcast", O_RDONLY);
    if (fd > 0) {
        char buf[131072];
        int n = (int)::read(fd, buf, sizeof(buf));
        if ((n > 0) && (n < (int)sizeof(buf))) {
            buf[n] = (char)0;
            for (char* l = strtok_r(buf, "\r\n", &ptr); (l); l = strtok_r((char*)0, "\r\n", &ptr)) {
                int fno = 0;
                char* devname = (char*)0;
                char* mcastmac = (char*)0;
                for (char* f = strtok_r(l, " \t", &ptr2); (f); f = strtok_r((char*)0, " \t", &ptr2)) {
                    if (fno == 1)
                        devname = f;
                    else if (fno == 4)
                        mcastmac = f;
                    ++fno;
                }
                if ((devname) && (! strcmp(devname, _dev.c_str())) && (mcastmac) && (Utils::unhex(mcastmac, mac, 6) == 6))
                    newGroups.push_back(MulticastGroup(MAC(mac, 6), 0));
            }
        }
        ::close(fd);
    }

    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());
    newGroups.erase(std::unique(newGroups.begin(), newGroups.end()), 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 LinuxEthernetTap::setMtu(unsigned int mtu)
{
    if (_mtu != mtu) {
        _mtu = mtu;
        int sock = socket(AF_INET, SOCK_DGRAM, 0);
        if (sock > 0) {
            struct ifreq ifr;
            memset(&ifr, 0, sizeof(ifr));
            strcpy(ifr.ifr_name, _dev.c_str());
            ifr.ifr_ifru.ifru_mtu = (int)mtu;
            if (ioctl(sock, SIOCSIFMTU, (void*)&ifr) < 0) {
                printf("WARNING: ioctl() failed updating existing Linux tap device (set MTU)\n");
            }
            close(sock);
        }
    }
}

}   // namespace ZeroTier

#endif   // __LINUX__