lokinet/llarp/dns/sd_platform.cpp

#ifdef WITH_SYSTEMD
#include "sd_platform.hpp"

extern "C"
{
#include <net/if.h>
}

#include <llarp/linux/dbus.hpp>

using namespace std::literals;

namespace llarp::dns::sd
{
  void
  Platform::set_resolver(unsigned int if_ndx, llarp::SockAddr dns, bool global)
  {
    linux::DBUS _dbus{
        "org.freedesktop.resolve1",
        "/org/freedesktop/resolve1",
        "org.freedesktop.resolve1.Manager"};
    // This passing address by bytes and using two separate calls for ipv4/ipv6 is gross, but
    // the alternative is to build up a bunch of crap with va_args, which is slightly more
    // gross.
    const bool isStandardDNSPort = dns.getPort() == 53;
    if (dns.isIPv6())
    {
      auto ipv6 = dns.getIPv6();
      static_assert(sizeof(ipv6) == 16);
      auto* a = reinterpret_cast<const uint8_t*>(&ipv6);
      if (isStandardDNSPort)
      {
        _dbus(
            "SetLinkDNS",
            "ia(iay)",
            (int32_t)if_ndx,
            (int)1,             // number of "iayqs"s we are passing
            (int32_t)AF_INET6,  // network address type
            (int)16,            // network addr byte size
                                // clang-format off
              a[0], a[1], a[2],  a[3],  a[4],  a[5],  a[6],  a[7],
              a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15] // yuck
                                // clang-format on
        );
      }
      else
      {
        _dbus(
            "SetLinkDNSEx",
            "ia(iayqs)",
            (int32_t)if_ndx,
            (int)1,             // number of "iayqs"s we are passing
            (int32_t)AF_INET6,  // network address type
            (int)16,            // network addr byte size
            // clang-format off
              a[0], a[1], a[2],  a[3],  a[4],  a[5],  a[6],  a[7],
              a[8], a[9], a[10], a[11], a[12], a[13], a[14], a[15], // yuck
            // clang-format on
            (uint16_t)dns.getPort(),
            nullptr  // dns server name (for TLS SNI which we don't care about)
        );
      }
    }
    else
    {
      auto ipv4 = dns.getIPv4();
      static_assert(sizeof(ipv4) == 4);
      auto* a = reinterpret_cast<const uint8_t*>(&ipv4);
      if (isStandardDNSPort)
      {
        _dbus(
            "SetLinkDNS",
            "ia(iay)",
            (int32_t)if_ndx,
            (int)1,            // number of "iayqs"s we are passing
            (int32_t)AF_INET,  // network address type
            (int)4,            // network addr byte size
                               // clang-format off
              a[0], a[1], a[2], a[3] // yuck
                               // clang-format on
        );
      }
      else
      {
        _dbus(
            "SetLinkDNSEx",
            "ia(iayqs)",
            (int32_t)if_ndx,
            (int)1,            // number of "iayqs"s we are passing
            (int32_t)AF_INET,  // network address type
            (int)4,            // network addr byte size
            // clang-format off
              a[0], a[1], a[2], a[3], // yuck
            // clang-format on
            (uint16_t)dns.getPort(),
            nullptr  // dns server name (for TLS SNI which we don't care about)
        );
      }
    }

    if (global)
      // Setting "." as a routing domain gives this DNS server higher priority in resolution
      // compared to dns servers that are set without a domain (e.g. the default for a
      // DHCP-configured DNS server)
      _dbus(
          "SetLinkDomains",
          "ia(sb)",
          (int32_t)if_ndx,
          (int)1,  // array size
          "."      // global DNS root
      );
    else
      // Only resolve .loki and .snode through lokinet (so you keep using your local DNS
      // server for everything else, which is nicer than forcing everything though lokinet's
      // upstream DNS).
      _dbus(
          "SetLinkDomains",
          "ia(sb)",
          (int32_t)if_ndx,
          (int)2,   // array size
          "loki",   // domain
          (int)1,   // routing domain = true
          "snode",  // domain
          (int)1    // routing domain = true
      );
  }
}  // namespace llarp::dns::sd
#endif