lokinet/llarp/dns/unbound_resolver.cpp
Thomas Winget 4c630e0437 Large collection of changes to make android work
- Previous android java and jni code updated to work, but with much love
  still needed to make it work nicely, e.g. handling when the VPN is
  turned off.

- DNS handling refactored to allow android to intercept and handle DNS
  requests as we can't set the system DNS to use a high port
  (and apparently Chrome ignores system DNS settings anyway)

- add packet router structure to allow separate handling of specific
  intercepted traffic, e.g. UDP traffic to port 53 gets handled by our
  DNS handler rather than being naively forwarded as exit traffic.

- For now, android lokinet is exit-only and hard-coded to use exit.loki
  as its exit.  The exit will be configurable before release, but
  allowing to not use exit-only mode is more of a challenge.

- some old gitignore remnants which were matching to things we don't
  want them to (and are no longer relevant) removed

- some minor changes to CI configuration
2021-03-02 13:18:22 -05:00

153 lines
3.2 KiB
C++

#include <dns/unbound_resolver.hpp>
#include <dns/server.hpp>
#include <util/buffer.hpp>
namespace llarp::dns
{
struct PendingUnboundLookup
{
std::weak_ptr<UnboundResolver> resolver;
Message msg;
SockAddr source;
SockAddr replyFrom;
};
void
UnboundResolver::Stop()
{
Reset();
}
void
UnboundResolver::Reset()
{
started = false;
if (runner)
{
runner->join();
runner.reset();
}
if (unboundContext)
{
ub_ctx_delete(unboundContext);
}
unboundContext = nullptr;
}
UnboundResolver::UnboundResolver(
std::shared_ptr<Logic> logic, ReplyFunction reply, FailFunction fail)
: unboundContext(nullptr)
, started(false)
, replyFunc([logic, reply](auto res, auto source, auto buf) {
LogicCall(logic, [source, buf, reply, res]() { reply(res, source, buf); });
})
, failFunc([logic, fail](auto res, auto source, auto message) {
LogicCall(logic, [source, message, res, fail]() { fail(res, source, message); });
})
{}
// static callback
void
UnboundResolver::Callback(void* data, int err, ub_result* result)
{
std::unique_ptr<PendingUnboundLookup> lookup{static_cast<PendingUnboundLookup*>(data)};
auto this_ptr = lookup->resolver.lock();
if (not this_ptr)
return; // resolver is gone, so we don't reply.
if (err != 0)
{
Message& msg = lookup->msg;
msg.AddServFail();
this_ptr->failFunc(lookup->replyFrom, lookup->source, msg);
ub_resolve_free(result);
return;
}
std::vector<byte_t> pkt(result->answer_len);
std::copy_n(static_cast<byte_t*>(result->answer_packet), pkt.size(), pkt.data());
llarp_buffer_t buf(pkt);
MessageHeader hdr;
hdr.Decode(&buf);
hdr.id = lookup->msg.hdr_id;
buf.cur = buf.base;
hdr.Encode(&buf);
this_ptr->replyFunc(lookup->replyFrom, lookup->source, std::move(pkt));
ub_resolve_free(result);
}
bool
UnboundResolver::Init()
{
if (started)
{
Reset();
}
unboundContext = ub_ctx_create();
if (not unboundContext)
{
return false;
}
ub_ctx_async(unboundContext, 1);
runner = std::make_unique<std::thread>([&]() {
while (started)
{
if (unboundContext)
ub_wait(unboundContext);
std::this_thread::sleep_for(25ms);
}
});
started = true;
return true;
}
bool
UnboundResolver::AddUpstreamResolver(const std::string& upstreamResolverIP)
{
if (ub_ctx_set_fwd(unboundContext, upstreamResolverIP.c_str()) != 0)
{
Reset();
return false;
}
return true;
}
void
UnboundResolver::Lookup(SockAddr to, SockAddr from, Message msg)
{
if (not unboundContext)
{
msg.AddServFail();
failFunc(to, from, std::move(msg));
return;
}
const auto& q = msg.questions[0];
auto* lookup = new PendingUnboundLookup{weak_from_this(), msg, from, to};
int err = ub_resolve_async(
unboundContext,
q.Name().c_str(),
q.qtype,
q.qclass,
(void*)lookup,
&UnboundResolver::Callback,
nullptr);
if (err != 0)
{
msg.AddServFail();
failFunc(to, from, std::move(msg));
return;
}
}
} // namespace llarp::dns