transmission/libtransmission/global-ip-cache.cc

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// This file Copyright © Mnemosyne LLC.
// It may be used under GPLv2 (SPDX: GPL-2.0-only), GPLv3 (SPDX: GPL-3.0-only),
// or any future license endorsed by Mnemosyne LLC.
// License text can be found in the licenses/ folder.
#include <algorithm> // std::all_of
#include <array>
#include <cstddef>
#include <memory>
#include <mutex>
#include <optional>
#include <string_view>
#include <utility> // std::move
#ifdef _WIN32
#include <ws2tcpip.h>
#else
#include <cerrno>
#include <sys/socket.h>
#endif
#include <fmt/core.h>
#include "libtransmission/log.h"
#include "libtransmission/global-ip-cache.h"
#include "libtransmission/tr-assert.h"
#include "libtransmission/utils.h"
#include "libtransmission/web.h"
namespace
{
using namespace std::literals;
static_assert(TR_AF_INET == 0);
static_assert(TR_AF_INET6 == 1);
auto constexpr IPQueryServices = std::array{ std::array{ "https://ip4.transmissionbt.com/"sv },
std::array{ "https://ip6.transmissionbt.com/"sv } };
auto constexpr UpkeepInterval = 30min;
auto constexpr RetryUpkeepInterval = 30s;
// Normally there should only ever be 1 cache instance during the entire program execution
// This is a counter only to cater for SessionTest.honorsSettings
std::size_t cache_exists = 0;
} // namespace
namespace
{
// Functions contained in global_source_ip_helpers are modified from code
// by Juliusz Chroboczek and is covered under the same license as dht.cc.
// Please feel free to copy them into your software if it can help
// unbreaking the double-stack Internet.
namespace global_source_ip_helpers
{
// Get the source address used for a given destination address.
// Since there is no official interface to get this information,
// we create a connected UDP socket (connected UDP... hmm...)
// and check its source address.
//
// Since it's a UDP socket, this doesn't actually send any packets
[[nodiscard]] std::optional<tr_address> get_source_address(
tr_address const& dst_addr,
tr_port dst_port,
tr_address const& bind_addr,
int& err_out) noexcept
{
TR_ASSERT(dst_addr.type == bind_addr.type);
auto const save = errno;
auto const [dst_ss, dst_sslen] = tr_socket_address::to_sockaddr(dst_addr, dst_port);
auto const [bind_ss, bind_sslen] = tr_socket_address::to_sockaddr(bind_addr, {});
if (auto const sock = socket(dst_ss.ss_family, SOCK_DGRAM, 0); sock != TR_BAD_SOCKET)
{
if (bind(sock, reinterpret_cast<sockaddr const*>(&bind_ss), bind_sslen) == 0)
{
if (connect(sock, reinterpret_cast<sockaddr const*>(&dst_ss), dst_sslen) == 0)
{
auto src_ss = sockaddr_storage{};
auto src_sslen = socklen_t{ sizeof(src_ss) };
if (getsockname(sock, reinterpret_cast<sockaddr*>(&src_ss), &src_sslen) == 0)
{
if (auto const addrport = tr_socket_address::from_sockaddr(reinterpret_cast<sockaddr*>(&src_ss)); addrport)
{
tr_net_close_socket(sock);
errno = save;
return addrport->address();
}
}
}
}
tr_net_close_socket(sock);
}
err_out = errno;
errno = save;
return {};
}
[[nodiscard]] std::optional<tr_address> get_global_source_address(tr_address const& bind_addr, int& err_out) noexcept
{
// Pick some destination address to pretend to send a packet to
static auto constexpr DstIP = std::array{ "91.121.74.28"sv, "2001:1890:1112:1::20"sv };
auto const dst_addr = tr_address::from_string(DstIP[bind_addr.type]);
auto const dst_port = tr_port::from_host(6969);
// In order for address selection to work right,
// this should be a global unicast address, not Teredo or 6to4
TR_ASSERT(dst_addr && dst_addr->is_global_unicast_address());
if (dst_addr)
{
return get_source_address(*dst_addr, dst_port, bind_addr, err_out);
}
return {};
}
} // namespace global_source_ip_helpers
} // namespace
tr_global_ip_cache::tr_global_ip_cache(Mediator& mediator_in)
: mediator_{ mediator_in }
, upkeep_timers_{ mediator_in.timer_maker().create(), mediator_in.timer_maker().create() }
{
static_assert(TR_AF_INET == 0);
static_assert(TR_AF_INET6 == 1);
static_assert(NUM_TR_AF_INET_TYPES == 2);
for (std::size_t i = 0; i < NUM_TR_AF_INET_TYPES; ++i)
{
auto const type = static_cast<tr_address_type>(i);
auto const cb = [this, type]()
{
update_addr(type);
};
upkeep_timers_[i]->set_callback(cb);
start_timer(type, UpkeepInterval);
}
++cache_exists;
}
std::unique_ptr<tr_global_ip_cache> tr_global_ip_cache::create(tr_global_ip_cache::Mediator& mediator_in)
{
return std::unique_ptr<tr_global_ip_cache>(new tr_global_ip_cache(mediator_in));
}
tr_global_ip_cache::~tr_global_ip_cache()
{
// Destroying mutex while someone owns it is undefined behaviour, so we acquire it first
auto const locks = std::scoped_lock{ global_addr_mutex_[TR_AF_INET],
global_addr_mutex_[TR_AF_INET6],
source_addr_mutex_[TR_AF_INET],
source_addr_mutex_[TR_AF_INET6] };
if (!std::all_of(
std::begin(is_updating_),
std::end(is_updating_),
[](is_updating_t const& v) { return v == is_updating_t::ABORT; }))
{
tr_logAddDebug("Destructed while some global IP queries were pending.");
}
--cache_exists;
}
bool tr_global_ip_cache::try_shutdown() noexcept
{
for (auto& timer : upkeep_timers_)
{
timer->stop();
}
for (std::size_t i = 0; i < NUM_TR_AF_INET_TYPES; ++i)
{
if (is_updating_[i] == is_updating_t::YES)
{
return false;
}
is_updating_[i] = is_updating_t::ABORT; // Abort any future updates
}
return true;
}
tr_address tr_global_ip_cache::bind_addr(tr_address_type type) const noexcept
{
if (tr_address::is_valid(type))
{
if (auto const addr = tr_address::from_string(mediator_.settings_bind_addr(type)); addr && type == addr->type)
{
return *addr;
}
return tr_address::any(type);
}
TR_ASSERT_MSG(false, "invalid type");
return {};
}
bool tr_global_ip_cache::set_global_addr(tr_address_type type, tr_address const& addr) noexcept
{
if (type == addr.type && addr.is_global_unicast_address())
{
auto const lock = std::lock_guard{ global_addr_mutex_[addr.type] };
global_addr_[addr.type] = addr;
tr_logAddTrace(fmt::format("Cached global address {}", addr.display_name()));
return true;
}
return false;
}
void tr_global_ip_cache::update_addr(tr_address_type type) noexcept
{
update_source_addr(type);
if (global_source_addr(type))
{
update_global_addr(type);
}
}
void tr_global_ip_cache::update_global_addr(tr_address_type type) noexcept
{
TR_ASSERT(has_ip_protocol_[type]);
TR_ASSERT(ix_service_[type] < std::size(IPQueryServices[type]));
if (ix_service_[type] == 0U && !set_is_updating(type))
{
return;
}
TR_ASSERT(is_updating_[type] == is_updating_t::YES);
// Update global address
static auto constexpr IPProtocolMap = std::array{ tr_web::FetchOptions::IPProtocol::V4,
tr_web::FetchOptions::IPProtocol::V6 };
auto options = tr_web::FetchOptions{ IPQueryServices[type][ix_service_[type]],
[this, type](tr_web::FetchResponse const& response)
{
// Check to avoid segfault
if (cache_exists != 0)
{
this->on_response_ip_query(type, response);
}
},
nullptr };
options.ip_proto = IPProtocolMap[type];
options.sndbuf = 4096;
options.rcvbuf = 4096;
mediator_.fetch(std::move(options));
}
void tr_global_ip_cache::update_source_addr(tr_address_type type) noexcept
{
using namespace global_source_ip_helpers;
TR_ASSERT(has_ip_protocol_[type]);
if (!set_is_updating(type))
{
return;
}
TR_ASSERT(is_updating_[type] == is_updating_t::YES);
auto const protocol = tr_ip_protocol_to_sv(type);
auto err = int{ 0 };
auto const& source_addr = get_global_source_address(bind_addr(type), err);
if (source_addr)
{
set_source_addr(*source_addr);
tr_logAddDebug(fmt::format(
_("Successfully updated source {protocol} address to {ip}"),
fmt::arg("protocol", protocol),
fmt::arg("ip", source_addr->display_name())));
}
else
{
// Stop the update process since we have no public internet connectivity
unset_addr(type);
upkeep_timers_[type]->set_interval(RetryUpkeepInterval);
tr_logAddDebug(fmt::format("Couldn't obtain source {} address", protocol));
if (err == EAFNOSUPPORT)
{
stop_timer(type); // No point in retrying
has_ip_protocol_[type] = false;
tr_logAddInfo(fmt::format(_("Your machine does not support {protocol}"), fmt::arg("protocol", protocol)));
}
}
unset_is_updating(type);
}
void tr_global_ip_cache::on_response_ip_query(tr_address_type type, tr_web::FetchResponse const& response) noexcept
{
TR_ASSERT(is_updating_[type] == is_updating_t::YES);
TR_ASSERT(ix_service_[type] < std::size(IPQueryServices[type]));
auto const protocol = tr_ip_protocol_to_sv(type);
auto success = false;
if (response.status == 200 /* HTTP_OK */)
{
// Update member
if (auto const addr = tr_address::from_string(tr_strv_strip(response.body)); addr && set_global_addr(type, *addr))
{
success = true;
upkeep_timers_[type]->set_interval(UpkeepInterval);
tr_logAddDebug(fmt::format(
_("Successfully updated global {type} address to {ip} using {url}"),
fmt::arg("type", protocol),
fmt::arg("ip", addr->display_name()),
fmt::arg("url", IPQueryServices[type][ix_service_[type]])));
}
}
// Try next IP query URL
if (!success)
{
if (++ix_service_[type] < std::size(IPQueryServices[type]))
{
update_global_addr(type);
return;
}
tr_logAddDebug(fmt::format("Couldn't obtain global {} address", protocol));
unset_global_addr(type);
upkeep_timers_[type]->set_interval(RetryUpkeepInterval);
}
ix_service_[type] = 0U;
unset_is_updating(type);
}
void tr_global_ip_cache::unset_global_addr(tr_address_type type) noexcept
{
auto const lock = std::lock_guard{ global_addr_mutex_[type] };
global_addr_[type].reset();
tr_logAddTrace(fmt::format("Unset {} global address cache", tr_ip_protocol_to_sv(type)));
}
void tr_global_ip_cache::set_source_addr(tr_address const& addr) noexcept
{
auto const lock = std::lock_guard{ source_addr_mutex_[addr.type] };
source_addr_[addr.type] = addr;
tr_logAddTrace(fmt::format("Cached source address {}", addr.display_name()));
}
void tr_global_ip_cache::unset_addr(tr_address_type type) noexcept
{
auto const lock = std::lock_guard{ source_addr_mutex_[type] };
source_addr_[type].reset();
tr_logAddTrace(fmt::format("Unset {} source address cache", tr_ip_protocol_to_sv(type)));
// No public internet connectivity means no global IP address
unset_global_addr(type);
}
bool tr_global_ip_cache::set_is_updating(tr_address_type type) noexcept
{
if (is_updating_[type] != is_updating_t::NO)
{
return false;
}
is_updating_[type] = is_updating_t::YES;
return true;
}
void tr_global_ip_cache::unset_is_updating(tr_address_type type) noexcept
{
TR_ASSERT(is_updating_[type] == is_updating_t::YES);
is_updating_[type] = is_updating_t::NO;
}