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transmission/libtransmission/tr-udp.cc

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// This file Copyright © 2010 Juliusz Chroboczek.
// It may be used under the MIT (SPDX: MIT) license.
// License text can be found in the licenses/ folder.
#include <array>
#include <cerrno>
#include <cstdint>
#include <cstring> /* memcmp(), memset() */
#include <event2/event.h>
#include <fmt/core.h>
#include "transmission.h"
#include "log.h"
#include "net.h"
#include "session.h"
#include "tr-assert.h"
#include "tr-utp.h"
#include "utils.h"
/* Since we use a single UDP socket in order to implement multiple
µTP sockets, try to set up huge buffers. */
static auto constexpr RecvBufferSize = 4 * 1024 * 1024;
static auto constexpr SendBufferSize = 1 * 1024 * 1024;
static auto constexpr SmallBufferSize = 32 * 1024;
static void set_socket_buffers(tr_socket_t fd, bool large)
{
int rbuf = 0;
int sbuf = 0;
socklen_t rbuf_len = sizeof(rbuf);
socklen_t sbuf_len = sizeof(sbuf);
int size = large ? RecvBufferSize : SmallBufferSize;
int rc = setsockopt(fd, SOL_SOCKET, SO_RCVBUF, reinterpret_cast<char const*>(&size), sizeof(size));
if (rc < 0)
{
tr_logAddDebug(fmt::format("Couldn't set receive buffer: {}", tr_net_strerror(sockerrno)));
}
size = large ? SendBufferSize : SmallBufferSize;
rc = setsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char const*>(&size), sizeof(size));
if (rc < 0)
{
tr_logAddDebug(fmt::format("Couldn't set send buffer: {}", tr_net_strerror(sockerrno)));
}
if (large)
{
rc = getsockopt(fd, SOL_SOCKET, SO_RCVBUF, reinterpret_cast<char*>(&rbuf), &rbuf_len);
if (rc < 0)
{
rbuf = 0;
}
rc = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char*>(&sbuf), &sbuf_len);
if (rc < 0)
{
sbuf = 0;
}
if (rbuf < RecvBufferSize)
{
tr_logAddDebug(fmt::format("Couldn't set receive buffer: requested {}, got {}", RecvBufferSize, rbuf));
#ifdef __linux__
tr_logAddDebug(fmt::format("Please add the line 'net.core.rmem_max = {}' to /etc/sysctl.conf", RecvBufferSize));
#endif
}
if (sbuf < SendBufferSize)
{
tr_logAddDebug(fmt::format("Couldn't set send buffer: requested {}, got {}", SendBufferSize, sbuf));
#ifdef __linux__
tr_logAddDebug(fmt::format("Please add the line 'net.core.wmem_max = {}' to /etc/sysctl.conf", SendBufferSize));
#endif
}
}
}
void tr_session::tr_udp_core::set_socket_buffers()
{
bool const utp = session_.allowsUTP();
if (udp_socket_ != TR_BAD_SOCKET)
{
::set_socket_buffers(udp_socket_, utp);
}
if (udp6_socket_ != TR_BAD_SOCKET)
{
::set_socket_buffers(udp6_socket_, utp);
}
}
static tr_socket_t rebind_ipv6_impl(in6_addr sin6_addr, tr_port port)
{
auto const sock = socket(PF_INET6, SOCK_DGRAM, 0);
if (sock == TR_BAD_SOCKET)
{
return TR_BAD_SOCKET;
}
#ifdef IPV6_V6ONLY
/* Since we always open an IPv4 socket on the same port,
* this shouldn't matter. But I'm superstitious. */
int one = 1;
(void)setsockopt(sock, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<char const*>(&one), sizeof(one));
#endif
auto sin6 = sockaddr_in6{};
sin6.sin6_family = AF_INET6;
sin6.sin6_addr = sin6_addr;
sin6.sin6_port = port.network();
if (::bind(sock, reinterpret_cast<struct sockaddr*>(&sin6), sizeof(sin6)) == -1)
{
tr_netCloseSocket(sock);
return TR_BAD_SOCKET;
}
return sock;
}
/* BEP-32 has a rather nice explanation of why we need to bind to one
IPv6 address, if I may say so myself. */
void tr_session::tr_udp_core::rebind_ipv6(bool force)
{
auto const ipv6 = tr_globalIPv6(&session_);
/* We currently have no way to enable or disable IPv6 after initialisation.
No way to fix that without some surgery to the DHT code itself. */
if (!ipv6 || (!force && udp6_socket_ == TR_BAD_SOCKET))
{
udp6_bound_.reset();
return;
}
if (udp6_bound_ && memcmp(&*udp6_bound_, &*ipv6, sizeof(*ipv6)) == 0)
{
return;
}
auto const sock = rebind_ipv6_impl(*ipv6, udp_port_);
if (sock == TR_BAD_SOCKET)
{
/* Something went wrong. It's difficult to recover, so let's
* simply set things up so that we try again next time. */
auto const error_code = errno;
auto ipv6_readable = std::array<char, INET6_ADDRSTRLEN>{};
evutil_inet_ntop(AF_INET6, &*ipv6, std::data(ipv6_readable), std::size(ipv6_readable));
tr_logAddWarn(fmt::format(
_("Couldn't rebind IPv6 socket {address}: {error} ({error_code})"),
fmt::arg("address", std::data(ipv6_readable)),
fmt::arg("error", tr_strerror(error_code)),
fmt::arg("error_code", error_code)));
udp6_bound_.reset();
return;
}
if (udp6_socket_ != TR_BAD_SOCKET)
{
tr_netCloseSocket(udp6_socket_);
}
udp6_socket_ = sock;
udp6_bound_ = ipv6;
}
static void event_callback(evutil_socket_t s, [[maybe_unused]] short type, void* vsession)
{
TR_ASSERT(vsession != nullptr);
TR_ASSERT(type == EV_READ);
auto buf = std::array<unsigned char, 8192>{};
auto from = sockaddr_storage{};
auto fromlen = socklen_t{ sizeof(from) };
auto const rc = recvfrom(
s,
reinterpret_cast<char*>(std::data(buf)),
std::size(buf) - 1,
0,
reinterpret_cast<sockaddr*>(&from),
&fromlen);
/* Since most packets we receive here are µTP, make quick inline
checks for the other protocols. The logic is as follows:
- all DHT packets start with 'd'
- all UDP tracker packets start with a 32-bit (!) "action", which
is between 0 and 3
- the above cannot be µTP packets, since these start with a 4-bit
version number (1). */
auto* session = static_cast<tr_session*>(vsession);
if (rc > 0)
{
if (buf[0] == 'd')
{
if (session->dht_)
{
buf[rc] = '\0'; // libdht requires zero-terminated messages
session->dht_->handleMessage(std::data(buf), rc, reinterpret_cast<sockaddr*>(&from), fromlen);
}
}
else if (rc >= 8 && buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] <= 3)
{
if (!session->announcer_udp_->handleMessage(std::data(buf), rc))
{
tr_logAddTrace("Couldn't parse UDP tracker packet.");
}
}
else
{
if (session->allowsUTP() && (session->utp_context != nullptr))
{
if (!tr_utpPacket(std::data(buf), rc, (struct sockaddr*)&from, fromlen, session))
{
tr_logAddTrace("Unexpected UDP packet");
}
}
}
}
}
tr_session::tr_udp_core::tr_udp_core(tr_session& session, tr_port udp_port)
: udp_port_{ udp_port }
, session_{ session }
{
if (std::empty(udp_port_))
{
return;
}
udp_socket_ = socket(PF_INET, SOCK_DGRAM, 0);
if (udp_socket_ == TR_BAD_SOCKET)
{
tr_logAddWarn(_("Couldn't create IPv4 socket"));
}
else
{
auto const [public_addr, is_default] = session_.publicAddress(TR_AF_INET);
auto sin = sockaddr_in{};
sin.sin_family = AF_INET;
if (!is_default)
{
sin.sin_addr = public_addr.addr.addr4;
}
sin.sin_port = udp_port_.network();
int const rc = bind(udp_socket_, (struct sockaddr*)&sin, sizeof(sin));
if (rc == -1)
{
auto const error_code = errno;
tr_logAddWarn(fmt::format(
_("Couldn't bind IPv4 socket {address}: {error} ({error_code})"),
fmt::arg("address", public_addr.display_name(udp_port_)),
fmt::arg("error", tr_strerror(error_code)),
fmt::arg("error_code", error_code)));
tr_netCloseSocket(udp_socket_);
udp_socket_ = TR_BAD_SOCKET;
}
else
{
udp4_event_.reset(event_new(session_.eventBase(), udp_socket_, EV_READ | EV_PERSIST, event_callback, &session_));
}
}
// IPV6
if (tr_globalIPv6(nullptr).has_value())
{
rebind_ipv6(true);
}
if (udp6_socket_ != TR_BAD_SOCKET)
{
udp6_event_.reset(event_new(session_.eventBase(), udp6_socket_, EV_READ | EV_PERSIST, event_callback, &session_));
}
set_socket_buffers();
set_socket_tos();
if (udp4_event_ != nullptr)
{
event_add(udp4_event_.get(), nullptr);
}
if (udp6_event_)
{
event_add(udp6_event_.get(), nullptr);
}
}
tr_session::tr_udp_core::~tr_udp_core()
{
udp6_event_.reset();
if (udp6_socket_ != TR_BAD_SOCKET)
{
tr_netCloseSocket(udp6_socket_);
udp6_socket_ = TR_BAD_SOCKET;
}
udp4_event_.reset();
if (udp_socket_ != TR_BAD_SOCKET)
{
tr_netCloseSocket(udp_socket_);
udp_socket_ = TR_BAD_SOCKET;
}
udp6_bound_.reset();
}
void tr_session::tr_udp_core::sendto(void const* buf, size_t buflen, struct sockaddr const* to, socklen_t const tolen) const
{
int error = 0;
std::array<char, std::max(INET_ADDRSTRLEN, INET6_ADDRSTRLEN) + 1> peer = {};
if (to->sa_family == AF_INET)
{
if (udp_socket_ != TR_BAD_SOCKET)
{
if (::sendto(udp_socket_, static_cast<char const*>(buf), buflen, 0, to, tolen) == -1)
{
error = -1;
}
}
else
{
error = -1;
errno = EBADF;
}
if (error == -1)
{
evutil_inet_ntop(
AF_INET,
&((reinterpret_cast<struct sockaddr_in const*>(to))->sin_addr),
std::data(peer),
std::size(peer));
}
}
else if (to->sa_family == AF_INET6)
{
if (udp6_socket_ != TR_BAD_SOCKET)
{
if (::sendto(udp6_socket_, static_cast<char const*>(buf), buflen, 0, to, tolen) == -1)
{
error = -1;
}
}
else
{
error = -1;
errno = EBADF;
}
if (error == -1)
{
evutil_inet_ntop(
AF_INET6,
&((reinterpret_cast<struct sockaddr_in6 const*>(to))->sin6_addr),
std::data(peer),
std::size(peer));
}
}
else
{
error = -1;
errno = EAFNOSUPPORT;
}
if (error == -1)
{
tr_logAddWarn(fmt::format(
"Couldn't send to {address}: {errno} ({error})",
fmt::arg("address", std::data(peer)),
fmt::arg("errno", errno),
fmt::arg("error", tr_strerror(errno))));
}
}
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