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feat: µTP delayed ack (#6586) 

* chore: rename tr utp functions to snake_case

* refactor: make udp sockets non-blocking

* feat: rudimentary uTP delayed ACK

* chore: housekeeping

* chore: correct comment about µTP packet format
This commit is contained in:
Yat Ho 2024-03-25 09:48:23 +08:00 committed by GitHub
parent 20aef2f79d
commit 3e958cfbaf
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GPG Key ID: B5690EEEBB952194
4 changed files with 94 additions and 64 deletions
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4
libtransmission/session.cc
View File

@ -736,7 +736,7 @@ void tr_session::initImpl(init_data& data)
setSettings(settings, true);
tr_utpInit(this);
tr_utp_init(this);
/* cleanup */
data.done_cv.notify_one();
@ -1406,7 +1406,7 @@ void tr_session::closeImplPart2(std::promise<void>* closed_promise, std::chrono:
stats().save();
peer_mgr_.reset();
openFiles().close_all();
tr_utpClose(this);
tr_utp_close(this);
this->udp_core_.reset();
// tada we are done!

119
libtransmission/tr-udp.cc
View File

@ -27,8 +27,9 @@
namespace
{
/* Since we use a single UDP socket in order to implement multiple
µTP sockets, try to set up huge buffers. */
// Since we use a single UDP socket in order to implement multiple
// µTP sockets, try to set up huge buffers.
void set_socket_buffers(tr_socket_t fd, bool large)
{
static auto constexpr RecvBufferSize = 4 * 1024 * 1024;
@ -41,33 +42,25 @@ void set_socket_buffers(tr_socket_t fd, bool large)
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)
if (setsockopt(fd, SOL_SOCKET, SO_RCVBUF, reinterpret_cast<char const*>(&size), sizeof(size)) < 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)
if (setsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char const*>(&size), sizeof(size)) < 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)
if (getsockopt(fd, SOL_SOCKET, SO_RCVBUF, reinterpret_cast<char*>(&rbuf), &rbuf_len) < 0)
{
rbuf = 0;
}
rc = getsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char*>(&sbuf), &sbuf_len);
if (rc < 0)
if (getsockopt(fd, SOL_SOCKET, SO_SNDBUF, reinterpret_cast<char*>(&sbuf), &sbuf_len) < 0)
{
sbuf = 0;
}
@ -99,41 +92,55 @@ void event_callback(evutil_socket_t s, [[maybe_unused]] short type, void* vsessi
auto from = sockaddr_storage{};
auto fromlen = socklen_t{ sizeof(from) };
auto* const from_sa = reinterpret_cast<sockaddr*>(&from);
auto const rc = recvfrom(s, reinterpret_cast<char*>(std::data(buf)), std::size(buf) - 1, 0, from_sa, &fromlen);
if (rc <= 0)
{
return;
}
/* 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* const session = static_cast<tr_session*>(vsession);
if (buf[0] == 'd')
auto got_utp_packet = false;
for (;;)
{
if (session->dht_)
auto const n_read = recvfrom(s, reinterpret_cast<char*>(std::data(buf)), std::size(buf) - 1, 0, from_sa, &fromlen);
if (n_read <= 0)
{
buf[rc] = '\0'; // libdht requires zero-terminated messages
session->dht_->handle_message(std::data(buf), rc, from_sa, fromlen);
if (got_utp_packet)
{
// To reduce protocol overhead, we wait until we've read all UDP packets
// we can, then send one ACK for each µTP socket that received packet(s).
tr_utp_issue_deferred_acks(session);
}
return;
}
}
else if (rc >= 8 && buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] <= 3)
{
if (!session->announcer_udp_->handle_message(std::data(buf), rc))
// 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' (100)
// - 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
// "type" between 0 and 4, followed by a 4-bit version number (1)
if (buf[0] == 'd')
{
tr_logAddTrace("Couldn't parse UDP tracker packet.");
if (session->dht_)
{
buf[n_read] = '\0'; // libdht requires zero-terminated messages
session->dht_->handle_message(std::data(buf), n_read, from_sa, fromlen);
}
}
}
else if (session->allowsUTP() && (session->utp_context != nullptr))
{
if (!tr_utpPacket(std::data(buf), rc, from_sa, fromlen, session))
else if (n_read >= 8 && buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] <= 3)
{
tr_logAddTrace("Unexpected UDP packet");
if (!session->announcer_udp_->handle_message(std::data(buf), n_read))
{
tr_logAddTrace("Couldn't parse UDP tracker packet.");
}
}
else if (session->allowsUTP() && session->utp_context != nullptr)
{
if (tr_utp_packet(std::data(buf), n_read, from_sa, fromlen, session))
{
got_utp_packet = true;
}
else
{
tr_logAddTrace("Unexpected UDP packet");
}
}
}
}
@ -158,7 +165,18 @@ tr_session::tr_udp_core::tr_udp_core(tr_session& session, tr_port udp_port)
auto const addr = session_.bind_address(TR_AF_INET);
auto const [ss, sslen] = tr_socket_address::to_sockaddr(addr, udp_port_);
if (bind(sock, reinterpret_cast<sockaddr const*>(&ss), sslen) != 0)
if (evutil_make_socket_nonblocking(sock) != 0)
{
auto const error_code = errno;
tr_logAddWarn(fmt::format(
_("Couldn't make IPv4 socket non-blocking {address}: {error} ({error_code})"),
fmt::arg("address", tr_socket_address::display_name(addr, udp_port_)),
fmt::arg("error", tr_strerror(error_code)),
fmt::arg("error_code", error_code)));
tr_net_close_socket(sock);
}
else if (bind(sock, reinterpret_cast<sockaddr const*>(&ss), sslen) != 0)
{
auto const error_code = errno;
tr_logAddWarn(fmt::format(
@ -187,12 +205,23 @@ tr_session::tr_udp_core::tr_udp_core(tr_session& session, tr_port udp_port)
else if (auto sock = socket(PF_INET6, SOCK_DGRAM, 0); sock != TR_BAD_SOCKET)
{
auto optval = 1;
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char const*>(&optval), sizeof(optval));
(void)setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, reinterpret_cast<char const*>(&optval), sizeof(optval));
auto const addr = session_.bind_address(TR_AF_INET6);
auto const [ss, sslen] = tr_socket_address::to_sockaddr(addr, udp_port_);
if (bind(sock, reinterpret_cast<sockaddr const*>(&ss), sslen) != 0)
if (evutil_make_socket_nonblocking(sock) != 0)
{
auto const error_code = errno;
tr_logAddWarn(fmt::format(
_("Couldn't make IPv6 socket non-blocking {address}: {error} ({error_code})"),
fmt::arg("address", tr_socket_address::display_name(addr, udp_port_)),
fmt::arg("error", tr_strerror(error_code)),
fmt::arg("error_code", error_code)));
tr_net_close_socket(sock);
}
else if (bind(sock, reinterpret_cast<sockaddr const*>(&ss), sslen) != 0)
{
auto const error_code = errno;
tr_logAddWarn(fmt::format(

27
libtransmission/tr-utp.cc
View File

@ -155,11 +155,11 @@ void restart_timer(tr_session* session)
}
else
{
/* If somebody has disabled µTP, then we still want to run
utp_check_timeouts, in order to let closed sockets finish
gracefully and so on. However, since we're not particularly
interested in that happening in a timely manner, we might as
well use a large timeout. */
// If somebody has disabled µTP, then we still want to run
// utp_check_timeouts, in order to let closed sockets finish
// gracefully and so on. However, since we're not particularly
// interested in that happening in a timely manner, we might as
// well use a large timeout.
static auto constexpr MinInterval = 2s;
static auto constexpr MaxInterval = 3s;
auto const target = MinInterval + random_percent * (MaxInterval - MinInterval);
@ -173,15 +173,12 @@ void timer_callback(void* vsession)
{
auto* session = static_cast<tr_session*>(vsession);
/* utp_internal.cpp says "Should be called each time the UDP socket is drained" but it's tricky with libevent */
utp_issue_deferred_acks(session->utp_context);
utp_check_timeouts(session->utp_context);
restart_timer(session);
}
} // namespace
void tr_utpInit(tr_session* session)
void tr_utp_init(tr_session* session)
{
if (session->utp_context != nullptr)
{
@ -212,17 +209,19 @@ void tr_utpInit(tr_session* session)
restart_timer(session);
}
bool tr_utpPacket(unsigned char const* buf, size_t buflen, struct sockaddr const* from, socklen_t fromlen, tr_session* ss)
bool tr_utp_packet(unsigned char const* buf, size_t buflen, struct sockaddr const* from, socklen_t fromlen, tr_session* ss)
{
auto const ret = utp_process_udp(ss->utp_context, buf, buflen, from, fromlen);
/* utp_internal.cpp says "Should be called each time the UDP socket is drained" but it's tricky with libevent */
utp_issue_deferred_acks(ss->utp_context);
return ret != 0;
}
void tr_utpClose(tr_session* session)
void tr_utp_issue_deferred_acks(tr_session* ss)
{
utp_issue_deferred_acks(ss->utp_context);
}
void tr_utp_close(tr_session* session)
{
session->utp_timer.reset();

8
libtransmission/tr-utp.h
View File

@ -18,8 +18,10 @@
struct tr_session;
void tr_utpInit(tr_session* session);
void tr_utp_init(tr_session* session);
bool tr_utpPacket(unsigned char const* buf, size_t buflen, struct sockaddr const* from, socklen_t fromlen, tr_session* ss);
bool tr_utp_packet(unsigned char const* buf, size_t buflen, struct sockaddr const* from, socklen_t fromlen, tr_session* ss);
void tr_utpClose(tr_session*);
void tr_utp_issue_deferred_acks(tr_session* ss);
void tr_utp_close(tr_session* session);