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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 <cstdint>
#include <cstring> /* memcmp(), memcpy(), memset() */
#include <cstdlib> /* malloc(), free() */
#include <string_view>
#ifdef _WIN32
#include <io.h> /* dup2() */
#else
#include <unistd.h> /* dup2() */
#endif
#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-dht.h"
#include "tr-utp.h"
#include "tr-udp.h"
#include "utils.h"
/* Since we use a single UDP socket in order to implement multiple
uTP sockets, try to set up huge buffers. */
#define RECV_BUFFER_SIZE (4 * 1024 * 1024)
#define SEND_BUFFER_SIZE (1 * 1024 * 1024)
#define SMALL_BUFFER_SIZE (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 ? RECV_BUFFER_SIZE : SMALL_BUFFER_SIZE;
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 ? SEND_BUFFER_SIZE : SMALL_BUFFER_SIZE;
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 < RECV_BUFFER_SIZE)
{
tr_logAddDebug(fmt::format("Couldn't set receive buffer: requested {}, got {}", RECV_BUFFER_SIZE, rbuf));
#ifdef __linux__
tr_logAddDebug(fmt::format("Please add the line 'net.core.rmem_max = {}' to /etc/sysctl.conf", RECV_BUFFER_SIZE));
#endif
}
if (sbuf < SEND_BUFFER_SIZE)
{
tr_logAddDebug(fmt::format("Couldn't set send buffer: requested {}, got {}", SEND_BUFFER_SIZE, sbuf));
#ifdef __linux__
tr_logAddDebug(fmt::format("Please add the line 'net.core.wmem_max = {}' to /etc/sysctl.conf", SEND_BUFFER_SIZE));
#endif
}
}
}
void tr_udpSetSocketBuffers(tr_session* session)
{
bool utp = tr_sessionIsUTPEnabled(session);
if (session->udp_socket != TR_BAD_SOCKET)
{
set_socket_buffers(session->udp_socket, utp);
}
if (session->udp6_socket != TR_BAD_SOCKET)
{
set_socket_buffers(session->udp6_socket, utp);
}
}
void tr_udpSetSocketTOS(tr_session* session)
{
session->setSocketTOS(session->udp_socket, TR_AF_INET);
session->setSocketTOS(session->udp6_socket, TR_AF_INET6);
}
/* BEP-32 has a rather nice explanation of why we need to bind to one
IPv6 address, if I may say so myself. */
// TODO: remove goto, it prevents reducing scope of local variables
static void rebind_ipv6(tr_session* ss, bool force)
{
struct sockaddr_in6 sin6;
unsigned char const* ipv6 = tr_globalIPv6(ss);
tr_socket_t s = TR_BAD_SOCKET;
int rc = -1;
int one = 1;
/* 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 == nullptr || (!force && ss->udp6_socket == TR_BAD_SOCKET))
{
if (ss->udp6_bound != nullptr)
{
free(ss->udp6_bound);
ss->udp6_bound = nullptr;
}
return;
}
if (ss->udp6_bound != nullptr && memcmp(ipv6, ss->udp6_bound, 16) == 0)
{
return;
}
s = socket(PF_INET6, SOCK_DGRAM, 0);
if (s == TR_BAD_SOCKET)
{
goto FAIL;
}
#ifdef IPV6_V6ONLY
/* Since we always open an IPv4 socket on the same port, this
shouldn't matter. But I'm superstitious. */
(void)setsockopt(s, IPPROTO_IPV6, IPV6_V6ONLY, reinterpret_cast<char const*>(&one), sizeof(one));
#endif
memset(&sin6, 0, sizeof(sin6));
sin6.sin6_family = AF_INET6;
if (ipv6 != nullptr)
{
memcpy(&sin6.sin6_addr, ipv6, 16);
}
sin6.sin6_port = htons(ss->udp_port);
rc = bind(s, (struct sockaddr*)&sin6, sizeof(sin6));
if (rc == -1)
{
goto FAIL;
}
if (ss->udp6_socket == TR_BAD_SOCKET)
{
ss->udp6_socket = s;
}
else
{
/* FIXME: dup2 doesn't work for sockets on Windows */
rc = dup2(s, ss->udp6_socket);
if (rc == -1)
{
goto FAIL;
}
tr_netCloseSocket(s);
}
if (ss->udp6_bound == nullptr)
{
ss->udp6_bound = static_cast<unsigned char*>(malloc(16));
}
if (ss->udp6_bound != nullptr)
{
memcpy(ss->udp6_bound, ipv6, 16);
}
return;
FAIL:
/* 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)));
if (s != TR_BAD_SOCKET)
{
tr_netCloseSocket(s);
}
if (ss->udp6_bound != nullptr)
{
free(ss->udp6_bound);
ss->udp6_bound = nullptr;
}
}
static void event_callback(evutil_socket_t s, [[maybe_unused]] short type, void* vsession)
{
TR_ASSERT(tr_isSession(static_cast<tr_session*>(vsession)));
TR_ASSERT(type == EV_READ);
unsigned char buf[4096];
struct sockaddr_storage from;
auto* session = static_cast<tr_session*>(vsession);
socklen_t fromlen = sizeof(from);
int rc = recvfrom(s, reinterpret_cast<char*>(buf), 4096 - 1, 0, (struct 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). */
if (rc > 0)
{
if (buf[0] == 'd')
{
if (tr_sessionAllowsDHT(session))
{
buf[rc] = '\0'; /* required by the DHT code */
tr_dhtCallback(buf, rc, (struct sockaddr*)&from, fromlen, vsession);
}
}
else if (rc >= 8 && buf[0] == 0 && buf[1] == 0 && buf[2] == 0 && buf[3] <= 3)
{
if (!tau_handle_message(session, buf, rc))
{
tr_logAddTrace("Couldn't parse UDP tracker packet.");
}
}
else
{
if (tr_sessionIsUTPEnabled(session))
{
if (!tr_utpPacket(buf, rc, (struct sockaddr*)&from, fromlen, session))
{
tr_logAddTrace("Unexpected UDP packet");
}
}
}
}
}
void tr_udpInit(tr_session* ss)
{
TR_ASSERT(ss->udp_socket == TR_BAD_SOCKET);
TR_ASSERT(ss->udp6_socket == TR_BAD_SOCKET);
ss->udp_port = tr_sessionGetPeerPort(ss);
if (ss->udp_port <= 0)
{
return;
}
ss->udp_socket = socket(PF_INET, SOCK_DGRAM, 0);
if (ss->udp_socket == TR_BAD_SOCKET)
{
tr_logAddWarn(_("Couldn't create IPv4 socket"));
}
else
{
auto is_default = bool{};
tr_address const* public_addr = tr_sessionGetPublicAddress(ss, TR_AF_INET, &is_default);
auto sin = sockaddr_in{};
sin.sin_family = AF_INET;
if (public_addr != nullptr && !is_default)
{
memcpy(&sin.sin_addr, &public_addr->addr.addr4, sizeof(struct in_addr));
}
sin.sin_port = htons(ss->udp_port);
int const rc = bind(ss->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 != nullptr ? public_addr->to_string(ss->udp_port) : "?"),
fmt::arg("error", tr_strerror(error_code)),
fmt::arg("error_code", error_code)));
tr_netCloseSocket(ss->udp_socket);
ss->udp_socket = TR_BAD_SOCKET;
}
else
{
ss->udp_event = event_new(ss->event_base, ss->udp_socket, EV_READ | EV_PERSIST, event_callback, ss);
if (ss->udp_event == nullptr)
{
tr_logAddWarn(_("Couldn't allocate IPv4 event"));
}
}
}
// IPV6
if (tr_globalIPv6(nullptr) != nullptr)
{
rebind_ipv6(ss, true);
}
if (ss->udp6_socket != TR_BAD_SOCKET)
{
ss->udp6_event = event_new(ss->event_base, ss->udp6_socket, EV_READ | EV_PERSIST, event_callback, ss);
if (ss->udp6_event == nullptr)
{
tr_logAddWarn(_("Couldn't allocate IPv6 event"));
}
}
tr_udpSetSocketBuffers(ss);
tr_udpSetSocketTOS(ss);
if (ss->isDHTEnabled)
{
tr_dhtInit(ss);
}
if (ss->udp_event != nullptr)
{
event_add(ss->udp_event, nullptr);
}
if (ss->udp6_event != nullptr)
{
event_add(ss->udp6_event, nullptr);
}
}
void tr_udpUninit(tr_session* ss)
{
tr_dhtUninit(ss);
if (ss->udp_socket != TR_BAD_SOCKET)
{
tr_netCloseSocket(ss->udp_socket);
ss->udp_socket = TR_BAD_SOCKET;
}
if (ss->udp_event != nullptr)
{
event_free(ss->udp_event);
ss->udp_event = nullptr;
}
if (ss->udp6_socket != TR_BAD_SOCKET)
{
tr_netCloseSocket(ss->udp6_socket);
ss->udp6_socket = TR_BAD_SOCKET;
}
if (ss->udp6_event != nullptr)
{
event_free(ss->udp6_event);
ss->udp6_event = nullptr;
}
if (ss->udp6_bound != nullptr)
{
free(ss->udp6_bound);
ss->udp6_bound = nullptr;
}
}
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