unix_socket.cc | Explore in Territory

/*
 * Copyright (C) 2017 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

#include "perfetto/ext/base/unix_socket.h"

#include <errno.h>
#include <fcntl.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <sys/types.h>
#include "perfetto/base/compiler.h"
#include "perfetto/ext/base/string_utils.h"

#if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
// The include order matters on these three Windows header groups.
#include <Windows.h>

#include <WS2tcpip.h>
#include <WinSock2.h>

#include <afunix.h>
#else
#include <arpa/inet.h>
#include <netdb.h>
#include <netinet/in.h>
#include <netinet/tcp.h>
#include <poll.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <unistd.h>
#endif

#if PERFETTO_BUILDFLAG(PERFETTO_OS_APPLE)
#include <sys/ucred.h>
#endif

#include <algorithm>
#include <memory>

#include "perfetto/base/build_config.h"
#include "perfetto/base/logging.h"
#include "perfetto/base/task_runner.h"
#include "perfetto/base/time.h"
#include "perfetto/ext/base/string_utils.h"
#include "perfetto/ext/base/utils.h"

#if PERFETTO_BUILDFLAG(PERFETTO_OS_LINUX) || \
    PERFETTO_BUILDFLAG(PERFETTO_OS_ANDROID)
// Use a local stripped copy of vm_sockets.h from UAPI.
#include "src/base/vm_sockets.h"
#endif

namespace perfetto {
namespace base {

// The CMSG_* macros use NULL instead of nullptr.
// Note: MSVC doesn't have #pragma GCC diagnostic, hence the if __GNUC__.
#if defined(__GNUC__) && !PERFETTO_BUILDFLAG(PERFETTO_OS_APPLE)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wzero-as-null-pointer-constant"
#endif

namespace {

// Android takes an int instead of socklen_t for the control buffer size.
#if PERFETTO_BUILDFLAG(PERFETTO_OS_ANDROID)
using CBufLenType = size_t;
#else
CBufLenType;
#endif

#if PERFETTO_BUILDFLAG(PERFETTO_OS_LINUX) || \
    PERFETTO_BUILDFLAG(PERFETTO_OS_ANDROID)
constexpr char kVsockNamePrefix[] = …;
#endif

// A wrapper around variable-size sockaddr structs.
// This is solving the following problem: when calling connect() or bind(), the
// caller needs to take care to allocate the right struct (sockaddr_un for
// AF_UNIX, sockaddr_in for AF_INET).   Those structs have different sizes and,
// more importantly, are bigger than the base struct sockaddr.
struct SockaddrAny { … };

inline int MkSockFamily(SockFamily family) { … }

inline int MkSockType(SockType type) { … }

SockaddrAny MakeSockAddr(SockFamily family, const std::string& socket_name) { … }

ScopedSocketHandle CreateSocketHandle(SockFamily family, SockType type) { … }

}  // namespace

#if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
int CloseSocket(SocketHandle s) {
  return ::closesocket(s);
}
#endif

SockFamily GetSockFamily(const char* addr) { … }

// +-----------------------+
// | UnixSocketRaw methods |
// +-----------------------+

#if !PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
// static
void UnixSocketRaw::ShiftMsgHdrPosix(size_t n, struct msghdr* msg) { … }

// static
std::pair<UnixSocketRaw, UnixSocketRaw> UnixSocketRaw::CreatePairPosix(
    SockFamily family,
    SockType type) { … }
#endif

// static
UnixSocketRaw UnixSocketRaw::CreateMayFail(SockFamily family, SockType type) { … }

UnixSocketRaw::UnixSocketRaw() = default;

UnixSocketRaw::UnixSocketRaw(SockFamily family, SockType type)
    : … { … }

UnixSocketRaw::UnixSocketRaw(ScopedSocketHandle fd,
                             SockFamily family,
                             SockType type)
    : … { … }

void UnixSocketRaw::SetBlocking(bool is_blocking) { … }

void UnixSocketRaw::SetRetainOnExec(bool retain) { … }

void UnixSocketRaw::DcheckIsBlocking(bool expected) const { … }

bool UnixSocketRaw::Bind(const std::string& socket_name) { … }

bool UnixSocketRaw::Listen() { … }

bool UnixSocketRaw::Connect(const std::string& socket_name) { … }

void UnixSocketRaw::Shutdown() { … }

#if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)

ssize_t UnixSocketRaw::Send(const void* msg,
                            size_t len,
                            const int* /*send_fds*/,
                            size_t num_fds) {
  PERFETTO_DCHECK(num_fds == 0);
  return sendto(*fd_, static_cast<const char*>(msg), static_cast<int>(len), 0,
                nullptr, 0);
}

ssize_t UnixSocketRaw::Receive(void* msg,
                               size_t len,
                               ScopedFile* /*fd_vec*/,
                               size_t /*max_files*/) {
  return recv(*fd_, static_cast<char*>(msg), static_cast<int>(len), 0);
}

#else
// For the interested reader, Linux kernel dive to verify this is not only a
// theoretical possibility: sock_stream_sendmsg, if sock_alloc_send_pskb returns
// NULL [1] (which it does when it gets interrupted [2]), returns early with the
// amount of bytes already sent.
//
// [1]:
// https://elixir.bootlin.com/linux/v4.18.10/source/net/unix/af_unix.c#L1872
// [2]: https://elixir.bootlin.com/linux/v4.18.10/source/net/core/sock.c#L2101
ssize_t UnixSocketRaw::SendMsgAllPosix(struct msghdr* msg) { … }

ssize_t UnixSocketRaw::Send(const void* msg,
                            size_t len,
                            const int* send_fds,
                            size_t num_fds) { … }

ssize_t UnixSocketRaw::Receive(void* msg,
                               size_t len,
                               ScopedFile* fd_vec,
                               size_t max_files) { … }
#endif  // OS_WIN

bool UnixSocketRaw::SetTxTimeout(uint32_t timeout_ms) { … }

bool UnixSocketRaw::SetRxTimeout(uint32_t timeout_ms) { … }

std::string UnixSocketRaw::GetSockAddr() const { … }

#if defined(__GNUC__) && !PERFETTO_BUILDFLAG(PERFETTO_OS_APPLE)
#pragma GCC diagnostic pop
#endif

// +--------------------+
// | UnixSocket methods |
// +--------------------+

// TODO(primiano): Add ThreadChecker to methods of this class.

// static
std::unique_ptr<UnixSocket> UnixSocket::Listen(const std::string& socket_name,
                                               EventListener* event_listener,
                                               TaskRunner* task_runner,
                                               SockFamily sock_family,
                                               SockType sock_type) { … }

// static
std::unique_ptr<UnixSocket> UnixSocket::Listen(ScopedSocketHandle fd,
                                               EventListener* event_listener,
                                               TaskRunner* task_runner,
                                               SockFamily sock_family,
                                               SockType sock_type) { … }

// static
std::unique_ptr<UnixSocket> UnixSocket::Connect(
    const std::string& socket_name,
    EventListener* event_listener,
    TaskRunner* task_runner,
    SockFamily sock_family,
    SockType sock_type,
    SockPeerCredMode peer_cred_mode) { … }

// static
std::unique_ptr<UnixSocket> UnixSocket::AdoptConnected(
    ScopedSocketHandle fd,
    EventListener* event_listener,
    TaskRunner* task_runner,
    SockFamily sock_family,
    SockType sock_type,
    SockPeerCredMode peer_cred_mode) { … }

UnixSocket::UnixSocket(EventListener* event_listener,
                       TaskRunner* task_runner,
                       SockFamily sock_family,
                       SockType sock_type,
                       SockPeerCredMode peer_cred_mode)
    : … { … }

UnixSocket::UnixSocket(EventListener* event_listener,
                       TaskRunner* task_runner,
                       ScopedSocketHandle adopt_fd,
                       State adopt_state,
                       SockFamily sock_family,
                       SockType sock_type,
                       SockPeerCredMode peer_cred_mode)
    : … { … }

UnixSocket::~UnixSocket() { … }

UnixSocketRaw UnixSocket::ReleaseSocket() { … }

// Called only by the Connect() static constructor.
void UnixSocket::DoConnect(const std::string& socket_name) { … }

#if !PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
void UnixSocket::ReadPeerCredentialsPosix() { … }
#endif  // !OS_WIN

#if PERFETTO_BUILDFLAG(PERFETTO_OS_WIN)
void UnixSocket::OnEvent() {
  WSANETWORKEVENTS evts{};
  PERFETTO_CHECK(WSAEnumNetworkEvents(sock_raw_.fd(), sock_raw_.watch_handle(),
                                      &evts) == 0);
  if (state_ == State::kDisconnected)
    return;  // Some spurious event, typically queued just before Shutdown().

  if (state_ == State::kConnecting && (evts.lNetworkEvents & FD_CONNECT)) {
    PERFETTO_DCHECK(sock_raw_);
    int err = evts.iErrorCode[FD_CONNECT_BIT];
    if (err) {
      PERFETTO_DPLOG("Connection error: %d", err);
      Shutdown(false);
      event_listener_->OnConnect(this, false /* connected */);
      return;
    }

    // kReadOnConnect is not supported on Windows.
    PERFETTO_DCHECK(peer_cred_mode_ != SockPeerCredMode::kReadOnConnect);
    state_ = State::kConnected;
    event_listener_->OnConnect(this, true /* connected */);
  }

  // This is deliberately NOT an else-if. When a client socket connects and
  // there is already data queued, the following will happen within the same
  // OnEvent() call:
  // 1. The block above will transition kConnecting -> kConnected.
  // 2. This block will cause an OnDataAvailable() call.
  // Unlike UNIX, where poll() keeps signalling the event until the client
  // does a recv(), Windows is more picky and stops signalling the event until
  // the next call to recv() is made. In other words, in Windows we cannot
  // miss an OnDataAvailable() call or the event pump will stop.
  if (state_ == State::kConnected) {
    if (evts.lNetworkEvents & FD_READ) {
      event_listener_->OnDataAvailable(this);
      // TODO(primiano): I am very conflicted here. Because of the behavior
      // described above, if the event listener doesn't do a Recv() call in
      // the OnDataAvailable() callback, WinSock won't notify the event ever
      // again. On one side, I don't see any reason why a client should decide
      // to not do a Recv() in OnDataAvailable. On the other side, the
      // behavior here diverges from UNIX, where OnDataAvailable() would be
      // re-posted immediately. In both cases, not doing a Recv() in
      // OnDataAvailable, leads to something bad (getting stuck on Windows,
      // getting in a hot loop on Linux), so doesn't feel we should worry too
      // much about this. If we wanted to keep the behavrior consistent, here
      // we should do something like: `if (sock_raw_)
      // sock_raw_.SetBlocking(false)` (Note that the socket might be closed
      // by the time we come back here, hence the if part).
      return;
    }
    // Could read EOF and disconnect here.
    if (evts.lNetworkEvents & FD_CLOSE) {
      Shutdown(true);
      return;
    }
  }

  // New incoming connection.
  if (state_ == State::kListening && (evts.lNetworkEvents & FD_ACCEPT)) {
    // There could be more than one incoming connection behind each FD watch
    // notification. Drain'em all.
    for (;;) {
      // Note: right now we don't need the remote endpoint, hence we pass
      // nullptr to |addr| and |addrlen|. If we ever need to do so, be
      // extremely careful. Windows' WinSock API will happily write more than
      // |addrlen| (hence corrupt the stack) if the |addr| argument passed is
      // not big enough (e.g. passing a struct sockaddr_in to a AF_UNIX
      // socket, where sizeof(sockaddr_un) is >> sizef(sockaddr_in)). It seems
      // a Windows / CRT bug in the AF_UNIX implementation.
      ScopedSocketHandle new_fd(accept(sock_raw_.fd(), nullptr, nullptr));
      if (!new_fd)
        return;
      std::unique_ptr<UnixSocket> new_sock(new UnixSocket(
          event_listener_, task_runner_, std::move(new_fd), State::kConnected,
          sock_raw_.family(), sock_raw_.type(), peer_cred_mode_));
      event_listener_->OnNewIncomingConnection(this, std::move(new_sock));
    }
  }
}
#else
void UnixSocket::OnEvent() { … }
#endif

bool UnixSocket::Send(const void* msg,
                      size_t len,
                      const int* send_fds,
                      size_t num_fds) { … }

void UnixSocket::Shutdown(bool notify) { … }

size_t UnixSocket::Receive(void* msg,
                           size_t len,
                           ScopedFile* fd_vec,
                           size_t max_files) { … }

std::string UnixSocket::ReceiveString(size_t max_length) { … }

void UnixSocket::NotifyConnectionState(bool success) { … }

UnixSocket::EventListener::~EventListener() { … }
void UnixSocket::EventListener::OnNewIncomingConnection(
    UnixSocket*,
    std::unique_ptr<UnixSocket>) { … }
void UnixSocket::EventListener::OnConnect(UnixSocket*, bool) { … }
void UnixSocket::EventListener::OnDisconnect(UnixSocket*) { … }
void UnixSocket::EventListener::OnDataAvailable(UnixSocket*) { … }

}  // namespace base
}  // namespace perfetto
chromium/third_party/perfetto/src/base/unix_socket.cc
