/***************************************************************************
 *                                  _   _ ____  _
 *  Project                     ___| | | |  _ \| |
 *                             / __| | | | |_) | |
 *                            | (__| |_| |  _ <| |___
 *                             \___|\___/|_| \_\_____|
 *
 * Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
 *
 * This software is licensed as described in the file COPYING, which
 * you should have received as part of this distribution. The terms
 * are also available at https://curl.se/docs/copyright.html.
 *
 * You may opt to use, copy, modify, merge, publish, distribute and/or sell
 * copies of the Software, and permit persons to whom the Software is
 * furnished to do so, under the terms of the COPYING file.
 *
 * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
 * KIND, either express or implied.
 *
 * SPDX-License-Identifier: curl
 *
 ***************************************************************************/
#include "first.h"

#include <toolx/tool_time.h>

#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

#ifdef _WIN32
#include <share.h>
#endif

void loghex(const unsigned char *buffer, ssize_t len)
{
  char data[12000];
  ssize_t i;
  const unsigned char *ptr = buffer;
  char *optr = data;
  ssize_t width = 0;
  int left = sizeof(data);

  for(i = 0; i < len && (left > 2); i++) {
    snprintf(optr, left, "%02x", ptr[i]);
    width += 2;
    optr += 2;
    left -= 2;
  }
  if(width)
    logmsg("'%s'", data);
}

void logmsg(const char *msg, ...)
{
  va_list ap;
  char buffer[2048 + 1];
  FILE *logfp;
  struct curltime tv;
  CURLcode result;
  time_t sec;
  struct tm now;
  char timebuf[50];
  static time_t epoch_offset;
  static int    known_offset;

  if(!serverlogfile) {
    fprintf(stderr, "Error: Server log file not set\n");
    return;
  }

  tv = curlx_now();
  if(!known_offset) {
    epoch_offset = time(NULL) - tv.tv_sec;
    known_offset = 1;
  }
  sec = epoch_offset + tv.tv_sec;
  result = toolx_localtime(sec, &now);
  if(result)
    memset(&now, 0, sizeof(now));

  snprintf(timebuf, sizeof(timebuf), "%02d:%02d:%02d.%06ld",
           now.tm_hour, now.tm_min, now.tm_sec, (long)tv.tv_usec);

  va_start(ap, msg);
/* Suppress for builds where CURL_PRINTF() is not set */
#ifdef CURL_HAVE_DIAG
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wformat-nonliteral"
#endif
  vsnprintf(buffer, sizeof(buffer), msg, ap);
#ifdef CURL_HAVE_DIAG
#pragma GCC diagnostic pop
#endif
  va_end(ap);

  do {
    logfp = curlx_fopen(serverlogfile, "ab");
    /* !checksrc! disable ERRNOVAR 1 */
  } while(!logfp && (errno == EINTR));
  if(logfp) {
    fprintf(logfp, "%s %s\n", timebuf, buffer);
    curlx_fclose(logfp);
  }
  else {
    char errbuf[STRERROR_LEN];
    int error = errno;
    fprintf(stderr, "fopen() failed with error (%d) %s\n",
            error, curlx_strerror(error, errbuf, sizeof(errbuf)));
    fprintf(stderr, "Error opening file '%s'\n", serverlogfile);
    fprintf(stderr, "Msg not logged: %s %s\n", timebuf, buffer);
  }
}

#ifdef _WIN32
static void win32_cleanup(void)
{
#ifdef USE_WINSOCK
  WSACleanup();
#endif

  /* flush buffers of all streams regardless of their mode */
  _flushall();
}

int win32_init(void)
{
  curlx_now_init();
#ifdef USE_WINSOCK
  {
    WORD wVersionRequested;
    WSADATA wsaData;
    int err;
    char buffer[STRERROR_LEN];

    wVersionRequested = MAKEWORD(2, 2);
    err = WSAStartup(wVersionRequested, &wsaData);
    if(err) {
      curlx_strerror(SOCKERRNO, buffer, sizeof(buffer));
      fprintf(stderr, "Winsock init failed: %s\n", buffer);
      logmsg("Error initializing Winsock -- aborting");
      return 1;
    }

    if(LOBYTE(wsaData.wVersion) != LOBYTE(wVersionRequested) ||
       HIBYTE(wsaData.wVersion) != HIBYTE(wVersionRequested)) {
      WSACleanup();
      curlx_strerror(SOCKERRNO, buffer, sizeof(buffer));
      fprintf(stderr, "Winsock init failed: %s\n", buffer);
      logmsg("No suitable winsock.dll found -- aborting");
      return 1;
    }
  }
#endif /* USE_WINSOCK */
  atexit(win32_cleanup);
  return 0;
}
#endif /* _WIN32 */

/* fopens the test case file */
FILE *test2fopen(long testno, const char *logdir2)
{
  FILE *stream;
  char filename[256];
  /* first try the alternative, preprocessed, file */
  snprintf(filename, sizeof(filename), "%s/test%ld", logdir2, testno);
  stream = curlx_fopen(filename, "rb");

  return stream;
}

#ifdef _WIN32
#define t_getpid() GetCurrentProcessId()
#else
#define t_getpid() getpid()
#endif

curl_off_t our_getpid(void)
{
  curl_off_t pid = (curl_off_t)t_getpid();
#ifdef _WIN32
  /* store pid + MAX_PID to avoid conflict with Cygwin/msys PIDs, see also:
   * - 2019-01-31: https://cygwin.com/git/?p=newlib-cygwin.git;a=commit;h=b5e1003722cb14235c4f166be72c09acdffc62ea
   * - 2019-02-02: https://cygwin.com/git/?p=newlib-cygwin.git;a=commit;h=448cf5aa4b429d5a9cebf92a0da4ab4b5b6d23fe
   * - 2024-12-19: https://cygwin.com/git/?p=newlib-cygwin.git;a=commit;h=363357c023ce01e936bdaedf0f479292a8fa4e0f
   */
  pid += 4194304;
#endif
  return pid;
}

int write_pidfile(const char *filename)
{
  FILE *pidfile;
  curl_off_t pid;

  pid = our_getpid();
  pidfile = curlx_fopen(filename, "wb");
  if(!pidfile) {
    char errbuf[STRERROR_LEN];
    logmsg("Could not write pid file: %s (%d) %s", filename,
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
    return 0; /* fail */
  }
  fprintf(pidfile, "%ld\n", (long)pid);
  curlx_fclose(pidfile);
  logmsg("Wrote pid %ld to %s", (long)pid, filename);
  return 1; /* success */
}

/* store the used port number in a file */
int write_portfile(const char *filename, int port)
{
  FILE *portfile = curlx_fopen(filename, "wb");
  if(!portfile) {
    char errbuf[STRERROR_LEN];
    logmsg("Could not write port file: %s (%d) %s", filename,
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
    return 0; /* fail */
  }
  fprintf(portfile, "%d\n", port);
  curlx_fclose(portfile);
  logmsg("Wrote port %d to %s", port, filename);
  return 1; /* success */
}

void set_advisor_read_lock(const char *filename)
{
  FILE *lockfile;
  int error = 0;
  char errbuf[STRERROR_LEN];

  do {
    lockfile = curlx_fopen(filename, "wb");
    /* !checksrc! disable ERRNOVAR 1 */
  } while(!lockfile && ((error = errno) == EINTR));
  if(!lockfile) {
    logmsg("Error creating lock file %s error (%d) %s", filename,
           error, curlx_strerror(error, errbuf, sizeof(errbuf)));
    return;
  }

  if(curlx_fclose(lockfile))
    logmsg("Error closing lock file %s error (%d) %s", filename,
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
}

void clear_advisor_read_lock(const char *filename)
{
  int error = 0;
  int rc;

  /*
   * Log all removal failures. Even those due to file not existing.
   * This allows to detect if unexpectedly the file has already been
   * removed by a process different than the one that should do this.
   */

  do {
    rc = unlink(filename);
    /* !checksrc! disable ERRNOVAR 1 */
  } while(rc && ((error = errno) == EINTR));
  if(rc) {
    char errbuf[STRERROR_LEN];
    logmsg("Error removing lock file %s error (%d) %s", filename,
           error, curlx_strerror(error, errbuf, sizeof(errbuf)));
  }
}

/* store the entire request in a file */
void storerequest(const char *reqbuf, size_t totalsize, const char *filename)
{
  int error = 0;
  char errbuf[STRERROR_LEN];
  size_t written;
  size_t writeleft;
  FILE *dump;
  char dumpfile[256];

  snprintf(dumpfile, sizeof(dumpfile), "%s/%s", logdir, filename);

  if(!reqbuf)
    return;
  if(totalsize == 0)
    return;

  do {
    dump = curlx_fopen(dumpfile, "ab");
    /* !checksrc! disable ERRNOVAR 1 */
  } while(!dump && ((error = errno) == EINTR));
  if(!dump) {
    logmsg("storerequest: Error opening file %s error (%d) %s", dumpfile,
           error, curlx_strerror(error, errbuf, sizeof(errbuf)));
    return;
  }

  writeleft = totalsize;
  do {
    written = fwrite(&reqbuf[totalsize - writeleft], 1, writeleft, dump);
    if(got_exit_signal)
      goto storerequest_cleanup;
    if(written > 0)
      writeleft -= written;
    error = errno;
    /* !checksrc! disable ERRNOVAR 1 */
  } while((writeleft > 0) && (error == EINTR));

  if(writeleft == 0)
    logmsg("Wrote request (%zu bytes) input to %s", totalsize, dumpfile);
  else if(writeleft > 0) {
    logmsg("Error writing file %s error (%d) %s", dumpfile,
           error, curlx_strerror(error, errbuf, sizeof(errbuf)));
    logmsg("Wrote only (%zu bytes) of (%zu bytes) request input to %s",
           totalsize - writeleft, totalsize, dumpfile);
  }

storerequest_cleanup:

  if(curlx_fclose(dump))
    logmsg("Error closing file %s error (%d) %s", dumpfile,
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
}

/* vars used to keep around previous signal handlers */

typedef void (*SIGHANDLER_T)(int);

#if defined(_MSC_VER) && (_MSC_VER <= 1700)
/* Workaround for warning C4306:
   'type cast' : conversion from 'int' to 'void (__cdecl *)(int)' */
#undef SIG_ERR
#define SIG_ERR  ((SIGHANDLER_T)(size_t)-1)
#endif

#ifdef SIGHUP
static SIGHANDLER_T old_sighup_handler  = SIG_ERR;
#endif
#ifdef SIGPIPE
static SIGHANDLER_T old_sigpipe_handler = SIG_ERR;
#endif
#ifdef SIGALRM
static SIGHANDLER_T old_sigalrm_handler = SIG_ERR;
#endif
#ifdef SIGINT
static SIGHANDLER_T old_sigint_handler  = SIG_ERR;
#endif
#ifdef SIGTERM
static SIGHANDLER_T old_sigterm_handler = SIG_ERR;
#endif
#if defined(SIGBREAK) && defined(_WIN32)
static SIGHANDLER_T old_sigbreak_handler = SIG_ERR;
#endif

#if defined(_WIN32) && !defined(CURL_WINDOWS_UWP)
static DWORD thread_main_id = 0;
static HANDLE thread_main_window = NULL;
static HWND hidden_main_window = NULL;
#endif

/* signal handler that is triggered to indicate that the program
 * should finish its execution in a controlled manner as soon as possible.
 * The first time this is called it sets got_exit_signal to 1 and
 * stores in exit_signal the signal that triggered its execution.
 *
 * Only call signal-safe functions from the signal handler, as required by
 * the POSIX specification:
 *   https://pubs.opengroup.org/onlinepubs/9699919799/functions/V2_chap02.html
 * Hence, do not call 'logmsg()', and instead use 'open/write/close' to
 * log errors.
 */
/* suppress warnings seen in configurations where 'write()' has the attribute
   'warn_unused_result', which is not silenced by casting to '(void)'. */
#if defined(CURL_HAVE_DIAG) && !defined(__clang__)
#pragma GCC diagnostic push
#pragma GCC diagnostic ignored "-Wunused-result" /* GCC 4.5+ */
#endif
static void exit_signal_handler(int signum)
{
  int old_errno = errno;
  if(!serverlogfile) {
    static const char msg[] = "exit_signal_handler: serverlogfile not set\n";
    (void)write(STDERR_FILENO, msg, sizeof(msg) - 1);
  }
  else {
    int fd = -1;
#ifdef _WIN32
    if(!_sopen_s(&fd, serverlogfile, _O_WRONLY | _O_CREAT | _O_APPEND,
                 _SH_DENYNO, _S_IREAD | _S_IWRITE) &&
       fd != -1) {
#else
    /* !checksrc! disable BANNEDFUNC 1 */
    fd = open(serverlogfile, O_WRONLY | O_CREAT | O_APPEND, S_IRUSR | S_IWUSR);
    if(fd != -1) {
#endif
      static const char msg[] = "exit_signal_handler: called\n";
      (void)write(fd, msg, sizeof(msg) - 1);
      curlx_close(fd);
    }
    else {
      static const char msg[] = "exit_signal_handler: failed opening ";
      (void)write(STDERR_FILENO, msg, sizeof(msg) - 1);
      (void)write(STDERR_FILENO, serverlogfile, strlen(serverlogfile));
      (void)write(STDERR_FILENO, "\n", 1);
    }
  }
  if(got_exit_signal == 0) {
    got_exit_signal = 1;
    exit_signal = signum;
#ifdef _WIN32
    if(exit_event)
      (void)SetEvent(exit_event);
#endif
  }
  (void)signal(signum, exit_signal_handler);
  errno = old_errno;
}
#if defined(CURL_HAVE_DIAG) && !defined(__clang__)
#pragma GCC diagnostic pop
#endif

#ifdef _WIN32
/* CTRL event handler for Windows Console applications to simulate
 * SIGINT, SIGTERM and SIGBREAK on CTRL events and trigger signal handler.
 *
 * Background information from MSDN:
 * SIGINT is not supported for any Win32 application. When a CTRL+C
 * interrupt occurs, Win32 operating systems generate a new thread
 * to specifically handle that interrupt. This can cause a single-thread
 * application, such as one in UNIX, to become multi-threaded and cause
 * unexpected behavior.
 * [...]
 * The SIGKILL and SIGTERM signals are not generated under Windows.
 * They are included for ANSI compatibility. Therefore, you can set
 * signal handlers for these signals by using signal, and you can also
 * explicitly generate these signals by calling raise. Source:
 * https://learn.microsoft.com/cpp/c-runtime-library/reference/signal
 */
static BOOL WINAPI ctrl_event_handler(DWORD dwCtrlType)
{
  int signum = 0;
  logmsg("ctrl_event_handler: %lu", dwCtrlType);
  switch(dwCtrlType) {
#ifdef SIGINT
  case CTRL_C_EVENT:
    signum = SIGINT;
    break;
#endif
#ifdef SIGTERM
  case CTRL_CLOSE_EVENT:
    signum = SIGTERM;
    break;
#endif
#ifdef SIGBREAK
  case CTRL_BREAK_EVENT:
    signum = SIGBREAK;
    break;
#endif
  default:
    return FALSE;
  }
  if(signum) {
    logmsg("ctrl_event_handler: %lu -> %d", dwCtrlType, signum);
    raise(signum);
  }
  return TRUE;
}
#endif

#if defined(_WIN32) && !defined(CURL_WINDOWS_UWP)
/* Window message handler for Windows applications to add support
 * for graceful process termination via taskkill (without /f) which
 * sends WM_CLOSE to all Windows of a process (even hidden ones).
 *
 * Therefore we create and run a hidden Window in a separate thread
 * to receive and handle the WM_CLOSE message as SIGTERM signal.
 */
static LRESULT CALLBACK main_window_proc(HWND hwnd, UINT uMsg,
                                         WPARAM wParam, LPARAM lParam)
{
  int signum = 0;
  if(hwnd == hidden_main_window) {
    switch(uMsg) {
#ifdef SIGTERM
    case WM_CLOSE:
      signum = SIGTERM;
      break;
#endif
    case WM_DESTROY:
      PostQuitMessage(0);
      break;
    }
    if(signum) {
      logmsg("main_window_proc: %u -> %d", uMsg, signum);
      raise(signum);
    }
  }
  return DefWindowProc(hwnd, uMsg, wParam, lParam);
}

/* Window message queue loop for hidden main window, details see above. */
static DWORD WINAPI main_window_loop(void *lpParameter)
{
  WNDCLASS wc;
  BOOL ret;
  MSG msg;
  DWORD err;
  char buffer[WINAPI_ERROR_LEN];

  ZeroMemory(&wc, sizeof(wc));
  wc.lpfnWndProc = (WNDPROC)main_window_proc;
  wc.hInstance = (HINSTANCE)lpParameter;
  wc.lpszClassName = TEXT("MainWClass");
  if(!RegisterClass(&wc)) {
    err = GetLastError();
    curlx_winapi_strerror(err, buffer, sizeof(buffer));
    fprintf(stderr, "RegisterClass failed: %s\n", buffer);
    return (DWORD)-1;
  }

  hidden_main_window = CreateWindowEx(0, TEXT("MainWClass"),
                                      TEXT("Recv WM_CLOSE msg"),
                                      WS_OVERLAPPEDWINDOW,
                                      CW_USEDEFAULT, CW_USEDEFAULT,
                                      CW_USEDEFAULT, CW_USEDEFAULT,
                                      (HWND)NULL, (HMENU)NULL,
                                      wc.hInstance, NULL);
  if(!hidden_main_window) {
    err = GetLastError();
    curlx_winapi_strerror(err, buffer, sizeof(buffer));
    fprintf(stderr, "CreateWindowEx failed: (0x%08lx) - %s\n", err, buffer);
    return (DWORD)-1;
  }

  do {
    ret = GetMessage(&msg, NULL, 0, 0);
    if(ret == -1) {
      err = GetLastError();
      curlx_winapi_strerror(err, buffer, sizeof(buffer));
      fprintf(stderr, "GetMessage failed: (0x%08lx) - %s\n", err, buffer);
      return (DWORD)-1;
    }
    else if(ret) {
      if(msg.message == WM_APP) {
        DestroyWindow(hidden_main_window);
      }
      else if(msg.hwnd && !TranslateMessage(&msg)) {
        DispatchMessage(&msg);
      }
    }
  } while(ret);

  hidden_main_window = NULL;
  return (DWORD)msg.wParam;
}
#endif

static SIGHANDLER_T set_signal(int signum, SIGHANDLER_T handler,
                               bool restartable)
{
#if defined(HAVE_SIGACTION) && defined(SA_RESTART)
  struct sigaction sa, oldsa;

  memset(&sa, 0, sizeof(sa));
  sa.sa_handler = handler;
  sigemptyset(&sa.sa_mask);
  sigaddset(&sa.sa_mask, signum);
  sa.sa_flags = restartable ? SA_RESTART : 0;

  if(sigaction(signum, &sa, &oldsa))
    return SIG_ERR;

  return oldsa.sa_handler;
#else
  SIGHANDLER_T oldhdlr = signal(signum, handler);

#ifdef HAVE_SIGINTERRUPT
  if(oldhdlr != SIG_ERR)
    siginterrupt(signum, (int)restartable);
#else
  (void)restartable;
#endif

  return oldhdlr;
#endif
}

void install_signal_handlers(bool keep_sigalrm)
{
  char errbuf[STRERROR_LEN];
  (void)errbuf;
#ifdef _WIN32
  /* setup Windows exit event before any signal can trigger */
  exit_event = CreateEvent(NULL, TRUE, FALSE, NULL);
  if(!exit_event)
    logmsg("cannot create exit event");
#endif
#ifdef SIGHUP
  /* ignore SIGHUP signal */
  old_sighup_handler = set_signal(SIGHUP, SIG_IGN, FALSE);
  if(old_sighup_handler == SIG_ERR)
    logmsg("cannot install SIGHUP handler: (%d) %s",
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
#endif
#ifdef SIGPIPE
  /* ignore SIGPIPE signal */
  old_sigpipe_handler = set_signal(SIGPIPE, SIG_IGN, FALSE);
  if(old_sigpipe_handler == SIG_ERR)
    logmsg("cannot install SIGPIPE handler: (%d) %s",
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
#endif
#ifdef SIGALRM
  if(!keep_sigalrm) {
    /* ignore SIGALRM signal */
    old_sigalrm_handler = set_signal(SIGALRM, SIG_IGN, FALSE);
    if(old_sigalrm_handler == SIG_ERR)
      logmsg("cannot install SIGALRM handler: (%d) %s",
             errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
  }
#else
  (void)keep_sigalrm;
#endif
#ifdef SIGINT
  /* handle SIGINT signal with our exit_signal_handler */
  old_sigint_handler = set_signal(SIGINT, exit_signal_handler, TRUE);
  if(old_sigint_handler == SIG_ERR)
    logmsg("cannot install SIGINT handler: (%d) %s",
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
#endif
#ifdef SIGTERM
  /* handle SIGTERM signal with our exit_signal_handler */
  old_sigterm_handler = set_signal(SIGTERM, exit_signal_handler, TRUE);
  if(old_sigterm_handler == SIG_ERR)
    logmsg("cannot install SIGTERM handler: (%d) %s",
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
#endif
#if defined(SIGBREAK) && defined(_WIN32)
  /* handle SIGBREAK signal with our exit_signal_handler */
  old_sigbreak_handler = set_signal(SIGBREAK, exit_signal_handler, TRUE);
  if(old_sigbreak_handler == SIG_ERR)
    logmsg("cannot install SIGBREAK handler: (%d) %s",
           errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
#endif
#ifdef _WIN32
  if(!SetConsoleCtrlHandler(ctrl_event_handler, TRUE))
    logmsg("cannot install CTRL event handler");

#ifndef CURL_WINDOWS_UWP
  thread_main_window = CreateThread(NULL, 0, &main_window_loop,
                                    GetModuleHandle(NULL), 0, &thread_main_id);
  if(!thread_main_window || !thread_main_id)
    logmsg("cannot start main window loop");
#endif
#endif
}

void restore_signal_handlers(bool keep_sigalrm)
{
#ifdef SIGHUP
  if(old_sighup_handler != SIG_ERR)
    (void)set_signal(SIGHUP, old_sighup_handler, FALSE);
#endif
#ifdef SIGPIPE
  if(old_sigpipe_handler != SIG_ERR)
    (void)set_signal(SIGPIPE, old_sigpipe_handler, FALSE);
#endif
#ifdef SIGALRM
  if(!keep_sigalrm) {
    if(old_sigalrm_handler != SIG_ERR)
      (void)set_signal(SIGALRM, old_sigalrm_handler, FALSE);
  }
#else
  (void)keep_sigalrm;
#endif
#ifdef SIGINT
  if(old_sigint_handler != SIG_ERR)
    (void)set_signal(SIGINT, old_sigint_handler, FALSE);
#endif
#ifdef SIGTERM
  if(old_sigterm_handler != SIG_ERR)
    (void)set_signal(SIGTERM, old_sigterm_handler, FALSE);
#endif
#if defined(SIGBREAK) && defined(_WIN32)
  if(old_sigbreak_handler != SIG_ERR)
    (void)set_signal(SIGBREAK, old_sigbreak_handler, FALSE);
#endif
#ifdef _WIN32
  (void)SetConsoleCtrlHandler(ctrl_event_handler, FALSE);
#ifndef CURL_WINDOWS_UWP
  if(thread_main_window && thread_main_id) {
    if(PostThreadMessage(thread_main_id, WM_APP, 0, 0)) {
      if(WaitForSingleObjectEx(thread_main_window, INFINITE, TRUE)) {
        if(CloseHandle(thread_main_window)) {
          thread_main_window = NULL;
          thread_main_id = 0;
        }
      }
    }
  }
  if(exit_event) {
    if(CloseHandle(exit_event)) {
      exit_event = NULL;
    }
  }
#endif
#endif
}

#ifdef USE_UNIX_SOCKETS

int bind_unix_socket(curl_socket_t sock, const char *unix_socket,
                     struct sockaddr_un *sau)
{
  char errbuf[STRERROR_LEN];
  int rc;
  size_t len;

  if(!unix_socket) {
    logmsg("Unix socket domain path not specified.");
    return -1;
  }

  len = strlen(unix_socket);

  memset(sau, 0, sizeof(struct sockaddr_un));
  sau->sun_family = AF_UNIX;
  if(len >= sizeof(sau->sun_path) - 1) {
    logmsg("Too long unix socket domain path (%zu)", len);
    return -1;
  }
  curlx_strcopy(sau->sun_path, sizeof(sau->sun_path), unix_socket, len);
  rc = bind(sock, (struct sockaddr *)sau, sizeof(struct sockaddr_un));
  if(rc && SOCKERRNO == SOCKEADDRINUSE) {
    int sockerr;
    /* socket already exists. Perhaps it is stale? */
    curl_socket_t unixfd = socket(AF_UNIX, SOCK_STREAM, 0);
    if(unixfd == CURL_SOCKET_BAD) {
      sockerr = SOCKERRNO;
      logmsg("Failed to create socket at %s (%d) %s", unix_socket,
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
      return -1;
    }
    /* check whether the server is alive */
    rc = connect(unixfd, (struct sockaddr*)sau, sizeof(struct sockaddr_un));
    sockerr = SOCKERRNO;
    sclose(unixfd);
    if(rc && sockerr != SOCKECONNREFUSED) {
      logmsg("Failed to connect to %s (%d) %s", unix_socket,
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
      return rc;
    }
#if !defined(_WIN32) && defined(S_IFSOCK) /* No lstat(), S_IFSOCK on Windows */
    /* socket server is not alive, now check if it was actually a socket. */
    {
      curlx_struct_stat statbuf;
      rc = lstat(unix_socket, &statbuf);
      if(rc && errno != ENOENT) {
        logmsg("Error binding socket, failed to stat %s (%d) %s", unix_socket,
               errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
        return -1;
      }
      if(!rc && (statbuf.st_mode & S_IFMT) != S_IFSOCK) {
        logmsg("Error binding socket, %s is not a socket", unix_socket);
        return -1;
      }
    }
#endif
    /* dead socket, cleanup and retry bind */
    if(unlink(unix_socket) && errno != ENOENT) {
      logmsg("Error binding socket, failed to unlink %s: %d (%s)", unix_socket,
             errno, curlx_strerror(errno, errbuf, sizeof(errbuf)));
      return -1;
    }
    /* stale socket is gone, retry bind */
    rc = bind(sock, (struct sockaddr *)sau, sizeof(struct sockaddr_un));
  }
  return rc;
}
#endif

curl_socket_t sockdaemon(curl_socket_t sock,
                         unsigned short *listenport,
                         const char *unix_socket,
                         bool bind_only)
{
  /* passive daemon style */
  srvr_sockaddr_union_t listener;
  int flag;
  int rc;
  int totdelay = 0;
  int maxretr = 10;
  int delay = 20;
  int attempt = 0;
  int sockerr = 0;
  char errbuf[STRERROR_LEN];

#ifndef USE_UNIX_SOCKETS
  (void)unix_socket;
#endif

#if defined(_WIN32) && defined(USE_UNIX_SOCKETS)
  if(socket_domain != AF_UNIX) {
#endif
    do {
      attempt++;
      flag = 1;
      rc = setsockopt(sock, SOL_SOCKET, SO_REUSEADDR,
                      (void *)&flag, sizeof(flag));
      if(rc) {
        sockerr = SOCKERRNO;
        logmsg("setsockopt(SO_REUSEADDR) failed with error (%d) %s",
               sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
        if(maxretr) {
          if(curlx_wait_ms(delay)) {
            /* should not happen */
            sockerr = SOCKERRNO;
            logmsg("curlx_wait_ms() failed with error (%d) %s",
                   sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
            sclose(sock);
            return CURL_SOCKET_BAD;
          }
          if(got_exit_signal) {
            logmsg("signalled to die, exiting...");
            sclose(sock);
            return CURL_SOCKET_BAD;
          }
          totdelay += delay;
          delay *= 2; /* double the sleep for next attempt */
        }
      }
    } while(rc && maxretr--);

    if(rc) {
      logmsg("setsockopt(SO_REUSEADDR) failed %d times in %d ms. "
             "Error (%d) %s", attempt, totdelay,
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
      logmsg("Continuing anyway...");
    }
#if defined(_WIN32) && defined(USE_UNIX_SOCKETS)
  }
#endif

  /* When the specified listener port is zero, it is actually a
     request to let the system choose a non-zero available port. */

  switch(socket_domain) {
  case AF_INET:
    memset(&listener.sa4, 0, sizeof(listener.sa4));
    listener.sa4.sin_family = AF_INET;
    listener.sa4.sin_addr.s_addr = INADDR_ANY;
    listener.sa4.sin_port = htons(*listenport);
    rc = bind(sock, &listener.sa, sizeof(listener.sa4));
    break;
#ifdef USE_IPV6
  case AF_INET6:
    memset(&listener.sa6, 0, sizeof(listener.sa6));
    listener.sa6.sin6_family = AF_INET6;
    listener.sa6.sin6_addr = in6addr_any;
    listener.sa6.sin6_port = htons(*listenport);
    rc = bind(sock, &listener.sa, sizeof(listener.sa6));
    break;
#endif /* USE_IPV6 */
#ifdef USE_UNIX_SOCKETS
  case AF_UNIX:
    rc = bind_unix_socket(sock, unix_socket, &listener.sau);
    break;
#endif
  default:
    rc = 1;
  }

  if(rc) {
    sockerr = SOCKERRNO;
#ifdef USE_UNIX_SOCKETS
    if(socket_domain == AF_UNIX)
      logmsg("Error binding socket on path %s (%d) %s", unix_socket,
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
    else
#endif
      logmsg("Error binding socket on port %hu (%d) %s", *listenport,
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
    sclose(sock);
    return CURL_SOCKET_BAD;
  }

  if(!*listenport
#ifdef USE_UNIX_SOCKETS
     && !unix_socket
#endif
    ) {
    /* The system was supposed to choose a port number, figure out which
       port we actually got and update the listener port value with it. */
    curl_socklen_t la_size;
    srvr_sockaddr_union_t localaddr;
    memset(&localaddr, 0, sizeof(localaddr));
#ifdef USE_IPV6
    if(socket_domain == AF_INET6)
      la_size = sizeof(localaddr.sa6);
    else
#endif
      la_size = sizeof(localaddr.sa4);
    if(getsockname(sock, &localaddr.sa, &la_size) < 0) {
      sockerr = SOCKERRNO;
      logmsg("getsockname() failed with error (%d) %s",
             sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
      sclose(sock);
      return CURL_SOCKET_BAD;
    }
    switch(localaddr.sa.sa_family) {
    case AF_INET:
      *listenport = ntohs(localaddr.sa4.sin_port);
      break;
#ifdef USE_IPV6
    case AF_INET6:
      *listenport = ntohs(localaddr.sa6.sin6_port);
      break;
#endif
    default:
      break;
    }
    if(!*listenport) {
      /* Real failure, listener port shall not be zero beyond this point. */
      logmsg("Apparently getsockname() succeeded, with listener port zero.");
      logmsg("A valid reason for this failure is a binary built without");
      logmsg("proper network library linkage. This might not be the only");
      logmsg("reason, but double check it before anything else.");
      sclose(sock);
      return CURL_SOCKET_BAD;
    }
  }

  /* bindonly option forces no listening */
  if(bind_only) {
    logmsg("instructed to bind port without listening");
    return sock;
  }

  /* start accepting connections */
  if(listen(sock, 5)) {
    sockerr = SOCKERRNO;
    logmsg("listen(%ld, 5) failed with error (%d) %s", (long)sock,
           sockerr, curlx_strerror(sockerr, errbuf, sizeof(errbuf)));
    sclose(sock);
    return CURL_SOCKET_BAD;
  }

  return sock;
}
