/* fhandler_netdrive.cc: fhandler for // and //MACHINE handling

This file is part of Cygwin.

This software is a copyrighted work licensed under the terms of the
Cygwin license.  Please consult the file "CYGWIN_LICENSE" for
details. */

#include "winsup.h"
#include "cygerrno.h"
#include "security.h"
#include "path.h"
#include "fhandler.h"
#include "dtable.h"
#include "cygheap.h"
#include "cygthread.h"
#include "tls_pbuf.h"

#define USE_SYS_TYPES_FD_SET
#include <shobjidl.h>
#include <shlobj.h>
#include <lm.h>
#include <ws2tcpip.h>

#include <stdlib.h>
#include <dirent.h>
#include <wctype.h>

/* SMBv1 is deprectated and not even installed by default anymore on
   Windows 10 and 11 machines or their servers.

   As a result, neither WNetOpenEnumW() nor NetServerEnum() work as
   expected anymore.

   So this fhandler class now uses Network Discovery to enumerate
   the "//" directory, which, unfortunately, requires to use the
   shell API. */

/* There's something REALLY fishy going on in Windows.  If the NFS
   enumeration via WNet functions is called *before* the share enumeration
   via Shell function, the Shell functions will enumerate the NFS shares
   instead of the SMB shares.  Un-be-lie-va-ble!
   FWIW, we reverted the SMB share enumeration using WNet. */

#ifndef WNNC_NET_9P
#define WNNC_NET_9P 0x00480000
#endif
#define TERMSRV_DIR "tsclient"
#define PLAN9_DIR   "wsl$"

/* Define the required GUIDs here to avoid linking with libuuid.a */
const GUID FOLDERID_NetworkFolder = {
  0xd20beec4, 0x5ca8, 0x4905,
  { 0xae, 0x3b, 0xbf, 0x25, 0x1e, 0xa0, 0x9b, 0x53 }
};

const GUID BHID_StorageEnum = {
  0x4621a4e3, 0xf0d6, 0x4773,
  { 0x8a, 0x9c, 0x46, 0xe7, 0x7b, 0x17, 0x48, 0x40 }
};

const GUID BHID_EnumItems = {
  0x94f60519, 0x2850, 0x4924,
  { 0xaa, 0x5a, 0xd1, 0x5e, 0x84, 0x86, 0x80, 0x39 }
};

class dir_cache
{
  size_t max_entries;
  size_t num_entries;
  wchar_t **entry;
public:
  dir_cache () : max_entries (0), num_entries (0), entry (NULL) {}
  ~dir_cache ()
  {
    while (num_entries > 0)
      free (entry[--num_entries]);
    free (entry);
  }
  size_t count () const { return num_entries; }
  void add (const wchar_t *str, bool downcase = false)
  {
    if (num_entries >= max_entries)
      {
	wchar_t **newentry;

	newentry = (wchar_t **) realloc (entry, (max_entries + 10)
						* sizeof (wchar_t *));
	if (!newentry)
	  return;
	entry = newentry;
	max_entries += 10;
      }
    entry[num_entries] = wcsdup (str);
    if (entry[num_entries])
      {
	if (downcase)
	  for (wchar_t *p = entry[num_entries]; (*p = towlower (*p)); ++p)
	    ;
	++num_entries;
      }
  }
  inline wchar_t *operator [](size_t idx) const
  {
    if (idx < num_entries)
      return entry[idx];
    return NULL;
  }
};

#define DIR_cache	(*reinterpret_cast<dir_cache *> (dir->__handle))

#define RETRY_SMB	INT_MAX

struct netdriveinf
{
  DIR *dir;
  int err;
  DWORD provider;
  HANDLE sem;
};

static inline int
hresult_to_errno (HRESULT wres)
{
  if (SUCCEEDED (wres))
    return 0;
  if (((ULONG) wres & 0xffff0000)
      == (ULONG) MAKE_HRESULT(SEVERITY_ERROR, FACILITY_WIN32, 0))
    return geterrno_from_win_error ((ULONG) wres & 0xffff);
  return EACCES;
}

/* Workaround incompatible definitions. */
#define u_long		__ms_u_long
#define WS_FIONBIO	_IOW('f', 126, u_long)
#define WS_POLLOUT	0x10

static bool
server_is_running_nfs (const wchar_t *servername)
{
  /* Hack alarm: Only test TCP port 2049 */
  struct addrinfoW hints = { 0 };
  struct addrinfoW *ai = NULL, *aip;
  bool ret = false;
  INT wres;

  hints.ai_family = AF_UNSPEC;
  hints.ai_socktype = SOCK_STREAM;
  /* The services contains "nfs" only as UDP service... sigh. */
  wres = GetAddrInfoW (servername, L"2049", &hints, &ai);
  if (wres)
    return false;
  for (aip = ai; !ret && aip; aip = aip->ai_next)
    {
      SOCKET sock = ::socket (aip->ai_family, aip->ai_socktype,
			      aip->ai_flags);
      if (sock != INVALID_SOCKET)
	{
	  __ms_u_long nonblocking = 1;
	  ::ioctlsocket (sock, WS_FIONBIO, &nonblocking);
	  wres = ::connect (sock, aip->ai_addr, aip->ai_addrlen);
	  if (wres == 0)
	    ret = true;
	  else if (WSAGetLastError () == WSAEWOULDBLOCK)
	    {
	      WSAPOLLFD fds = { .fd = sock,
				.events = WS_POLLOUT };
	      wres = WSAPoll (&fds, 1, 1500L);
	      if (wres > 0 && fds.revents == WS_POLLOUT)
		ret = true;
	    }
	  ::closesocket (sock);
	}
    }
  FreeAddrInfoW (ai);
  return ret;
}


/* Use only to enumerate the Network top level. */
static DWORD
thread_netdrive_wsd (void *arg)
{
  netdriveinf *ndi = (netdriveinf *) arg;
  DIR *dir = ndi->dir;
  IEnumShellItems *netitem_enum;
  IShellItem *netparent;
  HRESULT wres;

  ReleaseSemaphore (ndi->sem, 1, NULL);

  wres = CoInitialize (NULL);
  if (FAILED (wres))
    {
      ndi->err = hresult_to_errno (wres);
      goto out;
    }

  wres = SHGetKnownFolderItem (FOLDERID_NetworkFolder, KF_FLAG_DEFAULT,
			       NULL, IID_PPV_ARGS (&netparent));
  if (FAILED (wres))
    {
      ndi->err = hresult_to_errno (wres);
      goto out;
    }

  wres = netparent->BindToHandler (NULL, BHID_StorageEnum,
				   IID_PPV_ARGS (&netitem_enum));
  if (FAILED (wres))
    {
      ndi->err = hresult_to_errno (wres);
      netparent->Release ();
      goto out;
    }

  netitem_enum->Reset ();
  /* Don't look at me!

     Network discovery is very unreliable and the list of machines
     returned is just fly-by-night, if the enumerator doesn't have
     enough time.  The fact that you see *most* (but not necessarily
     *all*) machines on the network in Windows Explorer is a result of
     the enumeration running in a loop.  You can observe this when
     rebooting a remote machine and it disappears and reappears in the
     Explorer Network list.

     However, this is no option for the command line. We need to be able
     to enumerate in a single go, since we can't just linger during
     readdir() and reset the enumeration multiple times until we have a
     supposedly full list.

     This makes the following Sleep necessary.  Sleeping ~3secs after
     Reset fills the enumeration with high probability with almost all
     available machines. */
  Sleep (3000L);

  do
    {
      IShellItem *netitem = NULL;
      LPWSTR item_name = NULL;

      wres = netitem_enum->Next (1, &netitem, NULL);
      if (wres == S_OK)
	{
	  if (netitem->GetDisplayName (SIGDN_PARENTRELATIVEPARSING,
					    &item_name) == S_OK)
	    {
	      /* Skip "\\" on server names and downcase */
	      DIR_cache.add (item_name + 2, true);
	      CoTaskMemFree (item_name);
	    }
	  netitem->Release ();
	}
    }
  while (wres == S_OK);

  netitem_enum->Release ();
  netparent->Release ();

  ndi->err = 0;

out:
  CoUninitialize ();
  ReleaseSemaphore (ndi->sem, 1, NULL);
  return 0;
}

#define NO_PROVIDER_FOUND 1

static DWORD
wnet_find_server (wchar_t *srv_name, LPNETRESOURCEW nro, bool start)
{
  DWORD wres, cnt, size;
  DWORD provider = NO_PROVIDER_FOUND;
  HANDLE dom;

  wres = WNetOpenEnumW (RESOURCE_GLOBALNET, RESOURCETYPE_DISK,
			RESOURCEUSAGE_CONTAINER, start ? NULL : nro, &dom);
  if (wres != NO_ERROR)
    return NO_PROVIDER_FOUND;
  while ((wres = WNetEnumResourceW (dom, (cnt = 1, &cnt), nro,
				    (size = NT_MAX_PATH, &size))) == NO_ERROR)
    {
      NETINFOSTRUCT netinfo = { 0 };
      netinfo.cbStructure = sizeof netinfo;
      wres = WNetGetNetworkInformationW (nro->lpProvider, &netinfo);
      if (wres != NO_ERROR)
	continue;
      /* Do not even try to enumerate SMB servers!  It takes 10 seconds just to
         return with error 1208 ERROR_EXTENDED_ERROR, with extended error info
	 "The list of servers for this workgroup is not currently available". */
      if ((nro->dwDisplayType == RESOURCEDISPLAYTYPE_NETWORK
	   || nro->dwDisplayType == RESOURCEDISPLAYTYPE_DOMAIN)
	  && ((DWORD) netinfo.wNetType << 16) != WNNC_NET_SMB)
	provider = wnet_find_server (srv_name, nro, false);
      else if (nro->dwDisplayType == RESOURCEDISPLAYTYPE_SERVER
	       && !wcscasecmp (srv_name, nro->lpRemoteName))
	provider = ((DWORD) netinfo.wNetType << 16);
      if (provider != NO_PROVIDER_FOUND)
	break;
    }
  WNetCloseEnum (dom);
  return provider;
}

static DWORD
thread_netdrive_wnet (void *arg)
{
  netdriveinf *ndi = (netdriveinf *) arg;
  DIR *dir = ndi->dir;
  DWORD wres;

  DWORD connected_only = false;
  size_t srv_len = 0;

  size_t entry_cache_size = DIR_cache.count ();
  WCHAR provider[256], *dummy = NULL;
  wchar_t srv_name[CYG_MAX_PATH];
  wchar_t *nfs_namebuf = NULL;
  NETRESOURCEW nri = { 0 };
  LPNETRESOURCEW nro;
  NETINFOSTRUCT netinfo;
  DWORD net_type = 0;
  HANDLE dom = NULL;
  DWORD cnt, size;
  tmp_pathbuf tp;

  ReleaseSemaphore (ndi->sem, 1, NULL);

  sys_mbstowcs (srv_name, CYG_MAX_PATH, dir->__d_dirname);
  srv_name[0] = L'\\';
  srv_name[1] = L'\\';
  nri.lpRemoteName = srv_name;
  nri.dwType = RESOURCETYPE_DISK;
  nro = (LPNETRESOURCEW) tp.c_get ();

  if (ndi->provider)
    {
      wres = WNetGetProviderNameW (ndi->provider, provider,
				   (size = 256, &size));
      if (wres != NO_ERROR)
	{
	  ndi->err = geterrno_from_win_error (wres);
	  goto out;
	}
      nri.lpProvider = provider;

    }
  wres = WNetGetResourceInformationW (&nri, nro,
				      (size = NT_MAX_PATH, &size), &dummy);
  if (wres != NO_ERROR)
    {
      /* WNetGetResourceInformationW fails for instance for WebDAV server
         names, even if we have connected resources on the server.  We don't
	 want a "No such file or directory" in this case, so try to find the
	 server by WNet enumerating from the top. */
      ndi->provider = wnet_find_server (srv_name, nro, true);
      if (ndi->provider == NO_PROVIDER_FOUND)
	{
	  ndi->err = geterrno_from_win_error (wres);
	  goto out;
	}
    }

  if (ndi->provider)
    net_type = ndi->provider;
  else
    {
      netinfo.cbStructure = sizeof netinfo;
      wres = WNetGetNetworkInformationW (nro->lpProvider, &netinfo);
      if (wres == NO_ERROR)
	net_type = ((DWORD) netinfo.wNetType << 16);
    }

  /* More heuristics... */
  switch (net_type)
    {
    case 0:
    case NO_PROVIDER_FOUND:
      /* Nothing to enumerate. */
      goto out;
    case WNNC_NET_MS_NFS:
      /* If ndi->provider is 0 and the machine name contains dots, we already
	 handled NFS.  However, if the machine supports both, NFS and SMB,
	 sometimes WNetGetNetworkInformationW returns the NFS provider,
	 sometimes the SMB provider.  So if we get the NFS provider again
	 here, enforce the SMB provider. */
      if (ndi->provider == 0)
	{
	  ndi->err = RETRY_SMB;
	  goto out;
	}
      /* Check on port 2049 if the server is replying.  Otherwise the
         timeout on WNetOpenEnumW is excessive! */
      if (!server_is_running_nfs (srv_name + 2))
	{
	  ndi->err = ENOENT;
	  goto out;
	}
      /* We need a temporary buffer for the multibyte to widechar conversion
	 only required for NFS shares. */
      if (!nfs_namebuf)
	nfs_namebuf = tp.w_get ();
      break;
    case WNNC_NET_DAV:
      /* WebDAV enumeration isn't supported, by the provider, but we can
         find the connected shares of the server by enumerating all connected
	 disk resources. */
      connected_only = true;
      srv_len = wcslen (srv_name);
      break;
    case WNNC_NET_RDR2SAMPLE:
      /* Lots of OSS drivers uses this provider.  No idea yet, what
         to do with them. */
      fallthrough;
    default:
      break;
    }

  if (connected_only)
    wres = WNetOpenEnumW (RESOURCE_CONNECTED, RESOURCETYPE_DISK, 0, NULL, &dom);
  else
    wres = WNetOpenEnumW (RESOURCE_GLOBALNET, RESOURCETYPE_DISK,
			  RESOURCEUSAGE_ALL, nro, &dom);
  if (wres != NO_ERROR)
    {
      ndi->err = geterrno_from_win_error (wres);
      goto out;
    }

  while ((wres = WNetEnumResourceW (dom, (cnt = 1, &cnt), nro,
				    (size = NT_MAX_PATH, &size))) == NO_ERROR)
    {
      size_t cache_idx;

      /* Skip unrelated entries in connection list. */
      if (connected_only)
	{
	  if (wcsncasecmp (srv_name, nro->lpRemoteName, srv_len)
	      || wcslen (nro->lpRemoteName) <= srv_len
	      || nro->lpRemoteName[srv_len] != L'\\')
	    continue;
	}

      /* Skip server name and trailing backslash */
      wchar_t *name = nro->lpRemoteName + 2;
      name = wcschr (name, L'\\');
      if (!name)
	continue;
      ++name;

      if (net_type == WNNC_NET_MS_NFS)
	{
	  /* With MS NFS, the bytes of the share name on the remote side
	     are simply dropped into a WCHAR buffer without conversion to
	     Unicode.  So convert from "multibyte embedded in widechar" to
	     real multibyte and then convert back to widechar here.

	     Quirky: This conversion is already performed for files on an
	     MS NFS filesystem when calling NtQueryDirectoryFile, but it's
	     not performed on the strings returned by WNetEnumResourceW. */
	  char mbname[wcslen (name) + 1];
	  char *mb = mbname;
	  while ((*mb++ = *name++))
	    ;

	  name = nfs_namebuf;
	  MultiByteToWideChar (CP_ACP, 0, mbname, -1, name, NT_MAX_PATH);
	}
      /* Some providers have deep links so convert embedded '\\' to '/' here */
      for (wchar_t *bs = name; (bs = wcschr (bs, L'\\')); *bs++ = L'/')
	;
      /* If we already collected shares, drop duplicates. */
      for (cache_idx = 0; cache_idx < entry_cache_size; ++ cache_idx)
	if (!wcscmp (name, DIR_cache[cache_idx]))	// wcscasecmp?
	  break;
      if (cache_idx >= entry_cache_size)
	DIR_cache.add (name);
    }
out:
  if (dom)
    WNetCloseEnum (dom);
  ReleaseSemaphore (ndi->sem, 1, NULL);
  return 0;
}

static DWORD
create_thread_and_wait (DIR *dir)
{
  netdriveinf ndi = { dir, 0, 0, NULL };
  WCHAR provider[256];
  cygthread *thr;
  DWORD size;

  /* For the Network root, fetch WSD info. */
  if (strlen (dir->__d_dirname) == 2)
    {
      ndi.provider = WNNC_NET_SMB;
      ndi.sem = CreateSemaphore (&sec_none_nih, 0, 2, NULL);
      thr = new cygthread (thread_netdrive_wsd, &ndi, "netdrive_wsd");
      if (thr->detach (ndi.sem))
	ndi.err = EINTR;
      CloseHandle (ndi.sem);
      /* Add wsl$ if Plan 9 is installed */
      if (WNetGetProviderNameW (WNNC_NET_9P, provider, (size = 256, &size))
	  == NO_ERROR)
	DIR_cache.add (__CONCAT(L,PLAN9_DIR));
      goto out;
    }

  /* For shares, use WNet functions. */

  /* Try NFS first, if the name contains a dot (i. e., supposedly is a FQDN
     as used in NFS server enumeration) but no at-sign. */
  if (strchr (dir->__d_dirname, '.') && !strchr (dir->__d_dirname + 2, '@')
      && WNetGetProviderNameW (WNNC_NET_MS_NFS, provider, (size = 256, &size))
	 == NO_ERROR)
    {
      ndi.provider = WNNC_NET_MS_NFS;
      ndi.sem = CreateSemaphore (&sec_none_nih, 0, 2, NULL);
      thr = new cygthread (thread_netdrive_wnet, &ndi, "netdrive_nfs");
      if (thr->detach (ndi.sem))
	ndi.err = EINTR;
      CloseHandle (ndi.sem);

      if (ndi.err == EINTR)
	goto out;

    }

  ndi.sem = CreateSemaphore (&sec_none_nih, 0, 2, NULL);
  ndi.provider = 0;
  thr = new cygthread (thread_netdrive_wnet, &ndi, "netdrive_wnet");
  if (thr->detach (ndi.sem))
    ndi.err = EINTR;
  CloseHandle (ndi.sem);

  if (ndi.err == RETRY_SMB)
    {
      ndi.sem = CreateSemaphore (&sec_none_nih, 0, 2, NULL);
      ndi.provider = WNNC_NET_SMB;
      thr = new cygthread (thread_netdrive_wnet, &ndi, "netdrive_smb");
      if (thr->detach (ndi.sem))
	ndi.err = EINTR;
      CloseHandle (ndi.sem);
    }

out:
  return DIR_cache.count() > 0 ? 0 : ndi.err;
}

virtual_ftype_t
fhandler_netdrive::exists ()
{
  if (strlen (get_name ()) == 2)
    return virt_rootdir;

  wchar_t name[CYG_MAX_PATH], *dav_at;
  struct addrinfoW *ai;
  INT ret;
  DWORD protocol = 0;

  /* Handle "tsclient" (Microsoft Terminal Services) and
     "wsl$" (Plan 9 Network Provider) explicitely.
     Both obviously don't resolve with GetAddrInfoW. */
  if (!strcmp (get_name () + 2, TERMSRV_DIR))
    protocol = WNNC_NET_TERMSRV;
  else if (!strcmp (get_name () + 2, PLAN9_DIR))
    protocol = WNNC_NET_9P;
  if (protocol)
    {
      WCHAR provider[256];
      DWORD size = 256;

      if (WNetGetProviderNameW (protocol, provider, &size) == NO_ERROR)
	return virt_directory;
      return virt_none;
    }
  /* Hopefully we are allowed to assume an IP network with existing name
     resolution these days.  Therefore, just try to resolve the name
     into IP addresses.  This may take up to about 3 secs if the name
     doesn't exist, or about 8 secs if DNS is unavailable. */
  sys_mbstowcs (name, CYG_MAX_PATH, get_name ());
  /* Webdav URLs contain a @ after the hostname, followed by stuff.
     Drop @ for GetAddrInfoW to succeed. */
  if ((dav_at = wcschr (name, L'@')) != NULL)
    *dav_at = L'\0';

  ret = GetAddrInfoW (name + 2, NULL, NULL, &ai);
  if (ret)
    {
      debug_printf ("GetAddrInfoW(%W) returned %d", name + 2, ret);
      return virt_none;
    }

  FreeAddrInfoW (ai);
  return virt_directory;
}

fhandler_netdrive::fhandler_netdrive ():
  fhandler_virtual ()
{
}

int
fhandler_netdrive::fstat (struct stat *buf)
{
  const char *path = get_name ();
  debug_printf ("fstat (%s)", path);

  fhandler_base::fstat (buf);

  buf->st_mode = S_IFDIR | STD_RBITS | STD_XBITS;
  buf->st_ino = get_ino ();

  return 0;
}

DIR *
fhandler_netdrive::opendir (int fd)
{
  DIR *dir;
  int ret;

  dir = fhandler_virtual::opendir (fd);
  dir->__handle = (char *) new dir_cache ();
  if (dir && (ret = create_thread_and_wait (dir)))
    {
      free (dir->__d_dirname);
      free (dir->__d_dirent);
      free (dir);
      dir = NULL;
      set_errno (ret);
      syscall_printf ("%p = opendir (%s)", dir, get_name ());
    }
  return dir;
}

int
fhandler_netdrive::readdir (DIR *dir, dirent *de)
{
  int ret;

  if (!DIR_cache[dir->__d_position])
    {
      ret = ENMFILE;
      goto out;
    }

  sys_wcstombs (de->d_name, sizeof de->d_name, DIR_cache[dir->__d_position]);
  if (strlen (dir->__d_dirname) == 2)
    de->d_ino = hash_path_name (get_ino (), de->d_name);
  else
    {
      char full[2 * CYG_MAX_PATH];
      char *s;

      s = stpcpy (full, dir->__d_dirname);
      *s++ = '/';
      stpcpy (s, de->d_name);
      de->d_ino = readdir_get_ino (full, false);
    }
  dir->__d_position++;
  de->d_type = DT_DIR;
  ret = 0;

out:
  syscall_printf ("%d = readdir(%p, %p)", ret, dir, de);
  return ret;
}

void
fhandler_netdrive::seekdir (DIR *dir, long pos)
{
  ::rewinddir (dir);
  if (pos < 0)
    return;
  while (dir->__d_position < pos)
    if (readdir (dir, dir->__d_dirent))
      break;
}

void
fhandler_netdrive::rewinddir (DIR *dir)
{
  dir->__d_position = 0;
}

int
fhandler_netdrive::closedir (DIR *dir)
{
  if (dir->__handle != INVALID_HANDLE_VALUE)
    delete &DIR_cache;
  return fhandler_virtual::closedir (dir);
}

int
fhandler_netdrive::open (int flags, mode_t mode)
{
  if ((flags & (O_CREAT | O_EXCL)) == (O_CREAT | O_EXCL))
    {
      set_errno (EEXIST);
      return 0;
    }
  if (flags & O_WRONLY)
    {
      set_errno (EISDIR);
      return 0;
    }
  /* Open a fake handle to \\Device\\Null */
  return open_null (flags);
}

int
fhandler_netdrive::close (int flag)
{
  /* Skip fhandler_virtual::close, which is a no-op. */
  return fhandler_base::close ();
}