socat/xio-unix.c

/* source: xio-unix.c */
/* Copyright Gerhard Rieger and contributors (see file CHANGES) */
/* Published under the GNU General Public License V.2, see file COPYING */

/* this file contains the source for opening addresses of UNIX socket type */

#include "xiosysincludes.h"
#include "xioopen.h"

#include "xio-socket.h"
#include "xio-listen.h"
#include "xio-unix.h"
#include "xio-named.h"


#if WITH_UNIX

/* to avoid unneccessary runtime if () conditionals when no abstract support is
   compiled in (or at least to give optimizing compilers a good chance) we need
   a constant that can be used in C expressions */
#if WITH_ABSTRACT_UNIXSOCKET
#  define ABSTRACT 1
#else
#  define ABSTRACT 0
#endif

static int xioopen_unix_connect(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);
static int xioopen_unix_listen(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);
static int xioopen_unix_sendto(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);
static int xioopen_unix_recvfrom(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);
static int xioopen_unix_recv(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);
static int xioopen_unix_client(int argc, const char *argv[], struct opt *opts, int xioflags, xiofile_t *xxfd, const struct addrdesc *addrdesc);

/* the first free parameter is 0 for "normal" unix domain sockets, or 1 for
   abstract unix sockets (Linux); the second and third free parameter are
   unsused */
const struct addrdesc xioaddr_unix_connect = { "UNIX-CONNECT",  1+XIO_RDWR,   xioopen_unix_connect,  GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          0, 0, 0 HELP(":<filename>") };
#if WITH_LISTEN
const struct addrdesc xioaddr_unix_listen  = { "UNIX-LISTEN",   1+XIO_RDWR,   xioopen_unix_listen,   GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_LISTEN|GROUP_CHILD|GROUP_RETRY, 0, 0, 0 HELP(":<filename>") };
#endif /* WITH_LISTEN */
const struct addrdesc xioaddr_unix_sendto  = { "UNIX-SENDTO",   1+XIO_RDWR,   xioopen_unix_sendto,   GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          0, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_unix_recvfrom= { "UNIX-RECVFROM", 1+XIO_RDWR,   xioopen_unix_recvfrom, GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY|GROUP_CHILD,              0, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_unix_recv    = { "UNIX-RECV",     1+XIO_RDONLY, xioopen_unix_recv,     GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          0, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_unix_client  = { "UNIX-CLIENT",   1+XIO_RDWR,   xioopen_unix_client,   GROUP_FD|GROUP_NAMED|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          0, 0, 0 HELP(":<filename>") };
#if WITH_ABSTRACT_UNIXSOCKET
const struct addrdesc xioaddr_abstract_connect = { "ABSTRACT-CONNECT",  1+XIO_RDWR,   xioopen_unix_connect,  GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          1, 0, 0 HELP(":<filename>") };
#if WITH_LISTEN
const struct addrdesc xioaddr_abstract_listen  = { "ABSTRACT-LISTEN",   1+XIO_RDWR,   xioopen_unix_listen,   GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_LISTEN|GROUP_CHILD|GROUP_RETRY, 1, 0, 0 HELP(":<filename>") };
#endif /* WITH_LISTEN */
const struct addrdesc xioaddr_abstract_sendto  = { "ABSTRACT-SENDTO",   1+XIO_RDWR,   xioopen_unix_sendto,   GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          1, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_abstract_recvfrom= { "ABSTRACT-RECVFROM", 1+XIO_RDWR,   xioopen_unix_recvfrom, GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY|GROUP_CHILD,              1, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_abstract_recv    = { "ABSTRACT-RECV",     1+XIO_RDONLY, xioopen_unix_recv,     GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          1, 0, 0 HELP(":<filename>") };
const struct addrdesc xioaddr_abstract_client  = { "ABSTRACT-CLIENT",   1+XIO_RDWR,   xioopen_unix_client,   GROUP_FD|GROUP_SOCKET|GROUP_SOCK_UNIX|GROUP_RETRY,                          1, 0, 0 HELP(":<filename>") };
#endif /* WITH_ABSTRACT_UNIXSOCKET */

const struct optdesc xioopt_unix_tightsocklen = { "unix-tightsocklen",    "tightsocklen",  OPT_UNIX_TIGHTSOCKLEN,  GROUP_SOCK_UNIX, PH_PREBIND, TYPE_BOOL, OFUNC_OFFSET, XIO_OFFSETOF(para.socket.un.tight), XIO_SIZEOF(para.socket.un.tight) };


/* fills the socket address struct and returns its effective length.
   abstract is usually 0;  != 0 generates an abstract socket address on Linux.
   tight!=0 calculates the resulting length from the path length, not from the
   structures length; this is more common (see option unix-tightsocklen)
   the struct need not be initialized when calling this function.
*/
socklen_t
xiosetunix(int pf,
	   struct sockaddr_un *saun,
	   const char *path,
	   bool abstract,
	   bool tight) {
   size_t pathlen;
   socklen_t len;

   socket_un_init(saun);
#ifdef WITH_ABSTRACT_UNIXSOCKET
   if (abstract) {
      if ((pathlen = strlen(path)) >= sizeof(saun->sun_path)) {
	 Warn2("socket address "F_Zu" characters long, truncating to "F_Zu"",
	       pathlen+1, sizeof(saun->sun_path));
      }
      saun->sun_path[0] = '\0';	/* so it's abstract */
      strncpy(saun->sun_path+1, path, sizeof(saun->sun_path)-1);	/* ok */
      if (tight) {
	 len = sizeof(struct sockaddr_un)-sizeof(saun->sun_path)+
	    MIN(pathlen+1, sizeof(saun->sun_path));
#if HAVE_STRUCT_SOCKADDR_SALEN
	 saun->sun_len = len;
#endif
      } else {
	 len = sizeof(struct sockaddr_un);
      }
      return len;
   }
#endif /* WITH_ABSTRACT_UNIXSOCKET */

   if ((pathlen = strlen(path)) > sizeof(saun->sun_path)) {
      Warn2("unix socket address "F_Zu" characters long, truncating to "F_Zu"",
	    pathlen, sizeof(saun->sun_path));
   }
   strncpy(saun->sun_path, path, sizeof(saun->sun_path));	/* ok */
   if (tight) {
      len = sizeof(struct sockaddr_un)-sizeof(saun->sun_path)+
	 MIN(pathlen, sizeof(saun->sun_path));
#if HAVE_STRUCT_SOCKADDR_SALEN
      saun->sun_len = len;
#endif
   } else {
      len = sizeof(struct sockaddr_un);
   }
   return len;
}

#if WITH_LISTEN
static int xioopen_unix_listen(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   const char *name;
   xiosingle_t *sfd = &xxfd->stream;
   int pf = PF_UNIX;
   int socktype = SOCK_STREAM;
   int protocol = 0;
   struct sockaddr_un us;
   socklen_t uslen;
   struct opt *opts0 = NULL;
   pid_t pid = Getpid();
   bool opt_unlink_early = false;
   bool opt_unlink_close = (addrdesc->arg1/*abstract*/ != 1);
   int result;

   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }
   name = argv[1];

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_SHUTDOWN;

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      /* only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_EARLY, &opt_unlink_early);
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }

   if (applyopts_single(sfd, opts, PH_INIT) < 0) return STAT_NORETRY;
   applyopts(sfd, -1, opts, PH_INIT);
   applyopts_named(name, opts, PH_EARLY);	/* umask! */
   applyopts_offset(sfd, opts);
   applyopts(sfd, -1, opts, PH_EARLY);

   uslen = xiosetunix(pf, &us, name, addrdesc->arg1/*abstract*/,
		      sfd->para.socket.un.tight);

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      if (opt_unlink_early) {
	 xio_unlink(name, E_ERROR);
      } else {
	 struct stat buf;
	 if (Lstat(name, &buf) == 0) {
	    Error1("\"%s\" exists", name);
	    return STAT_RETRYLATER;
	 }
      }
      if (opt_unlink_close) {
	 if ((sfd->unlink_close = strdup(name)) == NULL) {
	    Error1("strdup(\"%s\"): out of memory", name);
	 }
	 sfd->opt_unlink_close = true;
      }

      /* trying to set user-early, perm-early etc. here is useless because
	 file system entry is available only past bind() call. */
   }

   opts0 = copyopts(opts, GROUP_ALL);

   /* this may fork() */
   if ((result =
	xioopen_listen(sfd, xioflags,
		       (struct sockaddr *)&us, uslen,
		       opts, opts0, pf, socktype, protocol))
       != 0)
      return result;

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      if (opt_unlink_close) {
	 if (pid != Getpid()) {
	    /* in a child process - do not unlink-close here! */
	    sfd->opt_unlink_close = false;
	 }
      }
   }

   return 0;
}
#endif /* WITH_LISTEN */


static int xioopen_unix_connect(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   const char *name;
   struct single *sfd = &xxfd->stream;
   const struct opt *namedopt;
   int pf = PF_UNIX;
   int socktype = SOCK_STREAM;
   int protocol = 0;
   struct sockaddr_un them, us;
   socklen_t themlen, uslen = sizeof(us);
   bool needbind = false;
   bool opt_unlink_close = (addrdesc->arg1/*abstract*/ != 1);
   bool dofork = false;
   struct opt *opts0;
   char infobuff[256];
   int level;
   int result;

   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }
   name = argv[1];

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_SHUTDOWN;
   if (applyopts_single(sfd, opts, PH_INIT) < 0)  return STAT_NORETRY;
   applyopts(sfd, -1, opts, PH_INIT);
   applyopts_offset(sfd, opts);
   applyopts(sfd, -1, opts, PH_EARLY);

   themlen = xiosetunix(pf, &them, name, addrdesc->arg1/*abstract*/,
			sfd->para.socket.un.tight);

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      /* Only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }
   if (retropt_bind(opts, pf, socktype, protocol, (struct sockaddr *)&us, &uslen,
		    (addrdesc->arg1/*abstract*/<<1)|sfd->para.socket.un.tight,
		    sfd->para.socket.ip.ai_flags)
      == STAT_OK) {
      needbind = true;
   }

   if (!needbind &&
       (namedopt = searchopt(opts, GROUP_NAMED, 0, 0, 0))) {
      Error1("Option \"%s\" only with bind option", namedopt->desc->defname);
   }

   if (opt_unlink_close && needbind) {
      if ((sfd->unlink_close = strdup(us.sun_path)) == NULL) {
	 Error1("strdup(\"%s\"): out of memory", name);
      }
      sfd->opt_unlink_close = true;
   }

   retropt_bool(opts, OPT_FORK, &dofork);

   opts0 = copyopts(opts, GROUP_ALL);

   Notice1("opening connection to %s",
	   sockaddr_info((struct sockaddr *)&them, themlen, infobuff, sizeof(infobuff)));

   do {	/* loop over retries and forks */

#if WITH_RETRY
      if (sfd->forever || sfd->retry) {
	 level = E_INFO;
      } else
#endif /* WITH_RETRY */
	 level = E_ERROR;

      result =
	_xioopen_connect(sfd,
			needbind?(union sockaddr_union *)&us:NULL, uslen,
			(struct sockaddr *)&them, themlen,
			 opts, pf, socktype, protocol, false, level);
      if (result != 0) {
	 char infobuff[256];
	 /* we caller must handle this */
	 Msg3(level, "connect(, %s, "F_socklen"): %s",
	      sockaddr_info((struct sockaddr *)&them, themlen, infobuff, sizeof(infobuff)),
	      themlen, strerror(errno));
      }
      switch (result) {
      case STAT_OK: break;
#if WITH_RETRY
      case STAT_RETRYLATER:
	 if (sfd->forever || sfd->retry) {
	    --sfd->retry;
	    if (result == STAT_RETRYLATER) {
	       Nanosleep(&sfd->intervall, NULL);
	    }
	    dropopts(opts, PH_ALL); opts = copyopts(opts0, GROUP_ALL);
	    continue;
	 }
	 return STAT_NORETRY;
#endif /* WITH_RETRY */
      default:
	 return result;
      }

      if (dofork) {
	 xiosetchilddied();	/* set SIGCHLD handler */
      }

#if WITH_RETRY
      if (dofork) {
	 pid_t pid;
	 int level = E_ERROR;
	 if (sfd->forever || sfd->retry) {
	    level = E_WARN;	/* most users won't expect a problem here,
				   so Notice is too weak */
	 }

	 while ((pid = xio_fork(false, level, sfd->shutup)) < 0) {
	    --sfd->retry;
	    if (sfd->forever || sfd->retry) {
	       dropopts(opts, PH_ALL); opts = copyopts(opts0, GROUP_ALL);
	       Nanosleep(&sfd->intervall, NULL); continue;
	    }
	    return STAT_RETRYLATER;
	 }

	 if (pid == 0) {	/* child process */
	    break;
	 }

	 /* parent process */
	 Close(sfd->fd);
	 /* with and without retry */
	 Nanosleep(&sfd->intervall, NULL);
	 dropopts(opts, PH_ALL); opts = copyopts(opts0, GROUP_ALL);
	 continue;	/* with next socket() bind() connect() */
      } else
#endif /* WITH_RETRY */
      {
	 break;
      }
   } while (true);

   if (opt_unlink_close && needbind) {
      if ((sfd->unlink_close = strndup(us.sun_path, sizeof(us.sun_path))) == NULL) {
	 Error2("strndup(\"%s\", "F_Zu"): out of memory", name, sizeof(us.sun_path));
      }
      sfd->opt_unlink_close = true;
   }

   if ((result = _xio_openlate(sfd, opts)) < 0) {
      return result;
   }
   return STAT_OK;
}


static int xioopen_unix_sendto(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   const char *name;
   xiosingle_t *sfd = &xxfd->stream;
   const struct opt *namedopt;
   int pf = PF_UNIX;
   int socktype = SOCK_DGRAM;
   int protocol = 0;
   union sockaddr_union us;
   socklen_t uslen = sizeof(us);
   bool needbind = false;
   bool opt_unlink_close = (addrdesc->arg1/*abstract*/ != 1);
   int result;

   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }
   name = argv[1];

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_SHUTDOWN;
   applyopts_offset(sfd, opts);

   sfd->salen = xiosetunix(pf, &sfd->peersa.un, name, addrdesc->arg1/*abstract*/, sfd->para.socket.un.tight);

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      /* only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }

   sfd->dtype = XIODATA_RECVFROM;

   if (retropt_bind(opts, pf, socktype, protocol, &us.soa, &uslen,
		    (addrdesc->arg1/*abstract*/<<1)| sfd->para.socket.un.tight,
		    sfd->para.socket.ip.ai_flags)
      == STAT_OK) {
      needbind = true;
   }

   if (!needbind &&
       (namedopt = searchopt(opts, GROUP_NAMED, 0, 0, 0))) {
      Error1("Option \"%s\" only with bind option", namedopt->desc->defname);
   }

   if (applyopts_single(sfd, opts, PH_INIT) < 0)  return -1;
   applyopts(sfd, -1, opts, PH_INIT);

   result =
      _xioopen_dgram_sendto(needbind?(union sockaddr_union *)&us:NULL, uslen,
			    opts, xioflags, sfd, addrdesc->groups,
			    pf, socktype, protocol, 0);
   if (result != 0) {
      return result;
   }

   if (opt_unlink_close && needbind) {
      if ((sfd->unlink_close = strndup(us.un.sun_path, sizeof(us.un.sun_path))) == NULL) {
	 Error2("strndup(\"%s\", "F_Zu"): out of memory", name, sizeof(us.un.sun_path));
      }
      sfd->opt_unlink_close = true;
   }
   return STAT_OK;
}


static
int xioopen_unix_recvfrom(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   const char *name;
   xiosingle_t *sfd = &xxfd->stream;
   int pf = PF_UNIX;
   int socktype = SOCK_DGRAM;
   int protocol = 0;
   struct sockaddr_un us;
   socklen_t uslen;
   bool needbind = true;
   bool opt_unlink_early = false;
   bool opt_unlink_close = (addrdesc->arg1/*abstract*/ != 1);

   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }
   name = argv[1];

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_NONE;
   if (applyopts_single(sfd, opts, PH_INIT) < 0)  return STAT_NORETRY;
   applyopts(sfd, -1, opts, PH_INIT);
   applyopts_named(name, opts, PH_EARLY);       /* umask! */
   applyopts_offset(sfd, opts);

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      /* only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_EARLY, &opt_unlink_early);
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }
   applyopts(sfd, -1, opts, PH_EARLY);

   uslen = xiosetunix(pf, &us, name, addrdesc->arg1/*abstract*/,
		      sfd->para.socket.un.tight);

#if 0
   if (retropt_bind(opts, pf, socktype, protocol, (struct sockaddr *)&us, &uslen,
		    (addrdesc->arg1/*abstract*/<<1)|sfd->para.socket.un.tight,
		    sfd->para.socket.ip.ai_flags)) {
      == STAT_OK) {
   }
#endif

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      if (opt_unlink_early) {
	 xio_unlink(name, E_ERROR);
      } else {
	 struct stat buf;
	 if (Lstat(name, &buf) == 0) {
	    Error1("\"%s\" exists", name);
	    return STAT_RETRYLATER;
	 }
      }
      if (opt_unlink_close) {
	 if ((sfd->unlink_close = strdup(name)) == NULL) {
	    Error1("strdup(\"%s\"): out of memory", name);
	 }
	 sfd->opt_unlink_close = true;
      }

      /* trying to set user-early, perm-early etc. here is useless because
	 file system entry is available only past bind() call. */
   }
   applyopts_named(name, opts, PH_EARLY);	/* umask! */

   sfd->para.socket.la.soa.sa_family = pf;

   sfd->dtype = XIODATA_RECVFROM_ONE;

   /* this may fork */
   return
      _xioopen_dgram_recvfrom(sfd, xioflags,
			      needbind?(struct sockaddr *)&us:NULL, uslen,
			      opts, pf, socktype, protocol, E_ERROR);
}


static int xioopen_unix_recv(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   const char *name;
   xiosingle_t *sfd = &xxfd->stream;
   int pf = PF_UNIX;
   int socktype = SOCK_DGRAM;
   int protocol = 0;
   union sockaddr_union us;
   socklen_t uslen;
   bool opt_unlink_early = false;
   bool opt_unlink_close = (addrdesc->arg1/*abstract*/ != 1);
   int result;

   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }
   name = argv[1];

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_SHUTDOWN;
   if (applyopts_single(sfd, opts, PH_INIT) < 0)  return STAT_NORETRY;
   applyopts(sfd, -1, opts, PH_INIT);
   applyopts_named(name, opts, PH_EARLY);       /* umask! */
   applyopts_offset(sfd, opts);

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      /* only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_EARLY, &opt_unlink_early);
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }
   applyopts(sfd, -1, opts, PH_EARLY);

   uslen = xiosetunix(pf, &us.un, name, addrdesc->arg1/*abstract*/,
		      sfd->para.socket.un.tight);

#if 0
   if (retropt_bind(opts, pf, socktype, protocol, &us.soa, &uslen,
		    (addrdesc->arg1/*abstract*/<<1)|sfd->para.socket.un.tight,
		    sfd->para.socket.ip.ai_flags)
       == STAT_OK) {
   }
#endif

   if (!(ABSTRACT && addrdesc->arg1/*abstract*/)) {
      if (opt_unlink_early) {
	 xio_unlink(name, E_ERROR);
      } else {
	 struct stat buf;
	 if (Lstat(name, &buf) == 0) {
	    Error1("\"%s\" exists", name);
	    return STAT_RETRYLATER;
	 }
      }
      if (opt_unlink_close) {
	 if ((sfd->unlink_close = strdup(name)) == NULL) {
	    Error1("strdup(\"%s\"): out of memory", name);
	 }
	 sfd->opt_unlink_close = true;
      }
   }
   applyopts_named(name, opts, PH_EARLY);	/* umask! */

   sfd->para.socket.la.soa.sa_family = pf;

   sfd->dtype = XIODATA_RECV;
   result = _xioopen_dgram_recv(sfd, xioflags, &us.soa, uslen,
				opts, pf, socktype, protocol, E_ERROR);
   return result;
}


/* generic UNIX socket client, tries connect, SEQPACKET, send(to) */
static int xioopen_unix_client(
	int argc,
	const char *argv[],
	struct opt *opts,
	int xioflags,
	xiofile_t *xxfd,
	const struct addrdesc *addrdesc)
{
   /* we expect the form: filename */
   if (argc != 2) {
      xio_syntax(argv[0], 1, argc-1, addrdesc->syntax);
      return STAT_NORETRY;
   }

   return
      _xioopen_unix_client(&xxfd->stream, xioflags, addrdesc->groups,
			   addrdesc->arg1/*abstract*/, opts, argv[1]);
}

/* establishes communication with an existing UNIX type socket. supports stream
   and datagram socket types: first tries to connect(), but when this fails it
   falls back to sendto().
   applies and consumes the following option:
   PH_INIT, PH_PASTSOCKET, PH_FD, PH_PREBIND, PH_BIND, PH_PASTBIND,
   PH_CONNECTED, PH_LATE, ?PH_CONNECT
   OFUNC_OFFSET,
   OPT_PROTOCOL_FAMILY, OPT_UNIX_TIGHTSOCKLEN, OPT_UNLINK_CLOSE, OPT_BIND,
   OPT_SO_TYPE, OPT_SO_PROTOTYPE, OPT_CLOEXEC, OPT_USER, OPT_GROUP, ?OPT_FORK,
*/
int
_xioopen_unix_client(xiosingle_t *sfd, int xioflags, groups_t groups,
		     int abstract, struct opt *opts, const char *name) {
   const struct opt *namedopt;
   int pf = PF_UNIX;
   int socktype = 0;	/* to be determined by server socket type */
   int protocol = 0;
   union sockaddr_union them, us;
   socklen_t themlen, uslen = sizeof(us);
   bool needbind = false;
   bool opt_unlink_close = false;
   struct opt *opts0;
   int result;

   sfd->para.socket.un.tight = true;
   retropt_socket_pf(opts, &pf);
   sfd->howtoend = END_SHUTDOWN;
   if (applyopts_single(sfd, opts, PH_INIT) < 0)  return STAT_NORETRY;
   applyopts(sfd, -1, opts, PH_INIT);
   applyopts_offset(sfd, opts);
   retropt_int(opts, OPT_SO_TYPE, &socktype);
   retropt_int(opts, OPT_SO_PROTOTYPE, &protocol);
   applyopts(sfd, -1, opts, PH_EARLY);

   themlen = xiosetunix(pf, &them.un, name, abstract, sfd->para.socket.un.tight);
   if (!(ABSTRACT && abstract)) {
      /* only for non abstract because abstract do not work in file system */
      retropt_bool(opts, OPT_UNLINK_CLOSE, &opt_unlink_close);
   }
   if (retropt_bind(opts, pf, socktype, protocol, &us.soa, &uslen,
		    (abstract<<1)|sfd->para.socket.un.tight,
		    sfd->para.socket.ip.ai_flags)
       != STAT_NOACTION) {
      needbind = true;
   }

   if (!needbind &&
       (namedopt = searchopt(opts, GROUP_NAMED, 0, 0, 0))) {
      Error1("Option \"%s\" only with bind option", namedopt->desc->defname);
   }

   if (opt_unlink_close) {
      if ((sfd->unlink_close = strdup(name)) == NULL) {
	 Error1("strdup(\"%s\"): out of memory", name);
      }
      sfd->opt_unlink_close = true;
   }

   /* save options, because we might have to start again */
   opts0 = copyopts(opts, GROUP_ALL);

   /* just a breakable block, helps to avoid goto */
   do {
      /* sfd->dtype = DATA_STREAM; // is default */
      /* this function handles AF_UNIX with EPROTOTYPE specially for us */
      if ((result =
	_xioopen_connect(sfd,
			 needbind?&us:NULL, uslen,
			 &them.soa, themlen,
			 opts, pf, socktype?socktype:SOCK_STREAM, protocol,
			 false, E_INFO)) == 0)
	 break;
      if (errno != EPROTOTYPE || socktype != 0)
	 break;
      if (needbind)
	 xio_unlink(us.un.sun_path, E_ERROR);
      dropopts2(opts, PH_INIT, PH_SPEC); opts = opts0;

      socktype = SOCK_SEQPACKET;
      if ((result =
	   _xioopen_connect(sfd,
			    needbind?&us:NULL, uslen,
			    (struct sockaddr *)&them, themlen,
			    opts, pf, SOCK_SEQPACKET, protocol,
			    false, E_INFO)) == 0)
	 break;
      if (errno != EPROTOTYPE && errno != EPROTONOSUPPORT/*AIX*/)
	 break;
      if (needbind)
	 xio_unlink(us.un.sun_path, E_ERROR);
      dropopts2(opts, PH_INIT, PH_SPEC); opts = opts0;

      sfd->peersa = them;
      sfd->salen = sizeof(struct sockaddr_un);
      if ((result =
	      _xioopen_dgram_sendto(needbind?&us:NULL, uslen,
				    opts, xioflags, sfd, groups,
				    pf, SOCK_DGRAM, protocol, 0))
	  == 0) {
	 sfd->dtype = XIODATA_RECVFROM;
	 break;
      }
   } while (0);

   if (result != 0) {
      Error2("UNIX-CLIENT:%s: %s", name, strerror(errno));
      if (needbind)
	 xio_unlink(us.un.sun_path, E_ERROR);
      return result;
   }

   if ((result = _xio_openlate(sfd, opts)) < 0) {
      return result;
   }
   return 0;
}


/* returns information that can be used for constructing an environment
   variable describing the socket address.
   if idx is 0, this function writes "ADDR" into namebuff and the path into
   valuebuff, and returns 0 (which means that no more info is there).
   if idx is != 0, it returns -1
   namelen and valuelen contain the max. allowed length of output chars in the
   respective buffer.
   on error this function returns -1.
*/
int
xiosetsockaddrenv_unix(int idx, char *namebuff, size_t namelen,
		       char *valuebuff, size_t valuelen,
		       struct sockaddr_un *sa, socklen_t salen, int ipproto) {
   if (idx != 0) {
      return -1;
   }
   strcpy(namebuff, "ADDR");
   sockaddr_unix_info(sa, salen, valuebuff, valuelen);
   return 0;
}

#endif /* WITH_UNIX */