text: /*
   * Unix networking abstraction.
   */
  
  #include <stdio.h>
  #include <stdlib.h>
  #include <assert.h>
  #include <errno.h>
  #include <fcntl.h>
  #include <unistd.h>
  #include <sys/types.h>
  #include <sys/socket.h>
  #include <sys/ioctl.h>
  #include <arpa/inet.h>
  #include <netinet/in.h>
  #include <netinet/tcp.h>
  #include <netdb.h>
  #include <sys/un.h>
  #include <pwd.h>
  #include <grp.h>
  
  #define DEFINE_PLUG_METHOD_MACROS
  #include "putty.h"
  #include "network.h"
  #include "tree234.h"
  
  /* Solaris needs <sys/sockio.h> for SIOCATMARK. */
  #ifndef SIOCATMARK
  #include <sys/sockio.h>
  #endif
  
  #ifndef X11_UNIX_PATH
  # define X11_UNIX_PATH "/tmp/.X11-unix/X"
  #endif
  
  /* 
   * Access to sockaddr types without breaking C strict aliasing rules.
   */
  union sockaddr_union {
  #ifdef NO_IPV6
      struct sockaddr_in storage;
  #else
      struct sockaddr_storage storage;
      struct sockaddr_in6 sin6;
  #endif
      struct sockaddr sa;
      struct sockaddr_in sin;
      struct sockaddr_un su;
  };
  
  /*
   * We used to typedef struct Socket_tag *Socket.
   *
   * Since we have made the networking abstraction slightly more
   * abstract, Socket no longer means a tcp socket (it could mean
   * an ssl socket).  So now we must use Actual_Socket when we know
   * we are talking about a tcp socket.
   */
  typedef struct Socket_tag *Actual_Socket;
  
  /*
   * Mutable state that goes with a SockAddr: stores information
   * about where in the list of candidate IP(v*) addresses we've
   * currently got to.
   */
  typedef struct SockAddrStep_tag SockAddrStep;
  struct SockAddrStep_tag {
  #ifndef NO_IPV6
      struct addrinfo *ai;	       /* steps along addr->ais */
  #endif
      int curraddr;
  };
  
  struct Socket_tag {
      struct socket_function_table *fn;
      /* the above variable absolutely *must* be the first in this structure */
      const char *error;
      int s;
      Plug plug;
      bufchain output_data;
      int connected;		       /* irrelevant for listening sockets */
      int writable;
      int frozen; /* this causes readability notifications to be ignored */
      int localhost_only;		       /* for listening sockets */
      char oobdata[1];
      int sending_oob;
      int oobpending;		       /* is there OOB data available to read? */
      int oobinline;
      enum { EOF_NO, EOF_PENDING, EOF_SENT } outgoingeof;
      int incomingeof;
      int pending_error;		       /* in case send() returns error */
      int listener;
      int nodelay, keepalive;            /* for connect()-type sockets */
      int privport, port;                /* and again */
      SockAddr addr;
      SockAddrStep step;
      /*
       * We sometimes need pairs of Socket structures to be linked:
       * if we are listening on the same IPv6 and v4 port, for
       * example. So here we define `parent' and `child' pointers to
       * track this link.
       */
      Actual_Socket parent, child;
  };
  
  struct SockAddr_tag {
      int refcount;
      const char *error;
      enum { UNRESOLVED, UNIX, IP } superfamily;
  #ifndef NO_IPV6
      struct addrinfo *ais;	       /* Addresses IPv6 style. */
  #else
      unsigned long *addresses;	       /* Addresses IPv4 style. */
      int naddresses;
  #endif
      char hostname[512];		       /* Store an unresolved host name. */
  };
  
  /*
   * Which address family this address belongs to. AF_INET for IPv4;
   * AF_INET6 for IPv6; AF_UNSPEC indicates that name resolution has
   * not been done and a simple host name is held in this SockAddr
   * structure.
   */
  #ifndef NO_IPV6
  #define SOCKADDR_FAMILY(addr, step) \
      ((addr)->superfamily == UNRESOLVED ? AF_UNSPEC : \
       (addr)->superfamily == UNIX ? AF_UNIX : \
       (step).ai ? (step).ai->ai_family : AF_INET)
  #else
  /* Here we gratuitously reference 'step' to avoid gcc warnings about
   * 'set but not used' when compiling -DNO_IPV6 */
  #define SOCKADDR_FAMILY(addr, step) \
      ((addr)->superfamily == UNRESOLVED ? AF_UNSPEC : \
       (addr)->superfamily == UNIX ? AF_UNIX : \
       (step).curraddr ? AF_INET : AF_INET)
  #endif
  
  /*
   * Start a SockAddrStep structure to step through multiple
   * addresses.
   */
  #ifndef NO_IPV6
  #define START_STEP(addr, step) \
      ((step).ai = (addr)->ais, (step).curraddr = 0)
  #else
  #define START_STEP(addr, step) \
      ((step).curraddr = 0)
  #endif
  
  static tree234 *sktree;
  
  static void uxsel_tell(Actual_Socket s);
  
  static int cmpfortree(void *av, void *bv)
  {
      Actual_Socket a = (Actual_Socket) av, b = (Actual_Socket) bv;
      int as = a->s, bs = b->s;
      if (as < bs)
  	return -1;
      if (as > bs)
  	return +1;
      if (a < b)
         return -1;
      if (a > b)
         return +1;
      return 0;
  }
  
  static int cmpforsearch(void *av, void *bv)
  {
      Actual_Socket b = (Actual_Socket) bv;
      int as = *(int *)av, bs = b->s;
      if (as < bs)
  	return -1;
      if (as > bs)
  	return +1;
      return 0;
  }
  
  void sk_init(void)
  {
      sktree = newtree234(cmpfortree);
  }
  
  void sk_cleanup(void)
  {
      Actual_Socket s;
      int i;
  
      if (sktree) {
  	for (i = 0; (s = index234(sktree, i)) != NULL; i++) {
  	    close(s->s);
  	}
      }
  }
  
  SockAddr sk_namelookup(const char *host, char **canonicalname, int address_family)
  {
      SockAddr ret = snew(struct SockAddr_tag);
  #ifndef NO_IPV6
      struct addrinfo hints;
      int err;
  #else
      unsigned long a;
      struct hostent *h = NULL;
      int n;
  #endif
      char realhost[8192];
  
      /* Clear the structure and default to IPv4. */
      memset(ret, 0, sizeof(struct SockAddr_tag));
      ret->superfamily = UNRESOLVED;
      *realhost = '\0';
      ret->error = NULL;
      ret->refcount = 1;
  
  #ifndef NO_IPV6
      hints.ai_flags = AI_CANONNAME;
      hints.ai_family = (address_family == ADDRTYPE_IPV4 ? AF_INET :
  		       address_family == ADDRTYPE_IPV6 ? AF_INET6 :
  		       AF_UNSPEC);
      hints.ai_socktype = SOCK_STREAM;
      hints.ai_protocol = 0;
      hints.ai_addrlen = 0;
      hints.ai_addr = NULL;
      hints.ai_canonname = NULL;
      hints.ai_next = NULL;
      {
          char *trimmed_host = host_strduptrim(host); /* strip [] on literals */
          err = getaddrinfo(trimmed_host, NULL, &hints, &ret->ais);
          sfree(trimmed_host);
      }
      if (err != 0) {
  	ret->error = gai_strerror(err);
  	return ret;
      }
      ret->superfamily = IP;
      *realhost = '\0';
      if (ret->ais->ai_canonname != NULL)
  	strncpy(realhost, ret->ais->ai_canonname, sizeof(realhost) - 1);
      else
  	strncpy(realhost, host, sizeof(realhost) - 1);
  #else
      if ((a = inet_addr(host)) == (unsigned long)(in_addr_t)(-1)) {
  	/*
  	 * Otherwise use the IPv4-only gethostbyname... (NOTE:
  	 * we don't use gethostbyname as a fallback!)
  	 */
  	if (ret->superfamily == UNRESOLVED) {
  	    /*debug(("Resolving \"%s\" with gethostbyname() (IPv4 only)...\n", host)); */
  	    if ( (h = gethostbyname(host)) )
  		ret->superfamily = IP;
  	}
  	if (ret->superfamily == UNRESOLVED) {
  	    ret->error = (h_errno == HOST_NOT_FOUND ||
  			  h_errno == NO_DATA ||
  			  h_errno == NO_ADDRESS ? "Host does not exist" :
  			  h_errno == TRY_AGAIN ?
  			  "Temporary name service failure" :
  			  "gethostbyname: unknown error");
  	    return ret;
  	}
  	/* This way we are always sure the h->h_name is valid :) */
  	strncpy(realhost, h->h_name, sizeof(realhost));
  	for (n = 0; h->h_addr_list[n]; n++);
  	ret->addresses = snewn(n, unsigned long);
  	ret->naddresses = n;
  	for (n = 0; n < ret->naddresses; n++) {
  	    memcpy(&a, h->h_addr_list[n], sizeof(a));
  	    ret->addresses[n] = ntohl(a);
  	}
      } else {
  	/*
  	 * This must be a numeric IPv4 address because it caused a
  	 * success return from inet_addr.
  	 */
  	ret->superfamily = IP;
  	strncpy(realhost, host, sizeof(realhost));
  	ret->addresses = snew(unsigned long);
  	ret->naddresses = 1;
  	ret->addresses[0] = ntohl(a);
      }
  #endif
      realhost[lenof(realhost)-1] = '\0';
      *canonicalname = snewn(1+strlen(realhost), char);
      strcpy(*canonicalname, realhost);
      return ret;
  }
  
  SockAddr sk_nonamelookup(const char *host)
  {
      SockAddr ret = snew(struct SockAddr_tag);
      ret->error = NULL;
      ret->superfamily = UNRESOLVED;
      strncpy(ret->hostname, host, lenof(ret->hostname));
      ret->hostname[lenof(ret->hostname)-1] = '\0';
  #ifndef NO_IPV6
      ret->ais = NULL;
  #else
      ret->addresses = NULL;
  #endif
      ret->refcount = 1;
      return ret;
  }
  
  static int sk_nextaddr(SockAddr addr, SockAddrStep *step)
  {
  #ifndef NO_IPV6
      if (step->ai && step->ai->ai_next) {
  	step->ai = step->ai->ai_next;
  	return TRUE;
      } else
  	return FALSE;
  #else
      if (step->curraddr+1 < addr->naddresses) {
  	step->curraddr++;
  	return TRUE;
      } else {
  	return FALSE;
      }
  #endif    
  }
  
  void sk_getaddr(SockAddr addr, char *buf, int buflen)
  {
      if (addr->superfamily == UNRESOLVED || addr->superfamily == UNIX) {
  	strncpy(buf, addr->hostname, buflen);
  	buf[buflen-1] = '\0';
      } else {
  #ifndef NO_IPV6
  	if (getnameinfo(addr->ais->ai_addr, addr->ais->ai_addrlen, buf, buflen,
  			NULL, 0, NI_NUMERICHOST) != 0) {
  	    buf[0] = '\0';
  	    strncat(buf, "<unknown>", buflen - 1);
  	}
  #else
  	struct in_addr a;
  	SockAddrStep step;
  	START_STEP(addr, step);
  	assert(SOCKADDR_FAMILY(addr, step) == AF_INET);
  	a.s_addr = htonl(addr->addresses[0]);
  	strncpy(buf, inet_ntoa(a), buflen);
  	buf[buflen-1] = '\0';
  #endif
      }
  }
  
  int sk_addr_needs_port(SockAddr addr)
  {
      if (addr->superfamily == UNRESOLVED || addr->superfamily == UNIX) {
          return FALSE;
      } else {
          return TRUE;
      }
  }
  
  int sk_hostname_is_local(const char *name)
  {
      return !strcmp(name, "localhost") ||
  	   !strcmp(name, "::1") ||
  	   !strncmp(name, "127.", 4);
  }
  
  #define ipv4_is_loopback(addr) \
      (((addr).s_addr & htonl(0xff000000)) == htonl(0x7f000000))
  
  static int sockaddr_is_loopback(struct sockaddr *sa)
  {
      union sockaddr_union *u = (union sockaddr_union *)sa;
      switch (u->sa.sa_family) {
        case AF_INET:
  	return ipv4_is_loopback(u->sin.sin_addr);
  #ifndef NO_IPV6
        case AF_INET6:
  	return IN6_IS_ADDR_LOOPBACK(&u->sin6.sin6_addr);
  #endif
        case AF_UNIX:
  	return TRUE;
        default:
  	return FALSE;
      }
  }
  
  int sk_address_is_local(SockAddr addr)
  {
      if (addr->superfamily == UNRESOLVED)
  	return 0;                      /* we don't know; assume not */
      else if (addr->superfamily == UNIX)
  	return 1;
      else {
  #ifndef NO_IPV6
  	return sockaddr_is_loopback(addr->ais->ai_addr);
  #else
  	struct in_addr a;
  	SockAddrStep step;
  	START_STEP(addr, step);
  	assert(SOCKADDR_FAMILY(addr, step) == AF_INET);
  	a.s_addr = htonl(addr->addresses[0]);
  	return ipv4_is_loopback(a);
  #endif
      }
  }
  
  int sk_address_is_special_local(SockAddr addr)
  {
      return addr->superfamily == UNIX;
  }
  
  int sk_addrtype(SockAddr addr)
  {
      SockAddrStep step;
      int family;
      START_STEP(addr, step);
      family = SOCKADDR_FAMILY(addr, step);
  
      return (family == AF_INET ? ADDRTYPE_IPV4 :
  #ifndef NO_IPV6
  	    family == AF_INET6 ? ADDRTYPE_IPV6 :
  #endif
  	    ADDRTYPE_NAME);
  }
  
  void sk_addrcopy(SockAddr addr, char *buf)
  {
      SockAddrStep step;
      int family;
      START_STEP(addr, step);
      family = SOCKADDR_FAMILY(addr, step);
  
  #ifndef NO_IPV6
      if (family == AF_INET) {
          assert(step.ai);
  	memcpy(buf, &((struct sockaddr_in *)step.ai->ai_addr)->sin_addr,
  	       sizeof(struct in_addr));
      } else if (family == AF_INET6) {
          assert(step.ai);
  	memcpy(buf, &((struct sockaddr_in6 *)step.ai->ai_addr)->sin6_addr,
  	       sizeof(struct in6_addr));
      } else
  	assert(FALSE);
  #else
      struct in_addr a;
  
      assert(family == AF_INET);
      a.s_addr = htonl(addr->addresses[step.curraddr]);
      memcpy(buf, (char*) &a.s_addr, 4);
  #endif
  }
  
  void sk_addr_free(SockAddr addr)
  {
      if (--addr->refcount > 0)
  	return;
  #ifndef NO_IPV6
      if (addr->ais != NULL)
  	freeaddrinfo(addr->ais);
  #else
      sfree(addr->addresses);
  #endif
      sfree(addr);
  }
  
  SockAddr sk_addr_dup(SockAddr addr)
  {
      addr->refcount++;
      return addr;
  }
  
  static Plug sk_tcp_plug(Socket sock, Plug p)
  {
      Actual_Socket s = (Actual_Socket) sock;
      Plug ret = s->plug;
      if (p)
  	s->plug = p;
      return ret;
  }
  
  static void sk_tcp_flush(Socket s)
  {
      /*
       * We send data to the socket as soon as we can anyway,
       * so we don't need to do anything here.  :-)
       */
  }
  
  static void sk_tcp_close(Socket s);
  static int sk_tcp_write(Socket s, const char *data, int len);
  static int sk_tcp_write_oob(Socket s, const char *data, int len);
  static void sk_tcp_write_eof(Socket s);
  static void sk_tcp_set_frozen(Socket s, int is_frozen);
  static char *sk_tcp_peer_info(Socket s);
  static const char *sk_tcp_socket_error(Socket s);
  
  static struct socket_function_table tcp_fn_table = {
      sk_tcp_plug,
      sk_tcp_close,
      sk_tcp_write,
      sk_tcp_write_oob,
      sk_tcp_write_eof,
      sk_tcp_flush,
      sk_tcp_set_frozen,
      sk_tcp_socket_error,
      sk_tcp_peer_info,
  };
  
  static Socket sk_tcp_accept(accept_ctx_t ctx, Plug plug)
  {
      int sockfd = ctx.i;
      Actual_Socket ret;
  
      /*
       * Create Socket structure.
       */
      ret = snew(struct Socket_tag);
      ret->fn = &tcp_fn_table;
      ret->error = NULL;
      ret->plug = plug;
      bufchain_init(&ret->output_data);
      ret->writable = 1;		       /* to start with */
      ret->sending_oob = 0;
      ret->frozen = 1;
      ret->localhost_only = 0;	       /* unused, but best init anyway */
      ret->pending_error = 0;
      ret->oobpending = FALSE;
      ret->outgoingeof = EOF_NO;
      ret->incomingeof = FALSE;
      ret->listener = 0;
      ret->parent = ret->child = NULL;
      ret->addr = NULL;
      ret->connected = 1;
  
      ret->s = sockfd;
  
      if (ret->s < 0) {
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      ret->oobinline = 0;
  
      uxsel_tell(ret);
      add234(sktree, ret);
  
      return (Socket) ret;
  }
  
  static int try_connect(Actual_Socket sock)
  {
      int s;
      union sockaddr_union u;
      const union sockaddr_union *sa;
      int err = 0;
      short localport;
      int salen, family;
  
      /*
       * Remove the socket from the tree before we overwrite its
       * internal socket id, because that forms part of the tree's
       * sorting criterion. We'll add it back before exiting this
       * function, whether we changed anything or not.
       */
      del234(sktree, sock);
  
      if (sock->s >= 0)
          close(sock->s);
  
      plug_log(sock->plug, 0, sock->addr, sock->port, NULL, 0);
  
      /*
       * Open socket.
       */
      family = SOCKADDR_FAMILY(sock->addr, sock->step);
      assert(family != AF_UNSPEC);
      s = socket(family, SOCK_STREAM, 0);
      sock->s = s;
  
      if (s < 0) {
  	err = errno;
  	goto ret;
      }
  
      cloexec(s);
  
      if (sock->oobinline) {
  	int b = TRUE;
  	if (setsockopt(s, SOL_SOCKET, SO_OOBINLINE,
                         (void *) &b, sizeof(b)) < 0) {
              err = errno;
              close(s);
              goto ret;
          }
      }
  
      if (sock->nodelay) {
  	int b = TRUE;
  	if (setsockopt(s, IPPROTO_TCP, TCP_NODELAY,
                         (void *) &b, sizeof(b)) < 0) {
              err = errno;
              close(s);
              goto ret;
          }
      }
  
      if (sock->keepalive) {
  	int b = TRUE;
  	if (setsockopt(s, SOL_SOCKET, SO_KEEPALIVE,
                         (void *) &b, sizeof(b)) < 0) {
              err = errno;
              close(s);
              goto ret;
          }
      }
  
      /*
       * Bind to local address.
       */
      if (sock->privport)
  	localport = 1023;	       /* count from 1023 downwards */
      else
  	localport = 0;		       /* just use port 0 (ie kernel picks) */
  
      /* BSD IP stacks need sockaddr_in zeroed before filling in */
      memset(&u,'\0',sizeof(u));
  
      /* We don't try to bind to a local address for UNIX domain sockets.  (Why
       * do we bother doing the bind when localport == 0 anyway?) */
      if (family != AF_UNIX) {
  	/* Loop round trying to bind */
  	while (1) {
  	    int retcode;
  
  #ifndef NO_IPV6
  	    if (family == AF_INET6) {
  		/* XXX use getaddrinfo to get a local address? */
  		u.sin6.sin6_family = AF_INET6;
  		u.sin6.sin6_addr = in6addr_any;
  		u.sin6.sin6_port = htons(localport);
  		retcode = bind(s, &u.sa, sizeof(u.sin6));
  	    } else
  #endif
  	    {
  		assert(family == AF_INET);
  		u.sin.sin_family = AF_INET;
  		u.sin.sin_addr.s_addr = htonl(INADDR_ANY);
  		u.sin.sin_port = htons(localport);
  		retcode = bind(s, &u.sa, sizeof(u.sin));
  	    }
  	    if (retcode >= 0) {
  		err = 0;
  		break;		       /* done */
  	    } else {
  		err = errno;
  		if (err != EADDRINUSE) /* failed, for a bad reason */
  		  break;
  	    }
  	    
  	    if (localport == 0)
  	      break;		       /* we're only looping once */
  	    localport--;
  	    if (localport == 0)
  	      break;		       /* we might have got to the end */
  	}
  	
  	if (err)
  	    goto ret;
      }
  
      /*
       * Connect to remote address.
       */
      switch(family) {
  #ifndef NO_IPV6
        case AF_INET:
  	/* XXX would be better to have got getaddrinfo() to fill in the port. */
          assert(sock->step.ai);
  	((struct sockaddr_in *)sock->step.ai->ai_addr)->sin_port =
  	    htons(sock->port);
  	sa = (const union sockaddr_union *)sock->step.ai->ai_addr;
  	salen = sock->step.ai->ai_addrlen;
  	break;
        case AF_INET6:
          assert(sock->step.ai);
  	((struct sockaddr_in *)sock->step.ai->ai_addr)->sin_port =
  	    htons(sock->port);
  	sa = (const union sockaddr_union *)sock->step.ai->ai_addr;
  	salen = sock->step.ai->ai_addrlen;
  	break;
  #else
        case AF_INET:
  	u.sin.sin_family = AF_INET;
  	u.sin.sin_addr.s_addr = htonl(sock->addr->addresses[sock->step.curraddr]);
  	u.sin.sin_port = htons((short) sock->port);
  	sa = &u;
  	salen = sizeof u.sin;
  	break;
  #endif
        case AF_UNIX:
  	assert(sock->port == 0);       /* to catch confused people */
  	assert(strlen(sock->addr->hostname) < sizeof u.su.sun_path);
  	u.su.sun_family = AF_UNIX;
  	strcpy(u.su.sun_path, sock->addr->hostname);
  	sa = &u;
  	salen = sizeof u.su;
  	break;
  
        default:
  	assert(0 && "unknown address family");
  	exit(1); /* XXX: GCC doesn't understand assert() on some systems. */
      }
  
      nonblock(s);
  
      if ((connect(s, &(sa->sa), salen)) < 0) {
  	if ( errno != EINPROGRESS ) {
  	    err = errno;
  	    goto ret;
  	}
      } else {
  	/*
  	 * If we _don't_ get EWOULDBLOCK, the connect has completed
  	 * and we should set the socket as connected and writable.
  	 */
  	sock->connected = 1;
  	sock->writable = 1;
      }
  
      uxsel_tell(sock);
  
      ret:
  
      /*
       * No matter what happened, put the socket back in the tree.
       */
      add234(sktree, sock);
  
      if (err)
  	plug_log(sock->plug, 1, sock->addr, sock->port, strerror(err), err);
      return err;
  }
  
  Socket sk_new(SockAddr addr, int port, int privport, int oobinline,
  	      int nodelay, int keepalive, Plug plug)
  {
      Actual_Socket ret;
      int err;
  
      /*
       * Create Socket structure.
       */
      ret = snew(struct Socket_tag);
      ret->fn = &tcp_fn_table;
      ret->error = NULL;
      ret->plug = plug;
      bufchain_init(&ret->output_data);
      ret->connected = 0;		       /* to start with */
      ret->writable = 0;		       /* to start with */
      ret->sending_oob = 0;
      ret->frozen = 0;
      ret->localhost_only = 0;	       /* unused, but best init anyway */
      ret->pending_error = 0;
      ret->parent = ret->child = NULL;
      ret->oobpending = FALSE;
      ret->outgoingeof = EOF_NO;
      ret->incomingeof = FALSE;
      ret->listener = 0;
      ret->addr = addr;
      START_STEP(ret->addr, ret->step);
      ret->s = -1;
      ret->oobinline = oobinline;
      ret->nodelay = nodelay;
      ret->keepalive = keepalive;
      ret->privport = privport;
      ret->port = port;
  
      err = 0;
      do {
          err = try_connect(ret);
      } while (err && sk_nextaddr(ret->addr, &ret->step));
  
      if (err)
          ret->error = strerror(err);
  
      return (Socket) ret;
  }
  
  Socket sk_newlistener(char *srcaddr, int port, Plug plug, int local_host_only, int orig_address_family)
  {
      int s;
  #ifndef NO_IPV6
      struct addrinfo hints, *ai = NULL;
      char portstr[6];
  #endif
      union sockaddr_union u;
      union sockaddr_union *addr;
      int addrlen;
      Actual_Socket ret;
      int retcode;
      int address_family;
      int on = 1;
  
      /*
       * Create Socket structure.
       */
      ret = snew(struct Socket_tag);
      ret->fn = &tcp_fn_table;
      ret->error = NULL;
      ret->plug = plug;
      bufchain_init(&ret->output_data);
      ret->writable = 0;		       /* to start with */
      ret->sending_oob = 0;
      ret->frozen = 0;
      ret->localhost_only = local_host_only;
      ret->pending_error = 0;
      ret->parent = ret->child = NULL;
      ret->oobpending = FALSE;
      ret->outgoingeof = EOF_NO;
      ret->incomingeof = FALSE;
      ret->listener = 1;
      ret->addr = NULL;
      ret->s = -1;
  
      /*
       * Translate address_family from platform-independent constants
       * into local reality.
       */
      address_family = (orig_address_family == ADDRTYPE_IPV4 ? AF_INET :
  #ifndef NO_IPV6
  		      orig_address_family == ADDRTYPE_IPV6 ? AF_INET6 :
  #endif
  		      AF_UNSPEC);
  
  #ifndef NO_IPV6
      /* Let's default to IPv6.
       * If the stack doesn't support IPv6, we will fall back to IPv4. */
      if (address_family == AF_UNSPEC) address_family = AF_INET6;
  #else
      /* No other choice, default to IPv4 */
      if (address_family == AF_UNSPEC)  address_family = AF_INET;
  #endif
  
      /*
       * Open socket.
       */
      s = socket(address_family, SOCK_STREAM, 0);
  
  #ifndef NO_IPV6
      /* If the host doesn't support IPv6 try fallback to IPv4. */
      if (s < 0 && address_family == AF_INET6) {
      	address_family = AF_INET;
      	s = socket(address_family, SOCK_STREAM, 0);
      }
  #endif
  
      if (s < 0) {
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      cloexec(s);
  
      ret->oobinline = 0;
  
      if (setsockopt(s, SOL_SOCKET, SO_REUSEADDR,
                     (const char *)&on, sizeof(on)) < 0) {
          ret->error = strerror(errno);
          close(s);
          return (Socket) ret;
      }
  
      retcode = -1;
      addr = NULL; addrlen = -1;         /* placate optimiser */
  
      if (srcaddr != NULL) {
  #ifndef NO_IPV6
          hints.ai_flags = AI_NUMERICHOST;
          hints.ai_family = address_family;
          hints.ai_socktype = SOCK_STREAM;
          hints.ai_protocol = 0;
          hints.ai_addrlen = 0;
          hints.ai_addr = NULL;
          hints.ai_canonname = NULL;
          hints.ai_next = NULL;
  	assert(port >= 0 && port <= 99999);
          sprintf(portstr, "%d", port);
          {
              char *trimmed_addr = host_strduptrim(srcaddr);
              retcode = getaddrinfo(trimmed_addr, portstr, &hints, &ai);
              sfree(trimmed_addr);
          }
  	if (retcode == 0) {
  	    addr = (union sockaddr_union *)ai->ai_addr;
  	    addrlen = ai->ai_addrlen;
  	}
  #else
          memset(&u,'\0',sizeof u);
          u.sin.sin_family = AF_INET;
          u.sin.sin_port = htons(port);
          u.sin.sin_addr.s_addr = inet_addr(srcaddr);
          if (u.sin.sin_addr.s_addr != (in_addr_t)(-1)) {
              /* Override localhost_only with specified listen addr. */
              ret->localhost_only = ipv4_is_loopback(u.sin.sin_addr);
          }
          addr = &u;
          addrlen = sizeof(u.sin);
          retcode = 0;
  #endif
      }
  
      if (retcode != 0) {
          memset(&u,'\0',sizeof u);
  #ifndef NO_IPV6
          if (address_family == AF_INET6) {
              u.sin6.sin6_family = AF_INET6;
              u.sin6.sin6_port = htons(port);
              if (local_host_only)
                  u.sin6.sin6_addr = in6addr_loopback;
              else
                  u.sin6.sin6_addr = in6addr_any;
              addr = &u;
              addrlen = sizeof(u.sin6);
          } else
  #endif
          {
              u.sin.sin_family = AF_INET;
              u.sin.sin_port = htons(port);
  	    if (local_host_only)
  		u.sin.sin_addr.s_addr = htonl(INADDR_LOOPBACK);
  	    else
  		u.sin.sin_addr.s_addr = htonl(INADDR_ANY);
              addr = &u;
              addrlen = sizeof(u.sin);
          }
      }
  
      retcode = bind(s, &addr->sa, addrlen);
  
  #ifndef NO_IPV6
      if (ai)
          freeaddrinfo(ai);
  #endif
  
      if (retcode < 0) {
          close(s);
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      if (listen(s, SOMAXCONN) < 0) {
          close(s);
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
  #ifndef NO_IPV6
      /*
       * If we were given ADDRTYPE_UNSPEC, we must also create an
       * IPv4 listening socket and link it to this one.
       */
      if (address_family == AF_INET6 && orig_address_family == ADDRTYPE_UNSPEC) {
          Actual_Socket other;
  
          other = (Actual_Socket) sk_newlistener(srcaddr, port, plug,
                                                 local_host_only, ADDRTYPE_IPV4);
  
          if (other) {
              if (!other->error) {
                  other->parent = ret;
                  ret->child = other;
              } else {
                  /* If we couldn't create a listening socket on IPv4 as well
                   * as IPv6, we must return an error overall. */
                  close(s);
                  sfree(ret);
                  return (Socket) other;
              }
          }
      }
  #endif
  
      ret->s = s;
  
      uxsel_tell(ret);
      add234(sktree, ret);
  
      return (Socket) ret;
  }
  
  static void sk_tcp_close(Socket sock)
  {
      Actual_Socket s = (Actual_Socket) sock;
  
      if (s->child)
          sk_tcp_close((Socket)s->child);
  
      uxsel_del(s->s);
      del234(sktree, s);
      close(s->s);
      if (s->addr)
          sk_addr_free(s->addr);
      sfree(s);
  }
  
  void *sk_getxdmdata(void *sock, int *lenp)
  {
      Actual_Socket s = (Actual_Socket) sock;
      union sockaddr_union u;
      socklen_t addrlen;
      char *buf;
      static unsigned int unix_addr = 0xFFFFFFFF;
  
      /*
       * We must check that this socket really _is_ an Actual_Socket.
       */
      if (s->fn != &tcp_fn_table)
  	return NULL;		       /* failure */
  
      addrlen = sizeof(u);
      if (getsockname(s->s, &u.sa, &addrlen) < 0)
  	return NULL;
      switch(u.sa.sa_family) {
        case AF_INET:
  	*lenp = 6;
  	buf = snewn(*lenp, char);
  	PUT_32BIT_MSB_FIRST(buf, ntohl(u.sin.sin_addr.s_addr));
  	PUT_16BIT_MSB_FIRST(buf+4, ntohs(u.sin.sin_port));
  	break;
  #ifndef NO_IPV6
      case AF_INET6:
  	*lenp = 6;
  	buf = snewn(*lenp, char);
  	if (IN6_IS_ADDR_V4MAPPED(&u.sin6.sin6_addr)) {
  	    memcpy(buf, u.sin6.sin6_addr.s6_addr + 12, 4);
  	    PUT_16BIT_MSB_FIRST(buf+4, ntohs(u.sin6.sin6_port));
  	} else
  	    /* This is stupid, but it's what XLib does. */
  	    memset(buf, 0, 6);
  	break;
  #endif
        case AF_UNIX:
  	*lenp = 6;
  	buf = snewn(*lenp, char);
  	PUT_32BIT_MSB_FIRST(buf, unix_addr--);
          PUT_16BIT_MSB_FIRST(buf+4, getpid());
  	break;
  
  	/* XXX IPV6 */
  
        default:
  	return NULL;
      }
  
      return buf;
  }
  
  /*
   * Deal with socket errors detected in try_send().
   */
  static void socket_error_callback(void *vs)
  {
      Actual_Socket s = (Actual_Socket)vs;
  
      /*
       * Just in case other socket work has caused this socket to vanish
       * or become somehow non-erroneous before this callback arrived...
       */
      if (!find234(sktree, s, NULL) || !s->pending_error)
          return;
  
      /*
       * An error has occurred on this socket. Pass it to the plug.
       */
      plug_closing(s->plug, strerror(s->pending_error), s->pending_error, 0);
  }
  
  /*
   * The function which tries to send on a socket once it's deemed
   * writable.
   */
  void try_send(Actual_Socket s)
  {
      while (s->sending_oob || bufchain_size(&s->output_data) > 0) {
  	int nsent;
  	int err;
  	void *data;
  	int len, urgentflag;
  
  	if (s->sending_oob) {
  	    urgentflag = MSG_OOB;
  	    len = s->sending_oob;
  	    data = &s->oobdata;
  	} else {
  	    urgentflag = 0;
  	    bufchain_prefix(&s->output_data, &data, &len);
  	}
  	nsent = send(s->s, data, len, urgentflag);
  	noise_ultralight(nsent);
  	if (nsent <= 0) {
  	    err = (nsent < 0 ? errno : 0);
  	    if (err == EWOULDBLOCK) {
  		/*
  		 * Perfectly normal: we've sent all we can for the moment.
  		 */
  		s->writable = FALSE;
  		return;
  	    } else {
  		/*
  		 * We unfortunately can't just call plug_closing(),
  		 * because it's quite likely that we're currently
  		 * _in_ a call from the code we'd be calling back
  		 * to, so we'd have to make half the SSH code
  		 * reentrant. Instead we flag a pending error on
  		 * the socket, to be dealt with (by calling
  		 * plug_closing()) at some suitable future moment.
  		 */
  		s->pending_error = err;
                  /*
                   * Immediately cease selecting on this socket, so that
                   * we don't tight-loop repeatedly trying to do
                   * whatever it was that went wrong.
                   */
                  uxsel_tell(s);
                  /*
                   * Arrange to be called back from the top level to
                   * deal with the error condition on this socket.
                   */
                  queue_toplevel_callback(socket_error_callback, s);
  		return;
  	    }
  	} else {
  	    if (s->sending_oob) {
  		if (nsent < len) {
  		    memmove(s->oobdata, s->oobdata+nsent, len-nsent);
  		    s->sending_oob = len - nsent;
  		} else {
  		    s->sending_oob = 0;
  		}
  	    } else {
  		bufchain_consume(&s->output_data, nsent);
  	    }
  	}
      }
  
      /*
       * If we reach here, we've finished sending everything we might
       * have needed to send. Send EOF, if we need to.
       */
      if (s->outgoingeof == EOF_PENDING) {
          shutdown(s->s, SHUT_WR);
          s->outgoingeof = EOF_SENT;
      }
  
      /*
       * Also update the select status, because we don't need to select
       * for writing any more.
       */
      uxsel_tell(s);
  }
  
  static int sk_tcp_write(Socket sock, const char *buf, int len)
  {
      Actual_Socket s = (Actual_Socket) sock;
  
      assert(s->outgoingeof == EOF_NO);
  
      /*
       * Add the data to the buffer list on the socket.
       */
      bufchain_add(&s->output_data, buf, len);
  
      /*
       * Now try sending from the start of the buffer list.
       */
      if (s->writable)
  	try_send(s);
  
      /*
       * Update the select() status to correctly reflect whether or
       * not we should be selecting for write.
       */
      uxsel_tell(s);
  
      return bufchain_size(&s->output_data);
  }
  
  static int sk_tcp_write_oob(Socket sock, const char *buf, int len)
  {
      Actual_Socket s = (Actual_Socket) sock;
  
      assert(s->outgoingeof == EOF_NO);
  
      /*
       * Replace the buffer list on the socket with the data.
       */
      bufchain_clear(&s->output_data);
      assert(len <= sizeof(s->oobdata));
      memcpy(s->oobdata, buf, len);
      s->sending_oob = len;
  
      /*
       * Now try sending from the start of the buffer list.
       */
      if (s->writable)
  	try_send(s);
  
      /*
       * Update the select() status to correctly reflect whether or
       * not we should be selecting for write.
       */
      uxsel_tell(s);
  
      return s->sending_oob;
  }
  
  static void sk_tcp_write_eof(Socket sock)
  {
      Actual_Socket s = (Actual_Socket) sock;
  
      assert(s->outgoingeof == EOF_NO);
  
      /*
       * Mark the socket as pending outgoing EOF.
       */
      s->outgoingeof = EOF_PENDING;
  
      /*
       * Now try sending from the start of the buffer list.
       */
      if (s->writable)
  	try_send(s);
  
      /*
       * Update the select() status to correctly reflect whether or
       * not we should be selecting for write.
       */
      uxsel_tell(s);
  }
  
  static int net_select_result(int fd, int event)
  {
      int ret;
      char buf[20480];		       /* nice big buffer for plenty of speed */
      Actual_Socket s;
      u_long atmark;
  
      /* Find the Socket structure */
      s = find234(sktree, &fd, cmpforsearch);
      if (!s)
  	return 1;		       /* boggle */
  
      noise_ultralight(event);
  
      switch (event) {
        case 4:			       /* exceptional */
  	if (!s->oobinline) {
  	    /*
  	     * On a non-oobinline socket, this indicates that we
  	     * can immediately perform an OOB read and get back OOB
  	     * data, which we will send to the back end with
  	     * type==2 (urgent data).
  	     */
  	    ret = recv(s->s, buf, sizeof(buf), MSG_OOB);
  	    noise_ultralight(ret);
  	    if (ret <= 0) {
                  return plug_closing(s->plug,
  				    ret == 0 ? "Internal networking trouble" :
  				    strerror(errno), errno, 0);
  	    } else {
                  /*
                   * Receiving actual data on a socket means we can
                   * stop falling back through the candidate
                   * addresses to connect to.
                   */
                  if (s->addr) {
                      sk_addr_free(s->addr);
                      s->addr = NULL;
                  }
  		return plug_receive(s->plug, 2, buf, ret);
  	    }
  	}
  
  	/*
  	 * If we reach here, this is an oobinline socket, which
  	 * means we should set s->oobpending and then deal with it
  	 * when we get called for the readability event (which
  	 * should also occur).
  	 */
  	s->oobpending = TRUE;
          break;
        case 1: 			       /* readable; also acceptance */
  	if (s->listener) {
  	    /*
  	     * On a listening socket, the readability event means a
  	     * connection is ready to be accepted.
  	     */
  	    union sockaddr_union su;
  	    socklen_t addrlen = sizeof(su);
              accept_ctx_t actx;
  	    int t;  /* socket of connection */
  
  	    memset(&su, 0, addrlen);
  	    t = accept(s->s, &su.sa, &addrlen);
  	    if (t < 0) {
  		break;
  	    }
  
              nonblock(t);
              actx.i = t;
  
  	    if ((!s->addr || s->addr->superfamily != UNIX) &&
                  s->localhost_only && !sockaddr_is_loopback(&su.sa)) {
  		close(t);	       /* someone let nonlocal through?! */
  	    } else if (plug_accepting(s->plug, sk_tcp_accept, actx)) {
  		close(t);	       /* denied or error */
  	    }
  	    break;
  	}
  
  	/*
  	 * If we reach here, this is not a listening socket, so
  	 * readability really means readability.
  	 */
  
  	/* In the case the socket is still frozen, we don't even bother */
  	if (s->frozen)
  	    break;
  
  	/*
  	 * We have received data on the socket. For an oobinline
  	 * socket, this might be data _before_ an urgent pointer,
  	 * in which case we send it to the back end with type==1
  	 * (data prior to urgent).
  	 */
  	if (s->oobinline && s->oobpending) {
  	    atmark = 1;
  	    if (ioctl(s->s, SIOCATMARK, &atmark) == 0 && atmark)
  		s->oobpending = FALSE; /* clear this indicator */
  	} else
  	    atmark = 1;
  
  	ret = recv(s->s, buf, s->oobpending ? 1 : sizeof(buf), 0);
  	noise_ultralight(ret);
  	if (ret < 0) {
  	    if (errno == EWOULDBLOCK) {
  		break;
  	    }
  	}
  	if (ret < 0) {
              /*
               * An error at this point _might_ be an error reported
               * by a non-blocking connect(). So before we return a
               * panic status to the user, let's just see whether
               * that's the case.
               */
              int err = errno;
  	    if (s->addr) {
  		plug_log(s->plug, 1, s->addr, s->port, strerror(err), err);
  		while (s->addr && sk_nextaddr(s->addr, &s->step)) {
  		    err = try_connect(s);
  		}
  	    }
              if (err != 0)
                  return plug_closing(s->plug, strerror(err), err, 0);
  	} else if (0 == ret) {
              s->incomingeof = TRUE;     /* stop trying to read now */
              uxsel_tell(s);
  	    return plug_closing(s->plug, NULL, 0, 0);
  	} else {
              /*
               * Receiving actual data on a socket means we can
               * stop falling back through the candidate
               * addresses to connect to.
               */
              if (s->addr) {
                  sk_addr_free(s->addr);
                  s->addr = NULL;
              }
  	    return plug_receive(s->plug, atmark ? 0 : 1, buf, ret);
  	}
  	break;
        case 2:			       /* writable */
  	if (!s->connected) {
  	    /*
  	     * select() reports a socket as _writable_ when an
  	     * asynchronous connection is completed.
  	     */
  	    s->connected = s->writable = 1;
  	    uxsel_tell(s);
  	    break;
  	} else {
  	    int bufsize_before, bufsize_after;
  	    s->writable = 1;
  	    bufsize_before = s->sending_oob + bufchain_size(&s->output_data);
  	    try_send(s);
  	    bufsize_after = s->sending_oob + bufchain_size(&s->output_data);
  	    if (bufsize_after < bufsize_before)
  		plug_sent(s->plug, bufsize_after);
  	}
  	break;
      }
  
      return 1;
  }
  
  /*
   * Special error values are returned from sk_namelookup and sk_new
   * if there's a problem. These functions extract an error message,
   * or return NULL if there's no problem.
   */
  const char *sk_addr_error(SockAddr addr)
  {
      return addr->error;
  }
  static const char *sk_tcp_socket_error(Socket sock)
  {
      Actual_Socket s = (Actual_Socket) sock;
      return s->error;
  }
  
  static void sk_tcp_set_frozen(Socket sock, int is_frozen)
  {
      Actual_Socket s = (Actual_Socket) sock;
      if (s->frozen == is_frozen)
  	return;
      s->frozen = is_frozen;
      uxsel_tell(s);
  }
  
  static char *sk_tcp_peer_info(Socket sock)
  {
      Actual_Socket s = (Actual_Socket) sock;
      struct sockaddr_storage addr;
      socklen_t addrlen = sizeof(addr);
      char buf[INET6_ADDRSTRLEN];
  
      if (getpeername(s->s, (struct sockaddr *)&addr, &addrlen) < 0)
          return NULL;
      if (addr.ss_family == AF_INET) {
          return dupprintf
              ("%s:%d",
               inet_ntoa(((struct sockaddr_in *)&addr)->sin_addr),
               (int)ntohs(((struct sockaddr_in *)&addr)->sin_port));
  #ifndef NO_IPV6
      } else if (addr.ss_family == AF_INET6) {
          return dupprintf
              ("[%s]:%d",
               inet_ntop(AF_INET6, &((struct sockaddr_in6 *)&addr)->sin6_addr,
                         buf, sizeof(buf)),
               (int)ntohs(((struct sockaddr_in6 *)&addr)->sin6_port));
  #endif
      } else if (addr.ss_family == AF_UNIX) {
          /*
           * For Unix sockets, the source address is unlikely to be
           * helpful. Instead, we try SO_PEERCRED and try to get the
           * source pid.
           */
          int pid, uid, gid;
          if (so_peercred(s->s, &pid, &uid, &gid)) {
              char uidbuf[64], gidbuf[64];
              sprintf(uidbuf, "%d", uid);
              sprintf(gidbuf, "%d", gid);
              struct passwd *pw = getpwuid(uid);
              struct group *gr = getgrgid(gid);
              return dupprintf("pid %d (%s:%s)", pid,
                               pw ? pw->pw_name : uidbuf,
                               gr ? gr->gr_name : gidbuf);
          }
          return NULL;
      } else {
          return NULL;
      }
  }
  
  static void uxsel_tell(Actual_Socket s)
  {
      int rwx = 0;
      if (!s->pending_error) {
          if (s->listener) {
              rwx |= 1;                  /* read == accept */
          } else {
              if (!s->connected)
                  rwx |= 2;              /* write == connect */
              if (s->connected && !s->frozen && !s->incomingeof)
                  rwx |= 1 | 4;          /* read, except */
              if (bufchain_size(&s->output_data))
                  rwx |= 2;              /* write */
          }
      }
      uxsel_set(s->s, rwx, net_select_result);
  }
  
  int net_service_lookup(char *service)
  {
      struct servent *se;
      se = getservbyname(service, NULL);
      if (se != NULL)
  	return ntohs(se->s_port);
      else
  	return 0;
  }
  
  char *get_hostname(void)
  {
      int len = 128;
      char *hostname = NULL;
      do {
  	len *= 2;
  	hostname = sresize(hostname, len, char);
  	if ((gethostname(hostname, len) < 0) &&
  	    (errno != ENAMETOOLONG)) {
  	    sfree(hostname);
  	    hostname = NULL;
  	    break;
  	}
      } while (strlen(hostname) >= len-1);
      return hostname;
  }
  
  SockAddr platform_get_x11_unix_address(const char *sockpath, int displaynum)
  {
      SockAddr ret = snew(struct SockAddr_tag);
      int n;
  
      memset(ret, 0, sizeof *ret);
      ret->superfamily = UNIX;
      /*
       * In special circumstances (notably Mac OS X Leopard), we'll
       * have been passed an explicit Unix socket path.
       */
      if (sockpath) {
  	n = snprintf(ret->hostname, sizeof ret->hostname,
  		     "%s", sockpath);
      } else {
  	n = snprintf(ret->hostname, sizeof ret->hostname,
  		     "%s%d", X11_UNIX_PATH, displaynum);
      }
  
      if (n < 0)
  	ret->error = "snprintf failed";
      else if (n >= sizeof ret->hostname)
  	ret->error = "X11 UNIX name too long";
  
  #ifndef NO_IPV6
      ret->ais = NULL;
  #else
      ret->addresses = NULL;
      ret->naddresses = 0;
  #endif
      ret->refcount = 1;
      return ret;
  }
  
  SockAddr unix_sock_addr(const char *path)
  {
      SockAddr ret = snew(struct SockAddr_tag);
      int n;
  
      memset(ret, 0, sizeof *ret);
      ret->superfamily = UNIX;
      n = snprintf(ret->hostname, sizeof ret->hostname, "%s", path);
  
      if (n < 0)
  	ret->error = "snprintf failed";
      else if (n >= sizeof ret->hostname)
  	ret->error = "socket pathname too long";
  
  #ifndef NO_IPV6
      ret->ais = NULL;
  #else
      ret->addresses = NULL;
      ret->naddresses = 0;
  #endif
      ret->refcount = 1;
      return ret;
  }
  
  Socket new_unix_listener(SockAddr listenaddr, Plug plug)
  {
      int s;
      union sockaddr_union u;
      union sockaddr_union *addr;
      int addrlen;
      Actual_Socket ret;
      int retcode;
  
      /*
       * Create Socket structure.
       */
      ret = snew(struct Socket_tag);
      ret->fn = &tcp_fn_table;
      ret->error = NULL;
      ret->plug = plug;
      bufchain_init(&ret->output_data);
      ret->writable = 0;		       /* to start with */
      ret->sending_oob = 0;
      ret->frozen = 0;
      ret->localhost_only = TRUE;
      ret->pending_error = 0;
      ret->parent = ret->child = NULL;
      ret->oobpending = FALSE;
      ret->outgoingeof = EOF_NO;
      ret->incomingeof = FALSE;
      ret->listener = 1;
      ret->addr = listenaddr;
      ret->s = -1;
  
      assert(listenaddr->superfamily == UNIX);
  
      /*
       * Open socket.
       */
      s = socket(AF_UNIX, SOCK_STREAM, 0);
      if (s < 0) {
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      cloexec(s);
  
      ret->oobinline = 0;
  
      memset(&u, '\0', sizeof(u));
      u.su.sun_family = AF_UNIX;
      strncpy(u.su.sun_path, listenaddr->hostname, sizeof(u.su.sun_path)-1);
      addr = &u;
      addrlen = sizeof(u.su);
  
      if (unlink(u.su.sun_path) < 0 && errno != ENOENT) {
          close(s);
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      retcode = bind(s, &addr->sa, addrlen);
      if (retcode < 0) {
          close(s);
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      if (listen(s, SOMAXCONN) < 0) {
          close(s);
  	ret->error = strerror(errno);
  	return (Socket) ret;
      }
  
      ret->s = s;
  
      uxsel_tell(ret);
      add234(sktree, ret);
  
      return (Socket) ret;
  }
  