winnet.c

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	    int got_addr = 0;
	    a.sin_family = AF_INET;

	    /*
	     * Bind to source address. First try an explicitly
	     * specified one...
	     */
	    if (srcaddr) {
		a.sin_addr.s_addr = p_inet_addr(srcaddr);
		if (a.sin_addr.s_addr != INADDR_NONE) {
		    /* Override localhost_only with specified listen addr. */
		    ret->localhost_only = ipv4_is_loopback(a.sin_addr);
		    got_addr = 1;
		}
	    }

	    /*
	     * ... and failing that, go with one of the standard ones.
	     */
	    if (!got_addr) {
		if (local_host_only)
		    a.sin_addr.s_addr = p_htonl(INADDR_LOOPBACK);
		else
		    a.sin_addr.s_addr = p_htonl(INADDR_ANY);
	    }

	    a.sin_port = p_htons((short)port);
	}
#ifdef IPV6
	retcode = p_bind(s, (addr->family == AF_INET6 ?
			   (struct sockaddr *) &a6 :
			   (struct sockaddr *) &a),
		       (addr->family ==
			AF_INET6 ? sizeof(a6) : sizeof(a)));
#else
	retcode = p_bind(s, (struct sockaddr *) &a, sizeof(a));
#endif
	if (retcode != SOCKET_ERROR) {
	    err = 0;
	} else {
	    err = p_WSAGetLastError();
	}

    if (err) {
	ret->error = winsock_error_string(err);
	return (Socket) ret;
    }


    if (p_listen(s, SOMAXCONN) == SOCKET_ERROR) {
        p_closesocket(s);
	ret->error = winsock_error_string(err);
	return (Socket) ret;
    }

    /* Set up a select mechanism. This could be an AsyncSelect on a
     * window, or an EventSelect on an event object. */
    errstr = do_select(s, 1);
    if (errstr) {
	ret->error = errstr;
	return (Socket) ret;
    }

    add234(sktree, ret);

    return (Socket) ret;
}

static void sk_tcp_close(Socket sock)
{
    extern char *do_select(SOCKET skt, int startup);
    Actual_Socket s = (Actual_Socket) sock;

    del234(sktree, s);
    do_select(s->s, 0);
    p_closesocket(s->s);
    sfree(s);
}

/*
 * 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;
	DWORD 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 = p_send(s->s, data, len, urgentflag);
	noise_ultralight(nsent);
	if (nsent <= 0) {
	    err = (nsent < 0 ? p_WSAGetLastError() : 0);
	    if ((err < WSABASEERR && nsent < 0) || err == WSAEWOULDBLOCK) {
		/*
		 * Perfectly normal: we've sent all we can for the moment.
		 * 
		 * (Some WinSock send() implementations can return
		 * <0 but leave no sensible error indication -
		 * WSAGetLastError() is called but returns zero or
		 * a small number - so we check that case and treat
		 * it just like WSAEWOULDBLOCK.)
		 */
		s->writable = FALSE;
		return;
	    } else if (nsent == 0 ||
		       err == WSAECONNABORTED || err == WSAECONNRESET) {
		/*
		 * If send() returns CONNABORTED or CONNRESET, 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;
		return;
	    } else {
		/* We're inside the Windows frontend here, so we know
		 * that the frontend handle is unnecessary. */
		logevent(NULL, winsock_error_string(err));
		fatalbox("%s", winsock_error_string(err));
	    }
	} 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);
	    }
	}
    }
}

static int sk_tcp_write(Socket sock, const char *buf, int len)
{
    Actual_Socket s = (Actual_Socket) sock;

    /*
     * 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);

    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;

    /*
     * 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);

    return s->sending_oob;
}

int select_result(WPARAM wParam, LPARAM lParam)
{
    int ret, open;
    DWORD err;
    char buf[20480];		       /* nice big buffer for plenty of speed */
    Actual_Socket s;
    u_long atmark;

    /* wParam is the socket itself */

    if (wParam == 0)
	return 1;		       /* boggle */

    s = find234(sktree, (void *) wParam, cmpforsearch);
    if (!s)
	return 1;		       /* boggle */

    if ((err = WSAGETSELECTERROR(lParam)) != 0) {
	/*
	 * An error has occurred on this socket. Pass it to the
	 * plug.
	 */
	return plug_closing(s->plug, winsock_error_string(err), err, 0);
    }

    noise_ultralight(lParam);

    switch (WSAGETSELECTEVENT(lParam)) {
      case FD_CONNECT:
	s->connected = s->writable = 1;
	break;
      case FD_READ:
	/* In the case the socket is still frozen, we don't even bother */
	if (s->frozen) {
	    s->frozen_readable = 1;
	    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) {
	    atmark = 1;
	    p_ioctlsocket(s->s, SIOCATMARK, &atmark);
	    /*
	     * Avoid checking the return value from ioctlsocket(),
	     * on the grounds that some WinSock wrappers don't
	     * support it. If it does nothing, we get atmark==1,
	     * which is equivalent to `no OOB pending', so the
	     * effect will be to non-OOB-ify any OOB data.
	     */
	} else
	    atmark = 1;

	ret = p_recv(s->s, buf, sizeof(buf), 0);
	noise_ultralight(ret);
	if (ret < 0) {
	    err = p_WSAGetLastError();
	    if (err == WSAEWOULDBLOCK) {
		break;
	    }
	}
	if (ret < 0) {
	    return plug_closing(s->plug, winsock_error_string(err), err,
				0);
	} else if (0 == ret) {
	    return plug_closing(s->plug, NULL, 0, 0);
	} else {
	    return plug_receive(s->plug, atmark ? 0 : 1, buf, ret);
	}
	break;
      case FD_OOB:
	/*
	 * This will only happen on a non-oobinline socket. It
	 * 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 = p_recv(s->s, buf, sizeof(buf), MSG_OOB);
	noise_ultralight(ret);
	if (ret <= 0) {
	    char *str = (ret == 0 ? "Internal networking trouble" :
			 winsock_error_string(p_WSAGetLastError()));
	    /* We're inside the Windows frontend here, so we know
	     * that the frontend handle is unnecessary. */
	    logevent(NULL, str);
	    fatalbox("%s", str);
	} else {
	    return plug_receive(s->plug, 2, buf, ret);
	}
	break;
      case FD_WRITE:
	{
	    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;
      case FD_CLOSE:
	/* Signal a close on the socket. First read any outstanding data. */
	open = 1;
	do {
	    ret = p_recv(s->s, buf, sizeof(buf), 0);
	    if (ret < 0) {
		err = p_WSAGetLastError();
		if (err == WSAEWOULDBLOCK)
		    break;
		return plug_closing(s->plug, winsock_error_string(err),
				    err, 0);
	    } else {
		if (ret)
		    open &= plug_receive(s->plug, 0, buf, ret);
		else
		    open &= plug_closing(s->plug, NULL, 0, 0);
	    }
	} while (ret > 0);
	return open;
       case FD_ACCEPT:
	{
	    struct sockaddr_in isa;
	    int addrlen = sizeof(struct sockaddr_in);
	    SOCKET t;  /* socket of connection */

	    memset(&isa, 0, sizeof(struct sockaddr_in));
	    err = 0;
	    t = p_accept(s->s,(struct sockaddr *)&isa,&addrlen);
	    if (t == INVALID_SOCKET)
	    {
		err = p_WSAGetLastError();
		if (err == WSATRY_AGAIN)
		    break;
	    }

	    if (s->localhost_only && !ipv4_is_local_addr(isa.sin_addr)) {
		p_closesocket(t);      /* dodgy WinSock let nonlocal through */
	    } else if (plug_accepting(s->plug, (void*)t)) {
		p_closesocket(t);      /* denied or error */
	    }
	}
    }

    return 1;
}

/*
 * Deal with socket errors detected in try_send().
 */
void net_pending_errors(void)
{
    int i;
    Actual_Socket s;

    /*
     * This might be a fiddly business, because it's just possible
     * that handling a pending error on one socket might cause
     * others to be closed. (I can't think of any reason this might
     * happen in current SSH implementation, but to maintain
     * generality of this network layer I'll assume the worst.)
     * 
     * So what we'll do is search the socket list for _one_ socket
     * with a pending error, and then handle it, and then search
     * the list again _from the beginning_. Repeat until we make a
     * pass with no socket errors present. That way we are
     * protected against the socket list changing under our feet.
     */

    do {
	for (i = 0; (s = index234(sktree, i)) != NULL; i++) {
	    if (s->pending_error) {
		/*
		 * An error has occurred on this socket. Pass it to the
		 * plug.
		 */
		plug_closing(s->plug,
			     winsock_error_string(s->pending_error),
			     s->pending_error, 0);
		break;
	    }
	}
    } while (s);
}

/*
 * Each socket abstraction contains a `void *' private field in
 * which the client can keep state.
 */
static void sk_tcp_set_private_ptr(Socket sock, void *ptr)
{
    Actual_Socket s = (Actual_Socket) sock;
    s->private_ptr = ptr;
}

static void *sk_tcp_get_private_ptr(Socket sock)
{
    Actual_Socket s = (Actual_Socket) sock;
    return s->private_ptr;
}

/*
 * 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;
    if (!is_frozen && s->frozen_readable) {
	char c;
	p_recv(s->s, &c, 1, MSG_PEEK);
    }
    s->frozen_readable = 0;
}

/*
 * For Plink: enumerate all sockets currently active.
 */
SOCKET first_socket(int *state)
{
    Actual_Socket s;
    *state = 0;
    s = index234(sktree, (*state)++);
    return s ? s->s : INVALID_SOCKET;
}

SOCKET next_socket(int *state)
{
    Actual_Socket s = index234(sktree, (*state)++);
    return s ? s->s : INVALID_SOCKET;
}

int net_service_lookup(char *service)
{
    struct servent *se;
    se = p_getservbyname(service, NULL);
    if (se != NULL)
	return p_ntohs(se->s_port);
    else
	return 0;
}

SockAddr platform_get_x11_unix_address(int displaynum, char **canonicalname)
{
    SockAddr ret = snew(struct SockAddr_tag);
    memset(ret, 0, sizeof(struct SockAddr_tag));
    ret->error = "unix sockets not supported on this platform";
    return ret;
}