]> asedeno.scripts.mit.edu Git - PuTTY.git/blobdiff - portfwd.c
first pass
[PuTTY.git] / portfwd.c
index 00132ec6fa77578dea95e6ff2ede3cf41cb1218c..8a73a182d55329ab33a0ab763ff6d3c89d1cac39 100644 (file)
--- a/portfwd.c
+++ b/portfwd.c
@@ -1,3 +1,7 @@
+/*
+ * SSH port forwarding.
+ */
+
 #include <stdio.h>
 #include <stdlib.h>
 
 #define TRUE 1
 #endif
 
-#define GET_32BIT_LSB_FIRST(cp) \
-  (((unsigned long)(unsigned char)(cp)[0]) | \
-  ((unsigned long)(unsigned char)(cp)[1] << 8) | \
-  ((unsigned long)(unsigned char)(cp)[2] << 16) | \
-  ((unsigned long)(unsigned char)(cp)[3] << 24))
-
-#define PUT_32BIT_LSB_FIRST(cp, value) ( \
-  (cp)[0] = (value), \
-  (cp)[1] = (value) >> 8, \
-  (cp)[2] = (value) >> 16, \
-  (cp)[3] = (value) >> 24 )
-
-#define GET_16BIT_LSB_FIRST(cp) \
-  (((unsigned long)(unsigned char)(cp)[0]) | \
-  ((unsigned long)(unsigned char)(cp)[1] << 8))
-
-#define PUT_16BIT_LSB_FIRST(cp, value) ( \
-  (cp)[0] = (value), \
-  (cp)[1] = (value) >> 8 )
-
-#define GET_32BIT_MSB_FIRST(cp) \
-  (((unsigned long)(unsigned char)(cp)[0] << 24) | \
-  ((unsigned long)(unsigned char)(cp)[1] << 16) | \
-  ((unsigned long)(unsigned char)(cp)[2] << 8) | \
-  ((unsigned long)(unsigned char)(cp)[3]))
-
-#define PUT_32BIT_MSB_FIRST(cp, value) ( \
-  (cp)[0] = (value) >> 24, \
-  (cp)[1] = (value) >> 16, \
-  (cp)[2] = (value) >> 8, \
-  (cp)[3] = (value) )
-
-#define GET_16BIT_MSB_FIRST(cp) \
-  (((unsigned long)(unsigned char)(cp)[0] << 8) | \
-  ((unsigned long)(unsigned char)(cp)[1]))
-
-#define PUT_16BIT_MSB_FIRST(cp, value) ( \
-  (cp)[0] = (value) >> 8, \
-  (cp)[1] = (value) )
-
-struct PFwdPrivate {
+struct PortForwarding {
     const struct plug_function_table *fn;
     /* the above variable absolutely *must* be the first in this structure */
-    void *c;                          /* (channel) data used by ssh.c */
+    struct ssh_channel *c;        /* channel structure held by ssh.c */
     void *backhandle;                 /* instance of SSH backend itself */
     /* Note that backhandle need not be filled in if c is non-NULL */
     Socket s;
@@ -63,19 +27,21 @@ struct PFwdPrivate {
     /*
      * `dynamic' does double duty. It's set to 0 for an ordinary
      * forwarded port, and nonzero for SOCKS-style dynamic port
-     * forwarding; but it also represents the state of the SOCKS
-     * exchange.
+     * forwarding; but the nonzero values are also a state machine
+     * tracking where the SOCKS exchange has got to.
      */
     int dynamic;
     /*
      * `hostname' and `port' are the real hostname and port, once
-     * we know what we're connecting to; they're unused for this
-     * purpose while conducting a local SOCKS exchange, which means
-     * we can also use them as a buffer and pointer for reading
-     * data from the SOCKS client.
+     * we know what we're connecting to.
      */
-    char hostname[256+8];
+    char *hostname;
     int port;
+    /*
+     * `socksbuf' is the buffer we use to accumulate a SOCKS request.
+     */
+    char *socksbuf;
+    int sockslen, sockssize;
     /*
      * When doing dynamic port forwarding, we can receive
      * connection data before we are actually able to send it; so
@@ -86,70 +52,170 @@ struct PFwdPrivate {
     int buflen;
 };
 
+struct PortListener {
+    const struct plug_function_table *fn;
+    /* the above variable absolutely *must* be the first in this structure */
+    void *backhandle;                 /* instance of SSH backend itself */
+    Socket s;
+    /*
+     * `dynamic' is set to 0 for an ordinary forwarded port, and
+     * nonzero for SOCKS-style dynamic port forwarding.
+     */
+    int dynamic;
+    /*
+     * `hostname' and `port' are the real hostname and port, for
+     * ordinary forwardings.
+     */
+    char *hostname;
+    int port;
+};
+
+static struct PortForwarding *new_portfwd_state(void)
+{
+    struct PortForwarding *pf = snew(struct PortForwarding);
+    pf->hostname = NULL;
+    pf->socksbuf = NULL;
+    pf->sockslen = pf->sockssize = 0;
+    pf->buffer = NULL;
+    return pf;
+}
+
+static void free_portfwd_state(struct PortForwarding *pf)
+{
+    if (!pf)
+        return;
+    sfree(pf->hostname);
+    sfree(pf->socksbuf);
+    sfree(pf->buffer);
+    sfree(pf);
+}
+
+static struct PortListener *new_portlistener_state(void)
+{
+    struct PortListener *pl = snew(struct PortListener);
+    pl->hostname = NULL;
+    return pl;
+}
+
+static void free_portlistener_state(struct PortListener *pl)
+{
+    if (!pl)
+        return;
+    sfree(pl->hostname);
+    sfree(pl);
+}
+
+static void pfd_log(Plug plug, int type, SockAddr addr, int port,
+                   const char *error_msg, int error_code)
+{
+    /* we have to dump these since we have no interface to logging.c */
+}
+
+static void pfl_log(Plug plug, int type, SockAddr addr, int port,
+                   const char *error_msg, int error_code)
+{
+    /* we have to dump these since we have no interface to logging.c */
+}
+
 static int pfd_closing(Plug plug, const char *error_msg, int error_code,
                       int calling_back)
 {
-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
+
+    if (error_msg) {
+        /*
+         * Socket error. Slam the connection instantly shut.
+         */
+        if (pf->c) {
+            sshfwd_unclean_close(pf->c, error_msg);
+        } else {
+            /*
+             * We might not have an SSH channel, if a socket error
+             * occurred during SOCKS negotiation. If not, we must
+             * clean ourself up without sshfwd_unclean_close's call
+             * back to pfd_close.
+             */
+            pfd_close(pf);
+        }
+    } else {
+        /*
+         * Ordinary EOF received on socket. Send an EOF on the SSH
+         * channel.
+         */
+        if (pf->c)
+            sshfwd_write_eof(pf->c);
+    }
 
-    /*
-     * We have no way to communicate down the forwarded connection,
-     * so if an error occurred on the socket, we just ignore it
-     * and treat it like a proper close.
-     */
-    if (pr->c)
-       sshfwd_close(pr->c);
-    pfd_close(pr->s);
     return 1;
 }
 
+static int pfl_closing(Plug plug, const char *error_msg, int error_code,
+                      int calling_back)
+{
+    struct PortListener *pl = (struct PortListener *) plug;
+    pfl_terminate(pl);
+    return 1;
+}
+
+static void wrap_send_port_open(void *channel, const char *hostname, int port,
+                                Socket s)
+{
+    char *peerinfo, *description;
+    peerinfo = sk_peer_info(s);
+    if (peerinfo) {
+        description = dupprintf("forwarding from %s", peerinfo);
+        sfree(peerinfo);
+    } else {
+        description = dupstr("forwarding");
+    }
+    ssh_send_port_open(channel, hostname, port, description);
+    sfree(description);
+}
+
 static int pfd_receive(Plug plug, int urgent, char *data, int len)
 {
-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
-    if (pr->dynamic) {
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
+    if (pf->dynamic) {
        while (len--) {
-           if (pr->port >= lenof(pr->hostname)) {
-               if ((pr->dynamic >> 12) == 4) {
-                   /* Send back a SOCKS 4 error before closing. */
-                   char data[8];
-                   memset(data, 0, sizeof(data));
-                   data[1] = 91;      /* generic `request rejected' */
-                   sk_write(pr->s, data, 8);
-               }
-               pfd_close(pr->s);
-               return 1;
+           if (pf->sockslen >= pf->sockssize) {
+                pf->sockssize = pf->sockslen * 5 / 4 + 256;
+                pf->socksbuf = sresize(pf->socksbuf, pf->sockssize, char);
            }
-           pr->hostname[pr->port++] = *data++;
+           pf->socksbuf[pf->sockslen++] = *data++;
 
            /*
             * Now check what's in the buffer to see if it's a
             * valid and complete message in the SOCKS exchange.
             */
-           if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 4) &&
-               pr->hostname[0] == 4) {
+           if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 4) &&
+               pf->socksbuf[0] == 4) {
                /*
                 * SOCKS 4.
                 */
-               if (pr->dynamic == 1)
-                   pr->dynamic = 0x4000;
-               if (pr->port < 2) continue;/* don't have command code yet */
-               if (pr->hostname[1] != 1) {
+               if (pf->dynamic == 1)
+                   pf->dynamic = 0x4000;
+               if (pf->sockslen < 2)
+                    continue;        /* don't have command code yet */
+               if (pf->socksbuf[1] != 1) {
+                   /* Not CONNECT. */
                    /* Send back a SOCKS 4 error before closing. */
                    char data[8];
                    memset(data, 0, sizeof(data));
                    data[1] = 91;      /* generic `request rejected' */
-                   sk_write(pr->s, data, 8);
-                   pfd_close(pr->s);
+                   sk_write(pf->s, data, 8);
+                   pfd_close(pf);
                    return 1;
                }
-               if (pr->port < 8) continue;   /* haven't started username */
-               if (pr->hostname[pr->port-1] != 0)
-                   continue;          /* haven't _finished_ username */
+               if (pf->sockslen <= 8)
+                    continue;      /* haven't started user/hostname */
+               if (pf->socksbuf[pf->sockslen-1] != 0)
+                   continue;          /* haven't _finished_ user/hostname */
                /*
                 * Now we have a full SOCKS 4 request. Check it to
                 * see if it's a SOCKS 4A request.
                 */
-               if (pr->hostname[4] == 0 && pr->hostname[5] == 0 &&
-                   pr->hostname[6] == 0 && pr->hostname[7] != 0) {
+               if (pf->socksbuf[4] == 0 && pf->socksbuf[5] == 0 &&
+                   pf->socksbuf[6] == 0 && pf->socksbuf[7] != 0) {
                    /*
                     * It's SOCKS 4A. So if we haven't yet
                     * collected the host name, we should continue
@@ -157,17 +223,19 @@ static int pfd_receive(Plug plug, int urgent, char *data, int len)
                     * have, we can go ahead.
                     */
                    int len;
-                   if (pr->dynamic == 0x4000) {
-                       pr->dynamic = 0x4001;
-                       pr->port = 8;      /* reset buffer to overwrite name */
+                   if (pf->dynamic == 0x4000) {
+                       pf->dynamic = 0x4001;
+                       pf->sockslen = 8; /* reset buffer to overwrite name */
                        continue;
                    }
-                   pr->hostname[0] = 0;   /* reply version code */
-                   pr->hostname[1] = 90;   /* request granted */
-                   sk_write(pr->s, pr->hostname, 8);
-                   len= pr->port;
-                   pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
-                   memmove(pr->hostname, pr->hostname + 8, len);
+                   pf->socksbuf[0] = 0;   /* reply version code */
+                   pf->socksbuf[1] = 90;   /* request granted */
+                   sk_write(pf->s, pf->socksbuf, 8);
+                   len = pf->sockslen - 8;
+                   pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
+                    pf->hostname = snewn(len+1, char);
+                    pf->hostname[len] = '\0';
+                   memcpy(pf->hostname, pf->socksbuf + 8, len);
                    goto connect;
                } else {
                    /*
@@ -175,107 +243,125 @@ static int pfd_receive(Plug plug, int urgent, char *data, int len)
                     * the IP address into the hostname string and
                     * then just go.
                     */
-                   pr->hostname[0] = 0;   /* reply version code */
-                   pr->hostname[1] = 90;   /* request granted */
-                   sk_write(pr->s, pr->hostname, 8);
-                   pr->port = GET_16BIT_MSB_FIRST(pr->hostname+2);
-                   sprintf(pr->hostname, "%d.%d.%d.%d",
-                           (unsigned char)pr->hostname[4],
-                           (unsigned char)pr->hostname[5],
-                           (unsigned char)pr->hostname[6],
-                           (unsigned char)pr->hostname[7]);
+                   pf->socksbuf[0] = 0;   /* reply version code */
+                   pf->socksbuf[1] = 90;   /* request granted */
+                   sk_write(pf->s, pf->socksbuf, 8);
+                   pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+2);
+                   pf->hostname = dupprintf("%d.%d.%d.%d",
+                                             (unsigned char)pf->socksbuf[4],
+                                             (unsigned char)pf->socksbuf[5],
+                                             (unsigned char)pf->socksbuf[6],
+                                             (unsigned char)pf->socksbuf[7]);
                    goto connect;
                }
            }
 
-           if ((pr->dynamic == 1 || (pr->dynamic >> 12) == 5) &&
-               pr->hostname[0] == 5) {
+           if ((pf->dynamic == 1 || (pf->dynamic >> 12) == 5) &&
+               pf->socksbuf[0] == 5) {
                /*
                 * SOCKS 5.
                 */
-               if (pr->dynamic == 1)
-                   pr->dynamic = 0x5000;
+               if (pf->dynamic == 1)
+                   pf->dynamic = 0x5000;
 
-               if (pr->dynamic == 0x5000) {
+               if (pf->dynamic == 0x5000) {
                    int i, method;
                    char data[2];
                    /*
                     * We're receiving a set of method identifiers.
                     */
-                   if (pr->port < 2) continue;/* no method count yet */
-                   if (pr->port < 2 + (unsigned char)pr->hostname[1])
+                   if (pf->sockslen < 2)
+                        continue;      /* no method count yet */
+                   if (pf->sockslen < 2 + (unsigned char)pf->socksbuf[1])
                        continue;      /* no methods yet */
                    method = 0xFF;     /* invalid */
-                   for (i = 0; i < (unsigned char)pr->hostname[1]; i++)
-                       if (pr->hostname[2+i] == 0) {
+                   for (i = 0; i < (unsigned char)pf->socksbuf[1]; i++)
+                       if (pf->socksbuf[2+i] == 0) {
                            method = 0;/* no auth */
                            break;
                        }
                    data[0] = 5;
                    data[1] = method;
-                   sk_write(pr->s, data, 2);
-                   pr->dynamic = 0x5001;
-                   pr->port = 0;      /* re-empty the buffer */
+                   sk_write(pf->s, data, 2);
+                   pf->dynamic = 0x5001;
+                   pf->sockslen = 0;      /* re-empty the buffer */
                    continue;
                }
 
-               if (pr->dynamic == 0x5001) {
+               if (pf->dynamic == 0x5001) {
+                   /*
+                    * We're receiving a SOCKS request.
+                    */
+                   unsigned char reply[10]; /* SOCKS5 atyp=1 reply */
                    int atype, alen = 0;
-                   if (pr->port < 6) continue;
-                   atype = (unsigned char)pr->hostname[3];
+
+                   /*
+                    * Pre-fill reply packet.
+                    * In all cases, we set BND.{HOST,ADDR} to 0.0.0.0:0
+                    * (atyp=1) in the reply; if we succeed, we don't know
+                    * the right answers, and if we fail, they should be
+                    * ignored.
+                    */
+                   memset(reply, 0, lenof(reply));
+                   reply[0] = 5; /* VER */
+                   reply[3] = 1; /* ATYP = 1 (IPv4, 0.0.0.0:0) */
+
+                   if (pf->sockslen < 6) continue;
+                   atype = (unsigned char)pf->socksbuf[3];
                    if (atype == 1)    /* IPv4 address */
                        alen = 4;
                    if (atype == 4)    /* IPv6 address */
                        alen = 16;
                    if (atype == 3)    /* domain name has leading length */
-                       alen = 1 + (unsigned char)pr->hostname[4];
-                   if (pr->port < 6 + alen) continue;
-                   if (pr->hostname[1] != 1 || pr->hostname[2] != 0) {
-                       pr->hostname[1] = 1;   /* generic failure */
-                       pr->hostname[2] = 0;   /* reserved */
-                       sk_write(pr->s, pr->hostname, pr->port);
-                       pfd_close(pr->s);
+                       alen = 1 + (unsigned char)pf->socksbuf[4];
+                   if (pf->sockslen < 6 + alen) continue;
+                   if (pf->socksbuf[1] != 1 || pf->socksbuf[2] != 0) {
+                       /* Not CONNECT or reserved field nonzero - error */
+                       reply[1] = 1;   /* generic failure */
+                       sk_write(pf->s, (char *) reply, lenof(reply));
+                       pfd_close(pf);
                        return 1;
                    }
                    /*
                     * Now we have a viable connect request. Switch
                     * on atype.
                     */
-                   pr->port = GET_16BIT_MSB_FIRST(pr->hostname+4+alen);
+                   pf->port = GET_16BIT_MSB_FIRST(pf->socksbuf+4+alen);
                    if (atype == 1) {
-                       pr->hostname[1] = 0;   /* succeeded */
-                       sk_write(pr->s, pr->hostname, alen + 6);
-                       sprintf(pr->hostname, "%d.%d.%d.%d",
-                               (unsigned char)pr->hostname[4],
-                               (unsigned char)pr->hostname[5],
-                               (unsigned char)pr->hostname[6],
-                               (unsigned char)pr->hostname[7]);
+                       /* REP=0 (success) already */
+                       sk_write(pf->s, (char *) reply, lenof(reply));
+                       pf->hostname = dupprintf("%d.%d.%d.%d",
+                                                 (unsigned char)pf->socksbuf[4],
+                                                 (unsigned char)pf->socksbuf[5],
+                                                 (unsigned char)pf->socksbuf[6],
+                                                 (unsigned char)pf->socksbuf[7]);
                        goto connect;
                    } else if (atype == 3) {
-                       pr->hostname[1] = 0;   /* succeeded */
-                       sk_write(pr->s, pr->hostname, alen + 6);
-                       memmove(pr->hostname, pr->hostname + 5, alen-1);
-                       pr->hostname[alen-1] = '\0';
+                       /* REP=0 (success) already */
+                       sk_write(pf->s, (char *) reply, lenof(reply));
+                        pf->hostname = snewn(alen, char);
+                       pf->hostname[alen-1] = '\0';
+                       memcpy(pf->hostname, pf->socksbuf + 5, alen-1);
                        goto connect;
                    } else {
                        /*
                         * Unknown address type. (FIXME: support IPv6!)
                         */
-                       pr->hostname[1] = 8;   /* atype not supported */
-                       sk_write(pr->s, pr->hostname, pr->port);
-                       pfd_close(pr->s);
-                       return 1;                       
+                       reply[1] = 8;   /* atype not supported */
+                       sk_write(pf->s, (char *) reply, lenof(reply));
+                       pfd_close(pf);
+                       return 1;
                    }
                }
            }
-           
+
            /*
             * If we get here without either having done `continue'
             * or `goto connect', it must be because there is no
             * sensible interpretation of what's in our buffer. So
             * close the connection rudely.
             */
-           pfd_close(pr->s);
+           pfd_close(pf);
            return 1;
        }
        return 1;
@@ -285,36 +371,39 @@ static int pfd_receive(Plug plug, int urgent, char *data, int len)
         * connection.
         */
        connect:
+        sfree(pf->socksbuf);
+        pf->socksbuf = NULL;
 
-       pr->c = new_sock_channel(pr->backhandle, pr->s);
-       if (pr->c == NULL) {
-           pfd_close(pr->s);
+       /*
+        * Freeze the socket until the SSH server confirms the
+        * connection.
+        */
+       sk_set_frozen(pf->s, 1);
+
+       pf->c = new_sock_channel(pf->backhandle, pf);
+       if (pf->c == NULL) {
+           pfd_close(pf);
            return 1;
        } else {
            /* asks to forward to the specified host/port for this */
-           ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
+           wrap_send_port_open(pf->c, pf->hostname, pf->port, pf->s);
        }
-       pr->dynamic = 0;
+       pf->dynamic = 0;
 
-       /*
-        * Now freeze the socket until the SSH server confirms the
-        * connection.
-        */
-       sk_set_frozen(pr->s, 1);
        /*
         * If there's any data remaining in our current buffer,
         * save it to be sent on pfd_confirm().
         */
        if (len > 0) {
-           pr->buffer = snewn(len, char);
-           memcpy(pr->buffer, data, len);
-           pr->buflen = len;
+           pf->buffer = snewn(len, char);
+           memcpy(pf->buffer, data, len);
+           pf->buflen = len;
        }
     }
-    if (pr->ready) {
-       if (sshfwd_write(pr->c, data, len) > 0) {
-           pr->throttled = 1;
-           sk_set_frozen(pr->s, 1);
+    if (pf->ready) {
+       if (sshfwd_write(pf->c, data, len) > 0) {
+           pf->throttled = 1;
+           sk_set_frozen(pf->s, 1);
        }
     }
     return 1;
@@ -322,19 +411,24 @@ static int pfd_receive(Plug plug, int urgent, char *data, int len)
 
 static void pfd_sent(Plug plug, int bufsize)
 {
-    struct PFwdPrivate *pr = (struct PFwdPrivate *) plug;
+    struct PortForwarding *pf = (struct PortForwarding *) plug;
 
-    if (pr->c)
-       sshfwd_unthrottle(pr->c, bufsize);
+    if (pf->c)
+       sshfwd_unthrottle(pf->c, bufsize);
 }
 
 /*
- * Called when receiving a PORT OPEN from the server
+ * Called when receiving a PORT OPEN from the server to make a
+ * connection to a destination host.
+ *
+ * On success, returns NULL and fills in *pf_ret. On error, returns a
+ * dynamically allocated error message string.
  */
-const char *pfd_newconnect(Socket *s, char *hostname, int port,
-                          void *c, const Config *cfg)
+char *pfd_connect(struct PortForwarding **pf_ret, char *hostname,int port,
+                  void *c, Conf *conf, int addressfamily)
 {
     static const struct plug_function_table fn_table = {
+       pfd_log,
        pfd_closing,
        pfd_receive,
        pfd_sent,
@@ -344,36 +438,42 @@ const char *pfd_newconnect(Socket *s, char *hostname, int port,
     SockAddr addr;
     const char *err;
     char *dummy_realhost;
-    struct PFwdPrivate *pr;
+    struct PortForwarding *pf;
 
     /*
      * Try to find host.
      */
-    addr = name_lookup(hostname, port, &dummy_realhost, cfg);
-    if ((err = sk_addr_error(addr)) != NULL)
-       return err;
+    addr = name_lookup(hostname, port, &dummy_realhost, conf, addressfamily,
+                       NULL, NULL);
+    if ((err = sk_addr_error(addr)) != NULL) {
+        char *err_ret = dupstr(err);
+       sk_addr_free(addr);
+        sfree(dummy_realhost);
+       return err_ret;
+    }
 
     /*
      * Open socket.
      */
-    pr = snew(struct PFwdPrivate);
-    pr->buffer = NULL;
-    pr->fn = &fn_table;
-    pr->throttled = pr->throttle_override = 0;
-    pr->ready = 1;
-    pr->c = c;
-    pr->backhandle = NULL;            /* we shouldn't need this */
-    pr->dynamic = 0;
-
-    pr->s = *s = new_connection(addr, dummy_realhost, port,
-                               0, 1, 0, (Plug) pr, cfg);
-    if ((err = sk_socket_error(*s)) != NULL) {
-       sfree(pr);
-       return err;
+    pf = *pf_ret = new_portfwd_state();
+    pf->fn = &fn_table;
+    pf->throttled = pf->throttle_override = 0;
+    pf->ready = 1;
+    pf->c = c;
+    pf->backhandle = NULL;            /* we shouldn't need this */
+    pf->dynamic = 0;
+
+    pf->s = new_connection(addr, dummy_realhost, port,
+                           0, 1, 0, 0, (Plug) pf, conf);
+    sfree(dummy_realhost);
+    if ((err = sk_socket_error(pf->s)) != NULL) {
+        char *err_ret = dupstr(err);
+        sk_close(pf->s);
+       free_portfwd_state(pf);
+        *pf_ret = NULL;
+       return err_ret;
     }
 
-    sk_set_private_ptr(*s, pr);
-    sk_addr_free(addr);
     return NULL;
 }
 
@@ -381,53 +481,52 @@ const char *pfd_newconnect(Socket *s, char *hostname, int port,
  called when someone connects to the local port
  */
 
-static int pfd_accepting(Plug p, OSSocket sock)
+static int pfl_accepting(Plug p, accept_fn_t constructor, accept_ctx_t ctx)
 {
     static const struct plug_function_table fn_table = {
+       pfd_log,
        pfd_closing,
        pfd_receive,
        pfd_sent,
        NULL
     };
-    struct PFwdPrivate *pr, *org;
+    struct PortForwarding *pf;
+    struct PortListener *pl;
     Socket s;
     const char *err;
 
-    org = (struct PFwdPrivate *)p;
-    pr = snew(struct PFwdPrivate);
-    pr->buffer = NULL;
-    pr->fn = &fn_table;
+    pl = (struct PortListener *)p;
+    pf = new_portfwd_state();
+    pf->fn = &fn_table;
 
-    pr->c = NULL;
-    pr->backhandle = org->backhandle;
+    pf->c = NULL;
+    pf->backhandle = pl->backhandle;
 
-    pr->s = s = sk_register(sock, (Plug) pr);
+    pf->s = s = constructor(ctx, (Plug) pf);
     if ((err = sk_socket_error(s)) != NULL) {
-       sfree(pr);
+       free_portfwd_state(pf);
        return err != NULL;
     }
 
-    sk_set_private_ptr(s, pr);
-
-    pr->throttled = pr->throttle_override = 0;
-    pr->ready = 0;
+    pf->throttled = pf->throttle_override = 0;
+    pf->ready = 0;
 
-    if (org->dynamic) {
-       pr->dynamic = 1;
-       pr->port = 0;                  /* hostname buffer is so far empty */
+    if (pl->dynamic) {
+       pf->dynamic = 1;
+       pf->port = 0;                  /* "hostname" buffer is so far empty */
        sk_set_frozen(s, 0);           /* we want to receive SOCKS _now_! */
     } else {
-       pr->dynamic = 0;
-       strcpy(pr->hostname, org->hostname);
-       pr->port = org->port;   
-       pr->c = new_sock_channel(org->backhandle, s);
+       pf->dynamic = 0;
+       pf->hostname = dupstr(pl->hostname);
+       pf->port = pl->port;    
+       pf->c = new_sock_channel(pl->backhandle, pf);
 
-       if (pr->c == NULL) {
-           sfree(pr);
+       if (pf->c == NULL) {
+           free_portfwd_state(pf);
            return 1;
        } else {
            /* asks to forward to the specified host/port for this */
-           ssh_send_port_open(pr->c, pr->hostname, pr->port, "forwarding");
+           wrap_send_port_open(pf->c, pf->hostname, pf->port, s);
        }
     }
 
@@ -435,114 +534,119 @@ static int pfd_accepting(Plug p, OSSocket sock)
 }
 
 
-/* Add a new forwarding from port -> desthost:destport
- sets up a listener on the local machine on (srcaddr:)port
+/*
+ * Add a new port-forwarding listener from srcaddr:port -> desthost:destport.
+ *
+ * On success, returns NULL and fills in *pl_ret. On error, returns a
+ * dynamically allocated error message string.
  */
-const char *pfd_addforward(char *desthost, int destport, char *srcaddr,
-                          int port, void *backhandle, const Config *cfg)
+char *pfl_listen(char *desthost, int destport, char *srcaddr,
+                 int port, void *backhandle, Conf *conf,
+                 struct PortListener **pl_ret, int address_family)
 {
     static const struct plug_function_table fn_table = {
-       pfd_closing,
-       pfd_receive,                   /* should not happen... */
-       pfd_sent,                      /* also should not happen */
-       pfd_accepting
+       pfl_log,
+       pfl_closing,
+        NULL,                          /* recv */
+        NULL,                          /* send */
+       pfl_accepting
     };
 
     const char *err;
-    struct PFwdPrivate *pr;
-    Socket s;
+    struct PortListener *pl;
 
     /*
      * Open socket.
      */
-    pr = snew(struct PFwdPrivate);
-    pr->buffer = NULL;
-    pr->fn = &fn_table;
-    pr->c = NULL;
+    pl = *pl_ret = new_portlistener_state();
+    pl->fn = &fn_table;
     if (desthost) {
-       strcpy(pr->hostname, desthost);
-       pr->port = destport;
-       pr->dynamic = 0;
+       pl->hostname = dupstr(desthost);
+       pl->port = destport;
+       pl->dynamic = 0;
     } else
-       pr->dynamic = 1;
-    pr->throttled = pr->throttle_override = 0;
-    pr->ready = 0;
-    pr->backhandle = backhandle;
-
-    pr->s = s = new_listener(srcaddr, port, (Plug) pr,
-                            !cfg->lport_acceptall, cfg);
-    if ((err = sk_socket_error(s)) != NULL) {
-       sfree(pr);
-       return err;
+       pl->dynamic = 1;
+    pl->backhandle = backhandle;
+
+    pl->s = new_listener(srcaddr, port, (Plug) pl,
+                         !conf_get_int(conf, CONF_lport_acceptall),
+                         conf, address_family);
+    if ((err = sk_socket_error(pl->s)) != NULL) {
+        char *err_ret = dupstr(err);
+        sk_close(pl->s);
+       free_portlistener_state(pl);
+        *pl_ret = NULL;
+       return err_ret;
     }
 
-    sk_set_private_ptr(s, pr);
-
     return NULL;
 }
 
-void pfd_close(Socket s)
+void pfd_close(struct PortForwarding *pf)
 {
-    struct PFwdPrivate *pr;
-
-    if (!s)
+    if (!pf)
        return;
 
-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
+    sk_close(pf->s);
+    free_portfwd_state(pf);
+}
 
-    sfree(pr->buffer);
-    sfree(pr);
+/*
+ * Terminate a listener.
+ */
+void pfl_terminate(struct PortListener *pl)
+{
+    if (!pl)
+       return;
 
-    sk_close(s);
+    sk_close(pl->s);
+    free_portlistener_state(pl);
 }
 
-void pfd_unthrottle(Socket s)
+void pfd_unthrottle(struct PortForwarding *pf)
 {
-    struct PFwdPrivate *pr;
-    if (!s)
+    if (!pf)
        return;
-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 
-    pr->throttled = 0;
-    sk_set_frozen(s, pr->throttled || pr->throttle_override);
+    pf->throttled = 0;
+    sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
 }
 
-void pfd_override_throttle(Socket s, int enable)
+void pfd_override_throttle(struct PortForwarding *pf, int enable)
 {
-    struct PFwdPrivate *pr;
-    if (!s)
+    if (!pf)
        return;
-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
 
-    pr->throttle_override = enable;
-    sk_set_frozen(s, pr->throttled || pr->throttle_override);
+    pf->throttle_override = enable;
+    sk_set_frozen(pf->s, pf->throttled || pf->throttle_override);
 }
 
 /*
  * Called to send data down the raw connection.
  */
-int pfd_send(Socket s, char *data, int len)
+int pfd_send(struct PortForwarding *pf, char *data, int len)
 {
-    if (s == NULL)
+    if (pf == NULL)
        return 0;
-    return sk_write(s, data, len);
+    return sk_write(pf->s, data, len);
 }
 
-
-void pfd_confirm(Socket s)
+void pfd_send_eof(struct PortForwarding *pf)
 {
-    struct PFwdPrivate *pr;
+    sk_write_eof(pf->s);
+}
 
-    if (s == NULL)
+void pfd_confirm(struct PortForwarding *pf)
+{
+    if (pf == NULL)
        return;
 
-    pr = (struct PFwdPrivate *) sk_get_private_ptr(s);
-    pr->ready = 1;
-    sk_set_frozen(s, 0);
-    sk_write(s, NULL, 0);
-    if (pr->buffer) {
-       sshfwd_write(pr->c, pr->buffer, pr->buflen);
-       sfree(pr->buffer);
-       pr->buffer = NULL;
+    pf->ready = 1;
+    sk_set_frozen(pf->s, 0);
+    sk_write(pf->s, NULL, 0);
+    if (pf->buffer) {
+       sshfwd_write(pf->c, pf->buffer, pf->buflen);
+       sfree(pf->buffer);
+       pf->buffer = NULL;
     }
 }