Fix handling of IPv6 dynamic forwardings.

During the Conf revamp, I changed the internal representation of
dynamic forwardings so that they were stored as the conceptually
sensible L12345=D rather than the old D12345, and added compensation
code to translate to the latter form for backwards-compatible data
storage and for OpenSSH-harmonised GUI display. Unfortunately I forgot
that keys in the forwarding data can also prefix the L/R with a
character indicating IPv4/IPv6, and my translations didn't take
account of that possibility. Fix them.

[originally from svn r10031]

config.c

@@ -1083,9 +1083,23 @@ static void portfwd_handler(union control *ctrl, void *dlg,
 		 val != NULL;
 		 val = conf_get_str_strs(conf, CONF_portfwd, key, &key)) {
 		char *p;
-                if (!strcmp(val, "D"))
-                    p = dupprintf("D%s\t", key+1);
-                else
+                if (!strcmp(val, "D")) {
+                    char *L;
+                    /*
+                     * A dynamic forwarding is stored as L12345=D or
+                     * 6L12345=D (since it's mutually exclusive with
+                     * L12345=anything else), but displayed as D12345
+                     * to match the fiction that 'Local', 'Remote' and
+                     * 'Dynamic' are three distinct modes and also to
+                     * align with OpenSSH's command line option syntax
+                     * that people will already be used to. So, for
+                     * display purposes, find the L in the key string
+                     * and turn it into a D.
+                     */
+                    p = dupprintf("%s\t", key);
+                    L = strchr(p, 'L');
+                    if (L) *L = 'D';
+                } else
                     p = dupprintf("%s\t%s", key, val);
 		dlg_listbox_add(ctrl, dlg, p);
 		sfree(p);

settings.c

@@ -178,7 +178,7 @@ static int gppmap(void *handle, char *name, Conf *conf, int primary)
 	    val = q;
 	*q = '\0';
 
-        if (primary == CONF_portfwd && buf[0] == 'D') {
+        if (primary == CONF_portfwd && strchr(buf, 'D') != NULL) {
             /*
              * Backwards-compatibility hack: dynamic forwardings are
              * indexed in the data store as a third type letter in the
@@ -188,9 +188,10 @@ static int gppmap(void *handle, char *name, Conf *conf, int primary)
              * _listening_ on a local port, and are hence mutually
              * exclusive on the same port number. So here we translate
              * the legacy storage format into the sensible internal
-             * form.
+             * form, by finding the D and turning it into a L.
              */
-            char *newkey = dupcat("L", buf+1, NULL);
+            char *newkey = dupstr(buf);
+            *strchr(newkey, 'D') = 'L';
             conf_set_str_str(conf, primary, newkey, "D");
             sfree(newkey);
         } else {
@@ -232,9 +233,13 @@ static void wmap(void *handle, char const *outkey, Conf *conf, int primary)
              * conceptually incoherent legacy storage format (key
              * "D<port>", value empty).
              */
+            char *L;
+
             realkey = key;             /* restore it at end of loop */
             val = "";
-            key = dupcat("D", key+1, NULL);
+            key = dupstr(key);
+            L = strchr(key, 'L');
+            if (L) *L = 'D';
         } else {
             realkey = NULL;
         }