lib/inet6.c:INET6_rresolve() - various fixes

1) Fall-back to numeric address if getnameinfo fails.
   Reverse lookup is not mandatory, therefore its fail
   is not an error. Just return numeric address in that case.
   This makes netstat/route show IPv6 address instead of
   [UNKNOWN] in case of DNS problems.

2) Pass length of 'name' buffer into function.
   'name' is a pointer and therefore sizeof(name)
   returns size of pointer and not size of the buffer.
   see http://stackoverflow.com/questions/14298710/c-pointers-and-arrays-sizeof-operator
   The sizeof() usage was added with commit 604785ad,
   so I checked all the other changes in that commit
   and they seem to be OK.

3) remove unused 's' variable

lib/inet6.c

@@ -84,10 +84,9 @@ static int INET6_resolve(char *name, struct sockaddr_in6 *sin6)
 #endif
 
 
-static int INET6_rresolve(char *name, struct sockaddr_in6 *sin6, int numeric)
+static int INET6_rresolve(char *name, size_t namelen,
+			  struct sockaddr_in6 *sin6, int numeric)
 {
-    int s;
-
     /* Grmpf. -FvK */
     if (sin6->sin6_family != AF_INET6) {
 #ifdef DEBUG
@@ -98,21 +97,20 @@ static int INET6_rresolve(char *name, struct sockaddr_in6 *sin6, int numeric)
 	return (-1);
     }
     if (numeric & 0x7FFF) {
-	inet_ntop( AF_INET6, &sin6->sin6_addr, name, 80);
+	inet_ntop( AF_INET6, &sin6->sin6_addr, name, namelen);
 	return (0);
     }
     if (IN6_IS_ADDR_UNSPECIFIED(&sin6->sin6_addr)) {
         if (numeric & 0x8000)
-	    safe_strncpy(name, "default", sizeof(name));
+	    safe_strncpy(name, "default", namelen);
 	else
-	    safe_strncpy(name, "[::]", sizeof(name));
+	    safe_strncpy(name, "[::]", namelen);
 	return (0);
     }
 
-    if ((s = getnameinfo((struct sockaddr *) sin6, sizeof(struct sockaddr_in6),
-			 name, 255 /* !! */ , NULL, 0, 0))) {
-	fputs("getnameinfo failed\n", stderr);
-	return -1;
+    if (getnameinfo((struct sockaddr *) sin6, sizeof(struct sockaddr_in6),
+		    name, namelen , NULL, 0, 0)) {
+	inet_ntop( AF_INET6, &sin6->sin6_addr, name, namelen);
     }
     return (0);
 }
@@ -143,7 +141,8 @@ static const char *INET6_sprint(struct sockaddr *sap, int numeric)
 
     if (sap->sa_family == 0xFFFF || sap->sa_family == 0)
 	return safe_strncpy(buff, _("[NONE SET]"), sizeof(buff));
-    if (INET6_rresolve(buff, (struct sockaddr_in6 *) sap, numeric) != 0)
+    if (INET6_rresolve(buff, sizeof(buff),
+		       (struct sockaddr_in6 *) sap, numeric) != 0)
 	return safe_strncpy(buff, _("[UNKNOWN]"), sizeof(buff));
     return (fix_v4_address(buff, &((struct sockaddr_in6 *)sap)->sin6_addr));
 }