iprange: warn before disabling module due to /0 network with non-null IP

Using a /0 prefix on an IP different from 0.0.0.0 is valid, but might
be a configuration mistake. Log warning message in this case so that
user can easily troubleshoot it.
Signed-off-by: NGuillaume Nault <g.nault@alphalink.fr>

accel-pppd/iprange.c

@@ -114,8 +114,12 @@ static int parse_iprange(const char *str, struct iprange_t **range)
 		}
 
 		/* Interpret /0 as disable request */
-		if (prefix_len == 0)
+		if (prefix_len == 0) {
+			if (ipmin != INADDR_ANY)
+				log_warn("iprange: %s is equivalent to 0.0.0.0/0 and disables the iprange module\n",
+					 str);
 			goto disable;
+		}
 
 		mask = INADDR_BROADCAST << (32 - prefix_len);
 		if (ipmin != (ipmin & mask)) {