fix spelling error.

git-svn-id: https://rt-thread.googlecode.com/svn/trunk@2581 bbd45198-f89e-11dd-88c7-29a3b14d5316

components/net/lwip/src/core/ipv4/ip.c

@@ -83,7 +83,7 @@
          || (LWIP_IP_ACCEPT_UDP_PORT(port)))
 #elif defined(LWIP_IP_ACCEPT_UDP_PORT) /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
 /* accept custom port only */
-#define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (LWIP_IP_ACCEPT_UDP_PORT(dst_port))
+#define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) (LWIP_IP_ACCEPT_UDP_PORT(port))
 #else /* LWIP_DHCP && defined(LWIP_IP_ACCEPT_UDP_PORT) */
 /* accept DHCP client port only */
 #define IP_ACCEPT_LINK_LAYER_ADDRESSED_PORT(port) ((port) == PP_NTOHS(DHCP_CLIENT_PORT))