fixed compiling for various config combinations

src/core/ipv4/igmp.c

@@ -88,9 +88,6 @@ Steve Reynolds
 #include "lwip/ip.h"
 #include "lwip/inet_chksum.h"
 #include "lwip/netif.h"
-#include "lwip/icmp.h"
-#include "lwip/udp.h"
-#include "lwip/tcp.h"
 #include "lwip/stats.h"
 
 #include "string.h"

src/core/ipv4/ip4.c

@@ -336,8 +336,10 @@ ip4_forward(struct pbuf *p, struct ip_hdr *iphdr, struct netif *inp)
       /* @todo: send ICMP Destination Unreachable code 13 "Communication administratively prohibited"? */
 #endif /* IP_FRAG */
     } else {
+#if LWIP_ICMP
       /* send ICMP Destination Unreachable code 4: "Fragmentation Needed and DF Set" */
       icmp_dest_unreach(p, ICMP_DUR_FRAG);
+#endif /* LWIP_ICMP */
     }
     return;
   }