net - Support ping reply when processing net-loop

Add ICMP_ECHO_REQUEST packet support by responding with a ICMP_ECHO_REPLY.

This permits the ping command to test the phy interface when the phy
is put in loopback mode (typically by setting register 0 bit 14).

It also allows the port to respond to an external ping when u-boot is
processing some other net command (such as tftp).  This is useful when
tftp appears to hang.

Signed-off-by: Ed Swarthout <Ed.Swarthout@freescale.com>
Signed-off-by: Ben Warren <bwarren@qstreams.com>

net/net.c

@@ -1424,6 +1424,26 @@ NetReceive(volatile uchar * inpkt, int len)
 				/* XXX point to ip packet */
 				(*packetHandler)((uchar *)ip, 0, 0, 0);
 				return;
+			case ICMP_ECHO_REQUEST:
+#ifdef ET_DEBUG
+				printf ("Got ICMP ECHO REQUEST, return %d bytes \n",
+					ETHER_HDR_SIZE + len);
+#endif
+				memcpy (&et->et_dest[0], &et->et_src[0], 6);
+				memcpy (&et->et_src[ 0], NetOurEther, 6);
+
+				ip->ip_sum = 0;
+				ip->ip_off = 0;
+				NetCopyIP((void*)&ip->ip_dst, &ip->ip_src);
+				NetCopyIP((void*)&ip->ip_src, &NetOurIP);
+				ip->ip_sum = ~NetCksum((uchar *)ip, IP_HDR_SIZE_NO_UDP >> 1);
+
+				icmph->type = ICMP_ECHO_REPLY;
+				icmph->checksum = 0;
+				icmph->checksum = ~NetCksum((uchar *)icmph,
+						(len - IP_HDR_SIZE_NO_UDP) >> 1);
+				(void) eth_send((uchar *)et, ETHER_HDR_SIZE + len);
+				return;
 #endif
 			default:
 				return;