DHCP request fix for Windows Server 2003

Added option CONFIG_BOOTP_DHCP_REQUEST_DELAY. This provides an optional
delay before sending "DHCP Request" in net/bootp.c. Required to overcome
interoperability problems with Windows Server 200x DHCP server when U-Boot
client responds too fast for server to handle.

Signed-off-by: Aras Vaichas <arasv@magtech.com.au>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

README

@@ -1151,6 +1151,20 @@ The following options need to be configured:
 		of the "hostname" environment variable is passed as
 		option 12 to the DHCP server.
 
+		CONFIG_BOOTP_DHCP_REQUEST_DELAY
+
+		A 32bit value in microseconds for a delay between
+		receiving a "DHCP Offer" and sending the "DHCP Request".
+		This fixes a problem with certain DHCP servers that don't
+		respond 100% of the time to a "DHCP request". E.g. On an
+		AT91RM9200 processor running at 180MHz, this delay needed
+		to be *at least* 15,000 usec before a Windows Server 2003
+		DHCP server would reply 100% of the time. I recommend at
+		least 50,000 usec to be safe. The alternative is to hope
+		that one of the retries will be successful but note that
+		the DHCP timeout and retry process takes a longer than
+		this delay.
+
  - CDP Options:
 		CONFIG_CDP_DEVICE_ID
 

net/bootp.c

@@ -879,7 +879,10 @@ static void DhcpSendRequestPkt(Bootp_t *bp_offer)
 	iplen = BOOTP_HDR_SIZE - sizeof(bp->bp_vend) + extlen;
 	NetSetIP(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);
 
-	debug ("Transmitting DHCPREQUEST packet: len = %d\n", pktlen);
+        debug ("Transmitting DHCPREQUEST packet: len = %d\n", pktlen);
+#ifdef CONFIG_BOOTP_DHCP_REQUEST_DELAY
+	udelay(CONFIG_BOOTP_DHCP_REQUEST_DELAY);
+#endif	/* CONFIG_BOOTP_DHCP_REQUEST_DELAY */
 	NetSendPacket(NetTxPacket, pktlen);
 }