A VLAN tagged DHCP request/discover is 4 bytes short

The problem is that BOOTP_SIZE uses ETHER_HDR_SIZE which is 14 bytes.
If sending a VLAN tagged frame (when env variable vlan is set) this
should be VLAN_ETHER_HDR_SIZE=18 which is what NetSetEther returns.

Signed-off-by: Norbert van Bolhuis <nvbolhuis@aimvalley.nl>
Signed-off-by: Ben Warren <biggerbadderben@gmail.com>

net/bootp.c

@@ -687,7 +687,7 @@ BootpRequest (void)
 	 * Calculate proper packet lengths taking into account the
 	 * variable size of the options field
 	 */
-	pktlen = BOOTP_SIZE - sizeof(bp->bp_vend) + ext_len;
+	pktlen = ((int)(pkt-NetTxPacket)) + BOOTP_HDR_SIZE - sizeof(bp->bp_vend) + ext_len;
 	iplen = BOOTP_HDR_SIZE - sizeof(bp->bp_vend) + ext_len;
 	NetSetIP(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);
 	NetSetTimeout(SELECT_TIMEOUT, BootpTimeout);
@@ -860,7 +860,7 @@ static void DhcpSendRequestPkt(Bootp_t *bp_offer)
 	NetCopyIP(&OfferedIP, &bp_offer->bp_yiaddr);
 	extlen = DhcpExtended((u8 *)bp->bp_vend, DHCP_REQUEST, NetDHCPServerIP, OfferedIP);
 
-	pktlen = BOOTP_SIZE - sizeof(bp->bp_vend) + extlen;
+	pktlen = ((int)(pkt-NetTxPacket)) + BOOTP_HDR_SIZE - sizeof(bp->bp_vend) + extlen;
 	iplen = BOOTP_HDR_SIZE - sizeof(bp->bp_vend) + extlen;
 	NetSetIP(iphdr, 0xFFFFFFFFL, PORT_BOOTPS, PORT_BOOTPC, iplen);