udhcp: MAC_BCAST_ADDR and blank_chaddr are in fact constant, move to rodata.

a few global variables reduced to smallints
function                                             old     new   delta
add_lease                                             75     227    +152
static.blank_chaddr                                    -      16     +16
MAC_BCAST_ADDR                                         -       6      +6
sockfd                                                 4       8      +4
udhcp_run_script                                    1153    1155      +2
state                                                  8       5      -3
listen_mode                                            4       1      -3
perform_release                                      152     148      -4
fd                                                     8       4      -4
blank_chaddr                                          16       -     -16
udhcpc_main                                         2518    2497     -21
.rodata                                           131864  131832     -32
oldest_expired_lease                                  61       -     -61
clear_lease                                          127       -    -127
------------------------------------------------------------------------------
(add/remove: 2/3 grow/shrink: 3/6 up/down: 180/-271)          Total: -91 bytes

networking/udhcp/options.h

@@ -23,6 +23,80 @@ enum {
 #define OPTION_REQ	0x10 /* have the client request this option */
 #define OPTION_LIST	0x20 /* There can be a list of 1 or more of these */
 
+/*****************************************************************/
+/* Do not modify below here unless you know what you are doing!! */
+/*****************************************************************/
+
+/* DHCP protocol -- see RFC 2131 */
+#define SERVER_PORT		67
+#define CLIENT_PORT		68
+
+#define DHCP_MAGIC		0x63825363
+
+/* DHCP option codes (partial list) */
+#define DHCP_PADDING		0x00
+#define DHCP_SUBNET		0x01
+#define DHCP_TIME_OFFSET	0x02
+#define DHCP_ROUTER		0x03
+#define DHCP_TIME_SERVER	0x04
+#define DHCP_NAME_SERVER	0x05
+#define DHCP_DNS_SERVER		0x06
+#define DHCP_LOG_SERVER		0x07
+#define DHCP_COOKIE_SERVER	0x08
+#define DHCP_LPR_SERVER		0x09
+#define DHCP_HOST_NAME		0x0c
+#define DHCP_BOOT_SIZE		0x0d
+#define DHCP_DOMAIN_NAME	0x0f
+#define DHCP_SWAP_SERVER	0x10
+#define DHCP_ROOT_PATH		0x11
+#define DHCP_IP_TTL		0x17
+#define DHCP_MTU		0x1a
+#define DHCP_BROADCAST		0x1c
+#define DHCP_NTP_SERVER		0x2a
+#define DHCP_WINS_SERVER	0x2c
+#define DHCP_REQUESTED_IP	0x32
+#define DHCP_LEASE_TIME		0x33
+#define DHCP_OPTION_OVER	0x34
+#define DHCP_MESSAGE_TYPE	0x35
+#define DHCP_SERVER_ID		0x36
+#define DHCP_PARAM_REQ		0x37
+#define DHCP_MESSAGE		0x38
+#define DHCP_MAX_SIZE		0x39
+#define DHCP_T1			0x3a
+#define DHCP_T2			0x3b
+#define DHCP_VENDOR		0x3c
+#define DHCP_CLIENT_ID		0x3d
+#define DHCP_FQDN		0x51
+
+#define DHCP_END		0xFF
+
+
+#define BOOTREQUEST		1
+#define BOOTREPLY		2
+
+#define ETH_10MB		1
+#define ETH_10MB_LEN		6
+
+#define DHCPDISCOVER		1
+#define DHCPOFFER		2
+#define DHCPREQUEST		3
+#define DHCPDECLINE		4
+#define DHCPACK			5
+#define DHCPNAK			6
+#define DHCPRELEASE		7
+#define DHCPINFORM		8
+
+#define BROADCAST_FLAG		0x8000
+
+#define OPTION_FIELD		0
+#define FILE_FIELD		1
+#define SNAME_FIELD		2
+
+/* miscellaneous defines */
+#define OPT_CODE 0
+#define OPT_LEN 1
+#define OPT_DATA 2
+
 struct dhcp_option {
 	char name[12];
 	char flags;