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

9 files changed, 169 insertions, 156 deletions

diff --git a/networking/udhcp/common.c b/networking/udhcp/common.c
index 46cc0348f..721888f6d 100644
--- a/networking/udhcp/common.c
+++ b/networking/udhcp/common.c
@@ -15,6 +15,8 @@
 #include "common.h"
 
 
+const uint8_t MAC_BCAST_ADDR[6] = { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
+
 long uptime(void)
 {
 	struct sysinfo info;
diff --git a/networking/udhcp/common.h b/networking/udhcp/common.h
index 00890ac1c..6c0db5b4c 100644
--- a/networking/udhcp/common.h
+++ b/networking/udhcp/common.h
@@ -14,8 +14,7 @@
 
 #define DEFAULT_SCRIPT  "/usr/share/udhcpc/default.script"
 
-#define COMBINED_BINARY
-
+extern const uint8_t MAC_BCAST_ADDR[6]; /* six all-ones */
 
 /*** packet.h ***/
 
@@ -52,7 +51,8 @@ int udhcp_get_packet(struct dhcpMessage *packet, int fd);
 uint16_t udhcp_checksum(void *addr, int count);
 int udhcp_raw_packet(struct dhcpMessage *payload,
 		uint32_t source_ip, int source_port,
-		uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex);
+		uint32_t dest_ip, int dest_port,
+		const uint8_t *dest_arp, int ifindex);
 int udhcp_kernel_packet(struct dhcpMessage *payload,
 		uint32_t source_ip, int source_port,
 		uint32_t dest_ip, int dest_port);
diff --git a/networking/udhcp/dhcpc.c b/networking/udhcp/dhcpc.c
index e8cdd79df..362e70169 100644
--- a/networking/udhcp/dhcpc.c
+++ b/networking/udhcp/dhcpc.c
@@ -17,22 +17,23 @@
 #include "options.h"
 
 
-static int state;
 /* Something is definitely wrong here. IPv4 addresses
  * in variables of type long?? BTW, we use inet_ntoa()
  * in the code. Manpage says that struct in_addr has a member of type long (!)
  * which holds IPv4 address, and the struct is passed by value (!!)
  */
+static unsigned long timeout;
 static unsigned long requested_ip; /* = 0 */
 static uint32_t server_addr;
-static unsigned long timeout;
 static int packet_num; /* = 0 */
-static int fd = -1;
+static int sockfd = -1;
 
 #define LISTEN_NONE 0
 #define LISTEN_KERNEL 1
 #define LISTEN_RAW 2
-static int listen_mode;
+static smallint listen_mode;
+
+static smallint state;
 
 struct client_config_t client_config;
 
@@ -42,8 +43,10 @@ static void change_mode(int new_mode)
 {
 	DEBUG("entering %s listen mode",
 		new_mode ? (new_mode == 1 ? "kernel" : "raw") : "none");
-	if (fd >= 0) close(fd);
-	fd = -1;
+	if (sockfd >= 0) {
+		close(sockfd);
+		sockfd = -1;
+	}
 	listen_mode = new_mode;
 }
 
@@ -111,6 +114,7 @@ static void client_background(void)
  * If that will be properly disabled for NOMMU, client_background()
  * will work on NOMMU too */
 #else
+// chdir(/) is problematic. Imagine that e.g. pidfile name is RELATIVE! what will unlink do then, eh?
 	bb_daemonize(DAEMON_CHDIR_ROOT);
 	logmode &= ~LOGMODE_STDIO;
 #endif
@@ -289,13 +293,13 @@ int udhcpc_main(int argc, char **argv)
 		tv.tv_sec = timeout - uptime();
 		tv.tv_usec = 0;
 
-		if (listen_mode != LISTEN_NONE && fd < 0) {
+		if (listen_mode != LISTEN_NONE && sockfd < 0) {
 			if (listen_mode == LISTEN_KERNEL)
-				fd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
+				sockfd = listen_socket(INADDR_ANY, CLIENT_PORT, client_config.interface);
 			else
-				fd = raw_socket(client_config.ifindex);
+				sockfd = raw_socket(client_config.ifindex);
 		}
-		max_fd = udhcp_sp_fd_set(&rfds, fd);
+		max_fd = udhcp_sp_fd_set(&rfds, sockfd);
 
 		if (tv.tv_sec > 0) {
 			DEBUG("Waiting on select...");
@@ -342,7 +346,8 @@ int udhcpc_main(int argc, char **argv)
 					packet_num++;
 				} else {
 					/* timed out, go back to init state */
-					if (state == RENEW_REQUESTED) udhcp_run_script(NULL, "deconfig");
+					if (state == RENEW_REQUESTED)
+						udhcp_run_script(NULL, "deconfig");
 					state = INIT_SELECTING;
 					timeout = now;
 					packet_num = 0;
@@ -393,12 +398,12 @@ int udhcpc_main(int argc, char **argv)
 				timeout = 0x7fffffff;
 				break;
 			}
-		} else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(fd, &rfds)) {
+		} else if (retval > 0 && listen_mode != LISTEN_NONE && FD_ISSET(sockfd, &rfds)) {
 			/* a packet is ready, read it */
 
 			if (listen_mode == LISTEN_KERNEL)
-				len = udhcp_get_packet(&packet, fd);
-			else len = get_raw_packet(&packet, fd);
+				len = udhcp_get_packet(&packet, sockfd);
+			else len = get_raw_packet(&packet, sockfd);
 
 			if (len == -1 && errno != EINTR) {
 				DEBUG("error on read, %s, reopening socket", strerror(errno));
@@ -418,7 +423,8 @@ int udhcpc_main(int argc, char **argv)
 				continue;
 			}
 
-			if ((message = get_option(&packet, DHCP_MESSAGE_TYPE)) == NULL) {
+			message = get_option(&packet, DHCP_MESSAGE_TYPE);
+			if (message == NULL) {
 				bb_error_msg("cannot get option from packet - ignoring");
 				continue;
 			}
diff --git a/networking/udhcp/dhcpd.h b/networking/udhcp/dhcpd.h
index 40959e4ae..7c4fe695a 100644
--- a/networking/udhcp/dhcpd.h
+++ b/networking/udhcp/dhcpd.h
@@ -14,81 +14,6 @@
 /* where to find the DHCP server configuration file */
 #define DHCPD_CONF_FILE         "/etc/udhcpd.conf"
 
-/*****************************************************************/
-/* 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 MAC_BCAST_ADDR		(uint8_t *) "\xff\xff\xff\xff\xff\xff"
-#define OPT_CODE 0
-#define OPT_LEN 1
-#define OPT_DATA 2
-
 struct option_set {
 	uint8_t *data;
 	struct option_set *next;
@@ -140,13 +65,9 @@ struct dhcpOfferedAddr {
 	uint32_t expires;	/* host order */
 };
 
-extern uint8_t blank_chaddr[];
-
-void clear_lease(uint8_t *chaddr, uint32_t yiaddr);
-struct dhcpOfferedAddr *add_lease(uint8_t *chaddr, uint32_t yiaddr, unsigned long lease);
+struct dhcpOfferedAddr *add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease);
 int lease_expired(struct dhcpOfferedAddr *lease);
-struct dhcpOfferedAddr *oldest_expired_lease(void);
-struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr);
+struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr);
 struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr);
 uint32_t find_address(int check_expired);
 
diff --git a/networking/udhcp/leases.c b/networking/udhcp/leases.c
index 2f7847d74..5d8775f63 100644
--- a/networking/udhcp/leases.c
+++ b/networking/udhcp/leases.c
@@ -8,25 +8,41 @@
 #include "dhcpd.h"
 
 
-uint8_t blank_chaddr[] = {[0 ... 15] = 0};
+/* Find the oldest expired lease, NULL if there are no expired leases */
+static struct dhcpOfferedAddr *oldest_expired_lease(void)
+{
+	struct dhcpOfferedAddr *oldest = NULL;
+	unsigned long oldest_lease = time(0);
+	unsigned i;
+
+
+	for (i = 0; i < server_config.max_leases; i++)
+		if (oldest_lease > leases[i].expires) {
+			oldest_lease = leases[i].expires;
+			oldest = &(leases[i]);
+		}
+	return oldest;
+}
+
 
 /* clear every lease out that chaddr OR yiaddr matches and is nonzero */
-void clear_lease(uint8_t *chaddr, uint32_t yiaddr)
+static void clear_lease(const uint8_t *chaddr, uint32_t yiaddr)
 {
-	unsigned int i, j;
+	unsigned i, j;
 
 	for (j = 0; j < 16 && !chaddr[j]; j++);
 
 	for (i = 0; i < server_config.max_leases; i++)
-		if ((j != 16 && !memcmp(leases[i].chaddr, chaddr, 16)) ||
-		    (yiaddr && leases[i].yiaddr == yiaddr)) {
+		if ((j != 16 && memcmp(leases[i].chaddr, chaddr, 16) != 0)
+		 || (yiaddr && leases[i].yiaddr == yiaddr)
+		) {
 			memset(&(leases[i]), 0, sizeof(struct dhcpOfferedAddr));
 		}
 }
 
 
 /* add a lease into the table, clearing out any old ones */
-struct dhcpOfferedAddr *add_lease(uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
+struct dhcpOfferedAddr *add_lease(const uint8_t *chaddr, uint32_t yiaddr, unsigned long lease)
 {
 	struct dhcpOfferedAddr *oldest;
 
@@ -52,31 +68,14 @@ int lease_expired(struct dhcpOfferedAddr *lease)
 }
 
 
-/* Find the oldest expired lease, NULL if there are no expired leases */
-struct dhcpOfferedAddr *oldest_expired_lease(void)
-{
-	struct dhcpOfferedAddr *oldest = NULL;
-	unsigned long oldest_lease = time(0);
-	unsigned int i;
-
-
-	for (i = 0; i < server_config.max_leases; i++)
-		if (oldest_lease > leases[i].expires) {
-			oldest_lease = leases[i].expires;
-			oldest = &(leases[i]);
-		}
-	return oldest;
-
-}
-
-
 /* Find the first lease that matches chaddr, NULL if no match */
-struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr)
+struct dhcpOfferedAddr *find_lease_by_chaddr(const uint8_t *chaddr)
 {
-	unsigned int i;
+	unsigned i;
 
 	for (i = 0; i < server_config.max_leases; i++)
-		if (!memcmp(leases[i].chaddr, chaddr, 16)) return &(leases[i]);
+		if (!memcmp(leases[i].chaddr, chaddr, 16))
+			return &(leases[i]);
 
 	return NULL;
 }
@@ -85,10 +84,11 @@ struct dhcpOfferedAddr *find_lease_by_chaddr(uint8_t *chaddr)
 /* Find the first lease that matches yiaddr, NULL is no match */
 struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr)
 {
-	unsigned int i;
+	unsigned i;
 
 	for (i = 0; i < server_config.max_leases; i++)
-		if (leases[i].yiaddr == yiaddr) return &(leases[i]);
+		if (leases[i].yiaddr == yiaddr)
+			return &(leases[i]);
 
 	return NULL;
 }
@@ -97,6 +97,8 @@ struct dhcpOfferedAddr *find_lease_by_yiaddr(uint32_t yiaddr)
 /* check is an IP is taken, if it is, add it to the lease table */
 static int check_ip(uint32_t addr)
 {
+	static const uint8_t blank_chaddr[16]; /* 16 zero bytes */
+
 	struct in_addr temp;
 
 	if (arpping(addr, server_config.server, server_config.arp, server_config.interface) == 0) {
@@ -105,7 +107,8 @@ static int check_ip(uint32_t addr)
 			inet_ntoa(temp), server_config.conflict_time);
 		add_lease(blank_chaddr, addr, server_config.conflict_time);
 		return 1;
-	} else return 0;
+	}
+	return 0;
 }
 
 
@@ -125,7 +128,7 @@ uint32_t find_address(int check_expired)
 		/* ie, 192.168.55.255 */
 		if ((addr & 0xFF) == 0xFF) continue;
 
-		/* Only do if it isn't an assigned as a static lease */
+		/* Only do if it isn't assigned as a static lease */
 		if (!reservedIp(server_config.static_leases, htonl(addr))) {
 
 			/* lease is not taken */
@@ -133,11 +136,10 @@ uint32_t find_address(int check_expired)
 			lease = find_lease_by_yiaddr(ret);
 
 			/* no lease or it expired and we are checking for expired leases */
-			if ( (!lease || (check_expired && lease_expired(lease)))
+			if ((!lease || (check_expired && lease_expired(lease)))
 			 && /* and it isn't on the network */ !check_ip(ret)
 			) {
 				return ret;
-				break;
 			}
 		}
 	}
diff --git a/networking/udhcp/options.h b/networking/udhcp/options.h
index 11f013fd4..5e9adf881 100644
--- a/networking/udhcp/options.h
+++ b/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;
diff --git a/networking/udhcp/packet.c b/networking/udhcp/packet.c
index 25c55faab..da3807773 100644
--- a/networking/udhcp/packet.c
+++ b/networking/udhcp/packet.c
@@ -112,7 +112,7 @@ uint16_t udhcp_checksum(void *addr, int count)
 void BUG_sizeof_struct_udp_dhcp_packet_must_be_576(void);
 int udhcp_raw_packet(struct dhcpMessage *payload,
 		uint32_t source_ip, int source_port,
-		uint32_t dest_ip, int dest_port, uint8_t *dest_arp, int ifindex)
+		uint32_t dest_ip, int dest_port, const uint8_t *dest_arp, int ifindex)
 {
 	int fd;
 	int result;
diff --git a/networking/udhcp/script.c b/networking/udhcp/script.c
index dc8ff7a1c..98706a592 100644
--- a/networking/udhcp/script.c
+++ b/networking/udhcp/script.c
@@ -9,7 +9,6 @@
  */
 
 #include "common.h"
-#include "dhcpd.h"
 #include "dhcpc.h"
 #include "options.h"
 
@@ -77,7 +76,7 @@ static char *alloc_fill_opts(uint8_t *option, const struct dhcp_option *type_p)
 		switch (type) {
 		case OPTION_IP_PAIR:
 			dest += sprintip(dest, "", option);
-			*(dest++) = '/';
+			*dest++ = '/';
 			option += 4;
 			optlen = 4;
 		case OPTION_IP:	/* Works regardless of host byte order. */
@@ -132,34 +131,42 @@ static char **fill_envp(struct dhcpMessage *packet)
 	int num_options = 0;
 	int i, j;
 	char **envp;
+	char *var;
 	uint8_t *temp;
 	struct in_addr subnet;
 	char over = 0;
 
-	if (packet == NULL)
-		num_options = 0;
-	else {
-		for (i = 0; dhcp_options[i].code; i++)
+	if (packet) {
+		for (i = 0; dhcp_options[i].code; i++) {
 			if (get_option(packet, dhcp_options[i].code)) {
 				num_options++;
 				if (dhcp_options[i].code == DHCP_SUBNET)
 					num_options++; /* for mton */
 			}
-		if (packet->siaddr) num_options++;
-		if ((temp = get_option(packet, DHCP_OPTION_OVER)))
+		}
+		if (packet->siaddr)
+			num_options++;
+		temp = get_option(packet, DHCP_OPTION_OVER);
+		if (temp)
 			over = *temp;
-		if (!(over & FILE_FIELD) && packet->file[0]) num_options++;
-		if (!(over & SNAME_FIELD) && packet->sname[0]) num_options++;
+		if (!(over & FILE_FIELD) && packet->file[0])
+			num_options++;
+		if (!(over & SNAME_FIELD) && packet->sname[0])
+			num_options++;
 	}
 
 	envp = xzalloc(sizeof(char *) * (num_options + 5));
 	j = 0;
 	envp[j++] = xasprintf("interface=%s", client_config.interface);
-	envp[j++] = xasprintf("PATH=%s",
-		getenv("PATH") ? : "/bin:/usr/bin:/sbin:/usr/sbin");
-	envp[j++] = xasprintf("HOME=%s", getenv("HOME") ? : "/");
+	var = getenv("PATH");
+	if (var)
+		envp[j++] = xasprintf("PATH=%s", var);
+	var = getenv("HOME");
+	if (var)
+		envp[j++] = xasprintf("HOME=%s", var);
 
-	if (packet == NULL) return envp;
+	if (packet == NULL)
+		return envp;
 
 	envp[j] = xmalloc(sizeof("ip=255.255.255.255"));
 	sprintip(envp[j++], "ip=", (uint8_t *) &packet->yiaddr);
@@ -206,19 +213,20 @@ void udhcp_run_script(struct dhcpMessage *packet, const char *name)
 	DEBUG("vfork'ing and execle'ing %s", client_config.script);
 
 	envp = fill_envp(packet);
+
 	/* call script */
+// can we use wait4pid(spawn(...)) here?
 	pid = vfork();
-	if (pid) {
-		waitpid(pid, NULL, 0);
-		for (curr = envp; *curr; curr++) free(*curr);
-		free(envp);
-		return;
-	} else if (pid == 0) {
+	if (pid < 0) return;
+	if (pid == 0) {
 		/* close fd's? */
 		/* exec script */
 		execle(client_config.script, client_config.script,
 		       name, NULL, envp);
-		bb_perror_msg("script %s failed", client_config.script);
-		exit(1);
+		bb_perror_msg_and_die("script %s failed", client_config.script);
 	}
+	waitpid(pid, NULL, 0);
+	for (curr = envp; *curr; curr++)
+		free(*curr);
+	free(envp);
 }
diff --git a/networking/udhcp/serverpacket.c b/networking/udhcp/serverpacket.c
index 8889fda86..e1a88addd 100644
--- a/networking/udhcp/serverpacket.c
+++ b/networking/udhcp/serverpacket.c
@@ -38,7 +38,7 @@ static int send_packet_to_relay(struct dhcpMessage *payload)
 /* send a packet to a specific arp address and ip address by creating our own ip packet */
 static int send_packet_to_client(struct dhcpMessage *payload, int force_broadcast)
 {
-	uint8_t *chaddr;
+	const uint8_t *chaddr;
 	uint32_t ciaddr;
 
 	if (force_broadcast) {