dhcp: stop using magic constants; use (htonl(CONST) != a) - it's smaller

function                                             old     new   delta
udhcp_get_packet                                     146     134     -12
get_raw_packet                                       368     353     -15

networking/udhcp/clientpacket.c

@@ -171,7 +171,7 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
 	bytes = read(fd, &packet, sizeof(struct udp_dhcp_packet));
 	if (bytes < 0) {
 		DEBUG("Cannot read on raw listening socket - ignoring");
-		usleep(500000); /* possible down interface, looping condition */
+		sleep(1); /* possible down interface, looping condition */
 		return -1;
 	}
 
@@ -190,7 +190,7 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
 
 	/* Make sure its the right packet for us, and that it passes sanity checks */
 	if (packet.ip.protocol != IPPROTO_UDP || packet.ip.version != IPVERSION
-	 || packet.ip.ihl != sizeof(packet.ip) >> 2
+	 || packet.ip.ihl != (sizeof(packet.ip) >> 2)
 	 || packet.udp.dest != htons(CLIENT_PORT)
 	 || bytes > (int) sizeof(struct udp_dhcp_packet)
 	 || ntohs(packet.udp.len) != (uint16_t)(bytes - sizeof(packet.ip))
@@ -207,7 +207,7 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
 		return -1;
 	}
 
-	/* verify the UDP checksum by replacing the header with a psuedo header */
+	/* verify the UDP checksum by replacing the header with a pseudo header */
 	source = packet.ip.saddr;
 	dest = packet.ip.daddr;
 	check = packet.udp.check;
@@ -225,7 +225,7 @@ int get_raw_packet(struct dhcpMessage *payload, int fd)
 
 	memcpy(payload, &(packet.data), bytes - (sizeof(packet.ip) + sizeof(packet.udp)));
 
-	if (ntohl(payload->cookie) != DHCP_MAGIC) {
+	if (payload->cookie != htonl(DHCP_MAGIC)) {
 		bb_error_msg("received bogus message (bad magic) - ignoring");
 		return -2;
 	}

networking/udhcp/common.h

@@ -38,12 +38,18 @@ struct dhcpMessage {
 	uint8_t file[128];
 	uint32_t cookie;
 	uint8_t options[308]; /* 312 - cookie */
-};
+} ATTRIBUTE_PACKED;
 
 struct udp_dhcp_packet {
 	struct iphdr ip;
 	struct udphdr udp;
 	struct dhcpMessage data;
+} ATTRIBUTE_PACKED;
+
+/* Let's see whether compiler understood us right */
+struct BUG_bad_sizeof_struct_udp_dhcp_packet {
+	char BUG_bad_sizeof_struct_udp_dhcp_packet
+                [sizeof(struct udp_dhcp_packet) != 576 ? -1 : 1];
 };
 
 void udhcp_init_header(struct dhcpMessage *packet, char type);

networking/udhcp/options.c

@@ -73,12 +73,13 @@ uint8_t *get_option(struct dhcpMessage *packet, int code)
 {
 	int i, length;
 	uint8_t *optionptr;
-	int over = 0, done = 0, curr = OPTION_FIELD;
+	int over = 0;
+	int curr = OPTION_FIELD;
 
 	optionptr = packet->options;
 	i = 0;
-	length = 308;
-	while (!done) {
+	length = sizeof(packet->options);
+	while (1) {
 		if (i >= length) {
 			bb_error_msg("bogus packet, option fields too long");
 			return NULL;
@@ -103,17 +104,18 @@ uint8_t *get_option(struct dhcpMessage *packet, int code)
 			i += optionptr[OPT_LEN] + 2;
 			break;
 		case DHCP_END:
-			if (curr == OPTION_FIELD && over & FILE_FIELD) {
+			if (curr == OPTION_FIELD && (over & FILE_FIELD)) {
 				optionptr = packet->file;
 				i = 0;
-				length = 128;
+				length = sizeof(packet->file);
 				curr = FILE_FIELD;
-			} else if (curr == FILE_FIELD && over & SNAME_FIELD) {
+			} else if (curr == FILE_FIELD && (over & SNAME_FIELD)) {
 				optionptr = packet->sname;
 				i = 0;
-				length = 64;
+				length = sizeof(packet->sname);
 				curr = SNAME_FIELD;
-			} else done = 1;
+			} else
+				return NULL;
 			break;
 		default:
 			i += optionptr[OPT_LEN + i] + 2;

networking/udhcp/options.h

@@ -6,7 +6,7 @@
 #define TYPE_MASK	0x0F
 
 enum {
-	OPTION_IP=1,
+	OPTION_IP = 1,
 	OPTION_IP_PAIR,
 	OPTION_STRING,
 #if ENABLE_FEATURE_RFC3397

networking/udhcp/packet.c

@@ -57,7 +57,7 @@ int udhcp_get_packet(struct dhcpMessage *packet, int fd)
 		return -1;
 	}
 
-	if (ntohl(packet->cookie) != DHCP_MAGIC) {
+	if (packet->cookie != htonl(DHCP_MAGIC)) {
 		bb_error_msg("received bogus message, ignoring");
 		return -2;
 	}
@@ -123,7 +123,6 @@ uint16_t udhcp_checksum(void *addr, int count)
 
 
 /* Construct a ip/udp header for a packet, and specify the source and dest hardware address */
-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, const uint8_t *dest_arp, int ifindex)
@@ -169,9 +168,6 @@ int udhcp_raw_packet(struct dhcpMessage *payload,
 	packet.ip.ttl = IPDEFTTL;
 	packet.ip.check = udhcp_checksum(&(packet.ip), sizeof(packet.ip));
 
-	if (sizeof(struct udp_dhcp_packet) != 576)
-		BUG_sizeof_struct_udp_dhcp_packet_must_be_576();
-
 	result = sendto(fd, &packet, sizeof(struct udp_dhcp_packet), 0,
 			(struct sockaddr *) &dest, sizeof(dest));
 	if (result <= 0) {