Skip to content

Commit

Permalink
Translated magic numbers into defines to make it easier to read
Browse files Browse the repository at this point in the history
  • Loading branch information
@denisvm
denisvm committed Aug 22, 2016
1 parent 9253af1 commit 279f5ba
Show file tree
Hide file tree
Showing 2 changed files with 52 additions and 47 deletions.
97 changes: 50 additions & 47 deletions dhcp.cpp
View file
Expand Up @@ -81,7 +81,7 @@ typedef struct {
byte op, htype, hlen, hops;
uint32_t xid;
uint16_t secs, flags;
byte ciaddr[4], yiaddr[4], siaddr[4], giaddr[4];
byte ciaddr[IP_LEN], yiaddr[IP_LEN], siaddr[IP_LEN], giaddr[IP_LEN];
byte chaddr[16], sname[64], file[128];
// options
} DHCPdata;
Expand Down Expand Up @@ -120,6 +120,12 @@ static void addBytes (byte len, const byte* data) {
addToBuf(*data++);
}

static void addOption (byte opt, byte len, const byte* data) {
addToBuf(opt);
addToBuf(len);
addBytes(len, data);
}


// Main DHCP sending function

Expand All @@ -139,15 +145,20 @@ static void addBytes (byte len, const byte* data) {
// ----------------------------------------------------------

// options used (both send/receive)
// 12 Host Name Option
// 50 Requested IP Address
// 51 IP Address Lease Time
// 53 DHCP message type
// 54 Server-identifier
// 55 Parameter request list
// 58 Renewal (T1) Time Value
// 61 Client-identifier
// 255 End
#define DHCP_OPT_SUBNET_MASK 1
#define DHCP_OPT_ROUTERS 3
#define DHCP_OPT_DOMAIN_NAME_SERVERS 6
#define DHCP_OPT_HOSTNAME 12
#define DHCP_OPT_REQUESTED_ADDRESS 50
#define DHCP_OPT_LEASE_TIME 51
#define DHCP_OPT_MESSAGE_TYPE 53
#define DHCP_OPT_SERVER_IDENTIFIER 54
#define DHCP_OPT_PARAMETER_REQUEST_LIST 55
#define DHCP_OPT_RENEWAL_TIME 58
#define DHCP_OPT_CLIENT_IDENTIFIER 61
#define DHCP_OPT_END 255

#define DHCP_HTYPE_ETHER 1

static void send_dhcp_message(uint8_t *requestip) {

Expand Down Expand Up @@ -175,48 +186,41 @@ static void send_dhcp_message(uint8_t *requestip) {

// options defined as option, length, value
bufPtr = gPB + UDP_DATA_P + sizeof( DHCPdata );
// DHCP magic cookie, followed by message type
static byte cookie[] = { 99, 130, 83, 99, 53, 1 };
// DHCP magic cookie
static const byte cookie[] PROGMEM = { 0x63,0x82,0x53,0x63 };
addBytes(sizeof cookie, cookie);
// addToBuf(53); // DHCP_STATE_SELECTING, DHCP_STATE_REQUESTING
// addToBuf(1); // Length
addToBuf(DHCP_OPT_MESSAGE_TYPE); // DHCP_STATE_SELECTING, DHCP_STATE_REQUESTING
addToBuf(1); // Length
addToBuf(dhcpState == DHCP_STATE_INIT ? DHCP_DISCOVER : DHCP_REQUEST);

// Client Identifier Option, this is the client mac address
addToBuf(61); // Client identifier
addToBuf(7); // Length
addToBuf(0x01); // Ethernet
addBytes(6, EtherCard::mymac);
addToBuf(DHCP_OPT_CLIENT_IDENTIFIER);
addToBuf(1 + ETH_LEN); // Length (hardware type + client MAC)
addToBuf(DHCP_HTYPE_ETHER);
addBytes(ETH_LEN, EtherCard::mymac);

if (hostname[0]) {
byte hostnamelen = strlen(hostname);
addToBuf(12); // Host name Option
addToBuf(hostnamelen);
addBytes(hostnamelen, (byte*) hostname);
addOption(DHCP_OPT_HOSTNAME, strlen(hostname), (byte*) hostname);
}

if (requestip != NULL) {
addToBuf(50); // Request IP address
addToBuf(4);
addBytes(4, requestip);

addToBuf(54); // DHCP Server IP address
addToBuf(4);
addBytes(4, EtherCard::dhcpip);
addOption(DHCP_OPT_REQUESTED_ADDRESS, IP_LEN, requestip);
addOption(DHCP_OPT_SERVER_IDENTIFIER, IP_LEN, EtherCard::dhcpip);
}

// Additional info in parameter list - minimal list for what we need
byte len = 3;
if (dhcpCustomOptionNum)
len++;
addToBuf(55); // Parameter request list
addToBuf(DHCP_OPT_PARAMETER_REQUEST_LIST);
addToBuf(len); // Length
addToBuf(1); // Subnet mask
addToBuf(3); // Route/Gateway
addToBuf(6); // DNS Server
addToBuf(DHCP_OPT_SUBNET_MASK);
addToBuf(DHCP_OPT_ROUTERS);
addToBuf(DHCP_OPT_DOMAIN_NAME_SERVERS);
if (dhcpCustomOptionNum)
addToBuf(dhcpCustomOptionNum); // Custom option
addToBuf(255); // end option

addToBuf(DHCP_OPT_END);

// packet size will be under 300 bytes
EtherCard::udpTransmit((bufPtr - gPB) - UDP_DATA_P);
Expand All @@ -229,12 +233,12 @@ static void process_dhcp_offer(uint16_t len, uint8_t *offeredip) {
// Offered IP address is in yiaddr
EtherCard::copyIp(offeredip, dhcpPtr->yiaddr);

// Search for the
// Search for the server IP
byte *ptr = (byte*) (dhcpPtr + 1) + 4;
do {
byte option = *ptr++;
byte optionLen = *ptr++;
if (option == 54) {
if (option == DHCP_OPT_SERVER_IDENTIFIER) {
EtherCard::copyIp(EtherCard::dhcpip, ptr);
break;
}
Expand All @@ -256,25 +260,25 @@ static void process_dhcp_ack(uint16_t len) {
byte option = *ptr++;
byte optionLen = *ptr++;
switch (option) {
case 1:
case DHCP_OPT_SUBNET_MASK:
EtherCard::copyIp(EtherCard::netmask, ptr);
break;
case 3:
case DHCP_OPT_ROUTERS:
EtherCard::copyIp(EtherCard::gwip, ptr);
break;
case 6:
case DHCP_OPT_DOMAIN_NAME_SERVERS:
EtherCard::copyIp(EtherCard::dnsip, ptr);
break;
case 51:
case 58:
leaseTime = 0; // option 58 = Renewal Time, 51 = Lease Time
case DHCP_OPT_LEASE_TIME:
case DHCP_OPT_RENEWAL_TIME:
leaseTime = 0;
for (byte i = 0; i<4; i++)
leaseTime = (leaseTime << 8) + ptr[i];
if (leaseTime != DHCP_INFINITE_LEASE) {
leaseTime *= 1000; // milliseconds
}
break;
case 255:
case DHCP_OPT_END:
done = true;
break;
default: {
Expand All @@ -299,8 +303,7 @@ static bool dhcp_received_message_type (uint16_t len, byte msgType) {
do {
byte option = *ptr++;
byte optionLen = *ptr++;
if(option == 53 && *ptr == msgType ) {
// DHCP Message type match found
if(option == DHCP_OPT_MESSAGE_TYPE && *ptr == msgType ) {
return true;
}
ptr += optionLen;
Expand Down Expand Up @@ -390,7 +393,7 @@ void EtherCard::DhcpStateMachine (uint16_t len)

case DHCP_STATE_INIT:
currentXid = millis();
memset(myip,0,4); // force ip 0.0.0.0
memset(myip,0,IP_LEN); // force ip 0.0.0.0
send_dhcp_message(NULL);
enableBroadcast(true); //Temporarily enable broadcasts
dhcpState = DHCP_STATE_SELECTING;
Expand All @@ -399,7 +402,7 @@ void EtherCard::DhcpStateMachine (uint16_t len)

case DHCP_STATE_SELECTING:
if (dhcp_received_message_type(len, DHCP_OFFER)) {
uint8_t offeredip[4];
uint8_t offeredip[IP_LEN];
process_dhcp_offer(len, offeredip);
send_dhcp_message(offeredip);
dhcpState = DHCP_STATE_REQUESTING;
Expand Down
2 changes: 2 additions & 0 deletions net.h
View file
Expand Up @@ -15,6 +15,7 @@

// ******* ETH *******
#define ETH_HEADER_LEN 14
#define ETH_LEN 6
// values of certain bytes:
#define ETHTYPE_ARP_H_V 0x08
#define ETHTYPE_ARP_L_V 0x06
Expand Down Expand Up @@ -52,6 +53,7 @@

// ******* IP *******
#define IP_HEADER_LEN 20
#define IP_LEN 4
// ip.src
#define IP_SRC_P 0x1a
#define IP_DST_P 0x1e
Expand Down

0 comments on commit 279f5ba

Please sign in to comment.