ndhc/ndhc/packet.h

#ifndef PACKET_H_
#define PACKET_H_

#include <netinet/udp.h>
#include <netinet/ip.h>

#include "config.h"

struct dhcpMessage {
    uint8_t op; // Message type: 1 = BOOTREQUEST for clients.
    uint8_t htype; // ARP HW address type: always '1' for 10MB ethernet.
    uint8_t hlen; // Hardware address length: always '6' for 10MB ethernet.
    uint8_t hops; // Client sets to zero.
    uint32_t xid;  // Transaction ID: random number identifying session
    uint16_t secs; // Filled by client: seconds since client began address
                   // aquisition or renewal process.
    uint16_t flags; // DHCP flags
    uint32_t ciaddr; // Client IP: only filled in if client is inBOUND, RENEW,
                     // or REBINDING and can reply to ARP requests
    uint32_t yiaddr; // 'your' (client) IP address
    uint32_t siaddr; // IP address of next server to use in bootstrap; returned
                     // in DHCPOFFER or DHCPACK by server
    uint32_t giaddr; // relay agent IP: used when booting via relay agent
    uint8_t chaddr[16]; // Client MAC address
    uint8_t sname[64]; // Server host name (optional); null-terminated string
    uint8_t file[128]; // boot file name, null-terminated string
    uint32_t cookie;
    uint8_t options[308]; /* 312 - cookie */
};

struct ip_udp_dhcp_packet {
    struct iphdr ip;
    struct udphdr udp;
    struct dhcpMessage data;
};

struct udp_dhcp_packet {
    struct udphdr udp;
    struct dhcpMessage data;
};

enum {
	IP_UPD_DHCP_SIZE = sizeof(struct ip_udp_dhcp_packet),
	UPD_DHCP_SIZE    = sizeof(struct udp_dhcp_packet),
	DHCP_SIZE        = sizeof(struct dhcpMessage),
};

int get_packet(struct dhcpMessage *packet, int fd);
uint16_t checksum(void *addr, int count);
int raw_packet(struct dhcpMessage *payload, uint32_t source_ip,
               int source_port, uint32_t dest_ip, int dest_port,
               unsigned char *dest_arp, int ifindex);
int kernel_packet(struct dhcpMessage *payload, uint32_t source_ip,
                  int source_port, uint32_t dest_ip, int dest_port);
void change_listen_mode(struct client_state_t *cs, int new_mode);
void handle_packet(struct client_state_t *cs);
#endif