net_ipv4.h

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typedef struct icmphdr {
    uint8_t type;                       // ICMP_
    uint8_t code;
    uint16_t checksum;                  // checksum of ICMP header + data
    union {
        struct {
            uint16_t id;
            uint16_t sequence;
        } echo;                         // ICMP_ECHO, ICMP_ECHOREPLY
        uint32_t gateway;
        struct {
            uint16_t __unused;
            uint16_t mtu;
        } frag;
    } un;
    unsigned char data[MAX_ICMP_DATA];
} __attribute__((packed)) icmphdr_t;

// ICMP IP packet
typedef struct icmpip {
    struct iphdr ip;
    struct icmphdr icmp;
} __attribute__((packed)) icmpip_t;

/*
 * UDP related definitions
 * Some of these definitions are from /usr/include/linux/udp.h
 */

// UDP packet header
typedef struct udphdr {
    uint16_t src;                       // source : source port
    uint16_t dest;                      // dest : destination port
    uint16_t len;                       // len : length including header and data
    uint16_t checksum;                  // check : checksum of UDP header, pseudo header and data
} __attribute__((packed)) udphdr_t;

// pseudo TCP/UDP header
// used for calculating checksum of TCP/UDP packet
typedef struct tcpudp_pseudohdr {
    in_addr_t src;                      // source address
    in_addr_t dest;                     // destination address
    uint8_t zero;                       // 0
    uint8_t protocol;                   // protocol
    uint16_t length;                    // TCP/UDP length
} __attribute__((packed)) tcpudp_pseudohdr_t;

/*
 * BOOTP / DHCP related definitions
 */

// BOOTP retry maximum count
#define MAX_BOOTP_RETRIES       3

// DHCP option length
#define DHCP_OPT_LEN            312

// opcode : bp_op
#define BOOTP_REQUEST           1
#define BOOTP_REPLY             2

// DHCP_MESSAGE_TYPE code
#define DHCPDISCOVER            1
#define DHCPOFFER               2
#define DHCPREQUEST             3
#define DHCPDECLINE             4
#define DHCPACK                 5
#define DHCPNAK                 6
#define DHCPRELEASE             7
#define DHCPINFORM              8

// BOOTP/DHCP packet header and body (option)
typedef struct bootphdr {
    uint8_t bp_op;                      // opcode : BOOTP_REQUEST / BOOTP_REPLY
    uint8_t bp_htype;                   // hardware address type
    uint8_t bp_hlen;                    // hardware address length
    uint8_t bp_hops;                    // 0
    uint32_t bp_xid;                    // random transaction ID
    uint16_t bp_secs;                   // seconds elapsed
    uint16_t bp_flags;                  // unused
    in_addr_t bp_ciaddr;                // client IP address
    in_addr_t bp_yiaddr;                // your (client) IP address
    in_addr_t bp_siaddr;                // server IP address
    in_addr_t bp_giaddr;                // gateway IP address
    uint8_t bp_hwaddr[16];              // client hardware address
    uint8_t bp_sname[64];               // optional server hostname (null-terminated)
    uint8_t bp_file[128];               // boot file name(null-terminated)
    uint8_t bp_vend[DHCP_OPT_LEN];      // optional vendor-specific area
} __attribute__((packed)) bootphdr_t;

// BOOTP/DHCP IP packet
typedef struct bootpip {
    struct iphdr ip;
    struct udphdr udp;
    struct bootphdr bp;
} __attribute__((packed)) bootpip_t;

/*
 * TFTP related definitions
 */

// TFTP retry maximum count
#define MAX_TFTP_RETRIES        3

// TFTP packet size
#define TFTP_DEF_PACKET         512
#define TFTP_MAX_PACKET         1432 

// TFTP packet type
#define TFTPOP_RRQ              1       // Read Request
#define TFTPOP_WRQ              2       // Write Request
#define TFTPOP_DATA             3       // Data
#define TFTPOP_ACK              4       // Acknowledgment
#define TFTPOP_ERROR            5       // Error
#define TFTPOP_OACK             6       // Option Acknowledgment

// TFTP error code
#define TFTPERR_FILENOTFOUND    1       // File not found
#define TFTPERR_ACCESSDENIED    2       // Access violation
#define TFTPERR_DISKFULL        3       // Disk full or allocation exceeded
#define TFTPERR_ILLEGALOP       4       // Illeegal TFTP operation
#define TFTPERR_UNKNOWNID       5       // Unknown transfer ID
#define TFTPERR_FILEEXIST       6       // File already exists
#define TFTPERR_NOUSER          7       // No such user

// return code of ipv4_tftp()
#define TFTPRET_NETWORKERR      1   
#define TFTPRET_FILENOTFOUND    2
#define TFTPRET_ACCESSDENIED    3
#define TFTPRET_OTHER           4

// TFTP header and body
typedef struct tftphdr {
    uint16_t opcode;                    // TFTPOP_
    union {
        uint8_t rrq[TFTP_DEF_PACKET];   // TFTPOP_RRQ, TFTPOP_WRQ
        struct {
            uint16_t block;
            uint8_t data[TFTP_MAX_PACKET];
        } data;                         // TFTPOP_DATA
        struct {
            uint16_t block;
        } ack;                          // TFTPOP_ACK
        struct {
            uint16_t errcode;
            uint8_t errmsg[TFTP_DEF_PACKET];
        } err;                          // TFTPOP_ERROR
        struct {
            uint8_t data[TFTP_DEF_PACKET];
        } oack;                         // TFTPOP_OACK
    } u;
} __attribute__((packed)) tftphdr_t;

// TFTP IP packet
typedef struct tftpip {
    struct iphdr ip;
    struct udphdr udp;
    struct tftphdr tftp;
} __attribute__((packed)) tftpip_t;

/*
 * function prototypes
 */

struct sk_buff;

#define TIMEOUT         (5 * 1000)

// init
int ipv4_init(void);
void ipv4_setup_arptable(in_addr_t ipaddr, in_addr_t netmask, unsigned char *node, in_addr_t gateway, in_addr_t dns);

// TCP/IP basic
int ipv4_get_ipaddr_class(in_addr_t ipaddr);
in_addr_t ipv4_get_default_netmask(in_addr_t ipaddr);
int ipv4_ipaddr_valid(in_addr_t ipaddr);
int ipv4_alloc_port(void);

// packet processing
int ipv4_check_for_me(struct sk_buff *skb);
int ipv4_parsepacket(struct sk_buff *skb);
int ipv4_processpacket(struct sk_buff *skb);

// Ethernet
enum {
    WAIT_NOTHING,
    WAIT_ARP_REPLY,
    WAIT_ICMP_REPLY,
    WAIT_UDP,
};

int eth_transmit(unsigned char *dest, uint16_t type, unsigned int len, const void *buf, int async);
struct sk_buff *eth_receive(int type, int timeout);

// arp
arptable_t *arp_lookup(unsigned long ipaddr);
arptable_t *arp_alloc(void);
int arp_valid(arptable_t *arp);
void arp_setaddr(arptable_t *arp, in_addr_t ipaddr, in_addr_t netmask, unsigned char *node);
void arp_setaddr_index(int index, in_addr_t ipaddr, in_addr_t netmask, unsigned char *node);
void arp_listtable(arptable_t *arp);
int arp_transmit(int opcode, in_addr_t ipaddr, unsigned char *node, int async);
arptable_t *arp_dorequest(unsigned long ipaddr, int async);

// IP
int ip_transmit(in_addr_t destip, int protocol, int len, const void *buf, int async);
unsigned int ipv4_calc_sum(const void *ip, int len);
unsigned short ipv4_calc_checksum(const void *ip, int len);

// ICMP / IP
int icmp_ping(in_addr_t destip, int count);

// UDP / IP
int udp_transmit(in_addr_t destip, unsigned int srcsock, unsigned int destsock, int len, const void *buf, int async);
unsigned short ipv4_calc_tcpudp_checksum(const void *data, int len, in_addr_t src, in_addr_t dest);
struct sk_buff *udp_receive(in_addr_t fromip, unsigned int srcsock, unsigned int destsock, int timeout);

// BOOTP / DHCP (net_ipv4_bootp.c)
int ipv4_bootp(int bootp);

// TFTP (net_ipv4_tftp.c)
int ipv4_tftp(in_addr_t ipaddr, char *filename, unsigned int addr, unsigned int *datalen);

// DNS (net_ipv4_dns.c)
in_addr_t ipv4_gethostbyname(char *name);

// Miscellaneous
void ipv4_dump_packet(struct sk_buff *skb, int type, int need_parsing);
void bootp_dump_packet(struct sk_buff *skb, int need_parsing);
void tftp_dump_packet(struct sk_buff *skb, int need_parsing);

#endif