fw/icmp.c (00d70be) - mips_sys · BlinkenArea

icmp.c

#include "checksum.h"
#include "ethernet.h"
#include "icmp.h"
#include "ip.h"
#include "macros.h"
#include "nethelp.h"

/**
 * @brief send an ICMP packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 *
 * ptr must point to a icmp_packet of sufficient size (ethernet padding)
 * with icmp_hdr.type, icmp_hdr.code and ip_hdr.sest already initialized
 */
static void icmp_send(void *ptr, unsigned int sz)
{
  struct icmp_packet *icmp_pack;
  unsigned short chk;

// packet too short
  if (sz < sizeof(struct icmp_packet))
    return;

icmp_pack = ptr;

// fill in header values
  icmp_pack->icmp_hdr.chk = 0x0000;

// generate checksum
  chk = checksum(&icmp_pack->icmp_hdr,
                 sz - sizeof(struct ethernet_header)
                    - sizeof(struct ip_header),
                 0x0000, 0x0000);
  icmp_pack->icmp_hdr.chk = htons(chk);

// send ICMP packet
  icmp_pack->ip_hdr.proto = 0x01; // ICMP
  ip_send(icmp_pack, sz);
}

/**
 * @brief process a received ICMP echo request packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 */
static void icmp_echo_req_recv(void *ptr, unsigned int sz)
{
  struct icmp_echo_packet *icmp_echo_pack;

// packet too short
  if (sz < sizeof(struct icmp_echo_packet))
    return;

icmp_echo_pack = ptr;

// code not 0
  if (icmp_echo_pack->icmp_hdr.code != 0x00)
    return;

// send an ICMP echo reply
  //  - use same buffer to send reply
  //  - this saves us from needing to allocate a new buffer
  //  - this saves us from needing to copy echo_hdr.id, echo_hdr.seq and data
  icmp_echo_pack->icmp_hdr.type = 0x00; // ICMP echo reply
  icmp_echo_pack->icmp_hdr.code = 0x00;
  //   destination IP is source IP of request
  ip_cpy(icmp_echo_pack->ip_hdr.dest, icmp_echo_pack->ip_hdr.src);
  icmp_send(icmp_echo_pack, sz);
}

/**
 * @brief process a received ICMP packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 */
void icmp_recv(void *ptr, unsigned int sz)
{
  struct icmp_packet *icmp_pack;

// packet too short
  if (sz < sizeof(struct icmp_packet))
    return;

icmp_pack = ptr;

// test checksum
  if (checksum(&icmp_pack->icmp_hdr,
               sz - sizeof(struct ethernet_header) - sizeof(struct ip_header),
               0x0000, 0x0000))
    return;

// branch according to type
  switch (icmp_pack->icmp_hdr.type) {
    // ICMP echo request
    case 0x08:
      icmp_echo_req_recv(ptr, sz);
      break;
  }
}

mips_sys

implemented IP + ICMP, fixed ARP (padding overwriting stack)