fw/ip.c (3b2902e) - mips_sys · BlinkenArea

ip.c

#include "arp.h"
#include "checksum.h"
#include "config.h"
#include "ethernet.h"
#include "icmp.h"
#include "ip.h"
#include "macros.h"
#include "memcpy.h"
#include "nethelp.h"
#include "udp.h"

// timing parameters
#define IP_BUFFER_TICKS_MAX 50 // maximum age of buffered IP packet (in 200ms)

/**
 * buffers for IP packets to transmit
 *  - used if MAC is unknown when packet shall be transmitted
 *  - packet is sent when MAC becomes known
 *  - some buffers with different length (packets have different lengths)
 */
//@{
unsigned int ip_buffer0[20];
unsigned int ip_buffer1[20];
unsigned int ip_buffer2[40];
unsigned int ip_buffer3[80];
//@}
/// table with buffers
struct ip_buffer_table
{
  void *ptr; ///< pointer to buffer for packet
  unsigned int buf_sz; ///< size of buffer
  unsigned int pkg_sz; ///< size of packet in buffer, 0 for packet
  unsigned int ticks; ///< age of entry (in 200ms)
} ip_buffer_tab[] =
{ // put smaller buffers in front of larger buffers
  //  - then short packets will use smaller buffers more often
  { ip_buffer0, sizeof(ip_buffer0), 0, 0 },
  { ip_buffer1, sizeof(ip_buffer1), 0, 0 },
  { ip_buffer2, sizeof(ip_buffer2), 0, 0 },
  { ip_buffer3, sizeof(ip_buffer3), 0, 0 },
};

/// initialize
void ip_init(void)
{
  unsigned int i;
  for (i = 0; i < count(ip_buffer_tab); i++)
    ip_buffer_tab[i].pkg_sz = 0;
}

/// tick procedure - call every 200ms
void ip_tick200(void)
{
  unsigned int i;

// increase age of buffered IP packets and remove timed out ones
  for (i = 0; i < count(ip_buffer_tab); i++) {
    if (ip_buffer_tab[i].pkg_sz > 0) { // buffer in use
      ip_buffer_tab[i].ticks++; // increase age
      if (ip_buffer_tab[i].ticks > IP_BUFFER_TICKS_MAX) // too old
        ip_buffer_tab[i].pkg_sz = 0; // discard packet
    }
  }
}

/**
 * @brief process a received IP packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 */
void ip_recv(void *ptr, unsigned int sz)
{
  struct ip_packet *ip_pack;
  unsigned int len;

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

ip_pack = ptr;

// not IPv4 -> drop
  if (ip_pack->ip_hdr.ver__hdr_len != 0x45) // IPv4 with no options present
    return;

// not to own IP / broadcast -> drop
  while (1) {
    // own IP -> accept
    if (ip_eq(ip_pack->ip_hdr.dest, config_ip.ip))
      break;
    // local network's broadcast address -> accept
    if ((ip_pack->ip_hdr.dest[0] & config_ip.mask[0]) ==
          (config_ip.ip[0] & config_ip.mask[0]) &&
        (ip_pack->ip_hdr.dest[1] & config_ip.mask[1]) ==
          (config_ip.ip[1] & config_ip.mask[1]) &&
        (ip_pack->ip_hdr.dest[2] & config_ip.mask[2]) ==
          (config_ip.ip[2] & config_ip.mask[2]) &&
        (ip_pack->ip_hdr.dest[3] & config_ip.mask[3]) ==
          (config_ip.ip[3] & config_ip.mask[3]) &&
        (ip_pack->ip_hdr.dest[0] & ~config_ip.mask[0]) ==
          ~config_ip.mask[0] &&
        (ip_pack->ip_hdr.dest[1] & ~config_ip.mask[1]) ==
          ~config_ip.mask[1] &&
        (ip_pack->ip_hdr.dest[2] & ~config_ip.mask[2]) ==
          ~config_ip.mask[2] &&
        (ip_pack->ip_hdr.dest[3] & ~config_ip.mask[3]) ==
          ~config_ip.mask[3])
      break;
    // link local boradcast address -> accept
    if (ip_pack->ip_hdr.dest[0] == 0xFF &&
        ip_pack->ip_hdr.dest[1] == 0xFF &&
        ip_pack->ip_hdr.dest[2] == 0xFF &&
        ip_pack->ip_hdr.dest[3] == 0xFF)
      break;
    // drop
    return;
  }

// ignore packets sent from invalid source adresses
  //  - this might be some attack or some router fault
  if (ip_pack->ip_hdr.src[0] >= 0xE0 || // broadcast, reserved or multicast
      ip_pack->ip_hdr.src[0] == 0x7F || // loopback network
      ip_eq(ip_pack->ip_hdr.src, "\x00\x00\x00\x00")) // IP 0.0.0.0
    return;
  // ignore packets sent from local network or broadcast address
  if ((ip_pack->ip_hdr.src[0] & config_ip.mask[0]) ==
        (config_ip.ip[0] & config_ip.mask[0]) && // source IP is in own subnet
      (ip_pack->ip_hdr.src[1] & config_ip.mask[1]) ==
        (config_ip.ip[1] & config_ip.mask[1]) &&
      (ip_pack->ip_hdr.src[2] & config_ip.mask[2]) ==
        (config_ip.ip[2] & config_ip.mask[2]) &&
      (ip_pack->ip_hdr.src[3] & config_ip.mask[3]) ==
        (config_ip.ip[3] & config_ip.mask[3])) {
    // local network address
    if ((ip_pack->ip_hdr.src[0] & ~config_ip.mask[0]) == 0x00 &&
        (ip_pack->ip_hdr.src[1] & ~config_ip.mask[1]) == 0x00 &&
        (ip_pack->ip_hdr.src[2] & ~config_ip.mask[2]) == 0x00 &&
        (ip_pack->ip_hdr.src[3] & ~config_ip.mask[3]) == 0x00)
      return;
    // local broadcast address
    if ((ip_pack->ip_hdr.src[0] & ~config_ip.mask[0]) == 0xFF &&
        (ip_pack->ip_hdr.src[1] & ~config_ip.mask[1]) == 0xFF &&
        (ip_pack->ip_hdr.src[2] & ~config_ip.mask[2]) == 0xFF &&
        (ip_pack->ip_hdr.src[3] & ~config_ip.mask[3]) == 0xFF)
      return;
  }
  // ignore packets sent from own IP address
  if (ip_eq(ip_pack->ip_hdr.src, config_ip.ip))
    return;

// ignore fragmented packets
  // BUG: fragmentation must be supported according to RFC781
  //      but there is not enough RAM for assembling packets with up to 64kB
  // fragment offset 0, more_frags=0, dont_frag=x, reserved_flag=0
  if ((ntohs(ip_pack->ip_hdr.frag_ofs) & 0xBFFF) != 0x0000)
    return;

// check total length
  len = sizeof(struct ethernet_header) + ntohs(ip_pack->ip_hdr.total_len);
  if (sz < len) // packet is truncated
    return;
  sz = len; // remove ethernet padding from packet (maybe sz > len)

// test header checksum
  if (checksum(&ip_pack->ip_hdr, sizeof(struct ip_header), 0x0000, 0x0000))
    return;

// save MAC/IP information in ARP table
  arp_store(ip_pack->ip_hdr.src, ip_pack->eth_hdr.src);

// branch according to protocol
  switch (ip_pack->ip_hdr.proto) {
    // ICMP
    case 0x01:
      icmp_recv(ptr, sz);
      break;
    // UDP
    case 0x11:
      udp_recv(ptr, sz);
      break;
  }
}

/**
 * @brief send an IP packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 *
 * ptr must point to a ip_packet
 * with ip_hdr.proto and ip_hdr.dest already initialized
 */
void ip_send(void *ptr, unsigned int sz)
{
  struct ip_packet *ip_pack;
  unsigned short chk;
  unsigned int i;

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

ip_pack = ptr;

// fill in header values
  ip_pack->ip_hdr.ver__hdr_len = 0x45;
  ip_pack->ip_hdr.tos = 0x00;
  ip_pack->ip_hdr.total_len = htons(sz - sizeof(struct ethernet_header));
  ip_pack->ip_hdr.id = 0x0000;
  ip_pack->ip_hdr.frag_ofs = 0x0000;
  ip_pack->ip_hdr.ttl = 0x40;
  ip_pack->ip_hdr.hdr_chk = 0x0000;
  ip_cpy(ip_pack->ip_hdr.src, config_ip.ip);

// generate header checksum
  chk = checksum(&ip_pack->ip_hdr, sizeof(struct ip_header), 0x0000, 0x0000);
  ip_pack->ip_hdr.hdr_chk = htons(chk);

// MAC available
  if (i == 0x00) {
    // sent IP packet
    ip_pack->eth_hdr.type = htons(0x0800); // ethernet packet type: IP
    ethernet_send(ip_pack, sz);
    return;
  }

// find a buffer to store the packet in
  for (i = 0; i < count(ip_buffer_tab); i++) {
    if (ip_buffer_tab[i].pkg_sz == 0 && // buffer not in use
        sz <= ip_buffer_tab[i].buf_sz) { // buffer long enough
      // put packet into buffer
      memcpy(ip_buffer_tab[i].ptr, ptr, sz);
      ip_buffer_tab[i].pkg_sz = sz;
      ip_buffer_tab[i].ticks = 0;
      break;
    }
  }
  /* if no buffer was found, we cannnot do anything about it
     and must discard the packet (i.e. do nothing here) */
}

/**
 * @brief a MAC address was discovered
 * @param[in] ip the IP address the MAC was discovered for
 * @param[in] mac the MAC address corresponding to the IP address
 *
 * called by ARP to notify IP
 */
void ip_got_mac(unsigned char ip[4], unsigned char mac[6])
{
  unsigned char i;
  struct ip_packet *ip_pack;

// search for buffered packets that can be sent now
  for (i = 0; i < count(ip_buffer_tab); i++) {
    if (ip_buffer_tab[i].pkg_sz > 0) { // buffer in use
      ip_pack = ip_buffer_tab[i].ptr;

// destination is in own subnet
      if ((ip_pack->ip_hdr.dest[0] & config_ip.mask[0]) ==
            (config_ip.ip[0] & config_ip.mask[0]) &&
          (ip_pack->ip_hdr.dest[1] & config_ip.mask[1]) ==
            (config_ip.ip[1] & config_ip.mask[1]) &&
          (ip_pack->ip_hdr.dest[2] & config_ip.mask[2]) ==
            (config_ip.ip[2] & config_ip.mask[2]) &&
          (ip_pack->ip_hdr.dest[3] & config_ip.mask[3]) ==
            (config_ip.ip[3] & config_ip.mask[3])) {
        // packet can be sent to destination
        if (ip_eq(ip_pack->ip_hdr.dest, ip)) {
          // send IP packet
          ip_pack->eth_hdr.type = htons(0x0800); // ethernet packet type: IP
          mac_cpy(ip_pack->eth_hdr.dest, mac);
          ethernet_send(ip_buffer_tab[i].ptr, ip_buffer_tab[i].pkg_sz);
          // buffer is now free
          ip_buffer_tab[i].pkg_sz = 0;
        }
      }
      // destination is not in own subnet
      else {
        // packet can be sent to gateway
        if (ip_eq(config_ip.gw, ip)) {
          // send IP packet
          ip_pack->eth_hdr.type = htons(0x0800); // ethernet packet type: IP
          mac_cpy(ip_pack->eth_hdr.dest, mac);
          ethernet_send(ip_buffer_tab[i].ptr, ip_buffer_tab[i].pkg_sz);
          // buffer is now free
          ip_buffer_tab[i].pkg_sz = 0;
        }
      }
    }
  } // for (i ...
}

mips_sys

use implicit MAC/IP information in received IP packets