mips_sys

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#include "config.h"
#include "checksum.h"
#include "ethernet.h"
#include "ip.h"
#include "macros.h"
#include "nethelp.h"
#include "udp.h"
// some kind of "token bucket" for UDP echo
#define UDP_ECHO_TICKS 10 ///< allowed rate of UDP echo replies (in 200ms)
static unsigned int udp_echo_tick_cnt = 0; ///< tick counter
#define UDP_ECHO_REPLIES_MAX 3 ///< maximum value for udp_echo_replies
static unsigned int udp_echo_replies = 0; // # of allowed UDP echo replies
/// tick procedure - call every 200ms
void udp_tick200(void)
{
  // count ticks
  udp_echo_tick_cnt++;
  // time to allow one reply more
  if (udp_echo_tick_cnt >= UDP_ECHO_TICKS) {
    udp_echo_tick_cnt = 0;
    // increase reply count if not at maximum
    if (udp_echo_replies < UDP_ECHO_REPLIES_MAX)
      udp_echo_replies++;
  }
}
/**
 * @brief process a received UDP echo packet
 * @param[in] ptr pointer to data of packet
 * @param[in] sz size of packet
 */
static void udp_echo_recv(void *ptr, unsigned int sz)
{
  struct udp_packet *udp_pack;
  udp_pack = ptr;
  // source port is UDP echo port
  if (udp_pack->udp_hdr.src_port == htons(7))
    // ignore this packet
    //  - UDP echo answer to another UDP echo port will result
    //    in endless echoing
    return;
  // only reply with allowed packet rate
  if (udp_echo_replies <= 0)
    return;
  udp_echo_replies--;
 
 
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