anycast.c

It support IPv4 and IPv6 unicast and multicast and contains a trivial sender and a trivial receiver

#include "socket.h"
#include "ip4.h"
#include "ip6.h"
#include "uint16.h"
#include "open.h"
#include "byte.h"
#include "scan.h"
#include "strerr.h"
#include <stdlib.h>
#include <sys/time.h>
#include <unistd.h>

/* usage: anycast (ip4|\[ip6\]):port ... */

/* return pointer to first byte of payload data */
char *rtp_skipheader(unsigned char *packet) {
  char v=packet[0]>>6;
  char cc=packet[0] & 15;
  if (v==2)
    return packet+12+(cc*4);
  else
    return packet;
}

/* initialize RTP header according to RFC; version=2, all flags zero,
 * payload type as specified and sequence number, timestamp and SSRC
 * random. */
void rtp_initheader(char *header, char payloadtype) {
  int fd=open_read("/dev/urandom");
  int i;
  for (i=2; i<12; i++)
    header[i]=rand() & 255;
  read(fd,header+2,10);
  header[0]=0x80;
  header[1]=payloadtype;
}

/* increment sequence number */
void rtp_nextsequence(char *header) {
  uint16 s;
  uint16_unpack_big(header+2,&s);
  s++;
  uint16_pack_big(header+2,s);
}

/* read sequence number */
uint16 rtp_getsequence(char *header) {
  uint16 s;
  uint16_unpack_big(header+2,&s);
  return s;
}

/* read payload type */
char rtp_getpt(char *header) {
  return header[1]<<1;
}

int main(int argc,char *argv[]) {
  char buf[1500];
  char ip[16];
  long len,type=14,port=5004;
  int v6=0;
  int s;
  uint32 ts;
  struct timeval start,now;

  if (argc<2)
    strerr_die1x(0,"usage: anycast ip [port]\nWill multi/unicast stdin, default port is 5004.");
  if (argc>2) {
    len=scan_ulong(argv[2],&port);
    if (argv[2][len])
      strerr_die1x(0,"anycast: invalid port number: parse error.");
    if (port>0xffff)
      strerr_die1x(0,"anycast: invalid port number: too large.");
  }
  if (argc>3) {
    len=scan_ulong(argv[3],&type);
    if (argv[3][len])
      strerr_die1x(0,"anycast: invalid type: parse error.");
    if (type>127)
      strerr_die1x(0,"anycast: invalid type: too large.");
  }
  len=ip4_scan(argv[1],ip);
  if (argv[1][len]) {
    len=ip6_scan(argv[1],ip);
    if (argv[1][len])
      strerr_die1x(0,"anycast: invalid ip: parse error.");
    v6=1;
  }
  rtp_initheader(buf,type); /* default 14 == MPEG Audio */

  uint32_unpack_big(buf+4,&ts);

  if (v6) {
    if ((s=socket_udp6())==-1)
      strerr_die1sys(111,"anycast: unable to create UDP socket: ");
    if (socket_bind6_reuse(s,(char *)V6any,port,0) == -1)
      strerr_die1sys(111,"anycast: unable to bind: ");
  } else {
    if ((s=socket_udp())==-1)
      strerr_die1sys(111,"anycast: unable to create UDP socket: ");
    if (socket_bind4_reuse(s,(char *)V6any,port) == -1)
      strerr_die1sys(111,"anycast: unable to bind: ");
  }

  gettimeofday(&start,0);
  for (;;) {
    len=read(0,buf+12,1400);
    if (len<1)
      return 0;

    gettimeofday(&now,0);
    now.tv_sec-start.tv_sec;
    if (now.tv_usec<start.tv_usec) now.tv_sec--;
    now.tv_usec-=start.tv_usec;

    uint32_pack_big(buf+4,ts+(now.tv_sec*256+(now.tv_usec>>24)));

    if (v6) {
      if (socket_send6(s,buf,len+12,ip,port,0)==-1)
	strerr_die1sys(111,"anycast: IPv6 sendmsg failed: ");
    } else {
      if (socket_send4(s,buf,len+12,ip,port)==-1)
	strerr_die1sys(111,"anycast: IPv4 sendmsg failed: ");
    }
    rtp_nextsequence(buf);
  }
  return 0;
}