cprogs/mcastsoundd.c

   1 /*
   2  * http://www.ibiblio.org/pub/Linux/docs/HOWTO/Multicast-HOWTO
   3  */
   4
   5 #include <stdio.h>
   6 #include <errno.h>
   7 #include <string.h>
   8 #include <assert.h>
   9 #include <unistd.h>
  10 #include <signal.h>
  11
  12 #include <endian.h>
  13 #include <sys/types.h>
  14 #include <fcntl.h>
  15 #include <sys/socket.h>
  16 #include <netinet/in.h>
  17 #include <arpa/inet.h>
  18
  19 typedef unsigned char Byte;
  20
  21 static const char *ov_mcast= "239.193.27.221";
  22 static int ov_port_ctrl= 4101;
  23 static int ov_port_data= -1;
  24
  25 static int mcast_fd;
  26 static struct sockaddr_in mcast_sa;
  27
  28 static void sysfail(const char *m) { perror(m); exit(16); }
  29
  30 static Byte packet[1024];
  31 static int packet_len;
  32
  33 static uint64_t htonll(uint64_t v) {
  34 #if LITTLE_ENDIAN
  35   return (v >> 32) | (v << 32);
  36 #endif
  37 #if BIG_ENDIAN
  38   return v;
  39 #endif
  40 }
  41
  42 #define OP_CTRL_PLAY 1
  43 #define OP_CTRL_STOP 2
  44 #define OP_CTRL_DATA 3
  45
  46 #define MAR_CTRL_PLAY                           \
  47   FI8(operation)                                \
  48   FI8(reserved)                                 \
  49   FI8(generation)                               \
  50   FI8(counter)                                  \
  51   FI64(totallen)                                \
  52   FI64(startts)                                 \
  53   FI32(starttns)                                \
  54   FI32(txrate)                                  \
  55   FR(trackfn,char,256)
  56
  57 #define MAR_CTRL_STOP                           \
  58   FI8(operation)                                \
  59   FI8(reserved)                                 \
  60   FR0
  61
  62 #define MAR_DATA                                \
  63   FI8(operation)                                \
  64   FI8(reserved)                                 \
  65   FI8(generation)                               \
  66   FI8(counter)                                  \
  67   FI64(offset)                                  \
  68   FR(data,Byte,1024)
  69
  70 #define FI8(f)      F(f, uint8_t,  v)
  71 #define FI32(f)     F(f, uint32_t, htonl(v))
  72 #define FI64(f)     F(f, uint64_t, htonll(v))
  73
  74 #define MARS                                    \
  75   MAR(CTRL_PLAY)                                \
  76   MAR(CTRL_STOP)                                \
  77   MAR(DATA)
  78
  79 #define F(f,t,c) t f;
  80 #define FR(f,t,l) t f[(l)]; int f##_l;
  81 #define FR0 /* */
  82 #define MAR(m) typedef struct Mar_##m { MAR_##m } Mar_##m;
  83 MARS
  84 #undef F
  85 #undef FR
  86 #undef FR0
  87 #undef MAR
  88
  89 #define F(f,t,c) { t v= d->f; *(t*)p= c; p += sizeof(t); };
  90 #define FR(f,t,l) assert(d->f##_l<=l); memcpy(p,d->f,d->f##_l); p+=d->f##_l;
  91 #define FR0 /* */
  92 #define MAR(m)                                  \
  93   static void mar_##m(const Mar_##m *d) {       \
  94     Byte *p= packet;                            \
  95     MAR_##m                                     \
  96     packet_len= p - packet;                     \
  97     assert(packet_len < sizeof(packet));        \
  98   }
  99 MARS
 100 #undef F
 101 #undef FR
 102 #undef FR0
 103 #undef MAR
 104
 105 #define F(f,t,c) {                              \
 106     t v;                                        \
 107     if (lr < sizeof(t)) return -1;              \
 108     v= *(const t*)p;                            \
 109     p += sizeof(t);  lr -= sizeof(t);           \
 110     d->f= c;                                    \
 111   };
 112 #define FR(f,t,l) {                             \
 113     if (lr > l) return -1;                      \
 114     memcpy(d->f, p, lr);                        \
 115     d->f##_l= lr;                               \
 116   };
 117 #define FR0                                     \
 118     if (lr) return -1;
 119 #define MAR(m)                                  \
 120   static int unmar_##m(Mar_##m *d) {            \
 121     const Byte *p= packet;                      \
 122     int lr= packet_len;                         \
 123     MAR_##m                                     \
 124     return 0;                                   \
 125   }
 126 MARS
 127 #undef F
 128 #undef FR
 129 #undef FR0
 130 #undef MAR
 131
 132 static void nonblock(int fd) {
 133   int r;
 134   r= fcntl(fd,F_GETFL);  if (r<0) sysfail("nonblock fcntl F_GETFL");
 135   r |= O_NONBLOCK;
 136   r= fcntl(fd,F_SETFL,r);  if (r<0) sysfail("nonblock fcntl F_GETFL");
 137 }
 138
 139 static void blocksignals(int how) {
 140   sigset_t set;
 141   int r;
 142
 143   sigemptyset(&set);
 144   sigaddset(&set,SIGCHLD);
 145   r= sigprocmask(how,&set,0);
 146   if (r) sysfail("sigprocmask");
 147 }
 148
 149 static void recvd_play(void) {
 150   Mar_CTRL_PLAY pkt;
 151   int r;
 152
 153   r= unmar_CTRL_PLAY(&pkt);
 154   if (r) { fprintf(stderr,"bad PLAY packet\n"); return; }
 155 }
 156
 157 static void recvd_stop(void) {
 158   Mar_CTRL_STOP pkt;
 159   int r;
 160
 161   r= unmar_CTRL_STOP(&pkt);
 162   if (r) { fprintf(stderr,"bad STOP packet\n"); return; }
 163 }
 164
 165 static void player(void) {
 166   struct sockaddr_in peer_sa, old_peer_sa;
 167   socklen_t peer_salen;
 168   struct ip_mreq mreq;
 169   int r;
 170
 171   memset(&old_peer_sa, 0, sizeof(old_peer_sa));
 172
 173   mcast_fd= socket(PF_INET, SOCK_DGRAM, IPPROTO_UDP);
 174   if (mcast_fd<0) sysfail("mcast_fd socket");
 175
 176   r= bind(mcast_fd, (struct sockaddr*)&mcast_sa, sizeof(mcast_sa));
 177   if (r) sysfail("mcast_fd bind");
 178
 179   mcast_sa.sin_port= htons(ov_port_ctrl);
 180
 181   mreq.imr_multiaddr= mcast_sa.sin_addr;
 182   mreq.imr_interface.s_addr= INADDR_ANY;
 183   r= setsockopt(mcast_fd, IPPROTO_IP, IP_ADD_MEMBERSHIP, &mreq, sizeof(mreq));
 184   if (r) sysfail("mcast_fd add memb");
 185
 186   for (;;) {
 187     peer_salen= sizeof(peer_sa);
 188     memset(&peer_sa, 0, sizeof(peer_sa));
 189
 190     blocksignals(SIG_UNBLOCK);
 191     packet_len= recvfrom(mcast_fd, packet, sizeof(packet),
 192                          MSG_TRUNC, (struct sockaddr*)&peer_sa, &peer_salen);
 193     blocksignals(SIG_BLOCK);
 194
 195     if (packet_len<0) {
 196       if (errno==EINTR) continue;
 197       perror("mcast_fd recvfrom");
 198       continue;
 199     }
 200     if (peer_salen != sizeof(peer_sa)) {
 201       fprintf(stderr,"mcast_fd recvfrom salen %ld not %ld\n",
 202               (unsigned long)peer_salen, (unsigned long)sizeof(peer_sa));
 203       continue;
 204     }
 205     if (packet_len > sizeof(packet)) {
 206       fprintf(stderr,"mcast_fd recvfrom packet len %ld longer than max %ld\n",
 207               (unsigned long)packet_len, (unsigned long)sizeof(packet));
 208       continue;
 209     }
 210     if (memcmp(&old_peer_sa, &peer_sa, sizeof(old_peer_sa))) {
 211       char *p= inet_ntoa(peer_sa.sin_addr);
 212       fprintf(stderr,"receiving from %s:%d\n",p,ntohs(peer_sa.sin_port));
 213       memcpy(&old_peer_sa, &peer_sa, sizeof(old_peer_sa));
 214     }
 215     if (packet_len==0) {
 216       fprintf(stderr,"empty packet!\n");
 217       continue;
 218     }
 219     switch (packet[0]) {
 220     case OP_CTRL_PLAY:
 221       recvd_play();
 222       break;
 223     case OP_CTRL_STOP:
 224       recvd_stop();
 225       break;
 226     default:
 227       fprintf(stderr,"unknown opcode %d\n",packet[0]);
 228     }
 229   }
 230 }
 231
 232 int main(int argc, const char *const *argv) {
 233   int r;
 234
 235   if (ov_port_data < 0) ov_port_data= ov_port_ctrl+1;
 236
 237   memset(&mcast_sa,0,sizeof(mcast_sa));
 238   mcast_sa.sin_family= AF_INET;
 239   r= inet_aton(ov_mcast, &mcast_sa.sin_addr);  assert(r);
 240
 241   player();
 242   nonblock(0);
 243   mar_CTRL_PLAY(0);
 244   mar_CTRL_STOP(0);
 245   mar_DATA(0);
 246   unmar_DATA(0);
 247   return 0;
 248 }