attempt to keep local multicast robust against network adapter going …

…downg

Makefile.linux

@@ -76,7 +76,7 @@ all: $(DAEMONS) $(EXECS) $(DYNAMICS)
 install: $(DAEMONS) $(EXECS)
 	/usr/sbin/adduser --quiet --system --group radio
 	/usr/sbin/adduser --quiet --system --ingroup radio aprsfeed
-	rsync -a aux/98-sockbuf.conf /etc/sysctl.d
+	rsync -a aux/98-sockbuf.conf aux/50-multicast.conf /etc/sysctl.d
 	sysctl --quiet -p /etc/sysctl.d/98-sockbuf.conf
 	rsync -a $(DAEMONS) $(DAEMONDIR)
 	rsync -a $(EXECS) start-ka9q-horus.sh $(BINDIR)

audio.c

@@ -304,7 +304,10 @@ int flush_output(struct channel * chan,bool marker,bool complete){
     if(chan->output.rp >= chan->output.queue_size)
       chan->output.rp -= chan->output.queue_size;
 
-    int r = sendto(Output_fd,&packet,bytes + (dp - packet),0,(struct sockaddr *)&chan->output.dest_socket,sizeof(chan->output.dest_socket));
+    int r = sendto(Output_fd_lo,&packet,bytes + (dp - packet),0,(struct sockaddr *)&chan->output.dest_socket,sizeof(chan->output.dest_socket));
+    if(Mcast_ttl > 0)
+      r = sendto(Output_fd,&packet,bytes + (dp - packet),0,(struct sockaddr *)&chan->output.dest_socket,sizeof(chan->output.dest_socket));
+
     chan->output.rtp.bytes += bytes;
     chan->output.rtp.packets++;
     chan->output.rtp.seq++;

control.c

@@ -59,7 +59,7 @@ int Mcast_ttl = DEFAULT_MCAST_TTL;
 int IP_tos = DEFAULT_IP_TOS;
 float Blocktime;
 int Overlap;
-int Output_fd,Status_fd;
+int Output_fd,Status_fd,Output_fd_lo;
 const char *App_path;
 int Verbose;
 
@@ -386,6 +386,14 @@ int main(int argc,char *argv[]){
     exit(EX_OSERR); // let systemd restart us
   }
   fcntl(Output_fd,F_SETFL,O_NONBLOCK); // Just drop instead of blocking real time
+  Output_fd_lo = socket(AF_INET,SOCK_DGRAM,0); // Eventually intended for all output with sendto()
+  if(Output_fd_lo < 0){
+    fprintf(stdout,"can't create output socket: %s\n",strerror(errno));
+    exit(EX_OSERR); // let systemd restart us
+  }
+  setup_loopback(Output_fd_lo);
+
+
 
   if(target == NULL){
     // Use avahi browser to find a radiod instance to control
@@ -662,10 +670,16 @@ int main(int argc,char *argv[]){
       wprintw(Debug_win,"sent command len %d\n",command_len);
       screen_update_needed = true; // show local change right away
 #endif
-      if(sendto(Output_fd, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len){
+      if(sendto(Output_fd_lo, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len){
 	wprintw(Debug_win,"command send error: %s\n",strerror(errno));
 	screen_update_needed = true; // show local change right away
       }
+      if(Mcast_ttl > 0){
+	if(sendto(Output_fd, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len){
+	  wprintw(Debug_win,"command send error: %s\n",strerror(errno));
+	  screen_update_needed = true; // show local change right away
+	}
+      }
       // This will elicit an answer, defer the next poll
       next_radio_poll = now + radio_poll_interval + arc4random_uniform(random_interval) - random_interval/2;
     }
@@ -1670,8 +1684,11 @@ static int send_poll(int ssrc){
   encode_int(&bp,OUTPUT_SSRC,ssrc); // poll specific SSRC, or request ssrc list with ssrc = 0
   encode_eol(&bp);
   int const command_len = bp - cmdbuffer;
-  if(sendto(Output_fd, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len)
+  if(sendto(Output_fd_lo, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len)
     return -1;
+  if(Mcast_ttl > 0)
+    if(sendto(Output_fd, cmdbuffer, command_len, 0, (struct sockaddr *)&Metadata_dest_socket,sizeof(struct sockaddr)) != command_len)
+      return -1;
 
   return 0;
 }

main.c

@@ -110,7 +110,8 @@ static int64_t Starttime;      // System clock at timestamp 0, for RTCP
 static pthread_t Status_thread;
 struct sockaddr_storage Metadata_dest_socket;      // Dest of global metadata
 static char const *Metadata_dest_string; // DNS name of default multicast group for status/commands
-int Output_fd = -1; // Unconnected socket used for all multicast output
+int Output_fd = -1; // Unconnected socket used for other hosts
+int Output_fd_lo = -1; // Socket for loopback
 struct channel Template;
 // If a channel is tuned to 0 Hz and then not polled for this many seconds, destroy it
 // Must be computed at run time because it depends on the block time
@@ -438,12 +439,25 @@ static int loadconfig(char const *file){
   Update = config_getint(Configtable,GLOBAL,"update",Update);
   IP_tos = config_getint(Configtable,GLOBAL,"tos",IP_tos);
   Mcast_ttl = config_getint(Configtable,GLOBAL,"ttl",Mcast_ttl);
-  Output_fd = socket(AF_INET,SOCK_DGRAM,0); // Eventually intended for all output with sendto()
+  Output_fd = socket(AF_INET,SOCK_DGRAM,0);
   if(Output_fd < 0){
     fprintf(stdout,"can't create output socket: %s\n",strerror(errno));
     exit(EX_NOHOST); // let systemd restart us
   }
   fcntl(Output_fd,F_SETFL,O_NONBLOCK); // Just drop instead of blocking real time
+  if(Output_fd < 0){
+    fprintf(stdout,"can't create output socket: %s\n",strerror(errno));
+    exit(EX_NOHOST); // let systemd restart us
+  }
+
+  Output_fd_lo = socket(AF_INET,SOCK_DGRAM,0);
+  if(Output_fd_lo < 0){
+    fprintf(stdout,"can't create output socket: %s\n",strerror(errno));
+    exit(EX_NOHOST); // let systemd restart us
+  }
+
+  setup_loopback(Output_fd_lo);
+
   // Set up default output stream file descriptor and socket
   // There can be multiple senders to an output stream, so let avahi suppress the duplicate addresses
 
@@ -960,6 +974,8 @@ static void *rtcp_send(void *arg){
 
     if(sendto(Output_fd,buffer,dp-buffer,0,(struct sockaddr *)&chan->rtcp.dest_socket,sizeof(chan->rtcp.dest_socket)) < 0)
       chan->output.errors++;
+    if(sendto(Output_fd_lo,buffer,dp-buffer,0,(struct sockaddr *)&chan->rtcp.dest_socket,sizeof(chan->rtcp.dest_socket)) < 0)
+      chan->output.errors++;
   done:;
     sleep(1);
   }

multicast.c

@@ -779,31 +779,39 @@ static void set_ipv4_options(int const fd,int const mcast_ttl,int const tos){
     if(setsockopt(fd,IPPROTO_IP,IP_MULTICAST_TTL,&mcast_ttl,sizeof(mcast_ttl)) != 0)
       perror("so_ttl failed");
   }
+#if 0 // Send explicit copies to loopback interface instead, and have everyone listen on both
   uint8_t const loop = true;
   if(setsockopt(fd,IPPROTO_IP,IP_MULTICAST_LOOP,&loop,sizeof(loop)) != 0)
     perror("so_loop failed");
+#endif
 
   if(tos >= 0){
     // Only needed on output
     if(setsockopt(fd,IPPROTO_IP,IP_TOS,&tos,sizeof(tos)) != 0)
       perror("so_tos failed");
   }
-  if(mcast_ttl == 0){
-    // TTL is zero, use loopback interface
-    struct ifreq ifr;
-    memset(&ifr,0,sizeof(ifr));
-    // Get loopback interface address. Probably 127.0.0.1
-    strncpy(ifr.ifr_name,"lo",sizeof(ifr.ifr_name));
-    if(ioctl(fd, SIOCGIFADDR, &ifr) < 0)
-      perror("set loopback interface failed");
-    else {
-      // Set our interface to it
-      struct in_addr *interface_addr = &((struct sockaddr_in *)&ifr.ifr_addr)->sin_addr;
-      if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, interface_addr, sizeof(*interface_addr)) < 0)
-        perror("setsockopt IP_MULTICAST_IF failed");
+}
+// Configure separate socket for transmission (only) through loopback interface
+// Most of the options aren't relevant here, just select the loopback interface
+int setup_loopback(int fd){
+  fcntl(fd,F_SETFL,O_NONBLOCK); // Just drop instead of blocking real time
+  struct ifreq ifr;
+  memset(&ifr,0,sizeof(ifr));
+
+  // Instead of hardwiring the loopback name (which can vary) find it in the system's list
+  struct ifaddrs *ifap = NULL;
+  getifaddrs(&ifap);
+  for(struct ifaddrs const *i = ifap; i != NULL; i = i->ifa_next){
+    if(i->ifa_addr->sa_family == AF_INET && (i->ifa_flags & IFF_LOOPBACK)){
+      struct sockaddr_in const *sin = (struct sockaddr_in *)i->ifa_addr;
+      if (setsockopt(fd, IPPROTO_IP, IP_MULTICAST_IF, &sin->sin_addr, sizeof sin->sin_addr) < 0)
+	perror("setsockopt IP_MULTICAST_IF failed");
+      break;
     }
   }
+  return 0;
 }
+
 // Set options on IPv6 multicast socket
 static void set_ipv6_options(int const fd,int const mcast_ttl,int const tos){
   // Failures here are not fatal

multicast.h

@@ -139,6 +139,7 @@ int setup_mcast(char const *target,struct sockaddr *,int output,int ttl,int tos,
 static inline int setup_mcast_in(char const *target,struct sockaddr *sock,int offset,int tries){
   return setup_mcast(target,sock,0,0,0,offset,tries);
 }
+int setup_loopback(int);
 int join_group(int fd,struct sockaddr const * const sock, char const * const iface,int const ttl,int const tos);
 int connect_mcast(void const *sock,char const *iface,int const ttl,int const tos);
 int listen_mcast(void const *sock,char const *iface);

radio.c

@@ -474,8 +474,11 @@ void *sap_send(void *p){
     wp += len;
     space -= len;
 
-    if(sendto(Output_fd,message,wp - message,0,(struct sockaddr *)&chan->sap.dest_socket,sizeof(chan->sap.dest_socket)) < 0)
+    if(sendto(Output_fd_lo,message,wp - message,0,(struct sockaddr *)&chan->sap.dest_socket,sizeof(chan->sap.dest_socket)) < 0)
       chan->output.errors++;
+    if(Mcast_ttl > 0)
+      if(sendto(Output_fd,message,wp - message,0,(struct sockaddr *)&chan->sap.dest_socket,sizeof(chan->sap.dest_socket)) < 0)
+	chan->output.errors++;
     sleep(5);
   }
 }

radio.h

@@ -292,6 +292,7 @@ extern pthread_mutex_t Channel_list_mutex;
 extern int Channel_idle_timeout;
 extern int Ctl_fd;     // File descriptor for receiving user commands
 extern int Output_fd;
+extern int Output_fd_lo;
 extern struct sockaddr_storage Metadata_dest_socket; // Socket for main metadata
 extern int Verbose;
 extern float Blocktime; // Common to all receiver slices. NB! Milliseconds, not seconds

radio_status.c

@@ -109,8 +109,11 @@ int send_radio_status(struct sockaddr const *sock,struct frontend const *fronten
   uint8_t packet[PKTSIZE];
   chan->status.packets_out++;
   int const len = encode_radio_status(frontend,chan,packet,sizeof(packet));
-  if(sendto(Output_fd,packet,len,0,sock,sizeof(struct sockaddr)) < 0)
+  if(sendto(Output_fd_lo,packet,len,0,sock,sizeof(struct sockaddr)) < 0)
     chan->output.errors++;
+  if(Mcast_ttl > 0)
+    if(sendto(Output_fd,packet,len,0,sock,sizeof(struct sockaddr)) < 0)
+      chan->output.errors++;
   return 0;
 }
 int reset_radio_status(struct channel *chan){