refactored packet radio code mostly into separate file.

began writing stateful packet decoder.

conf_schema.h

@@ -200,6 +200,7 @@ ATOM(char, overlayinterfaces,		0, cf_opt_char_boolean,, "")
 ATOM(char, broadcasts,		        0, cf_opt_char_boolean,, "")
 ATOM(char, packettx,		        0, cf_opt_char_boolean,, "")
 ATOM(char, packetrx,		        0, cf_opt_char_boolean,, "")
+ATOM(char, packetradio,		        0, cf_opt_char_boolean,, "")
 ATOM(char, packetconstruction,		0, cf_opt_char_boolean,, "")
 ATOM(char, rhizome,		        0, cf_opt_char_boolean,, "")
 ATOM(char, rhizome_tx,		        0, cf_opt_char_boolean,, "")

overlay_interface.c

@@ -412,7 +412,7 @@ overlay_interface_init(const char *name, struct in_addr src_addr, struct in_addr
 	return WHYF("dummy or packet radio interface file name overrun: %s", alloca_str_toprint(strbuf_str(d)));
     }
     if ((interface->alarm.poll.fd = open(dummyfile,O_APPEND|O_RDWR)) < 1) {
-      return WHYF("could not open dummy or packet radio interface file %s for append", dummyfile);
+      return WHYF("could not open dummy or packet radio interface file %s for append (errno=%d)", dummyfile,errno);
     }
 
     bzero(&interface->address, sizeof(interface->address));
@@ -564,43 +564,6 @@ struct dummy_packet{
   unsigned char payload[1400];
 };
 
-void overlay_packetradio_poll(struct sched_ent *alarm)
-{
-  overlay_interface *interface = (overlay_interface *)alarm;
-  time_ms_t now = gettime_ms();
-
-  // We will almost certainly support more than one type of packet radio
-  // so lets parameterise this.
-  switch(1) {
-  case 1:
-    // Read data from the serial port
-    break;
-  }
-
-  // tick the interface
-  if (interface->tick_ms>0 && 
-      (interface->last_tick_ms == -1 || now >= interface->last_tick_ms + interface->tick_ms)) {
-    // tick the interface
-    overlay_route_queue_advertisements(interface);
-    interface->last_tick_ms=now;
-  }
-  
-  unsigned char buffer[8192];
-  ssize_t nread = read(alarm->poll.fd, buffer,8192);
-  if (nread == -1){
-    WHY_perror("read");
-    return;
-  }
-  if (nread>0) {
-    buffer[8191]=0;
-    if (nread<8192) buffer[nread]=0;
-    DEBUGF("Read '%s'",buffer);
-  }
-
-  schedule(alarm);
-
-  return ;
-}
 
 void overlay_dummy_poll(struct sched_ent *alarm)
 {

overlay_packetradio.c

@@ -0,0 +1,149 @@
+#include "serval.h"
+#include "conf.h"
+
+/* interface decoder states. broadly based on RFC1055 */
+#define DC_NORMAL 0
+#define DC_ESC 1
+#define DC_END 2
+
+/* SLIP-style escape characters used for serial packet radio interfaces */
+#define SLIP_END 0300
+#define SLIP_ESC 0333
+#define SLIP_ESC_END 0334
+#define SLIP_ESC_ESC 0335
+
+int overlay_rx_packet_complete(overlay_interface *interface)
+{
+  if (interface->recv_offset) {
+    // dispatch received packet
+    if (packetOkOverlay(interface, interface->buffer, interface->recv_offset, -1, 
+			NULL,0)) {
+      if (config.debug.packetradio)
+	WARN("Corrupted or unsupported packet from packet radio interface");
+    }
+  }
+  interface->recv_offset=0;
+  return 0;
+}
+
+int overlay_rx_packet_append_byte(overlay_interface *interface,unsigned char byte)
+{
+  // Make sure we don't put the data outside the RX buffer
+  if (interface->recv_offset<0
+      ||interface->recv_offset>=OVERLAY_INTERFACE_RX_BUFFER_SIZE)
+    interface->recv_offset=0;
+  
+  interface->buffer[interface->recv_offset++]=byte;
+  if (interface->recv_offset==OVERLAY_INTERFACE_RX_BUFFER_SIZE) {
+    // packet fills buffer.  Who knows, we might be able to decode what we
+    // have of it.
+    return overlay_rx_packet_complete(interface);
+  } 
+
+  if (config.debug.packetradio) DEBUGF("RXd %d bytes",interface->recv_offset);
+  return 0;
+}
+
+void overlay_packetradio_poll(struct sched_ent *alarm)
+{
+  overlay_interface *interface = (overlay_interface *)alarm;
+  time_ms_t now = gettime_ms();
+
+  // Read data from the serial port
+  // We will almost certainly support more than one type of packet radio
+  // so lets parameterise this.
+  switch(1) {
+  case 1:
+    {
+      unsigned char buffer[OVERLAY_INTERFACE_RX_BUFFER_SIZE];
+      ssize_t nread = read(alarm->poll.fd, buffer, OVERLAY_INTERFACE_RX_BUFFER_SIZE);
+      if (nread == -1){
+	WHY_perror("read");
+	return;
+      }
+      if (nread>0) {
+	/*
+	  Examine received bytes for end of packet marker.
+	  The challenge is that we need to make sure that the packet encapsulation
+	  is self-synchronising in the event that a data error occurs (including
+	  failure to receive an arbitrary number of bytes).
+	  For now we will reuse the antiquated and sub-optimal method described in
+	  RFC1055 for SLIP, but with a couple of tweaks to reduce byte wastage when
+	  encountering ESC and END characters in packets.
+	*/
+	int i;
+	for(i=0;i<nread;i++)
+	  {
+	    switch (interface->decoder_state) {
+	    case DC_ESC:
+	      // escaped character
+	      switch(buffer[i]) {
+	      case SLIP_ESC_END: // escaped END byte
+		overlay_rx_packet_append_byte(interface,SLIP_END); break;
+	      case SLIP_ESC_ESC: // escaped escape character
+		overlay_rx_packet_append_byte(interface,SLIP_ESC); break;
+	      default: /* unknown escape character
+			  This is where the inefficiency comes, because
+			  we don't use the spare bits.
+			  We can reduce the inefficiency by making ESC <otherbyte>
+			  mean literally that. */
+		overlay_rx_packet_append_byte(interface,SLIP_ESC); 
+		overlay_rx_packet_append_byte(interface,buffer[i]);
+		break;
+	      }
+	      break;
+	    case DC_END:
+	      // character preceeded by END character
+	      switch(buffer[i]) {
+	      case SLIP_ESC_END:
+		overlay_rx_packet_complete(interface);
+		break;
+	      default:
+		overlay_rx_packet_append_byte(interface,SLIP_END); 
+		overlay_rx_packet_append_byte(interface,buffer[i]);
+		break;
+	      }
+	      break;
+	    default:
+	      // non-escape character
+	      switch(buffer[i]) {
+	      case SLIP_ESC:
+		interface->decoder_state=DC_ESC; break;
+	      case SLIP_END:
+		interface->decoder_state=DC_END; break;
+	      default:
+		overlay_rx_packet_append_byte(interface,buffer[i]);
+	      }
+	      break;
+	    }
+	  }
+      }
+    }
+    break;
+  }
+
+  // tick the interface
+  if (interface->tick_ms>0 && 
+      (interface->last_tick_ms == -1 || now >= interface->last_tick_ms + interface->tick_ms)) {
+    // tick the interface
+    overlay_route_queue_advertisements(interface);
+    interface->last_tick_ms=now;
+  }
+  
+  unsigned char buffer[8192];
+  ssize_t nread = read(alarm->poll.fd, buffer,8192);
+  if (nread == -1){
+    WHY_perror("read");
+    return;
+  }
+  if (nread>0) {
+    buffer[8191]=0;
+    if (nread<8192) buffer[nread]=0;
+    DEBUGF("Read '%s'",buffer);
+  }
+
+  schedule(alarm);
+
+  return ;
+}
+

serval.h

@@ -350,11 +350,19 @@ extern int overlayMode;
 #define INTERFACE_STATE_DOWN 2
 #define INTERFACE_STATE_DETECTING 3
 
+// Specify the size of the receive buffer.
+// This effectively sets the MRU for packet radio interfaces
+// where we have to buffer packets on the receive side
+#define OVERLAY_INTERFACE_RX_BUFFER_SIZE 2048
+
 typedef struct overlay_interface {
   struct sched_ent alarm;
   char name[256];
-  int recv_offset;
-  int fileP; // dummyP
+  unsigned char buffer[OVERLAY_INTERFACE_RX_BUFFER_SIZE];
+  int recv_offset; /* either dummy file offset or number of bytes in RX buffer
+		      for packet radio interfaces */
+  char decoder_state; // decoder state for packet radio interfaces
+  int fileP; // non-zero for dummy and packet radio serial interfaces
   char drop_broadcasts;
   char drop_unicasts;
   int port;

sourcefiles.mk

@@ -31,6 +31,7 @@ SERVAL_SOURCES = $(SERVAL_BASE)audiodevices.c \
 	$(SERVAL_BASE)overlay_buffer.c \
 	$(SERVAL_BASE)overlay_interface.c \
 	$(SERVAL_BASE)overlay_link.c \
+	$(SERVAL_BASE)overlay_packetradio.c \
 	$(SERVAL_BASE)overlay_queue.c \
 	$(SERVAL_BASE)overlay_mdp.c \
 	$(SERVAL_BASE)overlay_mdp_services.c \