more work on dna helper interface.

Also added missing dna_helper.c file from previous changes.
moved sigpipe/sigio detection code to own file.

Android.mk

@@ -43,6 +43,7 @@ SERVALD_SRC_FILES = \
 	serval-dna/vomp.c \
 	serval-dna/lsif.c \
 	serval-dna/dna_helper.c \
+	serval-dna/sighandlers.c \
 	serval-dna/monitor.c \
 	serval-dna/monitor-cli.c \
 	serval-dna/codecs.c \

Makefile.in

@@ -46,6 +46,7 @@ SRCS=	main.c \
 	monitor.c \
 	monitor-cli.c \
 	dna_helper.c \
+	sighandlers.c \
 	codecs.c \
 	audiodevices.c \
 	audio_msm_g1.c \

dna_helper.c

@@ -0,0 +1,118 @@
+/* 
+Serval Distributed Numbering Architecture (DNA)
+Copyright (C) 2012 Paul Gardner-Stephen 
+
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+#include "serval.h"
+
+/*
+  The challenge with making an interface for calling an external program to 
+  resolve a DID into a URI is that it really should be asynchronous, so that
+  servald can't pause due to delays in looking up DIDs by helper applications.
+  
+  This can be partially mitigated by having a cache, so that at least for repeated
+  requests the helper doesn't need to be called each time.  This is very important
+  because the DNA protocol relies on pre-emptive retries to ensure reception of
+  a request over a lossy network.
+
+  The second part of the solution is to create an asynchronous queue for requests,
+  by passing them via file descriptor to a single persistent instance of the DNA
+  helper application, and polling the output of that application for results, and
+  then passing them out to their destinations.  This ensures that the process is
+  asynchronous and non-blocking, regardless of how much time the helper application
+  requires.  Then the helper will just be another file descriptor to poll in the
+  main loop.
+ */
+
+int dna_helper_stdin=-1;
+int dna_helper_stdout=-1;
+
+int dna_helper_start(const char *command)
+{
+  return -1;
+}
+
+int dna_helper_enqueue(char *did, unsigned char *requestorSid)
+{
+  /* Check if we have a helper configured. If not, then set
+     dna_helper_stdin to magic value of -2 so that we don't waste time
+     in future looking up the dna helper configuration value. */
+  if (dna_helper_stdin==-2) return -1;
+  if (dna_helper_stdin==-1) {
+      const char *dna_helper = confValueGet("dna.helper",NULL);
+    if (!dna_helper||!dna_helper[0]) {
+      dna_helper_stdin=-2; 
+      return -1;
+    }
+
+    /* Okay, so we have a helper configured.
+       Run it */
+    dna_helper_start(dna_helper);
+    if (dna_helper_stdin<0) 
+      return -1;
+  }
+
+  /* Write request to dna helper.
+     Request takes form:  DID<space>SID-of-Requestor\n 
+     By passing the requestor's SID to the helper, we don't need to maintain
+     any state, as all we have to do is wait for responses from the helper,
+     which will include the requestor's SID.
+  */
+  signal(SIGPIPE,sigPipeHandler);
+  sigPipeFlag=0;
+  write(dna_helper_stdin,did,strlen(did));
+  write(dna_helper_stdin," ",1);
+  write(dna_helper_stdin,overlay_render_sid(requestorSid),SID_SIZE*2);
+  write(dna_helper_stdin,"\n",1);
+  if (sigPipeFlag) {
+    /* Assume broken pipe due to dead helper.
+       Next request will cause it to be restarted.
+       (Losing the current request is not a big problem, because
+       DNA preemptively retries, anyway.
+       XXX In fact, we should probably have a limit to the number of restarts
+       in quick succession so that we don't waste lots of time with a buggy or
+       suicidal helper.
+    */
+    close(dna_helper_stdin);
+    close(dna_helper_stdout);
+    dna_helper_stdin=-1;
+    dna_helper_stdout=-1;
+    return -1;
+  }
+
+  return 0;
+}
+
+int dna_return_resolution(overlay_mdp_frame *mdp, unsigned char *fromSid,
+			  const char *did,const char *name,const char *uri)
+{
+  /* copy SID out into source address of frame */	      
+  bcopy(fromSid,&mdp->out.src.sid[0],SID_SIZE);
+  
+  /* and build reply as did\nname\nURI<NUL> */
+  snprintf((char *)&mdp->out.payload[0],512,"%s\n%s\n%s",
+	   did,name,uri);
+  mdp->out.payload_length=strlen((char *)mdp->out.payload)+1;
+
+  /* Dispatch response */
+  mdp->packetTypeAndFlags&=MDP_FLAG_MASK;
+  mdp->packetTypeAndFlags|=MDP_TX;
+  overlay_mdp_dispatch(mdp,0 /* system generated */,
+		       NULL,0);
+
+  return 0;
+}

rhizome_http.c

@@ -31,8 +31,6 @@ Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
  */
 
 int rhizome_server_socket=-1;
-int sigPipeFlag=0;
-int sigIoFlag=0;
 
 rhizome_http_request *rhizome_live_http_requests[RHIZOME_SERVER_MAX_LIVE_REQUESTS];
 int rhizome_server_live_request_count=0;
@@ -62,19 +60,6 @@ unsigned char favicon_bytes[]={
 ,0,0,0,0,0,0,0,0,0,0,0,0,0,0};
 int favicon_len=318;
 
-void sigPipeHandler(int signal)
-{
-  sigPipeFlag++;
-  return;
-}
-
-void sigIoHandler(int signal)
-{
-  WHY("sigio");
-  sigIoFlag++;
-  return;
-}
-
 int rhizome_server_start()
 {
   if (rhizome_server_socket>-1) return 0;

serval.h

@@ -1523,3 +1523,8 @@ int server_probe(int *pid);
 int dna_helper_enqueue(char *did, unsigned char *requestorSid);
 int dna_return_resolution(overlay_mdp_frame *mdp, unsigned char *fromSid,
 			  const char *did,const char *name,const char *uri);
+
+extern int sigPipeFlag;
+extern int sigIoFlag;
+void sigPipeHandler(int signal);
+void sigIoHandler(int signal);

sighandlers.c

@@ -0,0 +1,33 @@
+/*
+Serval Distributed Numbering Architecture (DNA)
+Copyright (C) 2012 Paul Gardner-Stephen
+ 
+This program is free software; you can redistribute it and/or
+modify it under the terms of the GNU General Public License
+as published by the Free Software Foundation; either version 2
+of the License, or (at your option) any later version.
+ 
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+GNU General Public License for more details.
+ 
+You should have received a copy of the GNU General Public License
+along with this program; if not, write to the Free Software
+Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
+*/
+
+int sigPipeFlag=0;
+int sigIoFlag=0;
+
+void sigPipeHandler(int signal)
+{
+  sigPipeFlag++;
+  return;
+}
+
+void sigIoHandler(int signal)
+{  
+  sigIoFlag++;
+  return;
+}