From 98ea86bde0e2f2eee127643c22159fd00cf83e1a Mon Sep 17 00:00:00 2001
From: gardners <paul@servalproject.org>
Date: Thu, 3 May 2012 22:46:00 +0930
Subject: [PATCH] added new /proc/net/route method to find interfaces on
 android (would you believe that using ifconfig to READ about interfaces
 requires ROOT on android). should also help for interfaces with multiple
 addresses.

---
 lsif.c              | 44 ++++++++++++++++++++++++++++++-
 overlay_interface.c | 64 +++++++++++++++++++++++++--------------------
 serval.h            |  4 ++-
 3 files changed, 82 insertions(+), 30 deletions(-)

diff --git a/lsif.c b/lsif.c
index bfc9764d..77346202 100644
--- a/lsif.c
+++ b/lsif.c
@@ -59,6 +59,47 @@
 #define SIOCGIFBRDADDR OSIOCGIFBRDADDR
 #endif
 
+int overlay_interface_register(unsigned char *name,
+			       struct sockaddr_in local,
+			       struct sockaddr_in broadcast);
+
+/* for when all other options fail, as can happen on Android,
+   if the permissions for the socket-based method are broken.
+   Down side is that it while it gets the interface name and
+   broadcast, it doesn't get the local address for that
+   interface. 
+*/
+int scrapeProcNetRoute()
+{
+  FILE *f=fopen("/proc/net/route","r");
+  if (!f) return fprintf(stderr,"Can't read from /proc/net/route\n");
+
+  char line[1024],name[1024],dest[1024],mask[1024];
+
+  /* skip header line */
+  line[0]=0; fgets(line,1024,f);
+
+  line[0]=0; fgets(line,1024,f);
+  while(line[0]) {
+    int r;
+    if ((r=sscanf(line,"%s %s %*s %*s %*s %*s %*s %s",name,dest,mask))==3)
+      {
+	unsigned int d = strtol(dest,NULL,16);
+	unsigned int m = strtol(mask,NULL,16);
+	struct sockaddr_in local,broadcast;
+	if (!(d&(~m))) {
+	  local.sin_addr.s_addr=d;
+	  broadcast.sin_addr.s_addr=d|~m;
+	  overlay_interface_register((unsigned char *)name,local,broadcast);
+	}
+      }
+
+    line[0]=0; fgets(line,1024,f);    
+  }
+  fclose(f);
+  return 0;
+}
+
 #ifdef ANDROID
 int lsif(void)
 {
@@ -74,7 +115,8 @@ int lsif(void)
   /* Get a socket handle. */
   sck = socket(PF_INET, SOCK_DGRAM, 0);
   if(sck < 0) {
-    fprintf(stderr,"Failed to gt socket handle to list addresses\n");
+    fprintf(stderr,"Failed to gt socket handle to list addresses, errno=%d\n",
+	    errno);
     return 1;
   }
  
diff --git a/overlay_interface.c b/overlay_interface.c
index 6ff0c19c..77007469 100644
--- a/overlay_interface.c
+++ b/overlay_interface.c
@@ -178,7 +178,7 @@ int overlay_interface_args(char *arg)
 int overlay_interface_init_socket(int interface,struct sockaddr_in src_addr,struct sockaddr_in broadcast)
 {
 #define I(X) overlay_interfaces[interface].X
-  I(local_address)=src_addr;
+  //  I(local_address)=src_addr;
   I(broadcast_address)=broadcast;
   I(fileP)=0;
 
@@ -502,29 +502,36 @@ int overlay_interface_register(unsigned char *name,
     int i;
     for(i=0;i<overlay_interface_count;i++) if (!strcasecmp(overlay_interfaces[i].name,(char *)name)) break;
     if (i<overlay_interface_count) {
-      /* We already know about this interface, so just update it */
-      if (((overlay_interfaces[i].local_address.sin_addr.s_addr&0xffffffff)
-	   ==(local.sin_addr.s_addr&0xffffffff))
-	  &&((overlay_interfaces[i].broadcast_address.sin_addr.s_addr&0xffffffff)
-	     ==(broadcast.sin_addr.s_addr&0xffffffff)))
+      /* We already know about this interface, so just update it.
+         We actually only care about the broadcast address for the overlay mesh.
+         this is a good thing, because it turns out to be pretty hard to discover
+	 your own IP address on Android. */
+      if ( /* ((overlay_interfaces[i].local_address.sin_addr.s_addr&0xffffffff)
+	      ==(local.sin_addr.s_addr&0xffffffff))&& */
+	  ((overlay_interfaces[i].broadcast_address.sin_addr.s_addr&0xffffffff)
+	   ==(broadcast.sin_addr.s_addr&0xffffffff)))
 	{
 	  /* Mark it as being seen */
 	  overlay_interfaces[i].observed=1;
 	  return 0;
 	}
       else
-	{
-	  /* Interface has changed */
-	  WHYF("Interface changed %08llx.%08llx vs %08llx.%08llx",
-	       overlay_interfaces[i].local_address.sin_addr.s_addr,
-	       overlay_interfaces[i].broadcast_address.sin_addr.s_addr,
-	       local.sin_addr.s_addr,
-	       broadcast.sin_addr.s_addr);
-	  close(overlay_interfaces[i].fd);
-	  overlay_interfaces[i].fd=-1;
-	  if (overlay_interface_init_socket(i,local,broadcast))
-	    WHY("Could not reinitialise changed interface");
-	}
+	if (0)
+	  {
+	    /* Interface has changed.
+	       This old approach has problems for machines with multiple IP 
+	       addresses on a given interface, so now we allow multiple
+	       interfaces on the same underlying network adaptor. */
+	    WHYF("Interface changed %08llx.%08llx vs %08llx.%08llx",
+		 /* overlay_interfaces[i].local_address.sin_addr.s_addr */0,
+		 overlay_interfaces[i].broadcast_address.sin_addr.s_addr,
+		 local.sin_addr.s_addr,
+		 broadcast.sin_addr.s_addr);
+	    close(overlay_interfaces[i].fd);
+	    overlay_interfaces[i].fd=-1;
+	    if (overlay_interface_init_socket(i,local,broadcast))
+	      WHY("Could not reinitialise changed interface");
+	  }
     }
     else {
       /* New interface, so register it */
@@ -543,8 +550,12 @@ int overlay_interface_discover()
 {
   /* Don't waste too much time and effort on interface discovery,
      especially if we can't attach to a given interface for some reason. */
+  WHY("called");
+  if ((time(0)-overlay_last_interface_discover_time)<0)
+    overlay_last_interface_discover_time=time(0);
   if ((time(0)-overlay_last_interface_discover_time)<2) return 0;
   overlay_last_interface_discover_time=time(0);
+  WHY("checking");
 
   /* The Android ndk doesn't have ifaddrs.h, so we have to use the netlink interface.
      However, netlink is only available on Linux, so for BSD systems, e.g., Mac, we
@@ -578,6 +589,13 @@ int overlay_interface_discover()
     r=r->next;
   }
 
+#ifdef ANDROID
+  /* Use alternative linux-only method to find and register interfaces. */
+  lsif();
+#endif
+  /* /proc based approach */
+  scrapeProcNetRoute();
+
 #ifdef HAVE_IFADDRS_H
   struct ifaddrs *ifaddr,*ifa;
   int family;
@@ -607,16 +625,6 @@ int overlay_interface_discover()
   }
   freeifaddrs(ifaddr);
 #endif
-#ifdef ANDROID
-  /* Use alternative linux-only method to find and register interfaces. */
-  lsif();
-#else
-#ifdef HAVE_IFADDRS_H
-#else
-#error Don't know how to get interface list on this platform
-#endif
-#endif
-
 
   return 0;
 }
diff --git a/serval.h b/serval.h
index 8e10403b..7249a487 100755
--- a/serval.h
+++ b/serval.h
@@ -601,7 +601,9 @@ typedef struct overlay_interface {
   int sequence_number;
 
   /* Broadcast address and netmask, if known */
-  struct sockaddr_in local_address;
+  /* We really only case about distinct broadcast addresses on interfaces.
+     Also simplifies aliases on interfaces.
+     struct sockaddr_in local_address; */
   struct sockaddr_in broadcast_address;
 
   /* Not necessarily the real MTU, but the largest frame size we are willing to TX on this interface.