Bug#219108: [PATCH] using an interface without IP address

--- libnet/src/libnet_if_addr.c	2003-10-30 18:26:33.000000000 -0500
+++ ../libnet-1.1.1rel/src/libnet_if_addr.c	2004-02-27 12:35:28.000000000 -0500
@@ -47,6 +47,15 @@
 #define MAX_IPADDR 32
 
 #if !(__WIN32__)
+
+static struct ifreq * get_interface_list (int, int8_t *, unsigned int *);
+static struct ifreq * conf_interface_list (int, int8_t *, unsigned int *);
+#ifdef __linux__
+static struct ifreq * proc_interface_list (int8_t *, unsigned int *);
+static void discard_line (FILE *);
+static int proc_interface_name (FILE *, struct ifreq *);
+#endif
+
 /*
  *  Return the interface list
  */
@@ -58,11 +67,12 @@
 #ifdef HAVE_SOCKADDR_SA_LEN
     register int n;
 #endif
+    struct ifreq * ifcs;
+    unsigned int n_ifcs;
     register struct ifreq *ifrp, *ifend, *ifnext, *mp;
     register struct sockaddr_in *sin;
     register struct libnet_ifaddr_list *al;
-    struct ifconf ifc;
-    struct ifreq ibuf[MAX_IPADDR], ifr;
+    struct ifreq ifr;
     int8_t device[sizeof(ifr.ifr_name)];
     static struct libnet_ifaddr_list ifaddrlist[MAX_IPADDR];
 
@@ -73,20 +83,14 @@
         return (-1);
     }
 
-	memset(&ifc, 0, sizeof(ifc));
-	ifc.ifc_len = sizeof(ibuf);
-    ifc.ifc_buf = (caddr_t)ibuf;
-
-    if (ioctl(fd,
-            SIOCGIFCONF,
-            (int8_t *)&ifc) < 0 || ifc.ifc_len < sizeof(struct ifreq))
-    {
-        snprintf(errbuf, LIBNET_ERRBUF_SIZE, "SIOCGIFCONF: %s", strerror(errno));
-        close(fd);
+    ifcs = (get_interface_list (fd, errbuf, (&n_ifcs)));
+    if (ifcs == 0)
+      {
+        close (fd);
         return (-1);
-    }
-    ifrp = ibuf;
-    ifend = (struct ifreq *)((int8_t *)ibuf + ifc.ifc_len);
+      }
+    ifrp = ifcs;
+    ifend = (ifcs + n_ifcs);
 
     al = ifaddrlist;
     mp = NULL;
@@ -124,6 +128,7 @@
                     (int)sizeof(ifr.ifr_name),
                      ifr.ifr_name,
                      strerror(errno));
+	    free (ifcs);
             close(fd);
             return (-1);
         }
@@ -143,15 +148,25 @@
         device[sizeof(device) - 1] = '\0';
 
         if (ioctl(fd, SIOCGIFADDR, (int8_t *)&ifr) < 0)
-        {
-            snprintf(errbuf, LIBNET_ERRBUF_SIZE,
-				    "SIOCGIFADDR: %s: %s", device, strerror(errno));
-            close(fd);
-            return (-1);
-        }
-    
-        sin = (struct sockaddr_in *)&ifr.ifr_addr;
-        al->addr = sin->sin_addr.s_addr;
+	  {
+	    if (errno == EADDRNOTAVAIL)
+	      {
+		al->addr = INADDR_NONE;
+	      }
+	    else
+	      {
+		snprintf(errbuf, LIBNET_ERRBUF_SIZE,
+			 "SIOCGIFADDR: %s: %s", device, strerror(errno));
+		free (ifcs);
+		close(fd);
+		return (-1);
+	      }
+	  }
+	else
+	  {
+	    sin = (struct sockaddr_in *)&ifr.ifr_addr;
+	    al->addr = sin->sin_addr.s_addr;
+	  }
         /*
          *  Replaced savestr() with strdup().  -- MDS
          */
@@ -159,11 +174,208 @@
         ++al;
         ++nipaddr;
     }
+    free (ifcs);
     close(fd);
 
     *ipaddrp = ifaddrlist;
     return (nipaddr);
 }
+
+/* Use /proc/net/dev if available, since that will give us a list of
+   all of the interfaces.  Otherwise use SIOCGIFCONF, which will at
+   least give us the interfaces that are up.  */
+
+static struct ifreq *
+get_interface_list (int fd, int8_t * errbuf, unsigned int * n_ifcs_return)
+{
+#ifdef __linux__
+  struct ifreq * ifcs = (proc_interface_list (errbuf, n_ifcs_return));
+  return
+    ((ifcs == 0)
+     ? (conf_interface_list (fd, errbuf, n_ifcs_return))
+     : ifcs);
+#else
+  return (conf_interface_list (fd, errbuf, n_ifcs_return));
+#endif
+}
+
+static struct ifreq *
+conf_interface_list (int fd, int8_t * errbuf, unsigned int * n_ifcs_return)
+{
+  struct ifconf ifc;
+  unsigned int n_ifcs = 4;
+  unsigned int n_bytes = ((sizeof (struct ifreq)) * n_ifcs);
+
+  (ifc . ifc_len) = n_bytes;
+  (ifc . ifc_req) = (malloc (n_bytes));
+  if ((ifc . ifc_req) == 0)
+    {
+      snprintf (errbuf, LIBNET_ERRBUF_SIZE, "Can't malloc() interface list.");
+      return (0);
+    }
+  while (1)
+    {
+      if ((ioctl (fd, SIOCGIFCONF, (&ifc))) < 0)
+	{
+	  snprintf (errbuf, LIBNET_ERRBUF_SIZE, "SIOCGIFCONF: %s",
+		    (strerror (errno)));
+	  free (ifc . ifc_req);
+	  return (0);
+	}
+      if ((ifc . ifc_len) < n_bytes)
+	break;
+      n_ifcs *= 2;
+      n_bytes = ((sizeof (struct ifreq)) * n_ifcs);
+      (ifc . ifc_req) = (realloc ((ifc . ifc_req), n_bytes));
+      if ((ifc . ifc_req) == 0)
+	{
+	  snprintf (errbuf, LIBNET_ERRBUF_SIZE,
+		    "Can't realloc() interface list.");
+	  return (0);
+	}
+    }
+
+  (*n_ifcs_return) = ((ifc . ifc_len) / (sizeof (struct ifreq)));
+  return (ifc . ifc_req);
+}
+
+#ifdef __linux__
+
+static struct ifreq *
+proc_interface_list (int8_t * errbuf, unsigned int * n_ifcs_return)
+{
+  FILE * s = (fopen ("/proc/net/dev", "r"));
+  if (s == 0)
+    {
+      snprintf (errbuf, LIBNET_ERRBUF_SIZE, "Unable to open /proc/net/dev");
+      return (0);
+    }
+  discard_line (s);
+  discard_line (s);
+  {
+    unsigned int i = 0;
+    unsigned int n = 4;
+    struct ifreq * ifcs;
+    struct ifreq ifc;
+
+    ifcs = (malloc ((sizeof (struct ifreq)) * n));
+    if (ifcs == 0)
+      {
+	snprintf (errbuf, LIBNET_ERRBUF_SIZE,
+		  "Can't malloc() interface list.");
+	return (0);
+      }
+    while (proc_interface_name (s, (&ifc)))
+      {
+	if (i == n)
+	  {
+	    n *= 2;
+	    ifcs = (realloc (ifcs, ((sizeof (struct ifreq)) * n)));
+	    if (ifcs == 0)
+	      {
+		snprintf (errbuf, LIBNET_ERRBUF_SIZE,
+			  "Can't realloc() interface list.");
+		return (0);
+	      }
+	  }
+	(ifcs[i++]) = ifc;
+      }
+    fclose (s);
+    (*n_ifcs_return) = i;
+    return (ifcs);
+  }
+}
+
+static void
+discard_line (FILE * s)
+{
+  while (1)
+    {
+      int c = (getc (s));
+      if ((c == EOF) || (c == '\n'))
+	break;
+    }
+}
+
+#define PIN_GETC(c, s)							\
+{									\
+  c = (getc (s));							\
+  if (c == EOF)								\
+    return (0);								\
+  if (c == '\0')							\
+    {									\
+      discard_line (s);							\
+      goto restart;							\
+    }									\
+}
+
+#define PIN_ACCUM(c)							\
+{									\
+  if (i < n)								\
+    (name[i++]) = (c);							\
+  else									\
+    {									\
+      discard_line (s);							\
+      goto restart;							\
+    }									\
+}
+
+static int
+proc_interface_name (FILE * s, struct ifreq * ifc)
+{
+  char * name = (ifc -> ifr_name);
+  unsigned int n = (sizeof (ifc -> ifr_name));
+  unsigned int i;
+  int c;
+
+ restart:
+  do
+    {
+      PIN_GETC (c, s);
+    }
+  while (isspace (c));
+  i = 0;
+  while (1)
+    {
+      PIN_ACCUM (c);
+      PIN_GETC (c, s);
+      if (isspace (c))
+	{
+	  if (c != '\n')
+	    discard_line (s);
+	  break;
+	}
+      if (c == ':')
+	{
+	  if (i < n)
+	    /* Might be part of an alias; check.  */
+	    {
+	      unsigned int saved_i = i;
+	      while (1)
+		{
+		  PIN_ACCUM (c);
+		  PIN_GETC (c, s);
+		  if (!isdigit (c))
+		    {
+		      if (c != ':')
+			/* Not an alias; first colon was name terminator.  */
+			i = saved_i;
+		      if (c != '\n')
+			discard_line (s);
+		      break;
+		    }
+		}
+	    }
+	  break;
+	}
+    }
+  if (i < n)
+    (name[i]) = '\0';
+  return (1);
+}
+
+#endif /* __linux__ */
+
 #else
 /* From tcptraceroute, convert a numeric IP address to a string */
 #define IPTOSBUFFERS    12