diff --git a/winsup/cygwin/ChangeLog b/winsup/cygwin/ChangeLog
index 70afe9b71..6163e9120 100644
--- a/winsup/cygwin/ChangeLog
+++ b/winsup/cygwin/ChangeLog
@@ -1,3 +1,15 @@
+2007-01-16  Corinna Vinschen  <corinna@vinschen.de>
+
+	* fhandler_socket.cc (fhandler_socket::ioctl): Handle SIOCGIFINDEX.
+	* net.cc (get_2k_ifconf): Ditto.
+	(get_nt_ifconf): Fake SIOCGIFINDEX.
+	(get_95_ifconf): Ditto.
+	(get_ifconf): Handle SIOCGIFINDEX.  Fake it for loopback on systems
+	not supporting IP Helper Lib.
+	* include/asm/socket.h (SIOCGIFINDEX): Define.
+	* include/cygwin/if.h (struct ifreq): Add member for interface index.
+	(ifr_ifindex): Define.
+
 2007-01-16  Corinna Vinschen  <corinna@vinschen.de>
 
 	* include/cygwin/in6.h (struct ipv6_mreq): Change type of interface
diff --git a/winsup/cygwin/fhandler_socket.cc b/winsup/cygwin/fhandler_socket.cc
index 3f7799eec..0ef0f593d 100644
--- a/winsup/cygwin/fhandler_socket.cc
+++ b/winsup/cygwin/fhandler_socket.cc
@@ -1419,6 +1419,7 @@ fhandler_socket::ioctl (unsigned int cmd, void *p)
     case SIOCGIFHWADDR:
     case SIOCGIFMETRIC:
     case SIOCGIFMTU:
+    case SIOCGIFINDEX:
       {
 	ifc.ifc_len = 2048;
 	ifc.ifc_buf = (char *) alloca (2048);
@@ -1469,6 +1470,9 @@ fhandler_socket::ioctl (unsigned int cmd, void *p)
 		  case SIOCGIFMTU:
 		    ifr->ifr_mtu = ifrp->ifr_mtu;
 		    break;
+		  case SIOCGIFINDEX:
+		    ifr->ifr_ifindex = ifrp->ifr_ifindex;
+		    break;
 		  }
 		break;
 	      }
diff --git a/winsup/cygwin/include/asm/socket.h b/winsup/cygwin/include/asm/socket.h
index ed062190c..637cec294 100644
--- a/winsup/cygwin/include/asm/socket.h
+++ b/winsup/cygwin/include/asm/socket.h
@@ -1,6 +1,6 @@
 /* asm/socket.h
 
-   Copyright 1996, 1997, 1998, 2001 Red Hat, Inc.
+   Copyright 1996, 1997, 1998, 2001, 2005, 2007 Red Hat, Inc.
 
 This file is part of Cygwin.
 
@@ -41,6 +41,7 @@ details. */
 #define SIOCGIFHWADDR   _IOW('s', 105, struct ifreq) /* Get hw addr */
 #define SIOCGIFMETRIC   _IOW('s', 106, struct ifreq) /* get metric */
 #define SIOCGIFMTU      _IOW('s', 107, struct ifreq) /* get MTU size */
+#define SIOCGIFINDEX    _IOW('s', 108, struct ifreq) /* get if index */
 
 #define SOL_SOCKET      0xffff          /* options for socket level */
 
diff --git a/winsup/cygwin/include/cygwin/if.h b/winsup/cygwin/include/cygwin/if.h
index b0953de36..fe36afcf2 100644
--- a/winsup/cygwin/include/cygwin/if.h
+++ b/winsup/cygwin/include/cygwin/if.h
@@ -1,6 +1,6 @@
 /* cygwin/if.h
 
-   Copyright 1996, 2001 Red Hat, Inc.
+   Copyright 1996, 2001, 2007 Red Hat, Inc.
 
 This file is part of Cygwin.
 
@@ -51,6 +51,7 @@ struct ifreq
 		short   ifru_flags;
 		int     ifru_metric;
 		int     ifru_mtu;
+		int	ifru_ifindex;
 	} ifr_ifru;
 };
 
@@ -62,7 +63,7 @@ struct ifreq
 #define ifr_hwaddr      ifr_ifru.ifru_hwaddr    /* MAC address          */
 #define ifr_metric      ifr_ifru.ifru_metric    /* metric               */
 #define ifr_mtu         ifr_ifru.ifru_mtu       /* mtu                  */
-
+#define ifr_ifindex     ifr_ifru.ifru_ifindex   /* interface index      */
 
 /*
  * Structure used in SIOCGIFCONF request.
diff --git a/winsup/cygwin/net.cc b/winsup/cygwin/net.cc
index f70618d22..13a1ee9df 100644
--- a/winsup/cygwin/net.cc
+++ b/winsup/cygwin/net.cc
@@ -1299,6 +1299,9 @@ get_2k_ifconf (struct ifconf *ifc, int what)
 	      case SIOCGIFMTU:
 		ifr->ifr_mtu = ifrow->dwMtu;
 		break;
+	      case SIOCGIFINDEX:
+		ifr->ifr_ifindex = ifrow->dwIndex;
+		break;
 	    }
 	  ++cnt;
 	  if ((caddr_t)++ ifr >
@@ -1461,6 +1464,9 @@ get_nt_ifconf (struct ifconf *ifc, int what)
 			  case SIOCGIFMTU:
 			    ifr->ifr_mtu = 1500;
 			    break;
+			  case SIOCGIFINDEX:
+			    ifr->ifr_ifindex = -1;
+			    break;
 			}
 		    }
 		  else
@@ -1503,6 +1509,9 @@ get_nt_ifconf (struct ifconf *ifc, int what)
 			  case SIOCGIFMTU:
 			    ifr->ifr_mtu = 1500;
 			    break;
+			  case SIOCGIFINDEX:
+			    ifr->ifr_ifindex = -1;
+			    break;
 			}
 		    }
 		  ++cnt;
@@ -1638,6 +1647,9 @@ get_95_ifconf (struct ifconf *ifc, int what)
 	      case SIOCGIFMTU:
 		ifr->ifr_mtu = 1500;
 		break;
+	      case SIOCGIFINDEX:
+		ifr->ifr_ifindex = -1;
+		break;
 	    }
 	}
 
@@ -1747,6 +1759,9 @@ get_ifconf (struct ifconf *ifc, int what)
 	    /* Default value for MS TCP Loopback interface. */
 	    ifr->ifr_mtu = 1520;
 	    break;
+	  case SIOCGIFINDEX:
+	    ifr->ifr_ifindex = -1;
+	    break;
 	  default:
 	    set_errno (EINVAL);
 	    return -1;