Presence of linux's PF_PACKET sockets is now detected.

The acinclude.m4 merged in from packetfactory's 1.1.3-rc branch
mysteriously assumed that that there was no PF_PACKET if the target
OS was linux, which is the opposite of what we want.

libnet/acinclude.m4

@@ -39,17 +39,10 @@ dnl
 
 AC_DEFUN([AC_LIBNET_CHECK_PF_PACKET],
 [
-    AC_MSG_CHECKING(for packet socket (PF_SOCKET))
+    AC_MSG_CHECKING(for packet socket (PF_PACKET))
     AC_CACHE_VAL(libnet_cv_have_packet_socket,
 
-        [case "$target_os" in
-
-        linux*)
-                libnet_cv_have_packet_socket=no
-		AC_MSG_RESULT(no)
-                ;;
-        *)
-
+        [
     cat > pf_packet-test.c << EOF
 #include <stdio.h>
 #include <errno.h>
@@ -110,8 +103,8 @@ EOF
     fi
 
     rm -f pf_packet-test* core core.pf_packet-test
-    ;;
-    esac])
+
+    ])
 
     if test $libnet_cv_have_packet_socket = yes -o $libnet_cv_have_packet_socket = probably; then
         AC_DEFINE(HAVE_PACKET_SOCKET, 1,

libnet/configure.in

@@ -84,7 +84,7 @@ if test -n "${with_link_layer}"; then
         none) AC_LIBOBJ([libnet_link_none]) ;;
         *) AC_MSG_ERROR([Invalid link type "${with_link_layer}"]) ;;
     esac
-    AC_MSG_RESULT(forced link layer to ${with_link_layer})
+    AC_MSG_RESULT(user selected link layer ${with_link_layer})
 elif test "${cross_compiling}" != "yes" -a -r /dev/bpf0 ; then
     AC_LIBOBJ([libnet_link_bpf])
     AC_MSG_RESULT(found link layer bpf)