Better handle group refs to somewhere in the middle of the tree

doc/antora/modules/reference/pages/type/all_types.adoc

@@ -78,6 +78,10 @@ missing, then the relevant field is filled with zeros.
 
 group: A `group` contains an arbitrary collection of children, in any order.
 +
+A `group` is really a reference to some other attribute elsewhere in
+the same protocol dictionary, or to a different protocol dictionary.
+The `group` allows for dictionaries to contain cross-references.
++
 The `group` can contain any child attributes, so long as they are
 within the same protocol namespace.  See the
 dictionary/attribute.adoc[ATTRIBUTE] documentation for more
@@ -86,7 +90,7 @@ information.
 The `group` only encodes the child attributes which have been created
 and stored within the `group`.  The order of children does not matter.
 
-tlv:: A `tlv` is a `group` which has a limited subset of children.
+tlv:: A `tlv` defines a hierarchy of children, which can only be contained in the `tlv`.
 +
 The `tlv` can only contain child attributes which have been defined as
 children of the `tlv.`

src/lib/util/pair_print.c

@@ -14,6 +14,16 @@
  *   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301, USA
  */
 
+/*
+ *	Groups are printed from the referenced attribute.
+ */
+#define fr_pair_reset_parent(parent) do { \
+	if (parent && (parent->type == FR_TYPE_GROUP)) { \
+		parent = fr_dict_attr_ref(parent); \
+		if (parent->flags.is_root) parent = NULL; \
+	} \
+  } while (0)
+
 /** Pair serialisation API
  *
  * @file src/lib/util/pair_print.c
@@ -114,10 +124,7 @@ ssize_t fr_pair_print(fr_sbuff_t *out, fr_dict_attr_t const *parent, fr_pair_t c
 		token = "<INVALID-TOKEN>";
 	}
 
-	/*
-	 *	Groups are printed from the root.
-	 */
-	if (parent && (parent->type == FR_TYPE_GROUP)) parent = NULL;
+	fr_pair_reset_parent(parent);
 
 	if (vp->vp_raw) FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "raw.");
 	FR_DICT_ATTR_OID_PRINT_RETURN(&our_out, parent, vp->da, false);
@@ -176,10 +183,7 @@ ssize_t fr_pair_print_secure(fr_sbuff_t *out, fr_dict_attr_t const *parent, fr_p
 		token = "<INVALID-TOKEN>";
 	}
 
-	/*
-	 *	Groups are printed from the root.
-	 */
-	if (parent && (parent->type == FR_TYPE_GROUP)) parent = NULL;
+	fr_pair_reset_parent(parent);
 
 	if (vp->vp_raw) FR_SBUFF_IN_STRCPY_LITERAL_RETURN(&our_out, "raw.");
 	FR_DICT_ATTR_OID_PRINT_RETURN(&our_out, parent, vp->da, false);
@@ -241,10 +245,7 @@ ssize_t fr_pair_list_print(fr_sbuff_t *out, fr_dict_attr_t const *parent, fr_pai
 		return fr_sbuff_used(out);
 	}
 
-	/*
-	 *	Groups are printed from the root.
-	 */
-	if (parent && (parent->type == FR_TYPE_GROUP)) parent = NULL;
+	fr_pair_reset_parent(parent);
 
 	while (true) {
 		FR_SBUFF_RETURN(fr_pair_print, &our_out, parent, vp);

src/tests/unit/protocols/dhcpv6/dictionary

@@ -1,50 +1,9 @@
 BEGIN PROTOCOL	DHCPv6		3
 
-#
-#	Basic options needed by the DHCPv6 pair encoder and decoder
-#
-ATTRIBUTE	Packet-Type				65536	uint32	internal
-ATTRIBUTE	Transaction-ID				65537	uint32	internal
+ATTRIBUTE	test-tlv	6809	tlv
+ATTRIBUTE	child1		.1	uint32
+ATTRIBUTE	child2		.2	uint32
 
-ATTRIBUTE	Option-Request				65535	uint16 array	# Magic option listing requested options
-
-#
-#	Test attributes
-#
-ATTRIBUTE	Test-string				1	string
-ATTRIBUTE	Test-octets				2	octets
-
-ATTRIBUTE	Test-ipaddr				3	ipaddr
-ATTRIBUTE	Test-ipv4addr				4	ipv4addr
-ATTRIBUTE	Test-ipv4prefix				5	ipv4prefix
-ATTRIBUTE	Test-ipv6addr				6	ipv6addr
-ATTRIBUTE	Test-ipv6prefix				7	ipv6prefix
-ATTRIBUTE	Test-ifid				8	ifid
-ATTRIBUTE	Test-ether				11	ether
-
-ATTRIBUTE	Test-bool				12	bool
-
-ATTRIBUTE	Test-uint8				13	uint8
-ATTRIBUTE	Test-uint16				14	uint16
-ATTRIBUTE	Test-uint32				15	uint32
-ATTRIBUTE	Test-uint64				16	uint64
-
-ATTRIBUTE	Test-int8				17	int8
-ATTRIBUTE	Test-int16				18	int16
-ATTRIBUTE	Test-int32				19	int32
-ATTRIBUTE	Test-int64				20	int64
-
-ATTRIBUTE	Test-float32				21	float32
-
-ATTRIBUTE	Test-time-delta				23	time_delta
-ATTRIBUTE	Test-date				24	date
-
-ATTRIBUTE	Test-size				26	size
-
-ATTRIBUTE	Test-tlv				27	tlv
-ATTRIBUTE	Test-struct				28	struct
-
-ATTRIBUTE	Test-vsa				30	vsa
-ATTRIBUTE	Test-group				32	group
+ATTRIBUTE	test-group	6810	group ref=test-tlv
 
 END-PROTOCOL 	DHCPv6

src/tests/unit/protocols/dhcpv6/group-tlv.txt

@@ -0,0 +1,30 @@
+#  -*- text -*-
+#  Copyright (C) 2019 Network RADIUS SARL ([email protected])
+#  This work is licensed under CC-BY version 4.0 https://creativecommons.org/licenses/by/4.0
+#
+#  Version $Id$
+#
+
+proto dhcpv6
+proto-dictionary dhcpv6
+load-dictionary dictionary
+fuzzer-out dhcpv6
+
+pair test-group = { child1 = 1 }
+match test-group = { child1 = 1 }
+
+
+encode-pair	test-group = { child1 = 1 }
+match 1a 9a 00 0c 1a 99 00 08 00 01 00 04 00 00 00 01
+
+#
+#  Yeah, this is wrong.  The decoder can only handle group refs which
+#  point to the top of the tree.
+#
+#  @todo - fix it!
+#
+decode-pair -
+match test-group = {  = { child1 = 1 } }
+
+count
+match 10