New proto_tree header_field_info stuff. Header_field_infos now contain

the base for numbers to be displayed in, bitmasks for bitfields, and blurbs
(which are one or two sentences describing the field).

proto_tree_add*() routines now automatically handle bitfields. You tell
it which header field you are adding, and just pass it the value of the
entire field, and the proto_tree routines will do the masking and shifting
for you.

This means that bitfields are more naturally filtered via dfilter now.

Added Phil Techau's support for signed integers in dfilters/proto_tree.

Added the beginning of the SNA dissector. It's not complete, but I'm
committing it now because it has example after example of how to use
bitfields with the new header_field_info struct and proto_tree routines.
It was the impetus to change how header_field_info works.

svn path=/trunk/; revision=815

1 files changed, 273 insertions, 130 deletions

diff --git a/doc/proto_tree b/doc/proto_tree
index 12d322b89e..2a12ed6809 100644
--- a/doc/proto_tree
+++ b/doc/proto_tree
@@ -1,58 +1,56 @@
-$Id: proto_tree,v 1.4 1999/08/27 19:27:22 gram Exp $
+$Id: proto_tree,v 1.5 1999/10/12 06:21:15 gram Exp $
 
 The Ethereal Protocol Tree
 ==========================
 
-Up until version 0.6.3 of ethereal, the protocol tree that is displayed
-in the middle pane of the ethereal GUI had been created by having the
-protocol dissection routines add strings to a GTK+ tree. This GUI
-container was not easily manipulated; the print routines had to reach
-inside what should be an opaque structure and pull out the data. The
-tree of strings also did not lend itself to filtering on the data
-available in the tree.
-
-Mostly to solve the display filter problem, I decided to have the
-protocol dissection routines put their data into a logical tree instead
-of a GUI tree. This tree structure would provide a generic way for
-multiple routines, like the dissection routines, the display filter
-routines, and the print routines, to retrieve data about the protocol
-fields. The GUI routines would then be modified to draw the GUI tree
-based on the data in the logical tree. By structuring this logical tree
-well, with well-defined field types, ethereal can have a very powerful
-display filter option. No longer would display filters be limited to the
-ability of the BPF compiler (libpcap or wiretap), but would have access to the
-full range of C field types available within ethereal.
-
-The dissection routines are still passed a proto_tree pointer, but a
-proto_tree is no longer the same as a GtkTree. Now a proto_tree is a
-GNode, the N-way tree structure available within GLIB. Of course the
-protocol dissectors don't care what a proto_tree really is; they just
-pass the proto_tree pointer as an argument to the routines which allow
-them to add items and new branches to the tree.
-
-In packet_list_select_cb() you'll now find this:
-
-    if (protocol_tree)
-        proto_tree_free(protocol_tree);
-    protocol_tree = proto_tree_create_root();
-    dissect_packet(cf.pd, fd, protocol_tree);
-    proto_tree_draw(protocol_tree, tree_view);
-
-When a packet is selected in the packet-list pane, a new logical
-protocol tree (proto_tree) is created. The pointer to the proto_tree (in
-this case, 'protocol tree'), is passed to the top-level protocol
-dissector, and then the GUI tree is drawn via proto_tree_draw().
+Up until version 0.6.3 of Ethereal, the protocol tree that is displayed
+in the middle pane of the Ethereal GUI had been created by having
+the protocol dissection routines add strings to a GTK+ tree. This
+GUI container was not easily manipulated; the print routines had to
+reach inside what should be an opaque GUI structure and pull out the
+data. The tree of strings also did not lend itself to filtering on the
+data available in the tree.
+
+Mostly to solve the display filter problem, I decided to have the protocol
+dissection routines put their data into a logical tree instead of a
+GUI tree. This tree structure would provide a generic way for multiple
+routines, like the dissection routines, the display filter routines,
+and the print routines, to retrieve data about the protocol fields. The
+GUI routines would then be modified to draw the GUI tree based on the
+data in the logical tree. By structuring this logical tree well, with
+well-defined field types, Ethereal can have a very powerful display
+filter option. No longer would display filters be limited to the ability
+of the BPF compiler (libpcap or wiretap), but would have access to the
+full range of C field types available within Ethereal.
+
+In Ethereal 0.7.6, I decided to extend the information that the
+programmer must provide about each field. I was frustrated by the way
+in which the original proto_tree code handled bitfields. By providing
+a small amount of extra info, bitfields can now be added very easily
+to the proto_tree. In addition, filtering on bitfields now works
+more naturally.
+
+The protocol tree, or proto_tree, is a GNode, the N-way tree structure
+available within GLIB. Of course the protocol dissectors don't care
+what a proto_tree really is; they just pass the proto_tree pointer as an
+argument to the routines which allow them to add items and new branches
+to the tree.
+
+When a packet is selected in the packet-list pane, a new logical protocol
+tree (proto_tree) is created. The pointer to the proto_tree (in this
+case, 'protocol tree'), is passed to the top-level protocol dissector,
+and then to all subsequent protocol dissectors for that packet, and then
+the GUI tree is drawn via proto_tree_draw().
 
 Programming for the proto_tree
 ==============================
-The logical proto_tree now needs to know detail information about the
+The logical proto_tree needs to know detailed information about the
 protocols and fields about which information will be collected from the
-dissection routines. No longer will is the data just a bunch of strings.
-Now the data will be typed so that searching and filtering on protocol
-header fields will be possible. This means that the for every protocol
-and field (which I also call "header fields", since they are fields in
-the protocol headers) which might be attached to a tree, some
-information is needed.
+dissection routines. By strictly defining (or "typing") the data that can
+be attached to a proto tree, searching and filtering becomes possible.
+This means that the for every protocol and field (which I also call
+"header fields", since they are fields in the protocol headers) which
+might be attached to a tree, some information is needed.
 
 Every dissector routine will need to register its protocols and fields
 with the central protocol routines (in proto.c). At first I thought I
@@ -89,101 +87,189 @@ Here is how the frame "protocol" is registered.
 
 
 A header field is also registered with its name and abbreviation, but
-information about the its data type is needed. Some fields will use
-value_strings to represent their values, so the value_string
-is also passed. And of course the parent protocol for the field is indicated
-during registration.
-
-	int hf_frame_arrival_time;
-
-        hf_frame_arrival_time = proto_register_field (
-                /* name */      "Arrival Time",
-                /* abbrev */    "frame.time",
-                /* ftype */     FT_ABSOLUTE_TIME,
-                /* parent */    proto_frame,
-                /* vals[] */    NULL );
-
-Groups of header fields can be registered with one call to
-proto_register_field_array(). A static array of hf_register_info
-structs is declared, then passed to proto_register_field_array, along
-with a count of the number of records. Be sure that your array
-of hf_register_info structs is declared 'static', since the
-proto_register_field_array() function does not create a copy of
-the information in the array... it uses that static copy of the
-information that the compiler created inside your array. Here's
-the layout of the hf_register_info struct:
-
-typedef struct hf_register_info {
-	int			*p_id;	/* pointer to parent variable */
-	header_field_info	hfinfo;
-} hf_register_info;
-
-You can use the handy array_length() macro found in packet.h
-to have the compiler compute the array length for you at compile time:
+information about the its data type is needed. It helps to look at
+the header_field_info struct to see what information is expected:
+
+struct header_field_info {
+	char				*name;
+	char				*abbrev;
+	enum ftenum			type;
+	int				display;
+	void				*strings;
+	guint				bitmask;
+	char				*blurb;
+
+	int				id;	  /* calculated */
+	int				parent;
+	int				bitshift; /* calculated */
+};
 
+name
+----
+A string representing the name of the field. This is the name
+that will appear in the graphical protocol tree.
+
+abbrev
+------
+A string with an abbreviation of the field. We concatenate the
+abbreviation of the parent protocol with an abbreviation for the field,
+using a period as a separator. For example, the "src" field in an IP packet
+would have "ip.addr" as an abbreviation. It is acceptable to have
+multiple levels of periods if, for example, you have fields in your
+protocol that are then subdivided into subfields. For example, TRMAC
+has multiple error fields, so the abbreviations follow this pattern:
+"trmac.errors.iso", "trmac.errors.noniso", etc.
+
+The abbreviation is the identifier used in a display filter.
+
+type
+----
+The type of value this field holds. The current field types are:
+
+	FT_NONE,
+	FT_BOOLEAN,
+	FT_UINT8,
+	FT_UINT16,
+	FT_UINT24,
+	FT_UINT32,
+	FT_INT8,
+	FT_INT16,
+	FT_INT24,
+	FT_INT32,
+	FT_DOUBLE,
+	FT_ABSOLUTE_TIME,
+	FT_RELATIVE_TIME,
+	FT_STRING,
+	FT_ETHER,
+	FT_BYTES,
+	FT_IPv4,
+	FT_IPv6,
+	FT_IPXNET
+
+Some of these field types are still not handled in the display filter
+routines, but the most common ones are. The FT_UINT* variables all
+represent unsigned integers; the number on the end represent how many
+bits are used to represent the number.
+
+display
+-------
+The display field has a couple of overloaded uses. This is unfortunate,
+but since we're C as an application programming language, this sometimes
+makes for cleaner programs. Right now I still think that overloading
+this variable was okay.
+
+For integer fields (FT_UINT*), this variable represents the base in
+which you would like the value displayed. The acceptable bases are:
+	BASE_DEC,
+	BASE_HEX,
+	BASE_OCT,
+	BASE_BIN
+
+For FT_BOOLEAN fields that are also bitfields, 'display' is used
+to tell the proto_tree how wide the parent bitfield is. With integers
+this is not needed since the type of integer itself (FT_UINT8, FT_UINT16,
+FT_UINT24, FT_UINT32) tells the proto_tree how wide the parent bitfield is.
+
+Additionally, BASE_NONE is used for 'display' as a NULL-value. That is,
+for non-integers and non-bitfield FT_BOOLEANs, you'll want to use BASE_NONE
+in the 'display' field.
+
+It is possible that in the future we will record the endianness of
+integers. If so, it is likely that we'll use a bitmask on the display field
+so that integers would be represented as BEND|BASE_DEC or LEND|BASE_HEX.
+But that has not happened yet.
+
+strings
+-------
+Some integer fields need labels to represent the true value of a field.
+A value_string structure is a way to map values to strings.
+
+typedef struct _value_string {
+  guint32  value;
+  gchar   *strptr;
+} value_string;
+
+For FT_UINT* fields, the 'string' field is a pointer to an array of
+such value_string structs. (Note: before Ethereal 0.7.6, we had
+separate field types like FT_VALS_UINT8 which denoted the use of value_strings.
+Now, the non-NULLness of the pointer lets the proto_tree know that
+a value_string is meant for this field).
+
+FT_BOOLEANS have a default map of 0 = "False", 1 (or anything else) = "True".
+Sometimes it is useful to change the labels for boolean values (e.g.,
+to "Yes"/"No", "Fast"/"Slow", etc.).  For these mappings, a struct called
+true_false_string is used. (This struct is new as of Ethereal 0.7.6).
+
+typedef struct true_false_string {
+	char	*true_string;
+	char	*false_string;
+} true_false_string;
+
+It's two fields are pointers to the string representing truth, and
+the string representing falsehood. For FT_BOOLEAN fields that need a
+true_false_string struct, the 'strings' field is a pointer to that struct.
+
+bitmask
+-------
+If the field is not a bitfield, then bitmask should be set to 0.
+If it is a bitfield, then the bitmask is the mask which will
+leave only the bits needed to make the field when ANDed with a value.
+The proto_tree routines will calculate 'bitshift' automatically
+from 'bitmask', by finding the first set bit in the bitmask.
+
+blurb
+-----
+This is a string giving a sentence or two description of the field.
+It is meant to provide a more detailed description of the field than the
+name alone provides. This information will be used in the man page, and
+in a future GUI display-filter creation tool. We might also add tooltips
+to the labels in the GUI protocol tree, in which case the blurb would
+be used as the tooltip text.
+
+Field Registration
+------------------
+Protocol registration is handled by creating an instance of the
+header_field_info struct (or an arry of such structs), and
+calling the registration function along with the registration ID of
+the protocol that is the parent of the fields. Here is a complete example:
+
+	int proto_eg = -1;
 	int hf_field_a = -1;
 	int hf_field_b = -1;
 
 	static hf_register_info hf[] = {
 
 		{ &hf_field_a,
-		{ "Field A",	"proto.field_a", FT_UINT8, NULL }},
+		{ "Field A",	"proto.field_a", FT_UINT8, BASE_HEX, NULL,
+			0xf0, "Field A represents Apples" }},
 
 		{ &hf_field_b,
-		{ "Field B",	"proto.field_a", FT_VALS_UINT16, VALS(vs) }}
+		{ "Field B",	"proto.field_a", FT_UINT16, BASE_DEC, VALS(vs),
+			0x0, "Field B represents Bananas" }}
 	};
 
-	proto_tr = proto_register_protocol("Token-Ring", "tr");
-	proto_register_field_array(proto_tr, hf, array_length(hf));
-
-The name can be used in any type of display, either in the GUI tree, or
-in a display filter UI. The abbreviation is used when representing a
-display filter as a string. For example, the following strings could be a
-valid display filter, depending upon the implementation of the display
-filter parser and engine.
+	proto_eg = proto_register_protocol("Example Protocol", "proto");
+	proto_register_field_array(proto_eg, hf, array_length(hf));
 
-	frame[20:1] = 0x0a
-	frame.time > 'May 21, 1999 13:15:00'
+Be sure that your array of hf_register_info structs is declared 'static',
+since the proto_register_field_array() function does not create a copy
+of the information in the array... it uses that static copy of the
+information that the compiler created inside your array. Here's the
+layout of the hf_register_info struct:
 
-The field type come from an enum. Currently, enum ftenum is comprised
-of:
-
-/* field types */
-enum ftenum {
-        FT_NONE,        /* used for protocol labels (thus no field type) */
-        FT_UINT8,
-        FT_UINT16,
-        FT_UINT32,
-	FT_BOOLEAN,
-        FT_ABSOLUTE_TIME,
-        FT_RELATIVE_TIME,
-        FT_STRING,
-        FT_ETHER,
-        FT_BYTES,
-        FT_IPv4,
-        FT_IPv6,
-        FT_IPXSERVER,
-        FT_VALS_UINT8,
-        FT_VALS_UINT16,
-        FT_VALS_UINT24,
-        FT_VALS_UINT32,
-	FT_TEXT_ONLY,	 /* used internally, but should be used by dissectors */
-        NUM_FIELD_TYPES /* last item number plus one */
-};
-
-Previously, the sequence needed within a dissector to add a new branch
-to the GUI tree was this:
+typedef struct hf_register_info {
+	int			*p_id;	/* pointer to parent variable */
+	header_field_info	hfinfo;
+} hf_register_info;
 
-	item = proto_tree_add_item(....);
-	new_tree = proto_tree_new();
-	proto_item_add_subtree(item, new_tree, tree_type);
+Also be sure to use the handy array_length() macro found in packet.h
+to have the compiler compute the array length for you at compile time.
 
-With the new system, the call to proto_tree_new() is no longer needed,
-as proto_item_add_subtree creates the new tree for you. The change was
-necessary so that the proto_tree routines could maintain the
-parent/child relationship within the logical tree. But it has a nice
-side-effect of cleaning up the dissector code. The new method is like
-this:
+Adding Items and Values to the Protocol Tree
+--------------------------------------------
+A protocol item is added to an existing protocol tree with one of a
+handful of proto_tree_add_item*() funtions. Subtrees can be made
+with the proto_item_add_subtree() function:
 
 	item = proto_tree_add_item(....);
 	new_tree = proto_item_add_subtree(item, tree_type);
@@ -204,18 +290,73 @@ protocol or field labels to the proto_tree:
 	proto_item*
 	proto_tree_add_text(tree, start, length, format, ...);
 
+proto_tree_add_item()
+---------------------
 The first function, proto_tree_add_item, is used when you wish to do no
 special formatting. The item added to the GUI tree will contain the name
 (as passed in the proto_register_*() function) and any value. If your
 field does have a value, it is passed after the length variable (notice
 the ellipsis in the function prototype).
 
-The second function, proto_tree_add_free_format(), is used when the
+Now that the proto_tree has detailed information about bitfield fields,
+you an use proto_tree_add_item() with no extra processing to add bitfield
+values to your tree.  Here's an example. Take the Format Identifer (FID)
+field in the Tranmission Header (TH)  portion of the SNA protocol. The
+FID is the high nibble of the first byte of the TH. The FID would be
+registered like this:
+
+	name		= "Format Identifer"
+	abbrev		= "sna.th.fid"
+	type		= FT_UINT8
+	display		= BASE_HEX
+	strings		= sna_th_fid_vals
+	bitmask		= 0xf0
+
+The bitmask contains the value which would leave only the FID if bitwise-ANDed
+against the parent field, the first byte of the TH.
+
+The code to add the FID to the tree would be;
+
+	guint8 th_0 = pd[offset];
+	proto_tree_add_item(bf_tree, hf_sna_th_fid, offset, 1, th_0);
+
+Note: we do not do *any* manipulation of th_0 in order to ge the FID value.
+We just pass it to proto_tree_add_item(). The proto_tree already has
+the information about bitmasking and bitshifting, so it does the work
+of masking and shifting for us! This also means that you no longer
+have to crate value_string structs with the values bitshifted. The
+value_string for FID looks like this, even though the FID value is
+actually contained in the high nibble. (You'd expect the values to be
+0x0, 0x10, 0x20, etc.)
+
+/* Format Identifier */
+static const value_string sna_th_fid_vals[] = {
+	{ 0x0,	"SNA device <--> Non-SNA Device" },
+	{ 0x1,	"Subarea Node <--> Subarea Node" },
+	{ 0x2,	"Subarea Node <--> PU2" },
+	{ 0x3,	"Subarea Node or SNA host <--> Subarea Node" },
+	{ 0x4,	"?" },
+	{ 0x5,	"?" },
+	{ 0xf,	"Adjaced Subarea Nodes" },
+	{ 0,	NULL }
+};
+
+The final implication of this is that display filters work the way you'd
+naturally expect them to. You'd type "sna.th.fid == 0xf" to find Adjacent
+Subarea Nodes. The user does not have to shift the value of the FID to
+the high nibble of the byte ("sna.th.fid == 0xf0") as was necessary
+before Ethereal 0.7.6.
+
+proto_tree_add_item_format()
+----------------------------
+The second function, proto_tree_add_item_format(), is used when the
 dissector routines wants complete control over how the field and value
 will be represented on the GUI tree. The caller must pass include the
 name of the protocol or field; it is not added automatically as in
 proto_tree_add_item().
 
+proto_tree_add_item_hidden()
+----------------------------
 The third function is used to add fields and values to a tree, but not
 show them on a GUI tree. The caller may want a value to be included in a
 tree so that the packet can be filtered on this field, but the
@@ -262,11 +403,13 @@ filter is then possible:
 
 	tr.rif_ring eq 0x013
 
+proto_tree_add_text()
+---------------------
 The fourth function, proto_tree_add_text(), is used to add a label to the GUI tree.
 It will contain no value, so it is not searchable in the display filter process.
 This function was needed in the transition from the old-style proto_tree to this
-new-style proto_tree so that ethereal would still decode all protocols w/o being
+new-style proto_tree so that Ethereal would still decode all protocols w/o being
 able to filter on all protocols and fields. Otherwise we would have had to
-cripple ethereal's functionality while we converted all the old-style proto_tree
+cripple Ethereal's functionality while we converted all the old-style proto_tree
 calls to the new-style proto_tree calls.