Hi list,
Reading EDG 8.4.1 it struck me as a bit incomplete and inconsistent.
This patch hopes to work these kinks out.
Thanx,
Jaap
Index: EDG_chapter_dissection.xml
===================================================================
--- EDG_chapter_dissection.xml (revision 16108)
+++ EDG_chapter_dissection.xml (working copy)
@@ -743,17 +743,31 @@
</para>
<para>
To deal with such streams, we need several things to trigger
- from. We need to know that this is packet is part of a multi-packet
+ from. We need to know that this packet is part of a multi-packet
sequence. We need to know how many packets are in the sequence.
- We need to also know when we have all the packets.
+ We also need to know when we have all the packets.
</para>
<para>
For this example we'll assume there is a simple in-protocol
signaling mechanism to give details. A flag byte that signals
- the presence of a multi-packet and also the last packet,
- followed by an ID of the sequence,
- a packet sequence number.
+ the presence of a multi-packet sequence and also the last packet,
+ followed by an ID of the sequence and a packet sequence number.
</para>
+ <programlisting>
+<![CDATA[
+msg_pkt ::= SEQUENCE {
+ .....
+ flags ::= SEQUENCE {
+ fragment BOOLEAN,
+ last_fragment BOOLEAN,
+ .....
+ }
+ msg_id INTEGER(0..65535),
+ frag_id INTEGER(0..65565),
+ .....
+}
+]]>
+ </programlisting>
<example><title>Reassembling fragments - Part 1</title>
<programlisting>
<![CDATA[
@@ -761,7 +775,7 @@
...
save_fragmented = pinfo->fragmented;
flags = tvb_get_guint8(tvb, offset); offset++;
-if (flags & FL_FRAGMENT) { // fragmented
+if (flags & FL_FRAGMENT) { /* fragmented */
tvbuff_t* new_tvb = NULL;
fragment_data *frag_msg = NULL;
guint16 msg_seqid = tvb_get_ntohs(tvb, offset); offset += 2;
@@ -769,11 +783,11 @@
pinfo->fragmented = TRUE;
frag_msg = fragment_add_seq_check (tvb, offset, pinfo,
- msg_seqid, /* guint32 ID for fragments belonging together */
+ msg_seqid, /* ID for fragments belonging together */
msg_fragment_table, /* list of message fragments */
msg_reassembled_table, /* list of reassembled messages */
- msg_num, /* guint32 fragment sequence number */
- -1, /* guint32 fragment length - to the end */
+ msg_num, /* fragment sequence number */
+ -1, /* fragment length - to the end */
flags & FL_FRAG_LAST); /* More fragments? */
]]>
</programlisting></example>
@@ -827,20 +841,20 @@
if (check_col (pinfo->cinfo, COL_INFO))
col_append_str (pinfo->cinfo, COL_INFO,
" (Message Reassembled)");
- } else {
- /* Not last packet of reassembled Short Message */
+ } else { /* Not last packet of reassembled Short Message */
if (check_col (pinfo->cinfo, COL_INFO))
col_append_fstr (pinfo->cinfo, COL_INFO,
" (Message fragment %u)", msg_num);
}
- if (new_tvb) { // take it all
+
+ if (new_tvb) { /* take it all */
next_tvb = new_tvb;
+ } else { /* make a new subset */
+ next_tvb = tvb_new_subset(tvb, offset, -1, -1);
}
- else // make a new subset
- next_tvb = tvb_new_subset(next_tvb, offset, -1, -1);
}
-else {
- next_tvb = tvb_new_subset(next_tvb, offset, -1, -1);
+else { /* Not fragmented */
+ next_tvb = tvb_new_subset(tvb, offset, -1, -1);
}
offset = 0;
@@ -893,6 +907,19 @@
<example><title>Reassembling fragments - Data</title>
<programlisting>
<![CDATA[
+...
+static int hf_msg_fragments = -1;
+static int hf_msg_fragment = -1;
+static int hf_msg_fragment_overlap = -1;
+static int hf_msg_fragment_overlap_conflicts = -1;
+static int hf_msg_fragment_multiple_tails = -1;
+static int hf_msg_fragment_too_long_fragment = -1;
+static int hf_msg_fragment_error = -1;
+static int hf_msg_reassembled_in = -1;
+...
+static gint ett_msg_fragment = -1;
+static gint ett_msg_fragments = -1;
+...
static const fragment_items msg_frag_items = {
/* Fragment subtrees */
&ett_msg_fragment,
@@ -911,6 +938,9 @@
"Message fragments"
};
...
+static hf_register_info hf[] =
+{
+...
{&hf_msg_fragments,
{"Message fragments", "msg.fragments",
FT_NONE, BASE_NONE, NULL, 0x00, NULL, HFILL } },
@@ -937,6 +967,13 @@
{&hf_msg_reassembled_in,
{"Reassembled in", "msg.reassembled.in",
FT_FRAMENUM, BASE_NONE, NULL, 0x00, NULL, HFILL } },
+...
+static gint *ett[] =
+{
+...
+&ett_msg_fragment,
+&ett_msg_fragments
+...
]]>
</programlisting></example>
<para>
