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Note that a dissector heuristic test *must not* cause an exception before returning FALSE. 

Change-Id: I9f1ab000f7a2c554d1c20abf8ca4e4bab4b5ef27
Reviewed-on: https://code.wireshark.org/review/635
Reviewed-by: Bill Meier <wmeier@newsguy.com>
Tested-by: Bill Meier <wmeier@newsguy.com>
This commit is contained in:
Bill Meier 2014-03-11 10:28:41 -04:00
parent 36db2df1c1
commit 53dab8e1f1
1 changed files with 10 additions and 0 deletions
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doc/README.heuristic
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@ -91,6 +91,13 @@ Obviously, this is *not* 100% bullet proof, but it's the best WS can offer to
its users here - and improving the heuristic is always possible if it turns out its users here - and improving the heuristic is always possible if it turns out
that it's not good enough to distinguish between two given protocols. that it's not good enough to distinguish between two given protocols.
Note: The heuristic code in a dissector *must not* cause an exception
(before returning FALSE) as this will prevent following
heuristic dissector handoffs. In practce, this normally means
that a test should be done to verify that the required data is
available in the tvb before fetching from the tvb. (See the
example below).
Heuristic Code Example Heuristic Code Example
---------------------- ----------------------
@ -120,6 +127,9 @@ static gboolean
dissect_PROTOABBREV_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data) dissect_PROTOABBREV_heur(tvbuff_t *tvb, packet_info *pinfo, proto_tree *tree, void *data)
{ {
... ...
/* 0) Verify needed bytes available in tvb so tvb_get...() doesn't cause exception.
if (tvb_length(tvb) < 5)
return FALSE;
/* 1) first byte must be 0x42 */ /* 1) first byte must be 0x42 */
if ( tvb_get_guint8(tvb, 0) != 0x42 ) if ( tvb_get_guint8(tvb, 0) != 0x42 )