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The "8 mysterious bytes" are bytes reserved for a setup header - with 

the Linux USB capture mechanism, there are always 8 bytes of setup
header after the URB, regardless of whether there's a setup header or
not; if there is no setup header, we just skip those 8 bytes.

Don't skip them *twice*, however.

svn path=/trunk/; revision=27046
This commit is contained in:
Guy Harris 2008-12-18 09:17:16 +00:00
parent ea57cc5776
commit 57f910e107
1 changed files with 17 additions and 19 deletions
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36
epan/dissectors/packet-usb.c
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@ -1792,25 +1792,6 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
}
}
/* For DLT189 it seems
* that all INTERRUPT or BULK packets as well as all CONTROL responses
* are prepended with 8 mysterious bytes.
*/
switch(type){
case URB_CONTROL:
if(pinfo->pseudo_header->linux_usb.event_type!=URB_SUBMIT){
offset+=8;
}
break;
case URB_BULK:
case URB_ISOCHRONOUS:
case URB_INTERRUPT:
offset+=8;
break;
default:
DISSECTOR_ASSERT_NOT_REACHED();
}
tap_data=ep_alloc(sizeof(usb_tap_data_t));
tap_data->urb_type=(guint8)pinfo->pseudo_header->linux_usb.event_type;
tap_data->transfer_type=(guint8)type;
@ -1826,6 +1807,10 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
item=proto_tree_add_uint(tree, hf_usb_bInterfaceClass, tvb, 0, 0, usb_conv_info->interfaceClass);
PROTO_ITEM_SET_GENERATED(item);
/* Skip setup header - it's never present */
offset += 8;
if(tvb_reported_length_remaining(tvb, offset)){
tvbuff_t *next_tvb;
@ -1853,6 +1838,9 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
tvbuff_t *next_tvb;
/* this is a request */
/* Dissect the setup header - it's present */
ti = proto_tree_add_protocol_format(tree, proto_usb, tvb, offset, sizeof(struct usb_device_setup_hdr), "URB setup");
setup_tree = proto_item_add_subtree(ti, usb_setup_hdr);
usb_trans_info->requesttype=tvb_get_guint8(tvb, offset);
@ -1911,12 +1899,18 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
break;
}
} else {
/* Skip setup header - it's not present */
offset += 8;
}
} else {
tvbuff_t *next_tvb;
/* this is a response */
/* Skip setup header - it's never present for responses */
offset += 8;
if(usb_trans_info){
/* Try to find a class specific dissector */
next_tvb=tvb_new_subset(tvb, offset, -1, -1);
@ -1973,6 +1967,8 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
guint8 requesttype, request;
int type;
/* Dissect the setup header - it's present */
ti = proto_tree_add_protocol_format(tree, proto_usb, tvb, offset, sizeof(struct usb_device_setup_hdr), "URB setup");
setup_tree = proto_item_add_subtree(ti, usb_setup_hdr);
@ -1991,6 +1987,8 @@ dissect_linux_usb(tvbuff_t *tvb, packet_info *pinfo, proto_tree *parent)
proto_tree_add_item(tree, hf_usb_length, tvb, offset, 2, TRUE);
offset += 2;
} else {
/* Skip setup header - it's not present */
offset += 8;
}
break;