Wireshark · Wireshark-dev: Re: [Wireshark-dev] dissection question

[Jaap Keuter <jaap.keuter@xxxxxxxxx>]

Hi,

Is the sizeofroutername in the protocol a 8 bit value or 16 bit value?

You read a 8 bit value:

>                         sizeofroutername = tvb_get_guint8(tvb, offset);

, but present a 16 bit value:

>                         proto_tree_add_item(helen_sub_tree,
> hf_helen_sizeofRouterName, tvb, offset, 2, FALSE);
>                         offset += 2;

Thanks,
Jaap

Brian Oleksa wrote:
> Hello All
>
> What I am really looking to do is the following:
>
> proto_tree_add_item(helen_sub_tree, hf_helen_routername, tvb, offset, 
> *sizeofroutername*, FALSE);
>
> But putting in the "sizeofroutername" does not seem to work and does 
> indeed through off the rest of the packet.
>
> When I "hardcode" the value (which in this case it is 2... as I can see 
> it in the hex dump window).. it appears to work ok....but I know that I 
> cannot hard code that value.
> proto_tree_add_item(helen_sub_tree, hf_helen_routername, tvb, offset, 2, 
> FALSE);
>
> Any thoughts..??
>
> Code snippet is below
>
> Thanks,
> Brian
>
>
>
>
>
> //Router Ext:
>                 if (code == 1001) {
>                     guint8 routercount;
>                     guint8 interfacecount;
>                     guint8 sizeofinterfacename;
>                     guint8 sizeofroutername;
>                     guint i;
>                     guint k;
>
>                     //router count
>                     routercount = tvb_get_guint8(tvb, offset);
>                     proto_tree_add_item(helen_sub_tree, 
> hf_helen_routerCount, tvb, offset, 1, FALSE);
>                     offset += 1;
>
>
>                     //Router Data
>                     for (i = 0; i < routercount; i++) {
>                         nstime_t t;
>                         guint64 msecs_since_the_epoch;
>                         struct tm *tmp;
>
>                         //Size of router name
>                         sizeofroutername = tvb_get_guint8(tvb, offset);
>                         proto_tree_add_item(helen_sub_tree, 
> hf_helen_sizeofRouterName, tvb, offset, 2, FALSE);
>                         offset += 2;
>
> *Here is where the problem starts:*
>
>                         //Router Name
>                         //proto_tree_add_item(helen_sub_tree, 
> hf_helen_routername, tvb, offset, sizeofroutername, FALSE);
>                         proto_tree_add_item(helen_sub_tree, 
> hf_helen_routername, tvb, offset, 2, FALSE);
>                         offset += 2;
>                         //offset += sizeofroutername;
>
>                         //status
>                         proto_tree_add_uint(helen_sub_tree, 
> hf_helen_routerstatus, tvb, offset, 1, FALSE);
>                         offset += 1;
>
>                         //update time
>                         msecs_since_the_epoch = tvb_get_ntoh64(tvb, offset);
>                         t.secs = msecs_since_the_epoch / 1000;
>                         t.nsecs = (msecs_since_the_epoch % 
> 1000)*1000000; /* milliseconds to nanoseconds */
>                         tmp = gmtime(&t.secs);
>                         proto_tree_add_time(helen_sub_tree, 
> hf_helen_time, tvb, offset, 8, &t);
>                         offset += 8;
>
>                         //cpu % used
>                         proto_tree_add_uint(helen_sub_tree, 
> hf_helen_cpuusage, tvb, offset, 1, FALSE);
>                         offset += 1;
>
>                         //interface count
>                         interfacecount = tvb_get_guint8(tvb, offset);
>                         proto_tree_add_uint(helen_sub_tree, 
> hf_helen_interface_count, tvb, offset, 1, FALSE);
>                         offset += 1;
>
>                         //Interface Data
>                         for (k = 0; k < interfacecount; k++) {
>                             proto_tree_add_item(helen_sub_tree, 
> hf_helen_sizeofInterfaceName, tvb, offset, 2, FALSE);
>                             offset += 2;
>
>                             //Interface Name
>                             sizeofinterfacename = tvb_get_guint8(tvb, 
> offset);
>                             proto_tree_add_item(helen_sub_tree, 
> hf_helen_interfacename, tvb, offset, 8, FALSE);
>                             offset += sizeofinterfacename;
>
>                             //incoming bytes
>                                proto_tree_add_item(helen_sub_tree, 
> hf_helen_incomingBytes, tvb, offset, 4, FALSE);
>                             offset += 4;
>
>                             //outgoing bytes
>                             proto_tree_add_item(helen_sub_tree, 
> hf_helen_outgoingBytes, tvb, offset, 4, FALSE);
>                             offset += 4;
>
>                             //interface active?
>                            proto_tree_add_uint(helen_sub_tree, 
> hf_helen_interfaceActivity, tvb, offset, 1, FALSE);
>                            offset += 1;
>
>                         }
>
>                     }
>
>                 }
>
>
>         { &hf_helen_routername,
>             { "Router Name", "helen.routername", FT_STRING, BASE_NONE, 
> NULL, 0x0,
>                 NULL, HFILL}},
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