Wireshark-users: [Wireshark-users] Is that a bug in packet-gsm_sms.c ?
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From: "damker" <damker@xxxxxxxx>
Date: Sun, 3 Apr 2011 20:52:02 +0800

Begin with line 2945 , it said that :

 

    /*

     * there does not seem to be a way to determine that this

     * deliver report is from an RP-ERROR or RP-ACK other

     * than to look at the next octet

     *

     * FCS values are 0x80 and higher

     * PI uses bit 7 as an extension indicator

     *

     * will assume that if bit 7 is set then this octet

     * is an FCS otherwise PI

     */

    offset++;

    oct = tvb_get_guint8(tvb, offset);

 

    if (oct & 0x80)

    {

         dis_field_fcs(tvb, tree, offset, oct);

         offset++;

    }

 

    pi = tvb_get_guint8(tvb, offset);

 

    dis_field_pi(tvb, tree, offset, pi);

 

……

 

“will assume that if bit 7 is set then this octet is an FCS otherwise PI” means that the octet is a FCS or a PI , if it is a FCS ,it is not a PI ; If it is a PI , it is not a FCS .

 

    if (oct & 0x80)

    {

         dis_field_fcs(tvb, tree, offset, oct);

         offset++;

    }

 

    pi = tvb_get_guint8(tvb, offset);

 

    dis_field_pi(tvb, tree, offset, pi);

 

means that it can be a FCS with PI?