Wireshark · Wireshark-bugs: [Wireshark-bugs] [Bug 7932] New: Display Filter for GSM DTAP APN

[bugzilla-daemon@xxxxxxxxxxxxx]

https://bugs.wireshark.org/bugzilla/show_bug.cgi?id=7932

           Summary: Display Filter for GSM DTAP APN
           Product: Wireshark
           Version: 1.8.2
          Platform: All
        OS/Version: All
            Status: NEW
          Severity: Enhancement
          Priority: Low
         Component: Dissection engine (libwireshark)
        AssignedTo: bugzilla-admin@xxxxxxxxxxxxx
        ReportedBy: vineethvijaysv@xxxxxxxxx


Created attachment 9443
  --> https://bugs.wireshark.org/bugzilla/attachment.cgi?id=9443
DTAP-APN-Capture

Build Information:
wireshark 1.8.2 (SVN Rev Unknown from unknown)

Copyright 1998-2012 Gerald Combs <gerald@xxxxxxxxxxxxx> and contributors.
This is free software; see the source for copying conditions. There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Compiled (32-bit) with GTK+ 2.22.0, with Cairo 1.10.0, with Pango 1.28.2, with
GLib 2.26.1, with libpcap, with libz 1.2.3.4, without POSIX capabilities,
without SMI, without c-ares, without ADNS, without Lua, without Python, without
GnuTLS, without Gcrypt, without Kerberos, without GeoIP, without PortAudio,
with
AirPcap.

Running on Linux 2.6.35-22-generic, with locale en_IN, with libpcap version
1.1.1, with libz 1.2.3.4, without AirPcap.

Built using gcc 4.4.5.
--
GSM DTAP APN and GTP APN follow the same decoding/encoding rules. In wireshark,
GTP APN is a display filter whereas the DTAP APN is not. To make the same as
display filter, the following changes were made to 
epan/dissectors/packet-gsm_a_gm.c

2$ diff epan/dissectors/packet-gsm_a_gm.c epan/dissectors/packet-gsm_a_gm.c_bk
223d222
< static int hf_gsm_a_gm_apn = -1;
3746d3744
<         guint8 *apn = NULL;
3761,3769c3759,3765
<
<         apn = tvb_get_ephemeral_string(tvb, curr_offset+1, len-1);
<         proto_tree_add_string(tree,
<                hf_gsm_a_gm_apn, tvb,
<                curr_offset+1, len-1, apn);
<
<
<         curr_offset +=  len;
<
---
>
>       proto_tree_add_text(tree,
>               tvb, curr_offset, len,
>               "APN: %s %s", str+1, add_string ? add_string : "");
>
>       curr_offset +=  len;
>
3771c3767
<
---
>
7894,7898d7889
<                 { &hf_gsm_a_gm_apn,
<                    { "APN", "gsm_a.apn",
<                     FT_STRING,BASE_NONE, NULL,0x0,
<                     "Access Point Name", HFILL}
<                 }


After the changes, the issue is that any APN containing special characters like
dot are not getting stringified. Any way to do so??

Check the packet number #4 in the capture file for recreating the issue. Rest
of the APN's are decoded fine.

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