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Wireshark-users: Re: [Wireshark-users] The capturefile appears to be damaged orcorrupt. (pcap: Fi

From: "Gianluca Varenni" <gianluca.varenni@xxxxxxxxxxxx>
Date: Tue, 18 May 2010 10:51:33 -0700
The problem is that neither Sake nor I know why the trace is corrupted. From the code it looks impossible that dumpcap generated such corrupted capture.

GV

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From: "Joseph Laibach" <jlaibach@xxxxxxxxxxxxx>
Sent: Tuesday, May 18, 2010 5:56 AM
To: "Community support list for Wireshark" <wireshark-users@xxxxxxxxxxxxx>; "Sake Blok" <sake@xxxxxxxxxx>; <gianluca.varenni@xxxxxxxxxxxx>
Subject: RE: [Wireshark-users] The	capturefile	appears	to	be	damagedorcorrupt.(pcap:	Fileshas	109736-byte packet, bigger than maximum of 65535)

Sake/GV,
I don't fully understand all of this. If I have it correct the packet being captured has the wrong packet length counter in its header or am I missing something else? Is this something that can be corrected or compensated for by capturing in a different way?

Thanks for the help,

Joe

-----Original Message-----
From: wireshark-users-bounces@xxxxxxxxxxxxx [mailto:wireshark-users-bounces@xxxxxxxxxxxxx] On Behalf Of Gianluca Varenni
Sent: Monday, May 17, 2010 4:59 PM
To: Sake Blok; Community support list for Wireshark
Subject: Re: [Wireshark-users] The capturefile appears to be damaged or corrupt. (pcap: Fileshas 109736-byte packet, bigger than maximum of 65535)



--------------------------------------------------
From: "Sake Blok" <sake@xxxxxxxxxx>
Sent: Monday, May 17, 2010 1:38 PM
To: "Community support list for Wireshark" <wireshark-users@xxxxxxxxxxxxx>
Cc: "Gianluca Varenni" <gianluca.varenni@xxxxxxxxxxxx>
Subject: Re: [Wireshark-users] The capturefile appears to be damaged orcorrupt.(pcap: Fileshas 109736-byte packet, bigger than maximum of 65535)


On 17 mei 2010, at 22:17, Gianluca Varenni wrote:

the phdr struct is passed on from capture_loop_cb to
libpcap_write_packet unaltered. So in my understanding pcap_dispatch
must have supplied a wrong value of phdr->caplen for it to to faultly
written to file. However this contradicts with the fact that the whole
packet is indeed written after the header, because the following code
should have trimmed the data to phr->caplen:

     nwritten = fwrite(pd, 1, phdr->caplen, fp);

This is what I was expecting. In the corrupted file, what the is value of
the "len" field?

The packet header is:
BE 47 F1 4B FF ED 0B 00 62 00 00 00 66 00 00 00

ie incl_len is 98, while orig_len is 102

Which is totally legal... I have no idea, apart from adding assertions in
the dumpcap code, hoping to spot something weird.

GV


And the packet data is:
01 00 5E 00 05 DD 00 12 DA 9F 79 1B 08 00
45 00 00 58 00 00 40 00 18 11 7F A4 C6 8C 36 87 E0 00 05 DD
7E 35 20 1D 00 44 9F 74
00 3A 00 8C 00 0F DF 77 02 16 2C E4 6B 01 01 00 02 16 2C E2 00 00 00 00 00 05 30 20 00 00 00 07 00 05 2F 58 00 00 00 02 04 4E 45 52 43 41 48 00 00 00
00 00 00 00 00 00 00 00 00 00

ie 14 bytes ethernet header, 20 bytes IP header, 8 bytes UDP header and 60
bytes payload => 102 (0x66) bytes in total

Cheers,
Sake



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