[Sake Blok <sake@xxxxxxxxxx>]

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

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