[Winpcap-users] RE: Winpcap-users Digest, Vol 37, Issue 10

[Gianluca Varenni]

----- Original Message ----- 
From: "Paul Rocca" <Paul.Rocca at audiosoft.co.uk>
To: <winpcap-users at winpcap.org>
Sent: Tuesday, April 08, 2008 6:39 AM
Subject: [Winpcap-users] RE: Winpcap-users Digest, Vol 37, Issue 10


>
>
>   1. RE: first ethernet pkt gobbled by the next one...solved
>      (Har Yash Bahadur)
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 8 Apr 2008 13:29:01 +0530
> From: Har Yash Bahadur <har.bahadur at conexant.com>
> Subject: [Winpcap-users] RE: first ethernet pkt gobbled by the next
> one...solved
> To: Har Yash Bahadur <har.bahadur at conexant.com>,
> "winpcap-users at winpcap.org" <winpcap-users at winpcap.org>
> Message-ID:
> <9A42B16CBB815A4790B607652CD2DCB301F9FB5042 at noidahub1.bbnet.ad>
> Content-Type: text/plain; charset="iso-8859-1"
>
>>Hi All,
>
>>I found that WinPcap is not able to send or receive Ethernet packets of 
>>size >1514 bytes (inclusive of 14 byte MAC header).
>>The packet lost was of 1518 bytes which is the standard size in case of 
>>Ethernet packets. It means the payload cannot be more >than 1500 (=1514 - 
>>14) bytes.
>
>>I tried the same thing while sending a packet and I got an error from 
>>function "pcap_sendpacket". When I reduced
>>the total size to 1514 it works fine!
>
>>Anybody has any idea why this LIMIT? Ahs anybody else faced this issue?
>
>>Regards,
>>Har Yash
>
> Unless I'm missing something really obvious, looking at your code
> snippet, isn't it becasuse you have set the snaplen to 1530?
>

No. Snaplen influences the maximum number of bytes that you capture per 
packet. It doesn't influence transmission. If the snaplen is small (e.g. 50 
bytes), you will capture only the first X bytes of a packet, even if the 
original packet was bigger. If the snaplen is big (e.g. 64k), you will 
basically capture the whole packet.

Have a nice day
GV


>
> Paul
>
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