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

Gianluca Varenni gianluca.varenni at cacetech.com
Tue Apr 8 17:24:30 GMT 2008

----- 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?
>>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

> Paul
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