[Winpcap-users] question regarding retrieving ip_len

[Vasily Borovyak]

Because the length represents not amount if bytes (octets)
but amount of WORDs (32bit or 4 bytes).

That's why we should multiply by 4 to get actual amount of bytes.

Read rfc791 to get full information about ip header.


ahsan askari wrote:
> Could anybody please tell me what this piece of code will do
>
> ip_len = (ih->ver_ihl & 0xf) * 4;
>
> I know that we are "anding" ver_ihl to make all the bits equal to 1 
> but why are we multiplying it by 4.
>
> Thank you
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-- 
Best regards. Vasily Borovyak <vbor at isd.dp.ua>

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