[lwip-users] Re: [lwip] Mem alignment problem

[Kieran Mansley]

On Wed, 13 Mar 2002, Mumtaz Ahmad wrote:

> Hi
> I am  facing some troubles regarding memory alignment in lwip .I have set my
> memory alignment to 4 bytes .On incoming packet when etherheader (14bytes)
> is removed the payload pointer is set to startof ipheader . Obvioulsly the
> start address of ipheader is not 4 byte aligned . and my platform cannot
> read integers from non 4 byte aligned address so the packets are rejected at
> IP layer .

Most ethernet interfaces reserve two bytes in front of the packet so the
ip header is aligned on a 16-byte boundary after the 14 byte ethernet
header.

Kieran

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