Re: Offloading checksums to H/W
Re: Offloading checksums to H/W
- Subject: Re: Offloading checksums to H/W
- From: Platon Fomichev <email@hidden>
- Date: Fri, 24 Aug 2007 20:36:20 +0400
Hey mm
Yup exactly, that's what is written in Apple's docs but as we all
have access to the kernel and overall - why on earth we should need
to do this? Of course there are cases - when I change destination,
metric, etc, etc. But if f.ex. I just changed packet length? Imho
it's not the case for re-injection. And it actually works as expected
on my test-cases - I can do whatever I want as long as I keep its
destination, etc. But my case is simple I need to increase data size
for say 20 bytes.
I actually managed to get some weird checksum (wrong) from H/w - I
will keep you informed about my progress..
Best regards,
Platon
On Aug 24, 2007, at 7:54 PM, mm w wrote:
Hi Platon,
If your modifications involve changes to packet header information you
must swallow the packet entirely and reinject it.
Cheers
On 8/24/07, Platon Fomichev <email@hidden> wrote:
Hi Everybody
It seems I can't figure how to correctly offload my TCP/UDP packet to
the H/W network checksumming routines. It seems rather inconvenient
that I have to add all typical checksumming code into the driver -
because neither of mbuf API can actually re-checksum the packet. As
for H/W support - I can see from the flags that my H/W supports TCP
offload but if I set tcp checksum f.ex. to zero in my Interface
filter the packet will not be checksummed later in the hardware.
Thus some questions:
1) Seems that there is no kernel API to do IP checksumming in Mac -
is it true, if not how to do it? mbuf finalize func does not do it.
2) Seems that hardware TCP/UDP checksum offload is actually missing
from Mac at all? At least it is not present on MacBook/MacBook pro.
If yes why does it advertise itself using ifnet API as capable to do
it? If I am wrong how can I check that my network adapter is actually
doing its work and how can I benefit from this in my code (I am
actively changing the packet)
Best regards,
Platon.
On Aug 23, 2007, at 9:05 AM, JanakiRam wrote:
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