Subject: Re: UDP checksum trouble in -current
To: YAMAMOTO Takashi <>
From: Pavel Cahyna <>
List: tech-net
Date: 01/22/2005 09:20:53
On Fri, 21 Jan 2005 10:49:20 +0900, YAMAMOTO Takashi wrote:

>> > > i think you also need zero ui->ui_sum in the else {}, otherwise you could
>> > > just have garbage.
>> > 
>> > for what?
>> > in that case, the ui_sum should never used by anyone, afaik.
>> you still want it to "hit the wire" as zero don't you,
> no.
>> otherwise the receive
>> side (including things like tcpdump) thinks you're doing checksums.
> can you explain why it's a problem?
> "receive side" should be ourselves.  it should know about checksum omission.

Could I have a NAT rule like

map lo0 x.x.x.x -> y.y.y.y

where y.y.y.y is an address of one of the external interfaces, and x.x.x.x
an alias on lo0 ?

Would the packets then go to the wire from y.y.y.y without checksums?

Bye	Pavel