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Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good.

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We've put considerable effort into cleaning up the checksum interface
to make it as unambiguous as possible, please be very careful to
follow it. Broken checksum processing is really hard to detect and
debug.

CHECKSUM_UNNECESSARY means that some number of _specific_ checksums
(indicated by csum_level) have been verified to be correct in a
packet. Blindly promoting CHECKSUM_NONE to CHECKSUM_UNNECESSARY is
never right. If CHECKSUM_UNNECESSARY is set in such a manner but the
checksum it would refer to has not been verified and is incorrect this
is a major bug.

Tom

On Sat, Apr 30, 2016 at 12:40 PM, Ben Greear <greearb@candelatech.com> wrote:
>
>
> On 04/30/2016 11:33 AM, Ben Hutchings wrote:
>>
>> On Thu, 2016-04-28 at 12:29 +0200, Sabrina Dubroca wrote:
>>>
>>> Hello,
>
>
>>>>
>>>> http://dmz2.candelatech.com/?p=linux-4.4.dev.y/.git;a=commitdiff;h=8153e983c0e5eba1aafe1fc296248ed2a553f1ac;hp=454b07405d694dad52e7f41af5816eed0190da8a
>>>
>>> Actually, no, this is not really a regression.
>>
>> [...]
>>
>> It really is.  Even though the old behaviour was a bug (raw packets
>> should not be changed), if there are real applications that depend on
>> that then we have to keep those applications working somehow.
>
>
> To be honest, I fail to see why the old behaviour is a bug when sending
> raw packets from user-space.  If raw packets should not be changed, then
> we need some way to specify what the checksum setting is to begin with,
> otherwise, user-space has not enough control.
>
> A socket option for new programs, and sysctl configurable defaults for raw
> sockets
> for old binary programs would be sufficient I think.
>
>
> Thanks,
> Ben
>
> --
> Ben Greear <greearb@candelatech.com>
> Candela Technologies Inc  http://www.candelatech.com

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Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats  packets with bad checksums as good. Sabrina Dubroca <sd@queasysnail.net> - 2016-04-28 12:40 +0200
  Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-04-28 15:50 +0200
    Re: [PATCH 3.2 085/115] veth: don’t modify  ip_summed; doing so treats packets with bad checksums as good. Ben Hutchings <ben@decadent.org.uk> - 2016-04-30 21:30 +0200
  Re: [PATCH 3.2 085/115] veth: don’t modify  ip_summed; doing so treats packets with bad checksums as good. Ben Hutchings <ben@decadent.org.uk> - 2016-04-30 21:30 +0200
    Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-04-30 21:50 +0200
      Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Tom Herbert <tom@herbertland.com> - 2016-04-30 22:00 +0200
        Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-04-30 23:00 +0200
          Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Vijay Pandurangan <vijayp@vijayp.ca> - 2016-04-30 23:20 +0200
            Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-04-30 23:40 +0200
              Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Vijay Pandurangan <vijayp@vijayp.ca> - 2016-04-30 23:40 +0200
                Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-05-01 00:00 +0200
                Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Vijay Pandurangan <vijayp@vijayp.ca> - 2016-05-01 00:10 +0200
                Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Ben Greear <greearb@candelatech.com> - 2016-05-01 00:50 +0200
                Re: [PATCH 3.2 085/115] veth: don???t modify ip_summed; doing so  treats packets with bad checksums as good. Willy Tarreau <w@1wt.eu> - 2016-05-01 07:40 +0200
          Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Tom Herbert <tom@herbertland.com> - 2016-05-01 00:50 +0200
  Re: [PATCH 3.2 085/115] veth: don’t modify ip_summed; doing so treats packets with bad checksums as good. Vijay Pandurangan <vijayp@vijayp.ca> - 2016-04-30 22:20 +0200

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