Re: NAT stops forwarding ACKs after PMTU discovery

Christoph Paasch
2013-08-19T20:43:07Z

On 19/08/13 - 22:13:59, Jozsef Kadlecsik wrote:
> On Mon, 19 Aug 2013, Eric Dumazet wrote:
>
> > On Mon, 2013-08-19 at 15:49 +0200, Christoph Paasch wrote:
> >
> > > It's a TCP-patch, that interprets duplicate-acks with invalid SACK-blocks as
> > > duplicate acks in tcp_sock->sacked_out.
> >
> > Yeah, but here, this is conntrack who is blocking the thing.
> >
> > TCP receiver has no chance to 'fix' it.
> >
> > See conntrack is one of those buggy middle box as well.
> >
> > So if you want to properly handle this mess, you'll also have to fix
> > conntrack.
>
> I beg you pardon: why conntrack should be relaxed, when it is expected
> to do more strict TCP checkings (RFC5961, Section 5.).

There is no mention of SACK in this RFC.
The duplicate ACKs with invalid SACK-blocks are valid with respect to
RFC5961, Section 5.

Actually, no RFC says that dup-ACKs with invalid SACK-blocks should
be discarded.

Cheers,
Christoph