netdev - Re: [PATCH V4 net 0/2] ipv6: fix flowlabel issue for reset packet

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Message-ID: <20171108214111.hmynbtqyyk3lilh7@kafai-mbp.dhcp.thefacebook.com>
Date:   Wed, 8 Nov 2017 13:41:33 -0800
From:   Martin KaFai Lau <kafai@...com>
To:     Tom Herbert <tom@...bertland.com>
CC:     David Miller <davem@...emloft.net>, Shaohua Li <shli@...nel.org>,
        Linux Kernel Network Developers <netdev@...r.kernel.org>
Subject: Re: [PATCH V4 net 0/2] ipv6: fix flowlabel issue for reset packet

On Wed, Nov 08, 2017 at 12:01:53PM -0800, Tom Herbert wrote:
> On Wed, Nov 8, 2017 at 9:44 AM, Tom Herbert <tom@...bertland.com> wrote:
> >>
> > We're now seeing several router vendors recommending people to not use
> > flow labels for ECMP hashing. This is precisely because when a flow
> > label changes, network devices that maintain state (firewalls, NAT,
> > load balancers) can't deal with packets being rerouted so connections
> > are dropped. Unfortunately, the need for packets of a flow to always
> > follow the same path has become an implicit requirement that I think
> > we need follow at least as the default behavior.
> >
> > Martin: is there any change you could resurrect these patches? In
> > order to solve the general problem of making routing consistent, I
> > believe we want to keep sk_tx_hash consistent for the connection from
> > which a consistent flow label can be derived. To avoid the overhead of
> > a hash field in sk_common, maybe we could initially set a connection
> > hash to a five-tuple hash for a flow instead of a random value? So in
> > TW state the consistent hash can be computed on the fly.
> >
> Sorry, I failed to give credit to Shaohua for submitting the initial
> patch. Please take look!
Hi Tom, thanks for the info.  Shaohua will revisit this
when he returns next week.

Martin