linux-kernel - Re: [ovs-dev] [PATCH net-next v8] net: openvswitch: IPv6: Add IPv6 extension header support

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Message-ID: <20220309081732.1eafee91@kicinski-fedora-pc1c0hjn.dhcp.thefacebook.com>
Date:   Wed, 9 Mar 2022 08:17:32 -0800
From:   Jakub Kicinski <kuba@...nel.org>
To:     Ilya Maximets <i.maximets@....org>
Cc:     Roi Dayan <roid@...dia.com>,
        Johannes Berg <johannes@...solutions.net>, dev@...nvswitch.org,
        Toms Atteka <cpp.code.lv@...il.com>, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org, davem@...emloft.net,
        David Ahern <dsahern@...il.com>, Jiri Pirko <jiri@...nulli.us>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        "pshelar@....org" <pshelar@....org>
Subject: Re: [ovs-dev] [PATCH net-next v8] net: openvswitch: IPv6: Add IPv6
 extension header support

On Wed, 9 Mar 2022 14:43:07 +0100 Ilya Maximets wrote:
> >> It's a bit of an uncharted territory, hard to say what's right.
> >> It may be a little easier to code up the rejection if we have
> >> the types defined (which I think we need to do in
> >> __parse_flow_nlattrs()? seems OvS does its own nla parsing?)  
> 
> Ack.  And, yes, __parse_flow_nlattrs() seems to be the right spot.
> OVS has lots of nested attributes with some special treatment in a
> few cases and dependency tracking, AFAICT, so it parses attributes
> on it's own.  Is there a better way?

Looks like OvS has extra requirements like attributes can't be
duplicated and zeroed out attrs are ignored. I don't think generic
parsers can do that today, although the former seems like a useful
addition.

A problem for another time.

> >> Johannes, any preference?
> >
> > so why not again just flat enum without ifdefs and without values
> > commented out? even if we leave values in comments like above it doesn't
> > mean the userspace won't use them by mistake and send to the kernel.
> > but the kernel will probably ignore as not being used and at least
> > there won't be a conflict again even if by mistake.. and it's easiest
> > to read.  
> 
> OK.  Seems like we have some votes and a reason (explicit reject) to have
> them defined.  This will also make current user space and kernel definitions
> equal.  Let me put together a patch and we'll continue the discussion there.

Thanks!