netdev - Re: [PATCHv2 net-next 00/10] net: support ipv4 big tcp

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <CADvbK_d750m=r5LDyBXHPsceo2hEtQ0y=P17DWVWfQqOm=0zSA@mail.gmail.com>
Date:   Tue, 24 Jan 2023 10:51:33 -0500
From:   Xin Long <lucien.xin@...il.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     network dev <netdev@...r.kernel.org>, davem@...emloft.net,
        kuba@...nel.org, Paolo Abeni <pabeni@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        Pravin B Shelar <pshelar@....org>,
        Jamal Hadi Salim <jhs@...atatu.com>,
        Cong Wang <xiyou.wangcong@...il.com>,
        Jiri Pirko <jiri@...nulli.us>,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Florian Westphal <fw@...len.de>,
        Marcelo Ricardo Leitner <marcelo.leitner@...il.com>,
        Ilya Maximets <i.maximets@....org>,
        Aaron Conole <aconole@...hat.com>,
        Roopa Prabhu <roopa@...dia.com>,
        Nikolay Aleksandrov <razor@...ckwall.org>,
        Mahesh Bandewar <maheshb@...gle.com>,
        Paul Moore <paul@...l-moore.com>,
        Guillaume Nault <gnault@...hat.com>
Subject: Re: [PATCHv2 net-next 00/10] net: support ipv4 big tcp

On Tue, Jan 24, 2023 at 3:27 AM Eric Dumazet <edumazet@...gle.com> wrote:
>
> On Tue, Jan 24, 2023 at 3:20 AM Xin Long <lucien.xin@...il.com> wrote:
> >
> > This is similar to the BIG TCP patchset added by Eric for IPv6:
> >
> >   https://lwn.net/Articles/895398/
> >
> > Different from IPv6, IPv4 tot_len is 16-bit long only, and IPv4 header
> > doesn't have exthdrs(options) for the BIG TCP packets' length. To make
> > it simple, as David and Paolo suggested, we set IPv4 tot_len to 0 to
> > indicate this might be a BIG TCP packet and use skb->len as the real
> > IPv4 total length.
> >
> > This will work safely, as all BIG TCP packets are GSO/GRO packets and
> > processed on the same host as they were created; There is no padding
> > in GSO/GRO packets, and skb->len - network_offset is exactly the IPv4
> > packet total length; Also, before implementing the feature, all those
> > places that may get iph tot_len from BIG TCP packets are taken care
> > with some new APIs:
> >
> > Patch 1 adds some APIs for iph tot_len setting and getting, which are
> > used in all these places where IPv4 BIG TCP packets may reach in Patch
> > 2-8, and Patch 9 implements this feature and Patch 10 adds a selftest
> > for it.
> >
> > Note that the similar change as in Patch 2-6 are also needed for IPv6
> > BIG TCP packets, and will be addressed in another patchset.
> >
> > The similar performance test is done for IPv4 BIG TCP with 25Gbit NIC
> > and 1.5K MTU:
> >
> > No BIG TCP:
> > for i in {1..10}; do netperf -t TCP_RR -H 192.168.100.1 -- -r80000,80000 -O MIN_LATENCY,P90_LATENCY,P99_LATENCY,THROUGHPUT|tail -1; done
> > 168          322          337          3776.49
> > 143          236          277          4654.67
> > 128          258          288          4772.83
> > 171          229          278          4645.77
> > 175          228          243          4678.93
> > 149          239          279          4599.86
> > 164          234          268          4606.94
> > 155          276          289          4235.82
> > 180          255          268          4418.95
> > 168          241          249          4417.82
> >
>
> NACK again
>
> You have not addressed my feedback.
>
> Given the experimental nature of BIG TCP, we need separate netlink attributes,
> so that we can selectively enable BIG TCP for IPV6, and not for IPV4.
>
That will be some change, and I will try to work on it.

While at it, just try to be clearer, about the fixes for IPv6 BIG TCP
I mentioned in this patchset. Since skb->len is trustable for GSO TCP
packets. Are you still not okay with checking the skb_ipv6_pktlen()
API added to fix them in netfilter/tc/bridge/openvswitch?

Thanks.