From: Pravin Shelar <pshelar@ovn.org>
To: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Cc: Greg Rose <gvrose8192@gmail.com>, Ben Pfaff <blp@ovn.org>,
Linux Kernel Network Developers <netdev@vger.kernel.org>,
ovs dev <dev@openvswitch.org>
Subject: Re: [PATCH net-next v4] net: openvswitch: add hash info to upcall
Date: Wed, 13 Nov 2019 21:03:22 -0800 [thread overview]
Message-ID: <CAOrHB_Ci+iSL=Ctt_TjNuFc3=+gRTdWwdGH4hgpUVS1Thc8nGA@mail.gmail.com> (raw)
In-Reply-To: <1573657489-16067-1-git-send-email-xiangxia.m.yue@gmail.com>
On Wed, Nov 13, 2019 at 7:05 AM <xiangxia.m.yue@gmail.com> wrote:
>
> From: Tonghao Zhang <xiangxia.m.yue@gmail.com>
>
> When using the kernel datapath, the upcall don't
> include skb hash info relatived. That will introduce
> some problem, because the hash of skb is important
> in kernel stack. For example, VXLAN module uses
> it to select UDP src port. The tx queue selection
> may also use the hash in stack.
>
> Hash is computed in different ways. Hash is random
> for a TCP socket, and hash may be computed in hardware,
> or software stack. Recalculation hash is not easy.
>
> Hash of TCP socket is computed:
> tcp_v4_connect
> -> sk_set_txhash (is random)
>
> __tcp_transmit_skb
> -> skb_set_hash_from_sk
>
> There will be one upcall, without information of skb
> hash, to ovs-vswitchd, for the first packet of a TCP
> session. The rest packets will be processed in Open vSwitch
> modules, hash kept. If this tcp session is forward to
> VXLAN module, then the UDP src port of first tcp packet
> is different from rest packets.
>
> TCP packets may come from the host or dockers, to Open vSwitch.
> To fix it, we store the hash info to upcall, and restore hash
> when packets sent back.
>
> +---------------+ +-------------------------+
> | Docker/VMs | | ovs-vswitchd |
> +----+----------+ +-+--------------------+--+
> | ^ |
> | | |
> | | upcall v restore packet hash (not recalculate)
> | +-+--------------------+--+
> | tap netdev | | vxlan module
> +---------------> +--> Open vSwitch ko +-->
> or internal type | |
> +-------------------------+
>
> Reported-at: https://mail.openvswitch.org/pipermail/ovs-dev/2019-October/364062.html
> Signed-off-by: Tonghao Zhang <xiangxia.m.yue@gmail.com>
Acked-by: Pravin B Shelar <pshelar@ovn.org>
Thanks.
next prev parent reply other threads:[~2019-11-14 5:03 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-13 15:04 [PATCH net-next v4] net: openvswitch: add hash info to upcall xiangxia.m.yue
2019-11-14 5:03 ` Pravin Shelar [this message]
2019-11-15 1:30 ` David Miller
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