netdev - Re: [PATCH v2 net-next] net: openvswitch: Add a new action check_pkt

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Message-ID: <CAOrHB_C7ewjVuA4ToAgXFD4aELce4ByDQK=7Vq6X4fGh2WK7Wg@mail.gmail.com>
Date:   Tue, 26 Mar 2019 09:31:26 -0700
From:   Pravin Shelar <pshelar@....org>
To:     Numan Siddique <nusiddiq@...hat.com>
Cc:     Linux Kernel Network Developers <netdev@...r.kernel.org>,
        ovs dev <dev@...nvswitch.org>, Ben Pfaff <blp@....org>,
        Gregory Rose <gvrose8192@...il.com>
Subject: Re: [PATCH v2 net-next] net: openvswitch: Add a new action check_pkt_len

On Mon, Mar 25, 2019 at 5:44 PM <nusiddiq@...hat.com> wrote:
>
> From: Numan Siddique <nusiddiq@...hat.com>
>
> This patch adds a new action - 'check_pkt_len' which checks the
> packet length and executes a set of actions if the packet
> length is greater than the specified length or executes
> another set of actions if the packet length is lesser or equal to.
>
> This action takes below nlattrs
>   * OVS_CHECK_PKT_LEN_ATTR_PKT_LEN - 'pkt_len' to check for
>
>   * OVS_CHECK_PKT_LEN_ATTR_ACTIONS_IF_GREATER - Nested actions
>     to apply if the packet length is greater than the specified 'pkt_len'
>
>   * OVS_CHECK_PKT_LEN_ATTR_ACTIONS_IF_LESS_EQUAL - Nested
>     actions to apply if the packet length is lesser or equal to the
>     specified 'pkt_len'.
>
> The main use case for adding this action is to solve the packet
> drops because of MTU mismatch in OVN virtual networking solution.
> When a VM (which belongs to a logical switch of OVN) sends a packet
> destined to go via the gateway router and if the nic which provides
> external connectivity, has a lesser MTU, OVS drops the packet
> if the packet length is greater than this MTU.
>
> With the help of this action, OVN will check the packet length
> and if it is greater than the MTU size, it will generate an
> ICMP packet (type 3, code 4) and includes the next hop mtu in it
> so that the sender can fragment the packets.
>
> Reported-at:
> https://mail.openvswitch.org/pipermail/ovs-discuss/2018-July/047039.html
> Suggested-by: Ben Pfaff <blp@....org>
> Signed-off-by: Numan Siddique <nusiddiq@...hat.com>
> CC: Gregory Rose <gvrose8192@...il.com>
> CC: Pravin B Shelar <pshelar@....org>
> ---
> v1 -> v2
> -----
>    * Addressed the review comments.
>      - Removed the vlan-tag length when checking the packet length
>      - Reordered the netlink attributes
>      - Changed the comments to use 'attribute' instead of 'action'
>
> Corresponding OVS patch (submitted as RFC for now)  which makes use of this action can be
> found here - https://patchwork.ozlabs.org/patch/1059081/
>
Looks good to me.
Acked-by: Pravin B Shelar <pshelar@....org>