[ovs-dev] [PATCH v2 net-next] net: openvswitch: Add a new action check_pkt_len

[David Miller]

From: nusiddiq at redhat.com
Date: Tue, 26 Mar 2019 06:13:46 +0530

> From: Numan Siddique <nusiddiq at redhat.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 at ovn.org>
> Signed-off-by: Numan Siddique <nusiddiq at redhat.com>

Applied, thanks.