netdev - Re: [PATCH net] tuntap: add missing xdp flush

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Date:   Thu, 08 Feb 2018 14:11:12 -0500 (EST)
From:   David Miller <davem@...emloft.net>
To:     jasowang@...hat.com
Cc:     netdev@...r.kernel.org, mst@...hat.com
Subject: Re: [PATCH net] tuntap: add missing xdp flush

From: Jason Wang <jasowang@...hat.com>
Date: Wed,  7 Feb 2018 17:14:46 +0800

> When using devmap to redirect packets between interfaces,
> xdp_do_flush() is usually a must to flush any batched
> packets. Unfortunately this is missed in current tuntap
> implementation.
> 
> Unlike most hardware driver which did XDP inside NAPI loop and call
> xdp_do_flush() at then end of each round of poll. TAP did it in the
> context of process e.g tun_get_user(). So fix this by count the
> pending redirected packets and flush when it exceeds NAPI_POLL_WEIGHT
> or MSG_MORE was cleared by sendmsg() caller.
> 
> With this fix, xdp_redirect_map works again between two TAPs.
> 
> Fixes: 761876c857cb ("tap: XDP support")
> Signed-off-by: Jason Wang <jasowang@...hat.com>

Applied and queued up for -stable, thanks Jason.