netdev - Re: [PATCH bpf v2] xsk: fix memory leak and packet loss in Tx skb path

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Message-ID: <20200710163448.7bkuohez2lqkf5tt@bsd-mbp>
Date:   Fri, 10 Jul 2020 09:34:48 -0700
From:   Jonathan Lemon <jonathan.lemon@...il.com>
To:     Magnus Karlsson <magnus.karlsson@...el.com>
Cc:     bjorn.topel@...el.com, ast@...nel.org, daniel@...earbox.net,
        netdev@...r.kernel.org, A.Zema@...convsystems.com
Subject: Re: [PATCH bpf v2] xsk: fix memory leak and packet loss in Tx skb
 path

On Fri, Jul 10, 2020 at 08:45:54AM +0200, Magnus Karlsson wrote:
> In the skb Tx path, transmission of a packet is performed with
> dev_direct_xmit(). When QUEUE_STATE_FROZEN is set in the transmit
> routines, it returns NETDEV_TX_BUSY signifying that it was not
> possible to send the packet now, please try later. Unfortunately, the
> xsk transmit code discarded the packet, missed to free the skb, and
> returned EBUSY to the application. Fix this memory leak and
> unnecessary packet loss, by not discarding the packet in the Tx ring,
> freeing the allocated skb, and return EAGAIN. As EAGAIN is returned to the
> application, it can then retry the send operation and the packet will
> finally be sent as we will likely not be in the QUEUE_STATE_FROZEN
> state anymore. So EAGAIN tells the application that the packet was not
> discarded from the Tx ring and that it needs to call send()
> again. EBUSY, on the other hand, signifies that the packet was not
> sent and discarded from the Tx ring. The application needs to put the
> packet on the Tx ring again if it wants it to be sent.
> 
> Fixes: 35fcde7f8deb ("xsk: support for Tx")
> Signed-off-by: Magnus Karlsson <magnus.karlsson@...el.com>
> Reported-by: Arkadiusz Zema <A.Zema@...convsystems.com>
> Suggested-by: Arkadiusz Zema <A.Zema@...convsystems.com>

Acked-by: Jonathan Lemon <jonathan.lemon@...il.com>

-- 
Jonathan