netdev - Re: [PATCH] net: qrtr: Update packets cloning when broadcasting

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Message-ID: <a3abd3f6-6247-4933-9b8e-df2241a3ec75@quicinc.com>
Date: Tue, 17 Sep 2024 07:59:28 -0700
From: Chris Lew <quic_clew@...cinc.com>
To: Youssef Samir <quic_yabdulra@...cinc.com>, <mani@...nel.org>,
        <davem@...emloft.net>, <edumazet@...gle.com>, <kuba@...nel.org>,
        <pabeni@...hat.com>, <andersson@...nel.org>
CC: <quic_jhugo@...cinc.com>, <linux-arm-msm@...r.kernel.org>,
        <netdev@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        Carl Vanderlip
	<quic_carlv@...cinc.com>
Subject: Re: [PATCH] net: qrtr: Update packets cloning when broadcasting

Hi Youssef,

On 9/16/2024 10:08 AM, Youssef Samir wrote:
> When broadcasting data to multiple nodes via MHI, using skb_clone()
> causes all nodes to receive the same header data. This can result in
> packets being discarded by endpoints, leading to lost data.
> 
> This issue occurs when a socket is closed, and a QRTR_TYPE_DEL_CLIENT
> packet is broadcasted. All nodes receive the same destination node ID,
> causing the node connected to the client to discard the packet and
> remain unaware of the client's deletion.
> 

I guess this never happens for the SMD/RPMSG transport because the skb 
is consumed within the context of qrtr_node_enqueue where as MHI queues 
the skb to be transmitted later.

Does the duplicate destination node ID match the last node in the 
qrtr_all_nodes list?


> Replace skb_clone() with pskb_copy(), to create a separate copy of
> the header for each sk_buff.
> 
> Fixes: bdabad3e363d ("net: Add Qualcomm IPC router")
> Signed-off-by: Youssef Samir <quic_yabdulra@...cinc.com>
> Reviewed-by: Jeffery Hugo <quic_jhugo@...cinc.com>
> Reviewed-by: Carl Vanderlip <quic_carlv@...cinc.com>
> ---
>   net/qrtr/af_qrtr.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/net/qrtr/af_qrtr.c b/net/qrtr/af_qrtr.c
> index 41ece61eb57a..00c51cf693f3 100644
> --- a/net/qrtr/af_qrtr.c
> +++ b/net/qrtr/af_qrtr.c
> @@ -884,7 +884,7 @@ static int qrtr_bcast_enqueue(struct qrtr_node *node, struct sk_buff *skb,
>   
>   	mutex_lock(&qrtr_node_lock);
>   	list_for_each_entry(node, &qrtr_all_nodes, item) {
> -		skbn = skb_clone(skb, GFP_KERNEL);
> +		skbn = pskb_copy(skb, GFP_KERNEL);
>   		if (!skbn)
>   			break;
>   		skb_set_owner_w(skbn, skb->sk);