netdev - Re: [PATCH] net:tun: limit printing rate when illegal packet received by tun dev

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Message-ID: <0e5a96b6-0862-4c00-b07f-7485af232475@lunn.ch>
Date: Tue, 9 Apr 2024 14:52:08 +0200
From: Andrew Lunn <andrew@...n.ch>
To: Lei Chen <lei.chen@...rtx.com>
Cc: Willem de Bruijn <willemdebruijn.kernel@...il.com>,
	Jason Wang <jasowang@...hat.com>,
	"David S. Miller" <davem@...emloft.net>,
	Eric Dumazet <edumazet@...gle.com>,
	Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH] net:tun: limit printing rate when illegal packet
 received by tun dev

On Tue, Apr 09, 2024 at 02:24:05AM -0400, Lei Chen wrote:
> vhost_worker will call tun call backs to receive packets. If too many
> illegal packets arrives, tun_do_read will keep dumping packet contents.
> When console is enabled, it will costs much more cpu time to dump
> packet and soft lockup will be detected.
> 
> Rate limit mechanism can be used to limit the dumping rate.
> @@ -2125,14 +2126,16 @@ static ssize_t tun_put_user(struct tun_struct *tun,
>  					    tun_is_little_endian(tun), true,
>  					    vlan_hlen)) {
>  			struct skb_shared_info *sinfo = skb_shinfo(skb);
> -			pr_err("unexpected GSO type: "
> -			       "0x%x, gso_size %d, hdr_len %d\n",
> -			       sinfo->gso_type, tun16_to_cpu(tun, gso.gso_size),
> -			       tun16_to_cpu(tun, gso.hdr_len));
> -			print_hex_dump(KERN_ERR, "tun: ",
> -				       DUMP_PREFIX_NONE,
> -				       16, 1, skb->head,
> -				       min((int)tun16_to_cpu(tun, gso.hdr_len), 64), true);
> +
> +			if (__ratelimit(&ratelimit)) {

Maybe just use net_ratelimit() rather than add a new ratelimit
variable?

A separate issue, i wounder if rather than pr_err(),
netdev_err(tun->dev, ...) should be used to indicate which TUN device
has been given bad GSO packets?

    Andrew