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From: Kurt Kanzenbach <kurt@linutronix.de>
To: Vladimir Oltean <vladimir.oltean@nxp.com>,
	netdev@vger.kernel.org, Jakub Kicinski <kuba@kernel.org>,
	"David S. Miller" <davem@davemloft.net>
Cc: Florian Fainelli <f.fainelli@gmail.com>,
	Andrew Lunn <andrew@lunn.ch>,
	Vivien Didelot <vivien.didelot@gmail.com>,
	Vladimir Oltean <olteanv@gmail.com>,
	Hauke Mehrtens <hauke@hauke-m.de>,
	Egil Hjelmeland <privat@egil-hjelmeland.no>
Subject: Re: [PATCH net 1/4] net: dsa: hellcreek: fix broken backpressure in .port_fdb_dump
Date: Tue, 10 Aug 2021 13:39:36 +0200	[thread overview]
Message-ID: <87wnotle9z.fsf@kurt> (raw)
In-Reply-To: <20210810111956.1609499-2-vladimir.oltean@nxp.com>

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On Tue Aug 10 2021, Vladimir Oltean wrote:
> rtnl_fdb_dump() has logic to split a dump of PF_BRIDGE neighbors into
> multiple netlink skbs if the buffer provided by user space is too small
> (one buffer will typically handle a few hundred FDB entries).
>
> When the current buffer becomes full, nlmsg_put() in
> dsa_slave_port_fdb_do_dump() returns -EMSGSIZE and DSA saves the index
> of the last dumped FDB entry, returns to rtnl_fdb_dump() up to that
> point, and then the dump resumes on the same port with a new skb, and
> FDB entries up to the saved index are simply skipped.
>
> Since dsa_slave_port_fdb_do_dump() is pointed to by the "cb" passed to
> drivers, then drivers must check for the -EMSGSIZE error code returned
> by it. Otherwise, when a netlink skb becomes full, DSA will no longer
> save newly dumped FDB entries to it, but the driver will continue
> dumping. So FDB entries will be missing from the dump.
>
> Fix the broken backpressure by propagating the "cb" return code and
> allow rtnl_fdb_dump() to restart the FDB dump with a new skb.
>
> Fixes: e4b27ebc780f ("net: dsa: Add DSA driver for Hirschmann Hellcreek switches")
> Signed-off-by: Vladimir Oltean <vladimir.oltean@nxp.com>

Acked-by: Kurt Kanzenbach <kurt@linutronix.de>

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  reply	other threads:[~2021-08-10 11:39 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-08-10 11:19 [PATCH net 0/4] Fix broken backpressure during FDB dump in DSA drivers Vladimir Oltean
2021-08-10 11:19 ` [PATCH net 1/4] net: dsa: hellcreek: fix broken backpressure in .port_fdb_dump Vladimir Oltean
2021-08-10 11:39   ` Kurt Kanzenbach [this message]
2021-08-10 11:19 ` [PATCH net 2/4] net: dsa: lan9303: " Vladimir Oltean
2021-08-10 11:19 ` [PATCH net 3/4] net: dsa: lantiq: " Vladimir Oltean
2021-08-10 11:19 ` [PATCH net 4/4] net: dsa: sja1105: " Vladimir Oltean
2021-08-10 12:20 ` [PATCH net 0/4] Fix broken backpressure during FDB dump in DSA drivers patchwork-bot+netdevbpf

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