lists.openwall.net   lists  /  announce  owl-users  owl-dev  john-users  john-dev  passwdqc-users  yescrypt  popa3d-users  /  oss-security  kernel-hardening  musl  sabotage  tlsify  passwords  /  crypt-dev  xvendor  /  Bugtraq  Full-Disclosure  linux-kernel  linux-netdev  linux-ext4  linux-hardening  linux-cve-announce  PHC 
Open Source and information security mailing list archives
 
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <b2f505f2-0dd4-c0c7-89d1-fb9ddd040708@gmail.com>
Date:   Tue, 9 Apr 2019 19:17:15 -0700
From:   Florian Fainelli <f.fainelli@...il.com>
To:     Vladimir Oltean <olteanv@...il.com>, vivien.didelot@...il.com,
        andrew@...n.ch, davem@...emloft.net
Cc:     netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        georg.waibel@...sor-technik.de
Subject: Re: [PATCH v2 net-next 11/22] net: dsa: Allow drivers to modulate
 between presence and absence of tagging



On 4/9/2019 5:56 PM, Vladimir Oltean wrote:
> Frames get processed by DSA and redirected to switch port net devices
> based on the ETH_P_XDSA multiplexed packet_type handler found by the
> network stack when calling eth_type_trans().
> 
> The running assumption is that once the DSA .rcv function is called, DSA
> is always able to decode the switch tag in order to change the skb->dev
> from its master.
> 
> However there are tagging protocols (such as the new
> DSA_TAG_PROTO_SJA1105) where this assumption is not completely true,
> since switch tagging piggybacks on the absence of a vlan_filtering
> bridge.
> 
> Having DSA receive untagged traffic would put it in an impossible
> situation: the eth_type_trans() function would invoke the DSA .rcv(),
> which could not change skb->dev, then eth_type_trans() would be invoked
> again, which again would call the DSA .rcv, and the packet would never
> be able to exit the DSA filter and would spiral in a loop until the
> whole system dies.
> 
> This happens because eth_type_trans() doesn't actually look at the skb
> (so as to identify a potential tag) when it deems it as being
> ETH_P_XDSA. It just checks whether skb->dev has a DSA private pointer
> installed (therefore it's a DSA master) and that there exists a .rcv
> callback (everybody except DSA_TAG_PROTO_NONE has that). This is
> understandable as there are many switch tags out there, and exhaustively
> checking for all of them is far from ideal.
> 
> The solution lies in the observation that a more nuanced check can be
> made when eth_type_trans() determines that switch tagging is used or
> not. In a way, this reverts patch "717ffbfb28ac net: dsa: remove
> dsa_uses_tagged_protocol", but instead of adding it back as a DSA
> function, it is now a boolean property. This is because the driver might
> actually know better when it can and can't support switch tagging.
> 
> With this patch, all tagging protocols can morph at runtime into the
> DSA_TAG_PROTO_NONE on receive, by setting cpu_dp->uses_tag_protocol = 0.
> This permits them to at least terminate traffic through the master net
> device. Their .rcv callback no longer even gets called in this mode.
> 
> Signed-off-by: Vladimir Oltean <olteanv@...il.com>
> ---

[snip]

> +	/* Property used to allow traffic at runtime to bypass the DSA
> +	 * filter in eth_type_trans and be processed as regular on the
> +	 * master net device.
> +	 */
> +	bool			uses_tag_protocol;

This gets used in the hot path can you make sure this is part of the
first cache line of a dsa_port? pahole is a good tool for determining
where a member is in a given structure. With that:

Reviewed-by: Florian Fainelli <f.fainelli@...il.com>
-- 
Florian

Powered by blists - more mailing lists

Powered by Openwall GNU/*/Linux Powered by OpenVZ