netdev - Re: [PATCHv6 net-next 1/4] net: add a common function to compute features for upper devices

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: <a2e85a2b-58b0-4460-ae7a-b1ea01e4d7e4@redhat.com>
Date: Tue, 21 Oct 2025 10:46:22 +0200
From: Paolo Abeni <pabeni@...hat.com>
To: Sabrina Dubroca <sd@...asysnail.net>, Hangbin Liu <liuhangbin@...il.com>
Cc: netdev@...r.kernel.org, Jay Vosburgh <jv@...sburgh.net>,
 Andrew Lunn <andrew+netdev@...n.ch>, "David S. Miller"
 <davem@...emloft.net>, Eric Dumazet <edumazet@...gle.com>,
 Jakub Kicinski <kuba@...nel.org>, Jiri Pirko <jiri@...nulli.us>,
 Simon Horman <horms@...nel.org>, Ido Schimmel <idosch@...dia.com>,
 Shuah Khan <shuah@...nel.org>, Stanislav Fomichev <sdf@...ichev.me>,
 Stanislav Fomichev <stfomichev@...il.com>,
 Kuniyuki Iwashima <kuniyu@...gle.com>,
 Alexander Lobakin <aleksander.lobakin@...el.com>, bridge@...ts.linux.dev
Subject: Re: [PATCHv6 net-next 1/4] net: add a common function to compute
 features for upper devices

On 10/20/25 11:10 AM, Sabrina Dubroca wrote:
> 2025-10-17, 03:41:52 +0000, Hangbin Liu wrote:
>> Some high level software drivers need to compute features from lower
>> devices. But each has their own implementations and may lost some
>> feature compute. Let's use one common function to compute features
>> for kinds of these devices.
>>
>> The new helper uses the current bond implementation as the reference
>> one, as the latter already handles all the relevant aspects: netdev
>> features, TSO limits and dst retention.
>>
>> Suggested-by: Paolo Abeni <pabeni@...hat.com>
>> Signed-off-by: Hangbin Liu <liuhangbin@...il.com>
> 
> No objection to this patch/series, just a nit and some discussion below, so:
> 
> Reviewed-by: Sabrina Dubroca <sd@...asysnail.net>
> 
> 
> [...]
>> +/**
>> + *	netdev_compute_master_upper_features - compute feature from lowers
> 
> nit: I'm slightly annoyed (that's not quite the right word, sorry)
> that we're adding a new function to "compute features" that doesn't
> touch netdev->features, but I can't come up with a better name
> (the best I got was "compute extra features" and it doesn't help).

I'm not the right person to ask a good name, and I'm ok with the current
one, but since the question is pending... what about:

netdev_{compute,update}_offloads_from_lower()

?

As it actually updates (some of) the offloads available to the (upper)
device?

>> + *	@dev: the upper device
>> + *	@update_header: whether to update upper device's header_len/headroom/tailroom
>> + *
>> + *	Recompute the upper device's feature based on all lower devices.
>> + */
>> +void netdev_compute_master_upper_features(struct net_device *dev, bool update_header)
>> +{
> [...]
>> +	netif_set_tso_max_segs(dev, tso_max_segs);
>> +	netif_set_tso_max_size(dev, tso_max_size);
>> +
>> +	netdev_change_features(dev);
> 
> Maybe a dumb idea: I'm wondering if we're doing this from the wrong
> side.
> 
> Right now we have:
> 
> [some device op] -> [this new function] -> netdev_change_features -> __netdev_update_features -> ndo_fix_features
> 
> Would it make more sense to go instead:
> 
> [some device op] -> netdev_change_features -> __netdev_update_features -> ndo_fix_features -> [this new function]
> 
> ?

Uhmmm.... this function touches a few more things beyond dev->*features,
calling it from ndo_fix_features() looks a bit out-of-scope.

/P