Re: [PATCH v3 net-next 1/1] tcp: Replace min_tso_segs() with tso_segs() CC callback

["Alexei Starovoitov" <alexei.starovoitov@gmail.com>]

On Tue Jun 30, 2026 at 10:46 PM PDT, Chia-Yu Chang (Nokia) wrote:
>> > -     /* override sysctl_tcp_min_tso_segs (optional) */
>> > -     u32 (*min_tso_segs)(struct sock *sk);
>> > +     /*
>> > +      * Override tcp_tso_autosize (optional)
>> > +      *
>> > +      * If provided, this callback returns the final TSO segment number
>> > +      * and will bypass tcp_tso_autosize() entirely. The implementation
>> > +      * must derive an appropriate value and ensure the result is valid.
>> > +      */
>> > +     u32 (*tso_segs)(struct sock *sk, u32 mss_now);
>> 
>> I don't like this interface change.
>> It introduces churn for no good reason.
>> At least I don't see why you cannot live with the existing api.
>
> Hi Alexei,
>
> This patch was part of TCP Prague preparation series: https://lore.kernel.org/all/20260611161504.228319-4-chia-yu.chang@nokia-bell-labs.com/
> Our original patch is to add an extra tso_segs, and after discussion it's recommended to replace exisiting min_tso_segs.
>
> This is needed because TCP Prague would set the exact TSO size rather than using autosizing from TCP.
> The TCP Prague itself is planned to be submitted after all preparation commits are accepted.
> You can find its current stauts: https://github.com/L4STeam/linux-net-next/blob/upstream_l4steam/net/ipv4/tcp_prague.c

You have to explain why Prague CC cannot rely on autosizing.
To me it sounds like a red flag. autosizing logic was there for a decade, if not more.
And now you're arguing that your CC logic is special and it deserves new API
and breakage of existing convention.
Maybe you should step back and reconsider.