Re: [PATCH net 2/2] tcp_metrics: use ssthresh value from dst if there is no metrics

[Petr Tesarik]

On Tue, 17 Jun 2025 12:48:30 +0200
Paolo Abeni <pabeni@xxxxxxxxxx> wrote:

> On 6/13/25 12:20 PM, Petr Tesarik wrote:
> > @@ -537,6 +537,9 @@ void tcp_init_metrics(struct sock *sk)
> >  
> >  		inet_csk(sk)->icsk_rto = TCP_TIMEOUT_FALLBACK;
> >  	}
> > +
> > +	if (tp->snd_ssthresh > tp->snd_cwnd_clamp)
> > +		tp->snd_ssthresh = tp->snd_cwnd_clamp;  
> 
> I don't think we can do this unconditionally, as other parts of the TCP
> stack check explicitly for TCP_INFINITE_SSTHRESH.


Good catch! I noticed that the condition can never be true unless the
congestion window is explicitly clamped, but you're right that it is a
valid combination to lock the maximum cwnd but keep the initial TCP Slow
Start.

I'll fix that in v2.

Thank you,
Petr T