netdev - Re: [RFC net-next 07/15] net: psp: update the TCP MSS to reflect PSP packet overhead

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Date: Wed, 29 May 2024 20:52:38 -0400
From: Willem de Bruijn <willemdebruijn.kernel@...il.com>
To: Jakub Kicinski <kuba@...nel.org>, 
 Willem de Bruijn <willemdebruijn.kernel@...il.com>
Cc: netdev@...r.kernel.org, 
 pabeni@...hat.com, 
 borisp@...dia.com, 
 gal@...dia.com, 
 cratiu@...dia.com, 
 rrameshbabu@...dia.com, 
 steffen.klassert@...unet.com, 
 tariqt@...dia.com
Subject: Re: [RFC net-next 07/15] net: psp: update the TCP MSS to reflect PSP
 packet overhead

Jakub Kicinski wrote:
> On Sun, 12 May 2024 21:47:16 -0400 Willem de Bruijn wrote:
> > > -	inet_csk(newsk)->icsk_ext_hdr_len = 0;
> > > +	inet_csk(newsk)->icsk_ext_hdr_len = psp_sk_overhead(sk);
> > >  	if (opt)
> > > -		inet_csk(newsk)->icsk_ext_hdr_len = opt->opt_nflen +
> > > -						    opt->opt_flen;
> > > +		inet_csk(newsk)->icsk_ext_hdr_len += opt->opt_nflen +
> > > +						     opt->opt_flen;
> > >  
> > >  	tcp_ca_openreq_child(newsk, dst);  
> > 
> > The below code adjusts ext_hdr_len and recalculates mss when
> > setting the tx association.
> > 
> > Why already include it at connect and syn_recv, above?
> > 
> > My assumption was that the upgrade to PSP only happens during
> > TCP_ESTABLISHED. But perhaps I'm wrong.
> > 
> > Is it allowed to set rx and tx association even from as early as the
> > initial socket(), when still in TCP_CLOSE, client-side?
> > 
> > Server-side, there is no connection fd to pass to netlink commands
> > before TCP_ESTABLISHED.
> 
> Mostly for symmetry, really. IDK what's worse, the dead code or that
> someone may be surprised it's not there.. Should I delete it?

Symmetry with what?

This dead code had me scratching my head what it was doing, so my vote
to drop it. If you want something, maybe a code comment instead?