Re: [PATCH v2 net-next 4/9] tcp: Restrict SO_TXREHASH to TCP socket.

[Kuniyuki Iwashima <kuniyu@amazon.com>]

From: Willem de Bruijn <willemdebruijn.kernel@gmail.com>
Date: Mon, 12 May 2025 15:18:12 -0400
> Kuniyuki Iwashima wrote:
> > sk->sk_txrehash is only used for TCP.
> > 
> > Let's restrict SO_TXREHASH to TCP to reflect this.
> > 
> > Later, we will make sk_txrehash a part of the union for other
> > protocol families, so we set 0 explicitly in getsockopt().
> > 
> > Signed-off-by: Kuniyuki Iwashima <kuniyu@amazon.com>
> > ---
> >  net/core/sock.c | 9 +++++++--
> >  1 file changed, 7 insertions(+), 2 deletions(-)
> > 
> > diff --git a/net/core/sock.c b/net/core/sock.c
> > index b64df2463300..5c84a608ddd7 100644
> > --- a/net/core/sock.c
> > +++ b/net/core/sock.c
> > @@ -1276,6 +1276,8 @@ int sk_setsockopt(struct sock *sk, int level, int optname,
> >  		return 0;
> >  		}
> >  	case SO_TXREHASH:
> > +		if (!sk_is_tcp(sk))
> > +			return -EOPNOTSUPP;
> >  		if (val < -1 || val > 1)
> >  			return -EINVAL;
> >  		if ((u8)val == SOCK_TXREHASH_DEFAULT)
> > @@ -2102,8 +2104,11 @@ int sk_getsockopt(struct sock *sk, int level, int optname,
> >  		break;
> >  
> >  	case SO_TXREHASH:
> > -		/* Paired with WRITE_ONCE() in sk_setsockopt() */
> > -		v.val = READ_ONCE(sk->sk_txrehash);
> > +		if (sk_is_tcp(sk))
> > +			/* Paired with WRITE_ONCE() in sk_setsockopt() */
> > +			v.val = READ_ONCE(sk->sk_txrehash);
> > +		else
> > +			v.val = 0;
> 
> Here and in the following getsockopt calls: should the call fail with
> EOPNOTSUPP rather than return a value that is legal where the option
> is supported (in TCP).

I was wondering which is better but didn't have preference, so will
return -EOPNOTSUPP in v3.

Thanks!