Re: [PATCH] llc: Return -EINPROGRESS from llc_ui_connect()

[Ernestas Kulik]

On 2026-04-20 21:41, Jakub Kicinski wrote:
> On Wed, 15 Apr 2026 09:34:57 +0300 Ernestas Kulik wrote:
> > Given a zero sk_sndtimeo, llc_ui_connect() skips waiting for state
> > change and returns 0, confusing userspace applications that will assume
> > the socket is connected, making e.g. getpeername() calls error out.
> >
> > Set rc to -EINPROGRESS before considering blocking, akin to AF_INET
> > sockets.
>
> Please add a note on how you discovered this issue.
> Including whether you're actively using this code or just scanning it
> for bugs.

Will do. It was discovered while adding support for AF_LLC sockets in 
libcoap, the usual code path for client connections was failing due to 
this specific issue, so I figured the behavior should be analogous to 
AF_INET.

> > diff --git a/net/llc/af_llc.c b/net/llc/af_llc.c
> > index 59d593bb5d18..9317d092ba84 100644
> > --- a/net/llc/af_llc.c
> > +++ b/net/llc/af_llc.c
> > @@ -515,10 +515,12 @@ static int llc_ui_connect(struct socket *sock, struct sockaddr_unsized *uaddr,
> >   		sock->state  = SS_UNCONNECTED;
> >   		sk->sk_state = TCP_CLOSE;
> >   		goto out;
> >   	}
> >   
> > +	rc = -EINPROGRESS;
>
> Isn't this a bit of an odd placement? ..
>
> >   	if (sk->sk_state == TCP_SYN_SENT) {
> >   		const long timeo = sock_sndtimeo(sk, flags & O_NONBLOCK);
> >   
> >   		if (!timeo || !llc_ui_wait_for_conn(sk, timeo))
> >   			goto out;
>
> .. I suspect you mean to target this branch, right?

I can’t remember now why I put it there, but you’re right, that would be 
the better place.