From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: Re: tun(4)/tap(4): run the network stack with shared net lock
To: David Gwynne <david@gwynne.id.au>
Cc: tech@openbsd.org
Date: Tue, 25 Nov 2025 14:18:31 +0100

On Tue, Nov 25, 2025 at 10:01:02PM +1000, David Gwynne wrote:
> pretty sure we can push packets through the stack with NET_LOCK_SHARED.
> 
> ok?

Are we really there yet? See rev 1.221. It mentions pfsync and socket
layer as being affected. I don't remember the full story here so maybe it
is safe now because a lot changed in the last 5.5 years.
 
> Index: if_tun.c
> ===================================================================
> RCS file: /cvs/src/sys/net/if_tun.c,v
> diff -u -p -r1.253 if_tun.c
> --- if_tun.c	4 Nov 2025 12:02:39 -0000	1.253
> +++ if_tun.c	25 Nov 2025 11:59:33 -0000
> @@ -1034,9 +1034,9 @@ tun_dev_write(dev_t dev, struct uio *uio
>  		m = n;
>  	}
>  
> -	NET_LOCK();
> +	NET_LOCK_SHARED();
>  	if_vinput(ifp, m0, NULL);
> -	NET_UNLOCK();
> +	NET_UNLOCK_SHARED();
>  
>  	tun_put(sc);
>  	return (0);
> 

-- 
:wq Claudio