From: Claudio Jeker <cjeker@diehard.n-r-g.com>
Subject: Re: wireguard - prepend mbuf allocations
To: David Hill <dhill@mindcry.org>
Cc: tech@openbsd.org
Date: Sat, 28 Sep 2024 19:47:57 +0200

On Sat, Sep 28, 2024 at 10:47:33AM -0400, David Hill wrote:
> Something like this?
> 
> 
> Index: net/if_wg.c
> ===================================================================
> RCS file: /cvs/src/sys/net/if_wg.c,v
> retrieving revision 1.38
> diff -u -p -r1.38 if_wg.c
> --- net/if_wg.c	9 Apr 2024 12:53:08 -0000	1.38
> +++ net/if_wg.c	28 Sep 2024 14:46:51 -0000
> @@ -860,10 +860,14 @@ wg_send_buf(struct wg_softc *sc, struct
>  {
>  	struct mbuf	*m;
>  	int		 ret = 0;
> +	size_t		 mlen = len + max_hdr;
> 
>  retry:
>  	m = m_gethdr(M_WAIT, MT_DATA);
> +	if (mlen > MHLEN)
> +		MCLGETL(m, M_WAIT, mlen);
>  	m->m_len = 0;
> +	m_align(m, len);
>  	m_copyback(m, 0, len, buf, M_WAIT);

This code should not use m_copyback() it does not do what it think it
does. It is there for a different reason.
 
>  	/* As we're sending a handshake packet here, we want high priority */
> @@ -1522,8 +1526,9 @@ wg_encap(struct wg_softc *sc, struct mbu
>  	 * noise_remote_encrypt about mbufs, but we would need to sort out the
>  	 * p_encap_queue situation first.
>  	 */
> -	if ((mc = m_clget(NULL, M_NOWAIT, out_len)) == NULL)
> +	if ((mc = m_clget(NULL, M_NOWAIT, out_len + max_hdr)) == NULL)
>  		goto error;
> +	m_align(mc, out_len);
> 
>  	data = mtod(mc, struct wg_pkt_data *);
>  	m_copydata(m, 0, m->m_pkthdr.len, data->buf);
> 

-- 
:wq Claudio