svn commit: r282427 - stable/10/sys/net

[Julian Elischer]

On 5/5/15 3:33 AM, Alexander Motin wrote:
> Author: mav
> Date: Mon May  4 19:33:51 2015
> New Revision: 282427
> URL: https://svnweb.freebsd.org/changeset/base/282427
>
> Log:
>    MFC r281765:
>    Activate write-only optimization if bpf device opened with O_WRONLY.
>    
>    dhclient opens bpf as write-only to send packets. It never reads received
>    packets from that descriptor, but processing them in kernel takes time.
>    Especially much time takes packet timestamping on systems with expensive
>    timecounter, such as bhyve guest, where network speed dropped in half.

we probably should look at using a less weird way of sending raw packets.
using bpf (which is supposed to be a read-only interface) is just wrong..


>    
>    Sponsored by:	iXsystems, Inc.
>
> Modified:
>    stable/10/sys/net/bpf.c
> Directory Properties:
>    stable/10/   (props changed)
>
> Modified: stable/10/sys/net/bpf.c
> ==============================================================================
> --- stable/10/sys/net/bpf.c	Mon May  4 18:49:25 2015	(r282426)
> +++ stable/10/sys/net/bpf.c	Mon May  4 19:33:51 2015	(r282427)
> @@ -600,7 +600,7 @@ bpf_attachd(struct bpf_d *d, struct bpf_
>   	 * Save sysctl value to protect from sysctl change
>   	 * between reads
>   	 */
> -	op_w = V_bpf_optimize_writers;
> +	op_w = V_bpf_optimize_writers || d->bd_writer;
>   
>   	if (d->bd_bif != NULL)
>   		bpf_detachd_locked(d);
> @@ -802,6 +802,8 @@ bpfopen(struct cdev *dev, int flags, int
>   	 * particular buffer method.
>   	 */
>   	bpf_buffer_init(d);
> +	if ((flags & FREAD) == 0)
> +		d->bd_writer = 2;
>   	d->bd_hbuf_in_use = 0;
>   	d->bd_bufmode = BPF_BUFMODE_BUFFER;
>   	d->bd_sig = SIGIO;
>
>
>