RE: [PATCH V5 1/3] net/filter: Optimize transfer protocol for filter-mirror/redirector

[Zhang, Chen]

> -----Original Message-----
> From: Jason Wang <jasowang@redhat.com>
> Sent: Friday, October 29, 2021 11:11 AM
> To: Zhang, Chen <chen.zhang@intel.com>
> Cc: qemu-dev <qemu-devel@nongnu.org>; Markus Armbruster
> <armbru@redhat.com>; Li Zhijian <lizhijian@cn.fujitsu.com>
> Subject: Re: [PATCH V5 1/3] net/filter: Optimize transfer protocol for filter-
> mirror/redirector
> 
> 
> 在 2021/10/28 下午5:05, Zhang Chen 写道:
> > Make the vnet header a necessary part of filter transfer protocol.
> > It make other modules(like another filter-redirector,colo-compare...)
> > know how to parse net packet correctly. If local device is not the
> > virtio-net-pci, vnet_hdr_len will be 0.
> >
> > Signed-off-by: Zhang Chen <chen.zhang@intel.com>
> > ---
> >   net/filter-mirror.c | 34 ++++++++++++++++------------------
> >   1 file changed, 16 insertions(+), 18 deletions(-)
> >
> > diff --git a/net/filter-mirror.c b/net/filter-mirror.c index
> > f20240cc9f..24d3e498e9 100644
> > --- a/net/filter-mirror.c
> > +++ b/net/filter-mirror.c
> > @@ -39,6 +39,7 @@ struct MirrorState {
> >       CharBackend chr_in;
> >       CharBackend chr_out;
> >       SocketReadState rs;
> > +    /* Keep compatibility for the management layer */
> >       bool vnet_hdr;
> >   };
> >
> > @@ -48,7 +49,7 @@ static int filter_send(MirrorState *s,
> >   {
> >       NetFilterState *nf = NETFILTER(s);
> >       int ret = 0;
> > -    ssize_t size = 0;
> > +    ssize_t size = 0, vnet_hdr_len = 0;
> >       uint32_t len = 0;
> >       char *buf;
> >
> > @@ -63,21 +64,18 @@ static int filter_send(MirrorState *s,
> >           goto err;
> >       }
> >
> > -    if (s->vnet_hdr) {
> > -        /*
> > -         * If vnet_hdr = on, we send vnet header len to make other
> > -         * module(like colo-compare) know how to parse net
> > -         * packet correctly.
> > -         */
> > -        ssize_t vnet_hdr_len;
> > -
> > -        vnet_hdr_len = nf->netdev->vnet_hdr_len;
> > +    /*
> > +     * The vnet header is the necessary part of filter transfer protocol.
> > +     * It make other module(like colo-compare) know how to parse net
> > +     * packet correctly. If device is not the virtio-net-pci,
> > +     * vnet_hdr_len will be 0.
> > +     */
> > +    vnet_hdr_len = nf->netdev->vnet_hdr_len;
> >
> > -        len = htonl(vnet_hdr_len);
> > -        ret = qemu_chr_fe_write_all(&s->chr_out, (uint8_t *)&len,
> sizeof(len));
> > -        if (ret != sizeof(len)) {
> > -            goto err;
> > -        }
> > +    len = htonl(vnet_hdr_len);
> > +    ret = qemu_chr_fe_write_all(&s->chr_out, (uint8_t *)&len,
> > + sizeof(len));
> 
> 
> I wonder if we need to introduce new parameter, e.g force_vnet_hdr here,
> then we can always send vnet_hdr when it is enabled.
> 
> Otherwise the "vnet_hdr_support" seems meaningless.

Yes, Current "vnet_hdr_support"  default enabled, and vnet_hdr_len already 
forced from attached nf->netdev.
Maybe we can introduce a new parameter "force_no_vnet_hdr" here to make the 
vnet_hdr_len always keep 0.
If you think OK, I will update it in next version.

Thanks
Chen

> 
> Thanks
> 
> 
> > +    if (ret != sizeof(len)) {
> > +        goto err;
> >       }
> >
> >       buf = g_malloc(size);
> > @@ -252,7 +250,7 @@ static void filter_redirector_setup(NetFilterState
> *nf, Error **errp)
> >           }
> >       }
> >
> > -    net_socket_rs_init(&s->rs, redirector_rs_finalize, s->vnet_hdr);
> > +    net_socket_rs_init(&s->rs, redirector_rs_finalize, true);
> >
> >       if (s->indev) {
> >           chr = qemu_chr_find(s->indev); @@ -406,14 +404,14 @@ static
> > void filter_mirror_init(Object *obj)
> >   {
> >       MirrorState *s = FILTER_MIRROR(obj);
> >
> > -    s->vnet_hdr = false;
> > +    s->vnet_hdr = true;
> >   }
> >
> >   static void filter_redirector_init(Object *obj)
> >   {
> >       MirrorState *s = FILTER_REDIRECTOR(obj);
> >
> > -    s->vnet_hdr = false;
> > +    s->vnet_hdr = true;
> >   }
> >
> >   static void filter_mirror_fini(Object *obj)