RE: [PATCH V4 1/3] net/filter: Remove vnet_hdr from filter-mirror and filter-redirector

["Zhang, Chen" <chen.zhang@intel.com>]

> -----Original Message-----
> From: Jason Wang <jasowang@redhat.com>
> Sent: Wednesday, October 27, 2021 12:46 PM
> 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 V4 1/3] net/filter: Remove vnet_hdr from filter-mirror
> and filter-redirector
> 
> 
> 在 2021/10/27 上午2:17, Zhang Chen 写道:
> > Make the vnet header a necessary part of filter transfer protocol.
> > So remove the module's vnet_hdr_support switch here.
> > 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 | 88 ++++++++++-----------------------------------
> >   qemu-options.hx     | 14 ++++----
> >   2 files changed, 25 insertions(+), 77 deletions(-)
> >
> > diff --git a/net/filter-mirror.c b/net/filter-mirror.c index
> > f20240cc9f..4f0e26cc92 100644
> > --- a/net/filter-mirror.c
> > +++ b/net/filter-mirror.c
> > @@ -39,7 +39,6 @@ struct MirrorState {
> >       CharBackend chr_in;
> >       CharBackend chr_out;
> >       SocketReadState rs;
> > -    bool vnet_hdr;
> >   };
> >
> >   static int filter_send(MirrorState *s, @@ -48,7 +47,7 @@ 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 +62,18 @@ 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));
> > +    if (ret != sizeof(len)) {
> > +        goto err;
> >       }
> >
> >       buf = g_malloc(size);
> > @@ -232,6 +228,12 @@ static void redirector_rs_finalize(SocketReadState
> *rs)
> >       MirrorState *s = container_of(rs, MirrorState, rs);
> >       NetFilterState *nf = NETFILTER(s);
> >
> > +    /* Check remote vnet_hdr */
> > +    if (rs->vnet_hdr_len != nf->netdev->vnet_hdr_len) {
> > +        error_report("filter redirector got a different packet vnet_hdr"
> > +        " from local, please check the -device configuration");
> > +    }
> > +
> >       redirector_to_filter(nf, rs->buf, rs->packet_len);
> >   }
> >
> > @@ -252,7 +254,7 @@ 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); @@ -323,20 +325,6 @@ static
> > void filter_mirror_set_outdev(Object *obj,
> >       }
> >   }
> >
> > -static bool filter_mirror_get_vnet_hdr(Object *obj, Error **errp) -{
> > -    MirrorState *s = FILTER_MIRROR(obj);
> > -
> > -    return s->vnet_hdr;
> > -}
> > -
> > -static void filter_mirror_set_vnet_hdr(Object *obj, bool value, Error
> > **errp) -{
> > -    MirrorState *s = FILTER_MIRROR(obj);
> > -
> > -    s->vnet_hdr = value;
> > -}
> > -
> >   static char *filter_redirector_get_outdev(Object *obj, Error **errp)
> >   {
> >       MirrorState *s = FILTER_REDIRECTOR(obj); @@ -354,31 +342,12 @@
> > static void filter_redirector_set_outdev(Object *obj,
> >       s->outdev = g_strdup(value);
> >   }
> >
> > -static bool filter_redirector_get_vnet_hdr(Object *obj, Error **errp)
> > -{
> > -    MirrorState *s = FILTER_REDIRECTOR(obj);
> > -
> > -    return s->vnet_hdr;
> > -}
> > -
> > -static void filter_redirector_set_vnet_hdr(Object *obj,
> > -                                           bool value,
> > -                                           Error **errp)
> > -{
> > -    MirrorState *s = FILTER_REDIRECTOR(obj);
> > -
> > -    s->vnet_hdr = value;
> > -}
> > -
> >   static void filter_mirror_class_init(ObjectClass *oc, void *data)
> >   {
> >       NetFilterClass *nfc = NETFILTER_CLASS(oc);
> >
> >       object_class_property_add_str(oc, "outdev", filter_mirror_get_outdev,
> >                                     filter_mirror_set_outdev);
> > -    object_class_property_add_bool(oc, "vnet_hdr_support",
> > -                                   filter_mirror_get_vnet_hdr,
> > -                                   filter_mirror_set_vnet_hdr);
> >
> >       nfc->setup = filter_mirror_setup;
> >       nfc->cleanup = filter_mirror_cleanup; @@ -393,29 +362,12 @@
> > static void filter_redirector_class_init(ObjectClass *oc, void *data)
> >                                     filter_redirector_set_indev);
> >       object_class_property_add_str(oc, "outdev",
> filter_redirector_get_outdev,
> >                                     filter_redirector_set_outdev);
> > -    object_class_property_add_bool(oc, "vnet_hdr_support",
> > -                                   filter_redirector_get_vnet_hdr,
> > -                                   filter_redirector_set_vnet_hdr);
> >
> >       nfc->setup = filter_redirector_setup;
> >       nfc->cleanup = filter_redirector_cleanup;
> >       nfc->receive_iov = filter_redirector_receive_iov;
> >   }
> >
> > -static void filter_mirror_init(Object *obj) -{
> > -    MirrorState *s = FILTER_MIRROR(obj);
> > -
> > -    s->vnet_hdr = false;
> > -}
> > -
> > -static void filter_redirector_init(Object *obj) -{
> > -    MirrorState *s = FILTER_REDIRECTOR(obj);
> > -
> > -    s->vnet_hdr = false;
> > -}
> > -
> >   static void filter_mirror_fini(Object *obj)
> >   {
> >       MirrorState *s = FILTER_MIRROR(obj); @@ -435,7 +387,6 @@ static
> > const TypeInfo filter_redirector_info = {
> >       .name = TYPE_FILTER_REDIRECTOR,
> >       .parent = TYPE_NETFILTER,
> >       .class_init = filter_redirector_class_init,
> > -    .instance_init = filter_redirector_init,
> >       .instance_finalize = filter_redirector_fini,
> >       .instance_size = sizeof(MirrorState),
> >   };
> > @@ -444,7 +395,6 @@ static const TypeInfo filter_mirror_info = {
> >       .name = TYPE_FILTER_MIRROR,
> >       .parent = TYPE_NETFILTER,
> >       .class_init = filter_mirror_class_init,
> > -    .instance_init = filter_mirror_init,
> >       .instance_finalize = filter_mirror_fini,
> >       .instance_size = sizeof(MirrorState),
> >   };
> > diff --git a/qemu-options.hx b/qemu-options.hx index
> > 5f375bbfa6..38c03812a7 100644
> > --- a/qemu-options.hx
> > +++ b/qemu-options.hx
> > @@ -4946,18 +4946,16 @@ SRST
> >
> >           ``behind``: insert behind the specified filter (default).
> >
> > -    ``-object filter-
> mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx[,vnet_hdr
> _support][,position=head|tail|id=<id>][,insert=behind|before]``
> > +    ``-object
> > + filter-mirror,id=id,netdev=netdevid,outdev=chardevid,queue=all|rx|tx
> > + [,position=head|tail|id=<id>][,insert=behind|before]``
> 
> 
> I wonder if we break management layer. If yes, maybe it's better to keep the
> vnet_hdr_support here.

Yes and no,   With this series of patches, filters have ability to automatically
Configure the appropriate vnet_hdr_support flag according to the current environment.
And can report error when can't fixing the vnet_hdr(The user cannot fix it from the previous way ).
So I think no need for the user to configure this option, some relevant background knowledge required.

For the management layer, keep the vnet_hdr_support may be meaningless except for compatibility.
In this situation, Do you think we still need to keep the vnet_hdr_support for management layer?
Enable/disable it do the same things for filters.

Thanks
Chen

> 
> Thanks
> 
> 
> >           filter-mirror on netdev netdevid,mirror net packet to
> > -        chardevchardevid, if it has the vnet\_hdr\_support flag,
> > -        filter-mirror will mirror packet with vnet\_hdr\_len.
> > +        chardev chardevid, filter-mirror will mirror packet with
> vnet\_hdr\_len.
> >
> > -    ``-object filter-
> redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chardevid,queu
> e=all|rx|tx[,vnet_hdr_support][,position=head|tail|id=<id>][,insert=behind
> |before]``
> > +    ``-object
> > + filter-redirector,id=id,netdev=netdevid,indev=chardevid,outdev=chard
> > + evid,queue=all|rx|tx[,position=head|tail|id=<id>][,insert=behind|bef
> > + ore]``
> >           filter-redirector on netdev netdevid,redirect filter's net
> >           packet to chardev chardevid,and redirect indev's packet to
> > -        filter.if it has the vnet\_hdr\_support flag, filter-redirector
> > -        will redirect packet with vnet\_hdr\_len. Create a
> > -        filter-redirector we need to differ outdev id from indev id, id
> > -        can not be the same. we can just use indev or outdev, but at
> > +        filter. filter-redirector will redirect packet with vnet\_hdr\_len.
> > +        Create a filter-redirector we need to differ outdev id from indev id,
> > +        id can not be the same. we can just use indev or outdev, but
> > + at
> >           least one of indev or outdev need to be specified.
> >
> >       ``-object
> > filter-rewriter,id=id,netdev=netdevid,queue=all|rx|tx,[vnet_hdr_suppor
> > t][,position=head|tail|id=<id>][,insert=behind|before]``