filter: Add 'status' property for filter object

With this property, users can control if this filter is 'on'
or 'off'. The default behavior for filter is 'on'.

For some types of filters, they may need to react to status changing,
So here, we introduced status changing callback/notifier for filter class.

We will skip the disabled ('off') filter when delivering packets in net layer.
Signed-off-by: Nzhanghailiang <zhang.zhanghailiang@huawei.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Yang Hongyang <hongyang.yang@easystack.cn>
Signed-off-by: NJason Wang <jasowang@redhat.com>

include/net/filter.h

@@ -36,12 +36,15 @@ typedef ssize_t (FilterReceiveIOV)(NetFilterState *nc,
                                    int iovcnt,
                                    NetPacketSent *sent_cb);
 
+typedef void (FilterStatusChanged) (NetFilterState *nf, Error **errp);
+
 typedef struct NetFilterClass {
     ObjectClass parent_class;
 
     /* optional */
     FilterSetup *setup;
     FilterCleanup *cleanup;
+    FilterStatusChanged *status_changed;
     /* mandatory */
     FilterReceiveIOV *receive_iov;
 } NetFilterClass;
@@ -55,6 +58,7 @@ struct NetFilterState {
     char *netdev_id;
     NetClientState *netdev;
     NetFilterDirection direction;
+    bool on;
     QTAILQ_ENTRY(NetFilterState) next;
 };
 

net/filter.c

@@ -17,6 +17,11 @@
 #include "qom/object_interfaces.h"
 #include "qemu/iov.h"
 
+static inline bool qemu_can_skip_netfilter(NetFilterState *nf)
+{
+    return !nf->on;
+}
+
 ssize_t qemu_netfilter_receive(NetFilterState *nf,
                                NetFilterDirection direction,
                                NetClientState *sender,
@@ -25,6 +30,9 @@ ssize_t qemu_netfilter_receive(NetFilterState *nf,
                                int iovcnt,
                                NetPacketSent *sent_cb)
 {
+    if (qemu_can_skip_netfilter(nf)) {
+        return 0;
+    }
     if (nf->direction == direction ||
         nf->direction == NET_FILTER_DIRECTION_ALL) {
         return NETFILTER_GET_CLASS(OBJECT(nf))->receive_iov(
@@ -134,8 +142,38 @@ static void netfilter_set_direction(Object *obj, int direction, Error **errp)
     nf->direction = direction;
 }
 
+static char *netfilter_get_status(Object *obj, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    return nf->on ? g_strdup("on") : g_strdup("off");
+}
+
+static void netfilter_set_status(Object *obj, const char *str, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+    NetFilterClass *nfc = NETFILTER_GET_CLASS(obj);
+
+    if (strcmp(str, "on") && strcmp(str, "off")) {
+        error_setg(errp, "Invalid value for netfilter status, "
+                         "should be 'on' or 'off'");
+        return;
+    }
+    if (nf->on == !strcmp(str, "on")) {
+        return;
+    }
+    nf->on = !nf->on;
+    if (nfc->status_changed) {
+        nfc->status_changed(nf, errp);
+    }
+}
+
 static void netfilter_init(Object *obj)
 {
+    NetFilterState *nf = NETFILTER(obj);
+
+    nf->on = true;
+
     object_property_add_str(obj, "netdev",
                             netfilter_get_netdev_id, netfilter_set_netdev_id,
                             NULL);
@@ -143,6 +181,9 @@ static void netfilter_init(Object *obj)
                              NetFilterDirection_lookup,
                              netfilter_get_direction, netfilter_set_direction,
                              NULL);
+    object_property_add_str(obj, "status",
+                            netfilter_get_status, netfilter_set_status,
+                            NULL);
 }
 
 static void netfilter_complete(UserCreatable *uc, Error **errp)

qemu-options.hx

@@ -3788,11 +3788,13 @@ version by providing the @var{passwordid} parameter. This provides
 the ID of a previously created @code{secret} object containing the
 password for decryption.
 
-@item -object filter-buffer,id=@var{id},netdev=@var{netdevid},interval=@var{t}[,queue=@var{all|rx|tx}]
+@item -object filter-buffer,id=@var{id},netdev=@var{netdevid},interval=@var{t}[,queue=@var{all|rx|tx}][,status=@var{on|off}]
 
 Interval @var{t} can't be 0, this filter batches the packet delivery: all
 packets arriving in a given interval on netdev @var{netdevid} are delayed
 until the end of the interval. Interval is in microseconds.
+@option{status} is optional that indicate whether the netfilter is
+on (enabled) or off (disabled), the default status for netfilter will be 'on'.
 
 queue @var{all|rx|tx} is an option that can be applied to any netfilter.