[2/3] net/filter.c: Add Options to insert filters anywhere in the filter list

diff --git a/include/net/filter.h b/include/net/filter.h
index 49da666ac0..355c178f75 100644
--- a/include/net/filter.h
+++ b/include/net/filter.h
@@ -62,6 +62,8 @@  struct NetFilterState {
     NetClientState *netdev;
     NetFilterDirection direction;
     bool on;
+    char *position;
+    bool insert_before;
     QTAILQ_ENTRY(NetFilterState) next;
 };

diff --git a/net/filter.c b/net/filter.c
index 28d1930db7..1058100b83 100644
--- a/net/filter.c
+++ b/net/filter.c
@@ -171,11 +171,47 @@  static void netfilter_set_status(Object *obj, const char *str, Error **errp)
     }
 }

+static char *netfilter_get_position(Object *obj, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    return g_strdup(nf->position);
+}
+
+static void netfilter_set_position(Object *obj, const char *str, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    nf->position = g_strdup(str);
+}
+
+static char *netfilter_get_insert(Object *obj, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    return nf->insert_before ? g_strdup("before") : g_strdup("after");
+}
+
+static void netfilter_set_insert(Object *obj, const char *str, Error **errp)
+{
+    NetFilterState *nf = NETFILTER(obj);
+
+    if (strcmp(str, "before") && strcmp(str, "after")) {
+        error_setg(errp, "Invalid value for netfilter insert, "
+                         "should be 'head' or 'tail'");
+        return;
+    }
+
+    nf->insert_before = !strcmp(str, "before");
+}
+
 static void netfilter_init(Object *obj)
 {
     NetFilterState *nf = NETFILTER(obj);

     nf->on = true;
+    nf->insert_before = false;
+    nf->position = g_strdup("tail");

     object_property_add_str(obj, "netdev",
                             netfilter_get_netdev_id, netfilter_set_netdev_id,
@@ -187,16 +223,23 @@  static void netfilter_init(Object *obj)
     object_property_add_str(obj, "status",
                             netfilter_get_status, netfilter_set_status,
                             NULL);
+    object_property_add_str(obj, "position",
+                            netfilter_get_position, netfilter_set_position,
+                            NULL);
+    object_property_add_str(obj, "insert",
+                            netfilter_get_insert, netfilter_set_insert,
+                            NULL);
 }

 static void netfilter_complete(UserCreatable *uc, Error **errp)
 {
     NetFilterState *nf = NETFILTER(uc);
+    NetFilterState *position;
     NetClientState *ncs[MAX_QUEUE_NUM];
     NetFilterClass *nfc = NETFILTER_GET_CLASS(uc);
     int queues;
     Error *local_err = NULL;
-
+
     if (!nf->netdev_id) {
         error_setg(errp, "Parameter 'netdev' is required");
         return;
@@ -219,6 +262,20 @@  static void netfilter_complete(UserCreatable *uc, Error **errp)
         return;
     }

+    if (strcmp(nf->position, "head") && strcmp(nf->position, "tail")) {
+        /* Search for the position to insert before/after */
+        Object *container;
+        Object *obj;
+
+        container = object_get_objects_root();
+        obj = object_resolve_path_component(container, nf->position);
+        if (!obj) {
+            error_setg(errp, "filter '%s' not found", nf->position);
+            return;
+        }
+        position = NETFILTER(obj);
+    }
+
     nf->netdev = ncs[0];

     if (nfc->setup) {
@@ -228,7 +285,18 @@  static void netfilter_complete(UserCreatable *uc, Error **errp)
             return;
         }
     }
-    QTAILQ_INSERT_TAIL(&nf->netdev->filters, nf, next);
+
+    if (!strcmp(nf->position, "head")) {
+        QTAILQ_INSERT_HEAD(&nf->netdev->filters, nf, next);
+    } else if (!strcmp(nf->position, "tail")) {
+        QTAILQ_INSERT_TAIL(&nf->netdev->filters, nf, next);
+    } else {
+        if (nf->insert_before) {
+            QTAILQ_INSERT_BEFORE(position, nf, next);
+        } else {
+            QTAILQ_INSERT_AFTER(&nf->netdev->filters, position, nf, next);
+        }
+    }
 }

 static void netfilter_finalize(Object *obj)
@@ -245,6 +313,7 @@  static void netfilter_finalize(Object *obj)
         QTAILQ_REMOVE(&nf->netdev->filters, nf, next);
     }
     g_free(nf->netdev_id);
+    g_free(nf->position);
 }

 static void default_handle_event(NetFilterState *nf, int event, Error **errp)
diff --git a/qemu-options.hx b/qemu-options.hx
index 08749a3391..f0a47a0746 100644
--- a/qemu-options.hx
+++ b/qemu-options.hx
@@ -4368,7 +4368,7 @@  applications, they can do this through this parameter. Its format is
 a gnutls priority string as described at
 @url{https://gnutls.org/manual/html_node/Priority-Strings.html}.

-@item -object filter-buffer,id=@var{id},netdev=@var{netdevid},interval=@var{t}[,queue=@var{all|rx|tx}][,status=@var{on|off}]
+@item -object filter-buffer,id=@var{id},netdev=@var{netdevid},interval=@var{t}[,queue=@var{all|rx|tx}][,status=@var{on|off}][,position=@var{head|tail|id}][,insert=@var{after|before}]

 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
@@ -4387,11 +4387,11 @@  queue @var{all|rx|tx} is an option that can be applied to any netfilter.
 @option{tx}: the filter is attached to the transmit queue of the netdev,
              where it will receive packets sent by the netdev.

-@item -object filter-mirror,id=@var{id},netdev=@var{netdevid},outdev=@var{chardevid},queue=@var{all|rx|tx}[,vnet_hdr_support]
+@item -object filter-mirror,id=@var{id},netdev=@var{netdevid},outdev=@var{chardevid},queue=@var{all|rx|tx}[,vnet_hdr_support][,position=@var{head|tail|id}][,insert=@var{after|before}]

 filter-mirror on netdev @var{netdevid},mirror net packet to chardev@var{chardevid}, if it has the vnet_hdr_support flag, filter-mirror will mirror packet with vnet_hdr_len.

-@item -object filter-redirector,id=@var{id},netdev=@var{netdevid},indev=@var{chardevid},outdev=@var{chardevid},queue=@var{all|rx|tx}[,vnet_hdr_support]
+@item -object filter-redirector,id=@var{id},netdev=@var{netdevid},indev=@var{chardevid},outdev=@var{chardevid},queue=@var{all|rx|tx}[,vnet_hdr_support][,position=@var{head|tail|id}][,insert=@var{after|before}]

 filter-redirector on netdev @var{netdevid},redirect filter's net packet to chardev
 @var{chardevid},and redirect indev's packet to filter.if it has the vnet_hdr_support flag,
@@ -4400,7 +4400,7 @@  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.

-@item -object filter-rewriter,id=@var{id},netdev=@var{netdevid},queue=@var{all|rx|tx},[vnet_hdr_support]
+@item -object filter-rewriter,id=@var{id},netdev=@var{netdevid},queue=@var{all|rx|tx},[vnet_hdr_support][,position=@var{head|tail|id}][,insert=@var{after|before}]

 Filter-rewriter is a part of COLO project.It will rewrite tcp packet to
 secondary from primary to keep secondary tcp connection,and rewrite
@@ -4413,7 +4413,7 @@  colo secondary:
 -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1
 -object filter-rewriter,id=rew0,netdev=hn0,queue=all

-@item -object filter-dump,id=@var{id},netdev=@var{dev}[,file=@var{filename}][,maxlen=@var{len}]
+@item -object filter-dump,id=@var{id},netdev=@var{dev}[,file=@var{filename}][,maxlen=@var{len}][,position=@var{head|tail|id}][,insert=@var{after|before}]

 Dump the network traffic on netdev @var{dev} to the file specified by
 @var{filename}. At most @var{len} bytes (64k by default) per packet are stored.