[Qemu-devel] [PATCH RFC 6/7] net/filter: Add a default filter to each netdev

[zhanghailiang]

We add each netdev a default buffer filter, which the name is
'nop', and the default buffer filter is disabled, so it has
no side effect for packets delivering in qemu net layer.

The default buffer filter can be used by COLO or Micro-checkpoint,
The reason we add the default filter is we hope to support
hot add network during COLO state in future.

Signed-off-by: zhanghailiang <address@hidden>
---
 include/net/filter.h | 11 +++++++++++
 net/dump.c           |  2 --
 net/filter.c         | 15 ++++++++++++++-
 net/net.c            | 18 ++++++++++++++++++
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/include/net/filter.h b/include/net/filter.h
index c7bd8f9..2043609 100644
--- a/include/net/filter.h
+++ b/include/net/filter.h
@@ -22,6 +22,16 @@
 #define NETFILTER_CLASS(klass) \
     OBJECT_CLASS_CHECK(NetFilterClass, (klass), TYPE_NETFILTER)
 
+#define DEFAULT_FILTER_NAME "nop"
+
+#define TYPE_FILTER_BUFFER "filter-buffer"
+#define TYPE_FILTER_DUMP "filter-dump"
+
+#define NETFILTER_ID_BUFFER 1
+#define NETFILTER_ID_DUMP 2
+
+extern const char *const netfilter_type_lookup[];
+
 typedef void (FilterSetup) (NetFilterState *nf, Error **errp);
 typedef void (FilterCleanup) (NetFilterState *nf);
 /*
@@ -55,6 +65,7 @@ struct NetFilterState {
     char *netdev_id;
     NetClientState *netdev;
     NetFilterDirection direction;
+    bool is_default;
     bool enabled;
     QTAILQ_ENTRY(NetFilterState) next;
 };
diff --git a/net/dump.c b/net/dump.c
index 88d9582..82727a6 100644
--- a/net/dump.c
+++ b/net/dump.c
@@ -229,8 +229,6 @@ int net_init_dump(const NetClientOptions *opts, const char 
*name,
 
 /* Dumping via filter */
 
-#define TYPE_FILTER_DUMP "filter-dump"
-
 #define FILTER_DUMP(obj) \
     OBJECT_CHECK(NetFilterDumpState, (obj), TYPE_FILTER_DUMP)
 
diff --git a/net/filter.c b/net/filter.c
index 4d96301..a126a3b 100644
--- a/net/filter.c
+++ b/net/filter.c
@@ -21,6 +21,11 @@
 #include "qapi/qmp-input-visitor.h"
 #include "monitor/monitor.h"
 
+const char *const netfilter_type_lookup[] = {
+    [NETFILTER_ID_BUFFER] = TYPE_FILTER_BUFFER,
+    [NETFILTER_ID_DUMP] = TYPE_FILTER_DUMP,
+};
+
 ssize_t qemu_netfilter_receive(NetFilterState *nf,
                                NetFilterDirection direction,
                                NetClientState *sender,
@@ -200,7 +205,7 @@ static void netfilter_complete(UserCreatable *uc, Error 
**errp)
     NetFilterClass *nfc = NETFILTER_GET_CLASS(uc);
     int queues;
     Error *local_err = NULL;
-
+    char *path = object_get_canonical_path_component(OBJECT(nf));
 
     if (!nf->netdev_id) {
         error_setg(errp, "Parameter 'netdev' is required");
@@ -225,6 +230,14 @@ static void netfilter_complete(UserCreatable *uc, Error 
**errp)
     }
 
     nf->netdev = ncs[0];
+    nf->is_default = !strcmp(path, DEFAULT_FILTER_NAME);
+    /*
+    * For the default buffer filter, it will be disabled by default,
+    * So it will not buffer any packets.
+    */
+    if (nf->is_default) {
+        nf->enabled = false;
+    }
 
     if (nfc->setup) {
         nfc->setup(nf, &local_err);
diff --git a/net/net.c b/net/net.c
index ec43105..9630234 100644
--- a/net/net.c
+++ b/net/net.c
@@ -76,6 +76,12 @@ const char *host_net_devices[] = {
 
 int default_net = 1;
 
+/*
+ * FIXME: Export this with an option for users to control
+ * this with comand line ?
+ */
+int default_netfilter = NETFILTER_ID_BUFFER;
+
 /***********************************************************/
 /* network device redirectors */
 
@@ -1032,6 +1038,18 @@ static int net_client_init1(const void *object, int 
is_netdev, Error **errp)
         }
         return -1;
     }
+
+    if (is_netdev) {
+        const Netdev *netdev = object;
+        /*
+        * Here we add each netdev a default filter whose name is 'nop',
+        * it will disabled by default, Users can enable it when necessary.
+        */
+        netdev_add_filter(netdev->id,
+                          netfilter_type_lookup[default_netfilter],
+                          DEFAULT_FILTER_NAME,
+                          errp);
+    }
     return 0;
 }
 
-- 
1.8.3.1