[PATCH 1/4] qemu:net: Add infrastructure for setting an RX filter through the vlan

[Alex Williamson <alex.williamson@hp.com>]

Some interfaces, such as tap, can set a filter to prevent unwanted
packets from interrupting qemu.  This patch adds infrastructure for
vlan clients to request a set of filtering parameters.  The main
client interface for this is the new qemu_vlan_rxfilter() function.
For simplicity, we restrict the topology that can make use of a filter
to exactly two clients on a vlan.  To handle hotplug devices, we add
vlan_client_added/removed notifiers which can automatically revert
back to a shared media protocol.  Devices providing filtering can do
so via the new fd_rxfilter() interface.

Signed-off-by: Alex Williamson <alex.williamson@hp.com>
---

 net.c |   43 ++++++++++++++++++++++++++++++++++++++++++-
 net.h |   14 ++++++++++++++
 2 files changed, 56 insertions(+), 1 deletions(-)

diff --git a/net.c b/net.c
index e7c097e..e68cb40 100644
--- a/net.c
+++ b/net.c
@@ -345,8 +345,11 @@ VLANClientState *qemu_new_vlan_client(VLANState *vlan,
 
     vc->next = NULL;
     pvc = &vlan->first_client;
-    while (*pvc != NULL)
+    while (*pvc != NULL) {
+        if ((*pvc)->vlan_client_added)
+            (*pvc)->vlan_client_added((*pvc)->opaque);
         pvc = &(*pvc)->next;
+    }
     *pvc = vc;
     return vc;
 }
@@ -364,6 +367,12 @@ void qemu_del_vlan_client(VLANClientState *vc)
             break;
         } else
             pvc = &(*pvc)->next;
+
+    /* Notify other clients after removal for dependencies on new topology */
+    pvc = &vc->vlan->first_client;
+    while (*pvc != NULL)
+        if ((*pvc)->vlan_client_removed)
+            (*pvc)->vlan_client_removed((*pvc)->opaque);
 }
 
 int qemu_can_send_packet(VLANClientState *vc1)
@@ -458,6 +467,38 @@ ssize_t qemu_sendv_packet(VLANClientState *vc1, const struct iovec *iov,
     return max_len;
 }
 
+/*
+ * This function allows a qemu vlan client to request filtering on
+ * it's receiving interface.  We only use this for the typical case
+ * of having exactly two clients on the vlan.  Clients making use
+ * of this function should also implement a vlan_client_added()
+ * function to be notified when they need to fall back to their own
+ * filtering or disable filtering setup for a single consumer.
+ *
+ * A return value of 1 indicates the entire requested filter set
+ * is handled by the provided filter.
+ */
+int qemu_vlan_rxfilter(VLANClientState *vc1, int flags, int count,
+                       uint8_t *buf)
+{
+    VLANState *vlan = vc1->vlan;
+    VLANClientState *vc;
+
+    if (vlan->first_client == NULL || vlan->first_client->next == NULL ||
+        vlan->first_client->next->next != NULL)
+        return 0;
+
+    if (vlan->first_client == vc1)
+        vc = vc1->next;
+    else
+        vc = vlan->first_client;
+
+    if (vc->fd_rxfilter)
+        return (vc->fd_rxfilter(vc->opaque, flags, count, buf) == count);
+
+    return 0;
+}
+
 #if defined(CONFIG_SLIRP)
 
 /* slirp network adapter */
diff --git a/net.h b/net.h
index 291807a..2090111 100644
--- a/net.h
+++ b/net.h
@@ -11,13 +11,22 @@ typedef struct VLANClientState VLANClientState;
 
 typedef void (LinkStatusChanged)(VLANClientState *);
 
+typedef int (IORXFilter)(void *, unsigned int , int , uint8_t *);
+
+typedef void (VLANClientAdded)(void *);
+
+typedef void (VLANClientRemoved)(void *);
+
 struct VLANClientState {
     IOReadHandler *fd_read;
     IOReadvHandler *fd_readv;
     /* Packets may still be sent if this returns zero.  It's used to
        rate-limit the slirp code.  */
     IOCanRWHandler *fd_can_read;
+    IORXFilter *fd_rxfilter;
     LinkStatusChanged *link_status_changed;
+    VLANClientAdded *vlan_client_added;
+    VLANClientRemoved *vlan_client_removed;
     int link_down;
     void *opaque;
     struct VLANClientState *next;
@@ -51,10 +60,15 @@ void qemu_check_nic_model(NICInfo *nd, const char *model);
 void qemu_check_nic_model_list(NICInfo *nd, const char * const *models,
                                const char *default_model);
 void qemu_handler_true(void *opaque);
+int qemu_vlan_rxfilter(VLANClientState *vc1, int flags, int count,
+                       uint8_t *buf);
 
 void do_info_network(void);
 int do_set_link(const char *name, const char *up_or_down);
 
+#define QEMU_NET_PROMISC     1
+#define QEMU_NET_ALLMULTI    2
+
 /* NIC info */
 
 #define MAX_NICS 8