rocker: mark copy-to-cpu pkts as forwarding offloaded

For pkts copied to the CPU (to be processed by guest driver), mark the Rx
descriptor with flag "OFFLOAD_FWD" to indicate device has already forwarded
pkt.  The guest driver will use this indicator to avoid duplicate
forwarding in the guest OS.

Examples include bcast/mcast/unknown ucast pkts flooded to bridged ports.
We want to avoid both the device and the guest bridge driver flooding these
pkts, which would result in duplicates pkts on the wire.  Packet sampling,
such as sFlow, can also use this technique to mark pkts for the guest OS to
record but otherwise drop.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Message-id: 1435746792-41278-5-git-send-email-sfeldma@gmail.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

docs/specs/rocker.txt

@@ -637,6 +637,7 @@ The TLVs for Rx descriptor buffer are:
 				  (1 << 5): TCP packet
 				  (1 << 6): UDP packet
 				  (1 << 7): TCP/UDP csum good
+				  (1 << 8): Offload forward
 	RX_CSUM		2	IP calculated checksum:
 				  IPv4: IP payload csum
 				  IPv6: header and payload csum
@@ -645,6 +646,9 @@ The TLVs for Rx descriptor buffer are:
 	RX_FRAG_MAX_LEN	2	Packet maximum fragment length
 	RX_FRAG_LEN	2	Actual packet fragment length after receive
 
+Offload forward RX_FLAG indicates the device has already forwarded the packet
+so the host CPU should not also forward the packet.
+
 Possible status return codes in descriptor on completion are:
 
 	DESC_COMP_ERR	reason

hw/net/rocker/rocker.c

@@ -603,7 +603,7 @@ static DescRing *rocker_get_rx_ring_by_pport(Rocker *r,
 }
 
 int rx_produce(World *world, uint32_t pport,
-               const struct iovec *iov, int iovcnt)
+               const struct iovec *iov, int iovcnt, uint8_t copy_to_cpu)
 {
     Rocker *r = world_rocker(world);
     PCIDevice *dev = (PCIDevice *)r;
@@ -646,6 +646,10 @@ int rx_produce(World *world, uint32_t pport,
         goto out;
     }
 
+    if (copy_to_cpu) {
+        rx_flags |= ROCKER_RX_FLAGS_FWD_OFFLOAD;
+    }
+
     /* XXX calc rx flags/csum */
 
     tlv_size = rocker_tlv_total_size(sizeof(uint16_t)) + /* flags */

hw/net/rocker/rocker.h

@@ -77,7 +77,7 @@ int rocker_event_link_changed(Rocker *r, uint32_t pport, bool link_up);
 int rocker_event_mac_vlan_seen(Rocker *r, uint32_t pport, uint8_t *addr,
                                uint16_t vlan_id);
 int rx_produce(World *world, uint32_t pport,
-               const struct iovec *iov, int iovcnt);
+               const struct iovec *iov, int iovcnt, uint8_t copy_to_cpu);
 int rocker_port_eg(Rocker *r, uint32_t pport,
                    const struct iovec *iov, int iovcnt);
 

hw/net/rocker/rocker_hw.h

@@ -250,6 +250,7 @@ enum {
 #define ROCKER_RX_FLAGS_TCP                     (1 << 5)
 #define ROCKER_RX_FLAGS_UDP                     (1 << 6)
 #define ROCKER_RX_FLAGS_TCP_UDP_CSUM_GOOD       (1 << 7)
+#define ROCKER_RX_FLAGS_FWD_OFFLOAD             (1 << 8)
 
 /* Tx msg */
 enum {

hw/net/rocker/rocker_of_dpa.c

@@ -825,6 +825,8 @@ static OfDpaGroup *of_dpa_group_alloc(uint32_t id)
 static void of_dpa_output_l2_interface(OfDpaFlowContext *fc,
                                        OfDpaGroup *group)
 {
+    uint8_t copy_to_cpu = fc->action_set.apply.copy_to_cpu;
+
     if (group->l2_interface.pop_vlan) {
         of_dpa_flow_pkt_strip_vlan(fc);
     }
@@ -837,7 +839,8 @@ static void of_dpa_output_l2_interface(OfDpaFlowContext *fc,
      */
 
     if (group->l2_interface.out_pport == 0) {
-        rx_produce(fc->of_dpa->world, fc->in_pport, fc->iov, fc->iovcnt);
+        rx_produce(fc->of_dpa->world, fc->in_pport, fc->iov, fc->iovcnt,
+                   copy_to_cpu);
     } else if (group->l2_interface.out_pport != fc->in_pport) {
         rocker_port_eg(world_rocker(fc->of_dpa->world),
                        group->l2_interface.out_pport,