[ovs-dev] [PATCH V3 2/2] bfd: Implement forwarding_if_rx.

Alex Wang alexw at nicira.com
Thu Aug 22 00:01:27 UTC 2013


This commit adds a new boolean option "forwarding_if_rx" to bfd.

When forwarding_if_rx is true the interface will be considered
capable of packet I/O as long as there is packet received at
interface.  This is important in that when link becomes temporarily
conjested, consecutive BFD control packets can be lost.  And the
forwarding_if_rx can prevent link failover by detecting non-control
packets received at interface.

Signed-off-by: Alex Wang <alexw at nicira.com>

---

v2 -> v3:
- fix typo in commit log.
- fix indentation in bfd_forwarding__().
- refine the return logic in bfd_forwarding__().

v1 -> v2:
- update the forwarding_if_rx_detect_time when netdev is changed.
- use rate-limited log function.
- refine the commit log and vswitchd.xml.
- add unit test for situation when both forwarding_if_rx and bfd
  decay are enabled.

---
 lib/bfd.c            |   74 +++++++++++++--
 tests/bfd.at         |  251 +++++++++++++++++++++++++++++++++++++++++++++++++-
 vswitchd/vswitch.xml |    8 ++
 3 files changed, 323 insertions(+), 10 deletions(-)

diff --git a/lib/bfd.c b/lib/bfd.c
index 47e67df..7da6fd9 100644
--- a/lib/bfd.c
+++ b/lib/bfd.c
@@ -191,12 +191,19 @@ struct bfd {
     atomic_bool check_tnl_key;    /* Verify tunnel key of inbound packets? */
     atomic_int ref_cnt;
 
+    /* When forward_if_rx is true, bfd_forwarding() will return
+     * true as long as there are incoming packets received.
+     * Note, forwarding_override still has higher priority. */
+    bool forwarding_if_rx;
+    long long int forwarding_if_rx_detect_time;
+
     /* BFD decay related variables. */
     bool in_decay;                /* True when bfd is in decay. */
     int decay_min_rx;             /* min_rx is set to decay_min_rx when */
                                   /* in decay. */
     int decay_rx_ctl;             /* Count bfd packets received within decay */
                                   /* detect interval. */
+    uint64_t decay_rx_packets;    /* Packets received by 'netdev'. */
     long long int decay_detect_time; /* Decay detection time. */
 };
 
@@ -223,6 +230,8 @@ static void bfd_put_details(struct ds *, const struct bfd *)
 static uint64_t bfd_rx_packets(const struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_try_decay(struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_decay_update(struct bfd *) OVS_REQUIRES(mutex);
+static void bfd_check_rx(struct bfd *) OVS_REQUIRES(mutex);
+static void bfd_forwarding_if_rx_update(struct bfd *) OVS_REQUIRES(mutex);
 static void bfd_unixctl_show(struct unixctl_conn *, int argc,
                              const char *argv[], void *aux OVS_UNUSED);
 static void bfd_unixctl_set_forwarding_override(struct unixctl_conn *,
@@ -280,7 +289,7 @@ bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
     long long int min_tx, min_rx;
     bool need_poll = false;
     bool cfg_min_rx_changed = false;
-    bool cpath_down;
+    bool cpath_down, forwarding_if_rx;
     const char *hwaddr;
     uint8_t ea[ETH_ADDR_LEN];
 
@@ -311,6 +320,7 @@ bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
         bfd->mult = 3;
         atomic_init(&bfd->ref_cnt, 1);
         bfd->netdev = netdev_ref(netdev);
+        bfd->rx_packets = bfd_rx_packets(bfd);
         bfd->in_decay = false;
 
         /* RFC 5881 section 4
@@ -384,6 +394,16 @@ bfd_configure(struct bfd *bfd, const char *name, const struct smap *cfg,
         bfd->eth_dst_set = false;
     }
 
+    forwarding_if_rx = smap_get_bool(cfg, "forwarding_if_rx", false);
+    if (bfd->forwarding_if_rx != forwarding_if_rx) {
+        bfd->forwarding_if_rx = forwarding_if_rx;
+        if (bfd->state == STATE_UP && bfd->forwarding_if_rx) {
+            bfd_forwarding_if_rx_update(bfd);
+        } else {
+            bfd->forwarding_if_rx_detect_time = 0;
+        }
+    }
+
     if (need_poll) {
         bfd_poll(bfd);
     }
@@ -458,6 +478,9 @@ bfd_run(struct bfd *bfd) OVS_EXCLUDED(mutex)
         bfd_try_decay(bfd);
     }
 
+    /* Always checks the reception of any packet. */
+    bfd_check_rx(bfd);
+
     if (bfd->min_tx != bfd->cfg_min_tx
         || (bfd->min_rx != bfd->cfg_min_rx && bfd->min_rx != bfd->decay_min_rx)
         || bfd->in_decay != old_in_decay) {
@@ -752,9 +775,13 @@ bfd_set_netdev(struct bfd *bfd, const struct netdev *netdev)
     if (bfd->netdev != netdev) {
         netdev_close(bfd->netdev);
         bfd->netdev = netdev_ref(netdev);
-        if (bfd->decay_min_rx) {
+        if (bfd->decay_min_rx && bfd->state == STATE_UP) {
             bfd_decay_update(bfd);
         }
+        if (bfd->forwarding_if_rx && bfd->state == STATE_UP) {
+            bfd_forwarding_if_rx_update(bfd);
+        }
+        bfd->rx_packets = bfd_rx_packets(bfd);
     }
     ovs_mutex_unlock(&mutex);
 }
@@ -763,14 +790,18 @@ bfd_set_netdev(struct bfd *bfd, const struct netdev *netdev)
 static bool
 bfd_forwarding__(const struct bfd *bfd) OVS_REQUIRES(mutex)
 {
+    long long int time;
+
     if (bfd->forwarding_override != -1) {
         return bfd->forwarding_override == 1;
     }
 
-    return bfd->state == STATE_UP
-        && bfd->rmt_diag != DIAG_PATH_DOWN
-        && bfd->rmt_diag != DIAG_CPATH_DOWN
-        && bfd->rmt_diag != DIAG_RCPATH_DOWN;
+    time = bfd->forwarding_if_rx_detect_time;
+    return (bfd->state == STATE_UP
+            || (bfd->forwarding_if_rx && time > time_msec()))
+           && bfd->rmt_diag != DIAG_PATH_DOWN
+           && bfd->rmt_diag != DIAG_CPATH_DOWN
+           && bfd->rmt_diag != DIAG_RCPATH_DOWN;
 }
 
 /* Helpers. */
@@ -1001,7 +1032,7 @@ bfd_try_decay(struct bfd *bfd) OVS_REQUIRES(mutex)
      * asynchronously to the bfd_rx_packets() function, the 'diff' value
      * can be jittered.  Thusly, we double the decay_rx_ctl to provide
      * more wiggle room. */
-    diff = bfd_rx_packets(bfd) - bfd->rx_packets;
+    diff = bfd_rx_packets(bfd) - bfd->decay_rx_packets;
     expect = 2 * MAX(bfd->decay_rx_ctl, 1);
     bfd->in_decay = diff <= expect ? true : false;
     bfd_decay_update(bfd);
@@ -1011,11 +1042,38 @@ bfd_try_decay(struct bfd *bfd) OVS_REQUIRES(mutex)
 static void
 bfd_decay_update(struct bfd * bfd) OVS_REQUIRES(mutex)
 {
-    bfd->rx_packets = bfd_rx_packets(bfd);
+    bfd->decay_rx_packets = bfd_rx_packets(bfd);
     bfd->decay_rx_ctl = 0;
     bfd->decay_detect_time = MAX(bfd->decay_min_rx, 2000) + time_msec();
 }
 
+/* Checks if there are packets received during the time since last call.
+ * If forwarding_if_rx is enabled and packets are received, updates the
+ * forwarding_if_rx_detect_time. */
+static void
+bfd_check_rx(struct bfd *bfd) OVS_REQUIRES(mutex)
+{
+    uint64_t rx_packets = bfd_rx_packets(bfd);
+    int64_t diff;
+
+    diff = rx_packets - bfd->rx_packets;
+    bfd->rx_packets = rx_packets;
+    if (diff < 0) {
+        VLOG_INFO_RL(&rl, "rx_packets count is smaller than last time.");
+    }
+    if (bfd->forwarding_if_rx && diff > 0) {
+        bfd_forwarding_if_rx_update(bfd);
+    }
+}
+
+/* Updates the forwarding_if_rx_detect_time. */
+static void
+bfd_forwarding_if_rx_update(struct bfd *bfd) OVS_REQUIRES(mutex)
+{
+    int64_t incr = bfd_rx_interval(bfd) * bfd->mult;
+    bfd->forwarding_if_rx_detect_time = MAX(incr, 2000) + time_msec();
+}
+
 static uint32_t
 generate_discriminator(void)
 {
diff --git a/tests/bfd.at b/tests/bfd.at
index da45b27..16d1ef2 100644
--- a/tests/bfd.at
+++ b/tests/bfd.at
@@ -261,14 +261,14 @@ OVS_VSWITCHD_START([add-br br1 -- set bridge br1 datapath-type=dummy -- \
 ovs-appctl time/stop
 
 # wait for local session state to go from down to up.
-for i in `seq 0 2`; do ovs-appctl time/warp 500; done
+for i in `seq 0 1`; do ovs-appctl time/warp 500; done
 BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [init], [No Diagnostic])
 
 
 # Test-1 BFD decay: decay to decay_min_rx
 # bfd:decay_min_rx is set to 3000ms after the local state of p0 goes up,
 # so for the first 2500ms, there should be no change.
-for i in `seq 0 3`; do ovs-appctl time/warp 500; done
+for i in `seq 0 4`; do ovs-appctl time/warp 500; done
 BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
 BFD_CHECK_TX([p0], [500ms], [300ms], [500ms])
 BFD_CHECK_RX([p0], [500ms], [300ms], [500ms])
@@ -507,4 +507,251 @@ BFD_CHECK_RX([p0], [3000ms], [3000ms], [500ms])
 # End of Test-8 ################################################################
 
 OVS_VSWITCHD_STOP
+AT_CLEANUP
+
+# Tests below are for bfd forwarding_if_rx feature.
+# forwarding_if_rx Test1: bfd is enabled on one end of link.
+AT_SETUP([bfd - bfd forwarding_if_rx 1])
+OVS_VSWITCHD_START([add-br br1 -- set bridge br1 datapath-type=dummy -- \
+                    add-port br1 p1 -- set Interface p1 type=patch \
+                    options:peer=p0 ofport_request=2 -- \
+                    add-port br0 p0 -- set Interface p0 type=patch \
+                    options:peer=p1 ofport_request=1 -- \
+                    set Interface p0 bfd:enable=true bfd:min_tx=500 bfd:min_rx=500 -- \
+                    add-port br1 p2 -- set Interface p2 type=internal ofport_request=3])
+
+# check the inital status.
+BFD_CHECK([p0], [false], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+
+# enable forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=true], [0])
+
+# there should be no change of forwarding flag, since
+# there is no traffic.
+for i in `seq 0 3`
+do
+    ovs-appctl time/warp 500
+    BFD_CHECK([p0], [false], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+done
+
+# receive one packet.
+AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+             [0], [stdout], [])
+for i in `seq 0 14`
+do
+    ovs-appctl time/warp 100
+    # the forwarding flag should be true, since there is data received.
+    BFD_CHECK([p0], [true], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+    BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+    BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+done
+
+# Stop sending packets for 1000ms.
+for i in `seq 0 9`; do ovs-appctl time/warp 100; done
+BFD_CHECK([p0], [false], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+
+# receive packet at 1/100ms rate for 1000ms.
+for i in `seq 0 9`
+do
+    ovs-appctl time/warp 100
+    AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+             [0], [stdout], [])
+done
+# the forwarding flag should be true, since there is data received.
+BFD_CHECK([p0], [true], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+
+# reset bfd forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=false], [0])
+# forwarding flag should turn to false since the STATE is DOWN.
+BFD_CHECK([p0], [false], [false], [none], [down], [No Diagnostic], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+
+AT_CHECK([ovs-vsctl del-br br1], [0], [ignore])
+AT_CLEANUP
+
+# forwarding_if_rx Test2: bfd is enabled on both ends of link.
+AT_SETUP([bfd - bfd forwarding_if_rx 2])
+OVS_VSWITCHD_START([add-br br1 -- set bridge br1 datapath-type=dummy -- \
+                    add-port br1 p1 -- set Interface p1 type=patch \
+                    options:peer=p0 ofport_request=2 -- \
+                    add-port br0 p0 -- set Interface p0 type=patch \
+                    options:peer=p1 ofport_request=1 -- \
+                    set Interface p0 bfd:enable=true bfd:min_tx=500 bfd:min_rx=500 -- \
+                    set Interface p1 bfd:enable=true bfd:min_tx=300 bfd:min_rx=300 -- \
+                    add-port br1 p2 -- set Interface p2 type=internal ofport_request=3])
+
+# advance the clock, to stablize the states.
+for i in `seq 0 9`; do ovs-appctl time/warp 500; done
+
+# enable forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=true], [0])
+
+# there should be no change of the forwarding flag, since
+# the bfd on both ends is already up.
+for i in `seq 0 5`
+do
+    ovs-appctl time/warp 500
+    BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+done
+
+# stop the bfd on one side.
+AT_CHECK([ovs-vsctl set Interface p1 bfd:enable=false], [0])
+# for within 1500ms, the detection timer is not out.
+# there is no change to status.
+for i in `seq 0 1`
+do
+    ovs-appctl time/warp 500
+    BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+    for i in `seq 0 5`
+    do
+        AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+                 [0], [stdout], [])
+    done
+done
+
+# at 1500ms, the STATE should go DOWN, due to Control Detection Time Expired.
+# but forwarding flag should be still true.
+ovs-appctl time/warp 500
+BFD_CHECK([p0], [true], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+
+# receive packet at 1/100ms rate for 1000ms.
+for i in `seq 0 9`
+do
+    AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+             [0], [stdout], [])
+    ovs-appctl time/warp 100
+    # the forwarding flag should always be true during this time.
+    BFD_CHECK([p0], [true], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+done
+
+# reset bfd forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=false], [0])
+# forwarding flag should turn to false since the STATE is DOWN.
+BFD_CHECK([p0], [false], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [1ms])
+
+# re-enable bfd on the other end. the states should be up.
+AT_CHECK([ovs-vsctl set Interface p1 bfd:enable=true bfd:min_tx=300 bfd:min_rx=300])
+# advance the clock, to stablize the states.
+for i in `seq 0 9`; do ovs-appctl time/warp 500; done
+BFD_CHECK([p0], [true], [false], [none], [up], [Control Detection Time Expired], [none], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [none], [up], [Control Detection Time Expired])
+BFD_CHECK_TX([p0], [500ms], [500ms], [300ms])
+BFD_CHECK_RX([p0], [500ms], [500ms], [300ms])
+
+AT_CHECK([ovs-vsctl del-br br1], [0], [ignore])
+AT_CLEANUP
+
+# forwarding_if_rx Test3: bfd is enabled on both ends of link and decay is enabled.
+AT_SETUP([bfd - bfd forwarding_if_rx 3])
+OVS_VSWITCHD_START([add-br br1 -- set bridge br1 datapath-type=dummy -- \
+                    add-port br1 p1 -- set Interface p1 type=patch \
+                    options:peer=p0 ofport_request=2 -- \
+                    add-port br0 p0 -- set Interface p0 type=patch \
+                    options:peer=p1 ofport_request=1 -- \
+                    set Interface p0 bfd:enable=true bfd:min_tx=300 bfd:min_rx=300 bfd:decay_min_rx=3000 -- \
+                    set Interface p1 bfd:enable=true bfd:min_tx=500 bfd:min_rx=500])
+
+# advance the clock, to stablize the states.
+for i in `seq 0 19`; do ovs-appctl time/warp 500; done
+BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+BFD_CHECK_TX([p0], [500ms], [300ms], [500ms])
+BFD_CHECK_RX([p0], [3000ms], [3000ms], [500ms])
+
+# enable forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=true], [0])
+
+# there should be no change of the forwarding flag, since
+# the bfd on both ends is already up.
+for i in `seq 0 9`
+do
+    ovs-appctl time/warp 500
+    BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+done
+
+# reconfigure the decay_min_rx to 1000ms. check the poll sequence.
+AT_CHECK([ovs-vsctl set interface p0 bfd:decay_min_rx=1000])
+BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [final], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [poll], [up], [No Diagnostic])
+BFD_CHECK_TX([p0], [500ms], [300ms], [500ms])
+BFD_CHECK_RX([p0], [500ms], [300ms], [500ms])
+
+# wait for 2000ms to decay.
+for i in `seq 0 3`; do ovs-appctl time/warp 500; done
+BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [final], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [poll], [up], [No Diagnostic])
+BFD_CHECK_TX([p0], [500ms], [300ms], [500ms])
+BFD_CHECK_RX([p0], [1000ms], [1000ms], [500ms])
+
+# wait for 1000ms, so that the flags will go back to none.
+for i in `seq 0 1`; do ovs-appctl time/warp 500; done
+BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+BFD_CHECK_TX([p0], [500ms], [300ms], [500ms])
+BFD_CHECK_RX([p0], [1000ms], [1000ms], [500ms])
+
+# stop the bfd on one side.
+AT_CHECK([ovs-vsctl set Interface p1 bfd:enable=false], [0])
+# for within 2500ms, the detection timer is not out.
+# there is no change to status.
+for i in `seq 0 4`
+do
+    ovs-appctl time/warp 500
+    BFD_CHECK([p0], [true], [false], [none], [up], [No Diagnostic], [none], [up], [No Diagnostic])
+    AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+             [0], [stdout], [])
+done
+
+# at 3000ms, the STATE should go DOWN, due to Control Detection Time Expired.
+# but forwarding flag should be still true.
+ovs-appctl time/warp 500
+BFD_CHECK([p0], [true], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+
+# receive packet at 1/100ms rate for 1000ms.
+for i in `seq 0 9`
+do
+    AT_CHECK([ovs-ofctl packet-out br1 3 2  "90e2ba01475000101856b2e80806000108000604000100101856b2e80202020300000000000002020202"],
+             [0], [stdout], [])
+    ovs-appctl time/warp 100
+    # the forwarding flag should always be true during this time.
+    BFD_CHECK([p0], [true], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+done
+
+# stop receiving for 2000ms.
+for i in `seq 0 19`; do ovs-appctl time/warp 100; done
+BFD_CHECK([p0], [false], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+
+# reset bfd forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=false])
+# forwarding flag should turn to false since the STATE is DOWN.
+BFD_CHECK([p0], [false], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [300ms], [300ms], [1ms])
+
+# re-enable bfd forwarding_if_rx.
+AT_CHECK([ovs-vsctl set Interface p0 bfd:forwarding_if_rx=true])
+# there should be no change.
+BFD_CHECK([p0], [false], [false], [none], [down], [Control Detection Time Expired], [none], [down], [No Diagnostic])
+BFD_CHECK_TX([p0], [1000ms], [1000ms], [0ms])
+BFD_CHECK_RX([p0], [300ms], [300ms], [1ms])
+
+# re-enable bfd on the other end. the states should be up.
+AT_CHECK([ovs-vsctl set Interface p1 bfd:enable=true bfd:min_tx=300 bfd:min_rx=300])
+# advance the clock, to stablize the states.
+for i in `seq 0 9`; do ovs-appctl time/warp 500; done
+BFD_CHECK([p0], [true], [false], [none], [up], [Control Detection Time Expired], [none], [up], [No Diagnostic])
+BFD_CHECK([p1], [true], [false], [none], [up], [No Diagnostic], [none], [up], [Control Detection Time Expired])
+BFD_CHECK_TX([p0], [300ms], [300ms], [300ms])
+BFD_CHECK_RX([p0], [1000ms], [1000ms], [300ms])
+
+AT_CHECK([ovs-vsctl del-br br1], [0], [ignore])
 AT_CLEANUP
\ No newline at end of file
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index a697fbc..d7a15ab 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -1905,7 +1905,14 @@
           reconfigured.
       </column>
 
+      <column name="bfd" key="forwarding_if_rx" type='{"type": "boolean"}'>
+          When <code>forwarding_if_rx</code> is true the interface will be
+          considered capable of packet I/O as long as there is packet
+          received at interface.  This is important in that when link becomes
+          temporarily conjested, consecutive BFD control packets can be lost.
+          And the <code>forwarding_if_rx</code> can prevent link failover by
+          detecting non-control packets received at interface.
+      </column>
 
       <column name="bfd" key="cpath_down" type='{"type": "boolean"}'>
           Concatenated path down may be used when the local system should not
-- 
1.7.9.5




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