1/2: Fix packet drops on LACP bond after link up

Problem:
========
During port DOWN->UP of link (slave) in a LACP bond, after receiving the
LACPDU with SYNC set for both actor and partner, the bond-slave remains
"disabled" until OVS main thread runs LACP state machine and eventually
"enables" the bond-slave. With this, we have observed delays in the order
of 350ms and packets are  dropped in OVS due to bond-admissibility check
(packets received on slave in "disabled" state are dropped).

Fix:
====
When a LACPDU is received, evaluate whether LACP slave can be enabled
(slave_may_enable()) and set LACP slave's may_enable from the datapath
thread itself. When may_enable = TRUE, it means L1 state is UP and
LACP-SYNC is done and it is waiting for the main thread to enable the
slave. Relax the check in bond_check_admissibility() to check for both
"enable" and "may_enable" of the LACP slave. This would avoid dropping
of packets until the main thread enables the slave from bundle_run().

Signed-off-by: Manohar K C
<manohar.krishnappa.chidambarasw...@ericsson.com>
CC: Jan Scheurich <jan.scheur...@ericsson.com>
CC: Nitin Katiyar <nitin.kati...@ericsson.com>

---

v1 2/2: Avoid LACP negotiation when NIC driver reports PHY status as DOWN.

lib/lacp.c                   | 14 ++++++++++++--
lib/lacp.h                   |  3 ++-
ofproto/bond.c               | 18 +++++++++++++++---
ofproto/ofproto-dpif-xlate.c | 13 ++++++++++++-
4 files changed, 41 insertions(+), 7 deletions(-)

diff --git a/lib/lacp.c b/lib/lacp.c
index 8353746..8d97ad5 100644
--- a/lib/lacp.c
+++ b/lib/lacp.c
@@ -154,6 +154,7 @@ static struct slave *slave_lookup(const struct lacp *, 
const void *slave)
     OVS_REQUIRES(mutex);
static bool info_tx_equal(struct lacp_info *, struct lacp_info *)
     OVS_REQUIRES(mutex);
+static bool slave_may_enable__(struct slave *slave) OVS_REQUIRES(mutex);
static unixctl_cb_func lacp_unixctl_show;
static unixctl_cb_func lacp_unixctl_show_stats;
@@ -324,8 +325,8 @@ lacp_is_active(const struct lacp *lacp) OVS_EXCLUDED(mutex)
/* Processes 'packet' which was received on 'slave_'.  This function should be
  * called on all packets received on 'slave_' with Ethernet Type ETH_TYPE_LACP.
  */
-void
-lacp_process_packet(struct lacp *lacp, const void *slave_,
+bool
+lacp_process_packet(struct lacp *lacp, const void *bond, const void *slave_,
                     const struct dp_packet *packet)
     OVS_EXCLUDED(mutex)
{
@@ -333,6 +334,7 @@ lacp_process_packet(struct lacp *lacp, const void *slave_,
     const struct lacp_pdu *pdu;
     long long int tx_rate;
     struct slave *slave;
+    bool lacp_may_enable = false;
     lacp_lock();
     slave = slave_lookup(lacp, slave_);
@@ -362,8 +364,16 @@ lacp_process_packet(struct lacp *lacp, const void *slave_,
         slave->partner = pdu->actor;
     }
+    /*
+     * Evaluate may_enable here to avoid dropping of packets till main thread
+     * sets may_enable to true.
+     */
+    lacp_may_enable = slave_may_enable__(slave);
+
out:
     lacp_unlock();
+
+    return lacp_may_enable;
}
/* Returns the lacp_status of the given 'lacp' object (which may be NULL). */
diff --git a/lib/lacp.h b/lib/lacp.h
index f35cff5..1505c2c 100644
--- a/lib/lacp.h
+++ b/lib/lacp.h
@@ -46,7 +46,8 @@ struct lacp *lacp_ref(const struct lacp *);
void lacp_configure(struct lacp *, const struct lacp_settings *);
bool lacp_is_active(const struct lacp *);
-void lacp_process_packet(struct lacp *, const void *slave,
+bool lacp_process_packet(struct lacp *, const void *bond,
+                         const void *slave,
                          const struct dp_packet *packet);
enum lacp_status lacp_status(const struct lacp *);
diff --git a/ofproto/bond.c b/ofproto/bond.c
index 11d28e1..7ca3687 100644
--- a/ofproto/bond.c
+++ b/ofproto/bond.c
@@ -777,6 +777,7 @@ bond_check_admissibility(struct bond *bond, const void 
*slave_,
{
     enum bond_verdict verdict = BV_DROP;
     struct bond_slave *slave;
+    static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
     ovs_rwlock_rdlock(&rwlock);
     slave = bond_slave_lookup(bond, slave_);
@@ -794,7 +795,13 @@ bond_check_admissibility(struct bond *bond, const void 
*slave_,
      * drop all incoming traffic except if lacp_fallback_ab is enabled. */
     switch (bond->lacp_status) {
     case LACP_NEGOTIATED:
-        verdict = slave->enabled ? BV_ACCEPT : BV_DROP;
+        /*
+         * To reduce packet-drops due to delay in enabling of slave (post
+         * LACP-SYNC), from main thread, check for may_enable as well.
+         * When may_enable is TRUE, it means LACP is UP and waiting for
+         * the main thread to run LACP state machine and enable the slave.
+         */
+        verdict = (slave->enabled || slave->may_enable) ? BV_ACCEPT : BV_DROP;
         goto out;
     case LACP_CONFIGURED:
         if (!bond->lacp_fallback_ab) {
@@ -830,8 +837,6 @@ bond_check_admissibility(struct bond *bond, const void 
*slave_,
         /* Drop all packets which arrive on backup slaves.  This is similar to
          * how Linux bonding handles active-backup bonds. */
         if (bond->active_slave != slave) {
-            static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(1, 5);
-
             VLOG_DBG_RL(&rl, "active-backup bond received packet on backup"
                         " slave (%s) destined for " ETH_ADDR_FMT,
                         slave->name, ETH_ADDR_ARGS(eth_dst));
@@ -853,6 +858,13 @@ bond_check_admissibility(struct bond *bond, const void 
*slave_,
     OVS_NOT_REACHED();
out:
+    if (slave && (verdict != BV_ACCEPT)) {
+        VLOG_DBG_RL(&rl, "slave= %s actv-slave= %d may_enable %d enable %d "
+                    "LACP %d verdict(A/D/M=0/1/2) %d\n", slave->name,
+                    (bond->active_slave == slave), slave->may_enable,
+                    slave->enabled, bond->lacp_status, verdict);
+    }
+
     ovs_rwlock_unlock(&rwlock);
     return verdict;
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index 5641724..81dcdb6 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -3160,6 +3160,7 @@ process_special(struct xlate_ctx *ctx, const struct xport 
*xport)
     const struct xbridge *xbridge = ctx->xbridge;
     const struct dp_packet *packet = ctx->xin->packet;
     enum slow_path_reason slow;
+    bool lacp_may_enable;
     if (!xport) {
         slow = 0;
@@ -3180,7 +3181,17 @@ process_special(struct xlate_ctx *ctx, const struct 
xport *xport)
     } else if (xport->xbundle && xport->xbundle->lacp
                && flow->dl_type == htons(ETH_TYPE_LACP)) {
         if (packet) {
-            lacp_process_packet(xport->xbundle->lacp, xport->ofport, packet);
+            lacp_may_enable = lacp_process_packet(xport->xbundle->lacp,
+                                                  xport->xbundle->bond,
+                                                  xport->ofport, packet);
+            /*
+             * Update LACP status in bond-slave to avoid packet-drops until
+             * LACP state machine is run by the main thread.
+             */
+            if (xport->xbundle->bond && lacp_may_enable) {
+                bond_slave_set_may_enable(xport->xbundle->bond, xport->ofport,
+                                          lacp_may_enable);
+            }
         }
         slow = SLOW_LACP;
     } else if ((xbridge->stp || xbridge->rstp) &&
--
1.9.1

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