[ovs-dev,v5,1/2] Avoid packet drop on LACP bond after link up

Message ID 1551818911-10884-1-git-send-email-nitin.katiyar@ericsson.com
State New
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Series
  • [ovs-dev,v5,1/2] Avoid packet drop on LACP bond after link up
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Commit Message

Nitin Katiyar March 5, 2019, 12:47 p.m.
Problem:

Patch

========
During port DOWN->UP of link (slave) in a LACP bond, after receiving the
LACP PDU 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 LACP PDU 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 Krishnappa Chidambaraswamy <manukc@gmail.com>
Co-authored-by: Manohar Krishnappa Chidambaraswamy <manukc@gmail.com>
Signed-off-by: Nitin Katiyar <nitin.katiyar@ericsson.com>
---
 lib/lacp.c                   | 10 +++++++++-
 lib/lacp.h                   |  2 +-
 ofproto/bond.c               | 22 +++++++++++++++++++---
 ofproto/ofproto-dpif-xlate.c | 10 +++++++++-
 4 files changed, 38 insertions(+), 6 deletions(-)

diff --git a/lib/lacp.c b/lib/lacp.c
index d6b36aa..e768012 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;
@@ -324,7 +325,7 @@  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
+bool
 lacp_process_packet(struct lacp *lacp, 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 +364,14 @@  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..0dfaef0 100644
--- a/lib/lacp.h
+++ b/lib/lacp.h
@@ -46,7 +46,7 @@  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 *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 d2a8b1f..c5d5f2c 100644
--- a/ofproto/bond.c
+++ b/ofproto/bond.c
@@ -794,6 +794,7 @@  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_);
@@ -811,7 +812,11 @@  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) {
@@ -847,8 +852,6 @@  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));
@@ -870,6 +873,19 @@  bond_check_admissibility(struct bond *bond, const void *slave_,
 
     OVS_NOT_REACHED();
 out:
+    if (slave && (verdict != BV_ACCEPT)) {
+        VLOG_DBG_RL(&rl, "slave (%s): Admissibility verdict is to drop pkt %s."
+                    "active slave: %s, may_enable: %s enable: %s "
+                    "LACP status:%d",
+                    slave->name,
+                    (verdict == BV_DROP_IF_MOVED) ?
+                        "as different port is learned" : "",
+                    (bond->active_slave == slave) ? "true" : "false",
+                    slave->may_enable ? "true" : "false",
+                    slave->enabled ? "true" : "false",
+                    bond->lacp_status);
+    }
+
     ovs_rwlock_unlock(&rwlock);
     return verdict;
 
diff --git a/ofproto/ofproto-dpif-xlate.c b/ofproto/ofproto-dpif-xlate.c
index c4014d7..8f44566 100644
--- a/ofproto/ofproto-dpif-xlate.c
+++ b/ofproto/ofproto-dpif-xlate.c
@@ -3307,6 +3307,7 @@  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;
@@ -3327,7 +3328,14 @@  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->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) &&