[ovs-dev] [PATCH] ovs-ofctl: Fix memory exhaustion failures in corner cases.

[Ben Pfaff]

Inserting or removing a sequence of flows with different wildcard patterns
causes temporary use of O(n**2) memory due to pvector modifications inside
the classifier.  This commit fixes the problem in two easy cases.  There
is at least one more difficult case inside ovs-vswitchd that this does not
fix.

VMware-BZ: #1322017
CC: Jarno Rajahalme <jrajahalme at nicira.com>
Signed-off-by: Ben Pfaff <blp at nicira.com>
---
 tests/ovs-ofctl.at    | 13 +++++++++++++
 utilities/ovs-ofctl.c |  3 +++
 2 files changed, 16 insertions(+)

diff --git a/tests/ovs-ofctl.at b/tests/ovs-ofctl.at
index 446d8f5..7290ef1 100644
--- a/tests/ovs-ofctl.at
+++ b/tests/ovs-ofctl.at
@@ -2650,6 +2650,19 @@ AT_CHECK([ovs-ofctl diff-flows flows.txt br0], [2], [dnl
 OVS_VSWITCHD_STOP
 AT_CLEANUP
 
+AT_SETUP([ovs-ofctl diff-flows - N**2 memory use])
+# A bug in prior versions made this use on the order of 50000**2 * 8
+# bytes (about 20 GB) of RAM on 64-bit machines.  The fixed version
+# should use much less than 1 GB.  We try to set a virtual memory
+# limit of 1 GB, to force a failure in the presence of the bug even on
+# a machine with a ridiculous amount of RAM (and to prevent swap
+# death).  We don't bother to check for failure of the ulimit command
+# since it's really just a precaution.
+ulimit -v 1048576
+for i in `seq 1 50000`; do echo "reg0=$i/$i actions=drop"; done > flows
+AT_CHECK([ovs-ofctl diff-flows flows flows])
+AT_CLEANUP
+
 AT_SETUP([ovs-ofctl -F and -O interaction])
 AT_CHECK([ovs-ofctl -F oxm -O openflow10], [1], [],
   [ovs-ofctl: None of the enabled OpenFlow versions (OpenFlow10) supports any of the enabled flow formats (OXM).  (Use -O to enable additional OpenFlow versions or -F to enable additional flow formats.)
diff --git a/utilities/ovs-ofctl.c b/utilities/ovs-ofctl.c
index 211c276..3d1d589 100644
--- a/utilities/ovs-ofctl.c
+++ b/utilities/ovs-ofctl.c
@@ -50,6 +50,7 @@
 #include "ofproto/ofproto.h"
 #include "openflow/nicira-ext.h"
 #include "openflow/openflow.h"
+#include "ovs-rcu.h"
 #include "packets.h"
 #include "pcap-file.h"
 #include "poll-loop.h"
@@ -2349,6 +2350,7 @@ fte_free_all(struct classifier *cls)
     CLS_FOR_EACH_SAFE (fte, rule, cls) {
         classifier_remove(cls, &fte->rule);
         fte_free(fte);
+        ovsrcu_quiesce();
     }
     classifier_destroy(cls);
 }
@@ -2375,6 +2377,7 @@ fte_insert(struct classifier *cls, const struct match *match,
         cls_rule_destroy(&old->rule);
         free(old);
     }
+    ovsrcu_quiesce();
 }
 
 /* Reads the flows in 'filename' as flow table entries in 'cls' for the version
-- 
2.1.1