[ovs-dev] [PATCH ovn v6] ofctrl.c: Add a predictable resolution for conflicting flow actions.
Dumitru Ceara
dceara at redhat.com
Tue Oct 13 08:52:11 UTC 2020
Until now, in case the ACL configuration generates openflows that have
the same match but different actions, ovn-controller was using the
following approach:
1. If the flow being added contains conjunctive actions, merge its
actions with the already existing flow.
2. Otherwise, if the flow is being added incrementally
(update_installed_flows_by_track), don't install the new flow but
instead keep the old one.
3. Otherwise, (update_installed_flows_by_compare), don't install the
new flow but instead keep the old one.
Even though one can argue that having an ACL with a match that includes
the match of another ACL is a misconfiguration, it can happen that the
users provision OVN like this. Depending on the order of reading and
installing the logical flows, the above operations can yield
unpredictable results, e.g., allow specific traffic but then after
ovn-controller is restarted (or a recompute happens) that specific
traffic starts being dropped.
A simple example of ACL configuration is:
ovn-nbctl acl-add ls to-lport 3 '(ip4.src==10.0.0.1 ||
ip4.src==10.0.0.2) && (ip4.dst == 10.0.0.3 || ip4.dst == 10.0.0.4)' allow
ovn-nbctl acl-add ls to-lport 3 'ip4.src==10.0.0.1' allow
ovn-nbctl acl-add ls to-lport 2 'arp' allow
ovn-nbctl acl-add ls to-lport 1 'ip4' drop
This is a pattern used by most CMSs:
- define a default deny policy.
- punch holes in the default deny policy based on user specific
configurations.
Without this commit the behavior for traffic from 10.0.0.1 to 10.0.0.5
is unpredictable. Depending on the order of operations traffic might be
dropped or allowed.
It's also quite hard to force the CMS to ensure that such match overlaps
never occur.
To address this issue we now ensure that when selecting the active flow
from all desired flows refering the same installed flow we give
precedence to "allow" over "drop" over "conjunction" flows.
Essentially, less restrictive flows are always preferred over more
restrictive flows whenever a match conflict happens.
CC: Daniel Alvarez <dalvarez at redhat.com>
Reported-at: https://bugzilla.redhat.com/1871931
Signed-off-by: Dumitru Ceara <dceara at redhat.com>
---
v6:
- First 3 patches of the v5 series were already applied.
- Send patch 4 as v6 addressing Han's comments:
- Instead of maintaining a sorted list, select active flow by walking
the list of desired flows.
- Add missing ovn_flow_log() call.
v5:
- Turn the patch into a series.
- Address Han's comments.
- Ensure predictable flow ordering in all cases (during incremental
procesing
or full recomputation).
v4:
- Address Han's comments:
- make sure only flows with action conjunction are combined.
v3:
- Add Mark's ack.
- Add last missing pcap check in the test.
v2:
- Address Han's comments:
- Do not delete desired flow that cannot be merged, it might be
installed later.
- Fix typos in the commit log.
- Update the test to check the OVS flows.
---
controller/ofctrl.c | 96 +++++++++++++++++++++--
tests/ovn.at | 214 ++++++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 305 insertions(+), 5 deletions(-)
diff --git a/controller/ofctrl.c b/controller/ofctrl.c
index ba0c61c..0edb2b9 100644
--- a/controller/ofctrl.c
+++ b/controller/ofctrl.c
@@ -229,6 +229,8 @@ static struct installed_flow *installed_flow_lookup(
static void installed_flow_destroy(struct installed_flow *);
static struct installed_flow *installed_flow_dup(struct desired_flow *);
static struct desired_flow *installed_flow_get_active(struct installed_flow *);
+static struct desired_flow *installed_flow_select_active(
+ struct installed_flow *);
static uint32_t ovn_flow_match_hash(const struct ovn_flow *);
static char *ovn_flow_to_string(const struct ovn_flow *);
@@ -796,6 +798,12 @@ ofctrl_recv(const struct ofp_header *oh, enum ofptype type)
}
static bool
+flow_action_has_drop(const struct ovn_flow *f)
+{
+ return f->ofpacts_len == 0;
+}
+
+static bool
flow_action_has_conj(const struct ovn_flow *f)
{
const struct ofpact *a = NULL;
@@ -822,7 +830,7 @@ link_installed_to_desired(struct installed_flow *i, struct desired_flow *d)
{
d->installed_flow = i;
ovs_list_push_back(&i->desired_refs, &d->installed_ref_list_node);
- return installed_flow_get_active(i) == d;
+ return installed_flow_select_active(i) == d;
}
/* Replaces 'old_desired' with 'new_desired' in the list of desired flows
@@ -852,6 +860,7 @@ unlink_installed_to_desired(struct installed_flow *i, struct desired_flow *d)
ovs_assert(d && d->installed_flow == i);
ovs_list_remove(&d->installed_ref_list_node);
+ installed_flow_select_active(i);
d->installed_flow = NULL;
return old_active == d;
}
@@ -1274,6 +1283,70 @@ installed_flow_get_active(struct installed_flow *f)
return NULL;
}
+/* Walks the list of desired flows that refer 'f' and selects the least
+ * restrictive one to be used as active flow, moving it to the front of
+ * the list.
+ *
+ * Returns the new active flow.
+ */
+static struct desired_flow *
+installed_flow_select_active(struct installed_flow *f)
+{
+ struct desired_flow *old_active = installed_flow_get_active(f);
+ struct desired_flow *active = NULL;
+
+ /* If there is at most one desired_flow, no selection needed, return
+ * early.
+ */
+ if (!old_active || ovs_list_is_short(&f->desired_refs)) {
+ return old_active;
+ }
+
+ struct desired_flow *d_allow = NULL;
+ struct desired_flow *d_drop = NULL;
+ struct desired_flow *d_conj = NULL;
+ struct desired_flow *d;
+
+ LIST_FOR_EACH (d, installed_ref_list_node, &f->desired_refs) {
+ if (flow_action_has_drop(&d->flow)) {
+ if (!d_drop) {
+ d_drop = d;
+ }
+ } else if (flow_action_has_conj(&d->flow)) {
+ /* Conjunction flows are always merged together into a single
+ * flow. There should never be more than one referring the same
+ * installed flow.
+ */
+ ovs_assert(!d_conj);
+ d_conj = d;
+ } else {
+ if (!d_allow) {
+ d_allow = d;
+ }
+ }
+ }
+
+ /* Give precedence to "allow" over "drop" over "conjunction" action. */
+ if (d_allow) {
+ active = d_allow;
+ } else if (d_drop) {
+ active = d_drop;
+ } else {
+ active = d_conj;
+ }
+
+ /* There must be an active flow otherwise we should have returned early. */
+ ovs_assert(active);
+
+ /* Move the newly selected active flow to the front of the list. */
+ if (active != old_active) {
+ ovs_list_remove(&active->installed_ref_list_node);
+ ovs_list_push_front(&f->desired_refs,
+ &active->installed_ref_list_node);
+ }
+ return active;
+}
+
static struct desired_flow *
desired_flow_lookup__(struct ovn_desired_flow_table *flow_table,
const struct ovn_flow *target,
@@ -1789,8 +1862,14 @@ update_installed_flows_by_compare(struct ovn_desired_flow_table *flow_table,
link_installed_to_desired(i, d);
} else if (!d->installed_flow) {
/* This is a desired_flow that conflicts with one installed
- * previously but not linked yet. */
- link_installed_to_desired(i, d);
+ * previously but not linked yet. However, if this flow becomes
+ * active, e.g., it is less restrictive than the previous active
+ * flow then modify the installed flow.
+ */
+ if (link_installed_to_desired(i, d)) {
+ installed_flow_mod(&i->flow, &d->flow, msgs);
+ ovn_flow_log(&i->flow, "updating installed (conflict)");
+ }
}
}
}
@@ -1919,8 +1998,15 @@ update_installed_flows_by_track(struct ovn_desired_flow_table *flow_table,
installed_flow_mod(&i->flow, &f->flow, msgs);
} else {
/* Adding a new flow that conflicts with an existing installed
- * flow, so just add it to the link. */
- link_installed_to_desired(i, f);
+ * flow, so add it to the link. If this flow becomes active,
+ * e.g., it is less restrictive than the previous active flow
+ * then modify the installed flow.
+ */
+ if (link_installed_to_desired(i, f)) {
+ installed_flow_mod(&i->flow, &f->flow, msgs);
+ ovn_flow_log(&i->flow,
+ "updating installed (tracked conflict)");
+ }
}
/* The track_list_node emptyness is used to check if the node is
* already added to track list, so initialize it again here. */
diff --git a/tests/ovn.at b/tests/ovn.at
index 488fd11..9420b1e 100644
--- a/tests/ovn.at
+++ b/tests/ovn.at
@@ -13727,6 +13727,220 @@ grep conjunction.*conjunction.*conjunction | wc -l`])
OVN_CLEANUP([hv1])
AT_CLEANUP
+AT_SETUP([ovn -- Superseeding ACLs with conjunction])
+ovn_start
+
+ovn-nbctl ls-add ls1
+
+ovn-nbctl lsp-add ls1 ls1-lp1 \
+-- lsp-set-addresses ls1-lp1 "f0:00:00:00:00:01"
+
+ovn-nbctl lsp-add ls1 ls1-lp2 \
+-- lsp-set-addresses ls1-lp2 "f0:00:00:00:00:02"
+
+net_add n1
+sim_add hv1
+
+as hv1
+ovs-vsctl add-br br-phys
+ovn_attach n1 br-phys 192.168.0.1
+ovs-vsctl -- add-port br-int hv1-vif1 -- \
+ set interface hv1-vif1 external-ids:iface-id=ls1-lp1 \
+ options:tx_pcap=hv1/vif1-tx.pcap \
+ options:rxq_pcap=hv1/vif1-rx.pcap \
+ ofport-request=1
+
+ovs-vsctl -- add-port br-int hv1-vif2 -- \
+ set interface hv1-vif2 external-ids:iface-id=ls1-lp2 \
+ options:tx_pcap=hv1/vif2-tx.pcap \
+ options:rxq_pcap=hv1/vif2-rx.pcap \
+ ofport-request=2
+
+# test_ip INPORT SRC_MAC DST_MAC SRC_IP DST_IP OUTPORT...
+#
+# This shell function causes an ip packet to be received on INPORT.
+# The packet's content has Ethernet destination DST and source SRC
+# (each exactly 12 hex digits) and Ethernet type ETHTYPE (4 hex digits).
+# The OUTPORTs (zero or more) list the VIFs on which the packet should
+# be received. INPORT and the OUTPORTs are specified as logical switch
+# port numbers, e.g. 11 for vif11.
+test_ip() {
+ # This packet has bad checksums but logical L3 routing doesn't check.
+ local inport=$1 src_mac=$2 dst_mac=$3 src_ip=$4 dst_ip=$5
+ local packet=${dst_mac}${src_mac}08004500001c0000000040110000${src_ip}\
+${dst_ip}0035111100080000
+ shift; shift; shift; shift; shift
+ as hv1 ovs-appctl netdev-dummy/receive hv1-vif1 $packet
+ for outport; do
+ echo $packet >> $outport.expected
+ done
+}
+
+ip_to_hex() {
+ printf "%02x%02x%02x%02x" "$@"
+}
+
+reset_pcap_file() {
+ local iface=$1
+ local pcap_file=$2
+ ovs-vsctl -- set Interface $iface options:tx_pcap=dummy-tx.pcap \
+options:rxq_pcap=dummy-rx.pcap
+ rm -f ${pcap_file}*.pcap
+ ovs-vsctl -- set Interface $iface options:tx_pcap=${pcap_file}-tx.pcap \
+options:rxq_pcap=${pcap_file}-rx.pcap
+}
+
+# Add a default deny ACL and an allow ACL for specific IP traffic.
+ovn-nbctl acl-add ls1 to-lport 2 'arp' allow
+ovn-nbctl acl-add ls1 to-lport 1 'ip4' drop
+ovn-nbctl acl-add ls1 to-lport 3 '(ip4.src==10.0.0.1 || ip4.src==10.0.0.2) && (ip4.dst == 10.0.0.3 || ip4.dst == 10.0.0.4)' allow
+ovn-nbctl acl-add ls1 to-lport 3 '(ip4.src==10.0.0.1 || ip4.src==10.0.0.42) && (ip4.dst == 10.0.0.3 || ip4.dst == 10.0.0.4)' allow
+ovn-nbctl --wait=hv sync
+
+# Traffic 10.0.0.1, 10.0.0.2 -> 10.0.0.3, 10.0.0.4 should be allowed.
+for src in `seq 1 2`; do
+ for dst in `seq 3 4`; do
+ sip=`ip_to_hex 10 0 0 $src`
+ dip=`ip_to_hex 10 0 0 $dst`
+
+ test_ip 1 f00000000001 f00000000002 $sip $dip 2
+ done
+done
+
+# Traffic 10.0.0.1, 10.0.0.2 -> 10.0.0.5 should be dropped.
+dip=`ip_to_hex 10 0 0 5`
+for src in `seq 1 2`; do
+ sip=`ip_to_hex 10 0 0 $src`
+
+ test_ip 1 f00000000001 f00000000002 $sip $dip
+done
+
+cat 2.expected > expout
+$PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+AT_CHECK([cat 2.packets], [0], [expout])
+reset_pcap_file hv1-vif2 hv1/vif2
+rm -f 2.packets
+> 2.expected
+
+# Add two less restrictive allow ACLs for src IP 10.0.0.1.
+ovn-nbctl acl-add ls1 to-lport 3 'ip4.src==10.0.0.1 || ip4.src==10.0.0.1' allow
+ovn-nbctl acl-add ls1 to-lport 3 'ip4.src==10.0.0.1' allow
+ovn-nbctl --wait=hv sync
+
+# Check OVS flows, the less restrictive flows should have been installed.
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int table=45 | \
+ grep "priority=1003" | awk '{print $7 " " $8}' | sort], [0], [dnl
+priority=1003,conj_id=2,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,conj_id=3,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.3 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.4 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.2 actions=conjunction(2,2/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.42 actions=conjunction(3,2/2)
+])
+
+# Traffic 10.0.0.1, 10.0.0.2 -> 10.0.0.3, 10.0.0.4 should be allowed.
+for src in `seq 1 2`; do
+ for dst in `seq 3 4`; do
+ sip=`ip_to_hex 10 0 0 $src`
+ dip=`ip_to_hex 10 0 0 $dst`
+
+ test_ip 1 f00000000001 f00000000002 $sip $dip 2
+ done
+done
+
+# Traffic 10.0.0.2 -> 10.0.0.5 should be dropped.
+sip=`ip_to_hex 10 0 0 2`
+dip=`ip_to_hex 10 0 0 5`
+test_ip 1 f00000000001 f00000000002 $sip $dip
+
+# Traffic 10.0.0.1 -> 10.0.0.5 should be allowed.
+sip=`ip_to_hex 10 0 0 1`
+dip=`ip_to_hex 10 0 0 5`
+test_ip 1 f00000000001 f00000000002 $sip $dip 2
+
+cat 2.expected > expout
+$PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+AT_CHECK([cat 2.packets], [0], [expout])
+reset_pcap_file hv1-vif2 hv1/vif2
+rm -f 2.packets
+> 2.expected
+
+#sleep infinity
+
+# Remove the first less restrictive allow ACL.
+ovn-nbctl acl-del ls1 to-lport 3 'ip4.src==10.0.0.1 || ip4.src==10.0.0.1'
+ovn-nbctl --wait=hv sync
+
+# Check OVS flows, the second less restrictive allow ACL should have been installed.
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int table=45 | \
+ grep "priority=1003" | awk '{print $7 " " $8}' | sort], [0], [dnl
+priority=1003,conj_id=2,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,conj_id=3,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.3 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.4 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.2 actions=conjunction(2,2/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.42 actions=conjunction(3,2/2)
+])
+
+# Remove the less restrictive allow ACL.
+ovn-nbctl acl-del ls1 to-lport 3 'ip4.src==10.0.0.1'
+ovn-nbctl --wait=hv sync
+
+# Check OVS flows, the 10.0.0.1 conjunction should have been reinstalled.
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int table=45 | \
+ grep "priority=1003" | awk '{print $7 " " $8}' | sort], [0], [dnl
+priority=1003,conj_id=2,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,conj_id=3,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.3 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.4 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.1 actions=conjunction(2,2/2),conjunction(3,2/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.2 actions=conjunction(2,2/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.42 actions=conjunction(3,2/2)
+])
+
+# Traffic 10.0.0.1, 10.0.0.2 -> 10.0.0.3, 10.0.0.4 should be allowed.
+for src in `seq 1 2`; do
+ for dst in `seq 3 4`; do
+ sip=`ip_to_hex 10 0 0 $src`
+ dip=`ip_to_hex 10 0 0 $dst`
+
+ test_ip 1 f00000000001 f00000000002 $sip $dip 2
+ done
+done
+
+# Traffic 10.0.0.1, 10.0.0.2 -> 10.0.0.5 should be dropped.
+dip=`ip_to_hex 10 0 0 5`
+for src in `seq 1 2`; do
+ sip=`ip_to_hex 10 0 0 $src`
+
+ test_ip 1 f00000000001 f00000000002 $sip $dip
+done
+
+cat 2.expected > expout
+$PYTHON "$ovs_srcdir/utilities/ovs-pcap.in" hv1/vif2-tx.pcap > 2.packets
+AT_CHECK([cat 2.packets], [0], [expout])
+
+# Re-add the less restrictive allow ACL for src IP 10.0.0.1
+ovn-nbctl acl-add ls1 to-lport 3 'ip4.src==10.0.0.1' allow
+ovn-nbctl --wait=hv sync
+
+# Check OVS flows, the less restrictive flows should have been installed.
+AT_CHECK([as hv1 ovs-ofctl dump-flows br-int table=45 | \
+ grep "priority=1003" | awk '{print $7 " " $8}' | sort], [0], [dnl
+priority=1003,conj_id=2,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,conj_id=3,ip,metadata=0x1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.3 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_dst=10.0.0.4 actions=conjunction(2,1/2),conjunction(3,1/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.1 actions=resubmit(,46)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.2 actions=conjunction(2,2/2)
+priority=1003,ip,metadata=0x1,nw_src=10.0.0.42 actions=conjunction(3,2/2)
+])
+
+OVN_CLEANUP([hv1])
+AT_CLEANUP
+
# 3 hypervisors, one logical switch, 3 logical ports per hypervisor
AT_SETUP([ovn -- L2 Drop and Allow ACL w/ Stateful ACL])
ovn_start
--
1.8.3.1
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