From: Dumitru Ceara <dce...@redhat.com>
When monitoring and updating (Linux) neighbor tables through Netlink,
the interfaces in question are identified by if-index. It's more
CMS-friendly to allow OVN to be configured to track interfaces by name.
In order to achieve that, we introduce a new host-if-monitor module
which tracks the if-index <-> if-name mapping for relevant interfaces.
NOTE: OVS has the lib/if-notifier.[ch] module already. However, that is
not really useful for the OVN use case because it doesn't really pass
the struct rtnetlink_change message to its registered callbacks.
Signed-off-by: Dumitru Ceara <dce...@redhat.com>
---
controller/automake.mk | 5 +-
controller/host-if-monitor-stub.c | 43 +++++++++
controller/host-if-monitor.c | 150 ++++++++++++++++++++++++++++++
controller/host-if-monitor.h | 30 ++++++
4 files changed, 227 insertions(+), 1 deletion(-)
create mode 100644 controller/host-if-monitor-stub.c
create mode 100644 controller/host-if-monitor.c
create mode 100644 controller/host-if-monitor.h
diff --git a/controller/automake.mk b/controller/automake.mk
index 6af6ee2a9..6eca5e8ed 100644
--- a/controller/automake.mk
+++ b/controller/automake.mk
@@ -64,10 +64,12 @@ controller_ovn_controller_SOURCES = \
controller/route.c \
controller/garp_rarp.h \
controller/garp_rarp.c \
- controller/neighbor-table-notify.h
+ controller/neighbor-table-notify.h \
+ controller/host-if-monitor.h
if HAVE_NETLINK
controller_ovn_controller_SOURCES += \
+ controller/host-if-monitor.c \
controller/neighbor-exchange-netlink.h \
controller/neighbor-exchange-netlink.c \
controller/neighbor-table-notify.c \
@@ -77,6 +79,7 @@ controller_ovn_controller_SOURCES += \
controller/route-table-notify.c
else
controller_ovn_controller_SOURCES += \
+ controller/host-if-monitor-stub.c \
controller/neighbor-table-notify-stub.c \
controller/route-exchange-stub.c \
controller/route-table-notify-stub.c
diff --git a/controller/host-if-monitor-stub.c
b/controller/host-if-monitor-stub.c
new file mode 100644
index 000000000..b174cf996
--- /dev/null
+++ b/controller/host-if-monitor-stub.c
@@ -0,0 +1,43 @@
+/* Copyright (c) 2025, Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+
+#include <stdbool.h>
+
+#include "openvswitch/compiler.h"
+#include "host-if-monitor.h"
+
+void
+host_if_monitor_wait(void)
+{
+}
+
+bool
+host_if_monitor_run(void)
+{
+ return false;
+}
+
+void
+host_if_monitor_update_watches(const struct sset *if_names OVS_UNUSED)
+{
+}
+
+int32_t
+host_if_monitor_ifname_toindex(const char *if_name OVS_UNUSED)
+{
+ return 0;
+}
diff --git a/controller/host-if-monitor.c b/controller/host-if-monitor.c
new file mode 100644
index 000000000..26edb03d0
--- /dev/null
+++ b/controller/host-if-monitor.c
@@ -0,0 +1,150 @@
+/* Copyright (c) 2025, Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#include <config.h>
+
+#include <linux/rtnetlink.h>
+#include <net/if.h>
+
+#include "lib/rtnetlink.h"
+#include "lib/simap.h"
+#include "openvswitch/vlog.h"
+
+#include "host-if-monitor.h"
+
+VLOG_DEFINE_THIS_MODULE(host_if_monitor);
+
+static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 1);
+
+struct host_if_monitor {
+ struct nln_notifier *link_notifier;
+
+ struct sset watched_interfaces;
+ struct simap ifname_to_ifindex;
+
+ bool changes_detected;
+};
+
+static struct host_if_monitor monitor = (struct host_if_monitor) {
+ .link_notifier = NULL,
+ .watched_interfaces = SSET_INITIALIZER(&monitor.watched_interfaces),
+ .ifname_to_ifindex = SIMAP_INITIALIZER(&monitor.ifname_to_ifindex),
+ .changes_detected = false,
+};
+
+static void if_notifier_cb(const struct rtnetlink_change *, void *aux);
+
+void
+host_if_monitor_wait(void)
+{
+ rtnetlink_wait();
+}
+
+bool
+host_if_monitor_run(void)
+{
+ monitor.changes_detected = false;
+
+ /* If any relevant interface if-index <-> if-name mapping changes are
+ * dected, monitor.changes_detected will be updated accordingly by the
+ * if_notifier_cb(). */
+ rtnetlink_run();
+
+ return monitor.changes_detected;
+}
+
+void
+host_if_monitor_update_watches(const struct sset *if_names)
+{
+ struct sset new_if_names = SSET_INITIALIZER(&new_if_names);
+ const char *if_name;
+
+ /* The notifier only triggers the callback on interface updates.
+ * For newly added ones we need to fetch the initial if_index ourselves.
+ */
+ SSET_FOR_EACH (if_name, if_names) {
+ if (!sset_contains(&monitor.watched_interfaces, if_name)) {
+ sset_add(&new_if_names, if_name);
+ }
+ }
+
+ if (!sset_equals(&monitor.watched_interfaces, if_names)) {
+ sset_destroy(&monitor.watched_interfaces);
+ sset_clone(&monitor.watched_interfaces, if_names);
+ }
+
+ if (!sset_is_empty(&monitor.watched_interfaces)) {
+ if (!monitor.link_notifier) {
+ VLOG_INFO_RL(&rl, "Enabling host interface monitor");
+ monitor.link_notifier =
+ rtnetlink_notifier_create(if_notifier_cb, &monitor);
+ }
+ /* Get initial state for new interfaces.
+ *
+ * NOTE: it's important that we have the initial state (if-index) for
+ * newly watched interfaces because of two reasons:
+ * - we need to be able to reconcile and preserve still valid learned
+ * remote FDB entries and remote VTEPs
+ * - the if_notifier_cb is called only on updates of interfaces
+ * therefore if existing interfaces don't change the notifier
+ * callback is not called.
+ */
+ SSET_FOR_EACH (if_name, &new_if_names) {
+ simap_put(&monitor.ifname_to_ifindex, if_name,
+ if_nametoindex(if_name));
+ }
+ } else {
+ if (monitor.link_notifier) {
+ VLOG_INFO_RL(&rl, "Disabling host interface monitor");
+ rtnetlink_notifier_destroy(monitor.link_notifier);
+ monitor.link_notifier = NULL;
+ }
+ }
+
+ sset_destroy(&new_if_names);
+}
+
+int32_t
+host_if_monitor_ifname_toindex(const char *if_name)
+{
+ return simap_get(&monitor.ifname_to_ifindex, if_name);
+}
+
+static void
+if_notifier_cb(const struct rtnetlink_change *change, void *aux OVS_UNUSED)
+{
+ if (!change || change->irrelevant) {
+ return;
+ }
+
+ switch (change->nlmsg_type) {
+ case RTM_NEWLINK:
+ if ((change->ifi_flags & IFF_UP)
+ && sset_find(&monitor.watched_interfaces, change->ifname)) {
+ simap_put(&monitor.ifname_to_ifindex,
+ change->ifname, change->if_index);
+ monitor.changes_detected = true;
+ }
+ break;
+ case RTM_DELLINK:
+ if (sset_find(&monitor.watched_interfaces, change->ifname)) {
+ simap_find_and_delete(&monitor.ifname_to_ifindex, change->ifname);
+ monitor.changes_detected = true;
+ }
+ break;
+ default:
+ break;
+ }
+}
diff --git a/controller/host-if-monitor.h b/controller/host-if-monitor.h
new file mode 100644
index 000000000..a41c5869c
--- /dev/null
+++ b/controller/host-if-monitor.h
@@ -0,0 +1,30 @@
+/* Copyright (c) 2025, Red Hat, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at:
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+#ifndef HOST_IF_MONITOR_H
+#define HOST_IF_MONITOR_H 1
+
+#include <stdint.h>
+#include "lib/sset.h"
+#include "lib/smap.h"
+
+void host_if_monitor_wait(void);
+bool host_if_monitor_run(void);
+
+void host_if_monitor_update_watches(const struct sset *if_names);
+
+int32_t host_if_monitor_ifname_toindex(const char *if_name);
+
+#endif /* HOST_IF_MONITOR_H */
--
2.50.0
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