controller: Introduce route-exchange-netlink.

Introduce route-exchange-netlink module which implements interface
for maintaining VRFs [0] and routes through Netlink.

There is a desire to do this without having to (re-)implement
routing protocol state machines in OVN, and to accomplish this we
make use of Netlink.

Netlink was chosen because:
* Its ubiquitous nature with availability on any Linux system as
  as well other platforms.
* Presence of a very good Netlink library implementation in our
  sibling project and library, Open vSwitch.
* Popular routing protocol software conveniently already have
  support for redistributing routes to/from Netlink.
* Support for interacting with Virtual Routing and Forwarding
  domains [0], allowing full isolation between virtual network
  resources defined within OVN and the hosting system while
  retaining access to all system network interfaces.

It is important to note that the purpose of this integration is
generic exchange of control plane information, while allowing to
keep the datapath in OVS/OVN, enabling users to leverage its full
range of user-, kernel- and mixed- space datapath implementations.

0: https://docs.kernel.org/networking/vrf.html

This was orignally built by Frode Nordahl <fnordahl@ubuntu.com>

Signed-off-by: Felix Huettner <felix.huettner@stackit.cloud>
Signed-off-by: 0-day Robot <robot@bytheb.org>

configure.ac

@@ -87,6 +87,8 @@ OVS_CHECK_WIN32
 OVS_CHECK_VISUAL_STUDIO_DDK
 OVN_CHECK_COVERAGE
 OVS_CHECK_NDEBUG
+OVS_CHECK_NETLINK
+OVS_CHECK_LINUX_NETLINK
 OVS_CHECK_OPENSSL
 OVN_CHECK_LOGDIR
 OVN_CHECK_PYTHON3

controller/automake.mk

@@ -55,6 +55,12 @@ controller_ovn_controller_SOURCES = \
 	controller/route.h \
 	controller/route.c
 
+if HAVE_NETLINK
+controller_ovn_controller_SOURCES += \
+	controller/route-exchange-netlink.h \
+	controller/route-exchange-netlink.c
+endif
+
 controller_ovn_controller_LDADD = lib/libovn.la $(OVS_LIBDIR)/libopenvswitch.la
 man_MANS += controller/ovn-controller.8
 EXTRA_DIST += controller/ovn-controller.8.xml

controller/route-exchange-netlink.c

@@ -0,0 +1,249 @@
+/*
+ * 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 <errno.h>
+#include <inttypes.h>
+#include <linux/rtnetlink.h>
+#include <net/if.h>
+#include <netinet/in.h>
+
+#include "netlink-socket.h"
+#include "netlink.h"
+#include "openvswitch/hmap.h"
+#include "openvswitch/ofpbuf.h"
+#include "openvswitch/vlog.h"
+#include "packets.h"
+#include "route-table.h"
+#include "route.h"
+
+#include "route-exchange-netlink.h"
+
+VLOG_DEFINE_THIS_MODULE(route_exchange_netlink);
+static struct vlog_rate_limit rl = VLOG_RATE_LIMIT_INIT(5, 20);
+
+#define TABLE_ID_VALID(table_id) (table_id != RT_TABLE_UNSPEC &&              \
+                                  table_id != RT_TABLE_COMPAT &&              \
+                                  table_id != RT_TABLE_DEFAULT &&             \
+                                  table_id != RT_TABLE_MAIN &&                \
+                                  table_id != RT_TABLE_LOCAL &&               \
+                                  table_id != RT_TABLE_MAX)
+
+static int
+modify_vrf(uint32_t type, uint32_t flags_arg,
+           const char *ifname, uint32_t table_id)
+{
+    uint32_t flags = NLM_F_REQUEST | NLM_F_ACK;
+    size_t linkinfo_off, infodata_off;
+    struct ifinfomsg *ifinfo;
+    struct ofpbuf request;
+    int err;
+
+    flags |= flags_arg;
+
+    ofpbuf_init(&request, 0);
+    nl_msg_put_nlmsghdr(&request, 0, type, flags);
+    ifinfo = ofpbuf_put_zeros(&request, sizeof *ifinfo);
+    nl_msg_put_string(&request, IFLA_IFNAME, ifname);
+    if (type == RTM_DELLINK) {
+        goto out;
+    }
+
+    ifinfo->ifi_change = ifinfo->ifi_flags = IFF_UP;
+    linkinfo_off = nl_msg_start_nested(&request, IFLA_LINKINFO);
+    nl_msg_put_string(&request, IFLA_INFO_KIND, "vrf");
+    infodata_off = nl_msg_start_nested(&request, IFLA_INFO_DATA);
+    nl_msg_put_u32(&request, IFLA_VRF_TABLE, table_id);
+    nl_msg_end_nested(&request, infodata_off);
+    nl_msg_end_nested(&request, linkinfo_off);
+
+out:
+    err = nl_transact(NETLINK_ROUTE, &request, NULL);
+
+    ofpbuf_uninit(&request);
+
+    return err;
+}
+
+int
+re_nl_create_vrf(const char *ifname, uint32_t table_id)
+{
+    uint32_t flags = NLM_F_CREATE | NLM_F_EXCL;
+    uint32_t type = RTM_NEWLINK;
+
+    if (!TABLE_ID_VALID(table_id)) {
+        VLOG_WARN_RL(&rl,
+                     "attempt to create VRF using invalid table id %"PRIu32,
+                     table_id);
+        return EINVAL;
+    }
+
+    return modify_vrf(type, flags, ifname, table_id);
+}
+
+int
+re_nl_delete_vrf(const char *ifname)
+{
+    return modify_vrf(RTM_DELLINK, 0, ifname, 0);
+}
+
+static int
+modify_route(uint32_t type, uint32_t flags_arg, uint32_t table_id,
+             const struct in6_addr *dst, unsigned int plen)
+{
+    uint32_t flags = NLM_F_REQUEST | NLM_F_ACK;
+    bool is_ipv4 = IN6_IS_ADDR_V4MAPPED(dst);
+    struct ofpbuf request;
+    struct rtmsg *rt;
+    int err;
+
+    flags |= flags_arg;
+
+    ofpbuf_init(&request, 0);
+    nl_msg_put_nlmsghdr(&request, 0, type, flags);
+    rt = ofpbuf_put_zeros(&request, sizeof *rt);
+    rt->rtm_family = is_ipv4 ? AF_INET : AF_INET6;
+    rt->rtm_table = RT_TABLE_UNSPEC; /* RTA_TABLE attribute allows id > 256 */
+    /* Manage only OVN routes */
+    rt->rtm_protocol = RTPROT_OVN;
+    rt->rtm_type = RTN_BLACKHOLE;
+    if (type == RTM_DELROUTE) {
+        rt->rtm_scope = RT_SCOPE_NOWHERE;
+    } else {
+        rt->rtm_scope = RT_SCOPE_UNIVERSE;
+    }
+    rt->rtm_dst_len = plen;
+
+    nl_msg_put_u32(&request, RTA_TABLE, table_id);
+
+    if (is_ipv4) {
+        nl_msg_put_be32(&request, RTA_DST, in6_addr_get_mapped_ipv4(dst));
+    } else {
+        nl_msg_put_in6_addr(&request, RTA_DST, dst);
+    }
+
+    err = nl_transact(NETLINK_ROUTE, &request, NULL);
+    ofpbuf_uninit(&request);
+
+    return err;
+}
+
+int
+re_nl_add_route(uint32_t table_id, const struct in6_addr *dst,
+                unsigned int plen)
+{
+    uint32_t flags = NLM_F_CREATE | NLM_F_EXCL;
+    uint32_t type = RTM_NEWROUTE;
+
+    if (!TABLE_ID_VALID(table_id)) {
+        VLOG_WARN_RL(&rl,
+                     "attempt to add route using invalid table id %"PRIu32,
+                     table_id);
+        return EINVAL;
+    }
+
+    return modify_route(type, flags, table_id, dst, plen);
+}
+
+int
+re_nl_delete_route(uint32_t table_id, const struct in6_addr *dst,
+                   unsigned int plen)
+{
+    if (!TABLE_ID_VALID(table_id)) {
+        VLOG_WARN_RL(&rl,
+                     "attempt to delete route using invalid table id %"PRIu32,
+                     table_id);
+        return EINVAL;
+    }
+
+    return modify_route(RTM_DELROUTE, 0, table_id, dst, plen);
+}
+
+struct route_msg_handle_data {
+    const struct hmap *routes;
+};
+
+static void
+handle_route_msg_delete_routes(const struct route_table_msg *msg, void *data)
+{
+    const struct route_data *rd = &msg->rd;
+    struct route_msg_handle_data *handle_data = data;
+    const struct hmap *routes = handle_data->routes;
+    struct advertise_route_entry *ar;
+    int err;
+
+    /* This route is not from us, we should not touch it. */
+    if (rd->rtm_protocol != RTPROT_OVN) {
+        return;
+    }
+
+    uint32_t arhash = advertise_route_hash(&rd->rta_dst, rd->rtm_dst_len);
+    HMAP_FOR_EACH_WITH_HASH (ar, node, arhash, routes) {
+        if (ipv6_addr_equals(&ar->addr, &rd->rta_dst)
+                && ar->plen == rd->rtm_dst_len) {
+            ar->installed = true;
+            return;
+        }
+    }
+    err = re_nl_delete_route(rd->rta_table_id, &rd->rta_dst,
+                             rd->rtm_dst_len);
+    if (err) {
+        char addr_s[INET6_ADDRSTRLEN + 1];
+        VLOG_WARN_RL(&rl, "Delete route table_id=%"PRIu32" dst=%s plen=%d: %s",
+                     rd->rta_table_id,
+                     ipv6_string_mapped(
+                         addr_s, &rd->rta_dst) ? addr_s : "(invalid)",
+                     rd->rtm_dst_len,
+                     ovs_strerror(err));
+    }
+}
+
+void
+re_nl_sync_routes(uint32_t table_id,
+                  const struct hmap *routes)
+{
+    struct advertise_route_entry *ar;
+    HMAP_FOR_EACH (ar, node, routes) {
+        ar->installed = false;
+    }
+
+    /* Remove routes from the system that are not in the host_routes hmap and
+     * remove entries from host_routes hmap that match routes already installed
+     * in the system. */
+    struct route_msg_handle_data data = {
+        .routes = routes,
+    };
+    route_table_dump_one_table(table_id, handle_route_msg_delete_routes,
+                               &data);
+
+    /* Add any remaining routes in the host_routes hmap to the system routing
+     * table. */
+    HMAP_FOR_EACH (ar, node, routes) {
+        if (ar->installed) {
+            continue;
+        }
+        int err = re_nl_add_route(table_id, &ar->addr, ar->plen);
+        if (err) {
+            char addr_s[INET6_ADDRSTRLEN + 1];
+            VLOG_WARN_RL(&rl, "Add route table_id=%"PRIu32" dst=%s "
+                         "plen=%d: %s",
+                         table_id,
+                         ipv6_string_mapped(
+                             addr_s, &ar->addr) ? addr_s : "(invalid)",
+                         ar->plen,
+                         ovs_strerror(err));
+        }
+    }
+}

controller/route-exchange-netlink.h

@@ -0,0 +1,40 @@
+/*
+ * 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 ROUTE_EXCHANGE_NETLINK_H
+#define ROUTE_EXCHANGE_NETLINK_H 1
+
+#include <stdint.h>
+
+/* This value is arbitrary but currently unused.
+ * See https://github.com/iproute2/iproute2/blob/main/etc/iproute2/rt_protos */
+#define RTPROT_OVN 84
+
+struct in6_addr;
+struct hmap;
+
+int re_nl_create_vrf(const char *ifname, uint32_t table_id);
+int re_nl_delete_vrf(const char *ifname);
+
+int re_nl_add_route(uint32_t table_id, const struct in6_addr *dst,
+                    unsigned int plen);
+int re_nl_delete_route(uint32_t table_id, const struct in6_addr *dst,
+                       unsigned int plen);
+
+void re_nl_dump(uint32_t table_id);
+
+void re_nl_sync_routes(uint32_t table_id,
+                       const struct hmap *host_routes);
+
+#endif /* route-exchange-netlink.h */

m4/ovn.m4

@@ -576,3 +576,28 @@ AC_DEFUN([OVN_CHECK_UNBOUND],
    fi
    AM_CONDITIONAL([HAVE_UNBOUND], [test "$HAVE_UNBOUND" = yes])
    AC_SUBST([HAVE_UNBOUND])])
+
+dnl Checks for Netlink support.
+AC_DEFUN([OVS_CHECK_NETLINK],
+  [AC_CHECK_HEADER([linux/netlink.h],
+                   [HAVE_NETLINK=yes],
+                   [HAVE_NETLINK=no],
+                   [#include <sys/socket.h>
+   ])
+   AM_CONDITIONAL([HAVE_NETLINK], [test "$HAVE_NETLINK" = yes])
+   if test "$HAVE_NETLINK" = yes; then
+      AC_DEFINE([HAVE_NETLINK], [1],
+                [Define to 1 if Netlink protocol is available.])
+   fi])
+
+dnl OVS_CHECK_LINUX_NETLINK
+dnl
+dnl Configure Linux netlink compat.
+AC_DEFUN([OVS_CHECK_LINUX_NETLINK], [
+  AC_COMPILE_IFELSE([
+    AC_LANG_PROGRAM([#include <linux/netlink.h>], [
+        struct nla_bitfield32 x =  { 0 };
+    ])],
+    [AC_DEFINE([HAVE_NLA_BITFIELD32], [1],
+    [Define to 1 if struct nla_bitfield32 is available.])])
+])

tests/automake.mk

@@ -308,6 +308,11 @@ tests_ovstest_LDADD = $(OVS_LIBDIR)/daemon.lo \
 	controller/route.$(OBJEXT) \
 	northd/ipam.$(OBJEXT)
 
+if HAVE_NETLINK
+tests_ovstest_LDADD += \
+	controller/route-exchange-netlink.$(OBJEXT)
+endif
+
 # Python tests.
 CHECK_PYFILES = \
 	tests/test-l7.py \

tests/system-common-macros.at

@@ -530,3 +530,15 @@ OVS_TRAFFIC_VSWITCHD_STOP(["/.*error receiving.*/d
 /failed to query port patch-.*/d
 /.*terminating with signal 15.*/d"])
 ]))
+
+# CHECK_VRF()
+#
+# Perform a requirements check for running VRF tests.
+#
+m4_define([CHECK_VRF],
+[
+    rc=0
+    modprobe vrf || rc=$?
+    AT_SKIP_IF([test $rc -ne 0])
+    on_exit 'modprobe -r vrf'
+])