Currently, ovs-vswitchd is subscribed to all the routing changes in the
kernel. On each change, it marks the internal routing table cache as
invalid, then resets it and dumps all the routes from the kernel from
scratch. The reason for that is kernel routing updates not being
reliable in a sense that it's hard to tell which route is getting
removed or modified. Userspace application has to track the order in
which route entries are dumped from the kernel. Updates can get lost
or even duplicated and the kernel doesn't provide a good mechanism to
distinguish one route from another. To my knowledge, dumping all the
routes from a kernel after each change is the only way to keep the
cache consistent. Some more info can be found in the following never
addressed issues:
https://bugzilla.redhat.com/1337860
https://bugzilla.redhat.com/1337855
It seems to be believed that NetworkManager "mostly" does incremental
updates right. But it is still not completely correct, will re-dump
the whole table in certain cases, and it takes a huge amount of very
complicated code to do the accounting and route comparisons.
Going back to ovs-vswitchd, it currently dumps routes from all the
routing tables. If it will get conflicting routes from multiple
tables, the cache will not be useful. The routing cache in userspace
is primarily used for checking the egress port for tunneled traffic
and this way also detecting link state changes for a tunnel port.
For userspace datapath it is used for actual routing of the packet
after sending to a native tunnel.
With kernel datapath we don't really have a mechanism to know which
routing table will actually be used by the kernel after encapsulation,
so our lookups on a cache may be incorrect because of this as well.
So, unless all the relevant routes are in the standard tables, the
lookup in userspace route cache is unreliable.
Luckily, most setups are not using any complicated routing in
non-standard tables that OVS has to be aware of.
It is possible, but unlikely, that standard routing tables are
completely empty while some other custom table is not, and all the OVS
tunnel traffic is directed to that table. That would be the only
scenario where dumping non-standard tables would make sense. But it
seems like this kind of setup will likely need a way to tell OVS from
which table the routes should be taken, or we'll need to dump routing
rules and keep a separate cache for each table, so we can first match
on rules and then lookup correct routes in a specific table. I'm not
sure if trying to implement all that is justified.
For now, stop considering routes from non-standard tables to avoid
mixing different tables together and also wasting CPU resources.
This fixes a high CPU usage in ovs-vswitchd in case a BGP daemon is
running on a same host and in a same network namespace with OVS using
its own custom routing table.
Unfortunately, there seems to be no way to tell the kernel to send
updates only for particular tables. So, we'll still receive and parse
all of them. But they will not result in a full cache invalidation in
most cases.
Linux kernel v4.20 introduced filtering support for RTM_GETROUTE dumps.
So, we can make use of it and dump only standard tables when we get a
relevant route update. NETLINK_GET_STRICT_CHK has to be enabled on
the socket for filtering to work. There is no reason to not enable it
by default, if supported. It is not used outside of NETLINK_ROUTE.
Fixes: f0e167f0dbad ("route-table: Handle route updates more robustly.")
Fixes: ea83a2fcd0d3 ("lib: Show tunnel egress interface in ovsdb")
Reported-at: https://github.com/openvswitch/ovs-issues/issues/185
Reported-at:
https://mail.openvswitch.org/pipermail/ovs-discuss/2022-October/052091.html
Signed-off-by: Ilya Maximets <i.maxim...@ovn.org>
---
lib/netlink-protocol.h | 10 ++++++
lib/netlink-socket.c | 8 +++++
lib/route-table.c | 80 +++++++++++++++++++++++++++++++++---------
tests/system-route.at | 64 +++++++++++++++++++++++++++++++++
4 files changed, 146 insertions(+), 16 deletions(-)
diff --git a/lib/netlink-protocol.h b/lib/netlink-protocol.h
index 6eaa7035a..e4bb28ac9 100644
--- a/lib/netlink-protocol.h
+++ b/lib/netlink-protocol.h
@@ -155,6 +155,11 @@ enum {
#define NLA_TYPE_MASK ~(NLA_F_NESTED | NLA_F_NET_BYTEORDER)
#endif
+/* Introduced in v4.4. */
+#ifndef NLM_F_DUMP_FILTERED
+#define NLM_F_DUMP_FILTERED 0x20
+#endif
+
/* These were introduced all together in 2.6.14. (We want our programs to
* support the newer kernel features even if compiled with older headers.) */
#ifndef NETLINK_ADD_MEMBERSHIP
@@ -168,6 +173,11 @@ enum {
#define NETLINK_LISTEN_ALL_NSID 8
#endif
+/* Strict checking of netlink arguments introduced in Linux kernel v4.20. */
+#ifndef NETLINK_GET_STRICT_CHK
+#define NETLINK_GET_STRICT_CHK 12
+#endif
+
/* These were introduced all together in 2.6.23. (We want our programs to
* support the newer kernel features even if compiled with older headers.) */
#ifndef CTRL_ATTR_MCAST_GRP_MAX
diff --git a/lib/netlink-socket.c b/lib/netlink-socket.c
index 80da20d9f..eea880b2c 100644
--- a/lib/netlink-socket.c
+++ b/lib/netlink-socket.c
@@ -205,6 +205,14 @@ nl_sock_create(int protocol, struct nl_sock **sockp)
}
}
+ /* Strict checking only supported for NETLINK_ROUTE. */
+ if (protocol == NETLINK_ROUTE
+ && setsockopt(sock->fd, SOL_NETLINK, NETLINK_GET_STRICT_CHK,
+ &one, sizeof one) < 0) {
+ VLOG_INFO("netlink: could not enable strict checking (%s)",
+ ovs_strerror(errno));
+ }
+
retval = get_socket_rcvbuf(sock->fd);
if (retval < 0) {
retval = -retval;
diff --git a/lib/route-table.c b/lib/route-table.c
index 9927dcc18..f1fe32714 100644
--- a/lib/route-table.c
+++ b/lib/route-table.c
@@ -26,6 +26,7 @@
#include <linux/rtnetlink.h>
#include <net/if.h>
+#include "coverage.h"
#include "hash.h"
#include "netdev.h"
#include "netlink.h"
@@ -44,6 +45,8 @@
VLOG_DEFINE_THIS_MODULE(route_table);
+COVERAGE_DEFINE(route_table_dump);
+
struct route_data {
/* Copied from struct rtmsg. */
unsigned char rtm_dst_len;
@@ -80,7 +83,7 @@ static struct nln_notifier *name_notifier = NULL;
static bool route_table_valid = false;
-static int route_table_reset(void);
+static void route_table_reset(void);
static void route_table_handle_msg(const struct route_table_msg *);
static int route_table_parse(struct ofpbuf *, struct route_table_msg *);
static void route_table_change(const struct route_table_msg *, void *);
@@ -153,26 +156,22 @@ route_table_wait(void)
ovs_mutex_unlock(&route_table_mutex);
}
-static int
-route_table_reset(void)
+static bool
+route_table_dump_one_table(unsigned char id)
{
- struct nl_dump dump;
- struct rtgenmsg *rtgenmsg;
uint64_t reply_stub[NL_DUMP_BUFSIZE / 8];
struct ofpbuf request, reply, buf;
-
- route_map_clear();
- netdev_get_addrs_list_flush();
- route_table_valid = true;
- rt_change_seq++;
+ struct rtmsg *rq_msg;
+ bool filtered = true;
+ struct nl_dump dump;
ofpbuf_init(&request, 0);
- nl_msg_put_nlmsghdr(&request, sizeof *rtgenmsg, RTM_GETROUTE,
- NLM_F_REQUEST);
+ nl_msg_put_nlmsghdr(&request, sizeof *rq_msg, RTM_GETROUTE, NLM_F_REQUEST);
- rtgenmsg = ofpbuf_put_zeros(&request, sizeof *rtgenmsg);
- rtgenmsg->rtgen_family = AF_UNSPEC;
+ rq_msg = ofpbuf_put_zeros(&request, sizeof *rq_msg);
+ rq_msg->rtm_family = AF_UNSPEC;
+ rq_msg->rtm_table = id;
nl_dump_start(&dump, NETLINK_ROUTE, &request);
ofpbuf_uninit(&request);
@@ -182,12 +181,43 @@ route_table_reset(void)
struct route_table_msg msg;
if (route_table_parse(&reply, &msg)) {
+ struct nlmsghdr *nlmsghdr = nl_msg_nlmsghdr(&reply);
+
+ /* Older kernels do not support filtering. */
+ if (!(nlmsghdr->nlmsg_flags & NLM_F_DUMP_FILTERED)) {
+ filtered = false;
+ }
route_table_handle_msg(&msg);
}
}
ofpbuf_uninit(&buf);
+ nl_dump_done(&dump);
+
+ return filtered;
+}
+
+static void
+route_table_reset(void)
+{
+ unsigned char tables[] = {
+ RT_TABLE_DEFAULT,
+ RT_TABLE_MAIN,
+ RT_TABLE_LOCAL,
+ };
- return nl_dump_done(&dump);
+ route_map_clear();
+ netdev_get_addrs_list_flush();
+ route_table_valid = true;
+ rt_change_seq++;
+
+ COVERAGE_INC(route_table_dump);
+
+ for (size_t i = 0; i < ARRAY_SIZE(tables); i++) {
+ if (!route_table_dump_one_table(tables[i])) {
+ /* Got unfiltered reply, no need to dump further. */
+ break;
+ }
+ }
}
/* Return RTNLGRP_IPV4_ROUTE or RTNLGRP_IPV6_ROUTE on success, 0 on parse
@@ -203,6 +233,7 @@ route_table_parse(struct ofpbuf *buf, struct
route_table_msg *change)
[RTA_GATEWAY] = { .type = NL_A_U32, .optional = true },
[RTA_MARK] = { .type = NL_A_U32, .optional = true },
[RTA_PREFSRC] = { .type = NL_A_U32, .optional = true },
+ [RTA_TABLE] = { .type = NL_A_U32, .optional = true },
};
static const struct nl_policy policy6[] = {
@@ -211,6 +242,7 @@ route_table_parse(struct ofpbuf *buf, struct
route_table_msg *change)
[RTA_MARK] = { .type = NL_A_U32, .optional = true },
[RTA_GATEWAY] = { .type = NL_A_IPV6, .optional = true },
[RTA_PREFSRC] = { .type = NL_A_IPV6, .optional = true },
+ [RTA_TABLE] = { .type = NL_A_U32, .optional = true },
};
struct nlattr *attrs[ARRAY_SIZE(policy)];
@@ -232,6 +264,7 @@ route_table_parse(struct ofpbuf *buf, struct
route_table_msg *change)
if (parsed) {
const struct nlmsghdr *nlmsg;
+ uint32_t table_id;
int rta_oif; /* Output interface index. */
nlmsg = buf->data;
@@ -247,6 +280,19 @@ route_table_parse(struct ofpbuf *buf, struct
route_table_msg *change)
rtm->rtm_type != RTN_LOCAL) {
change->relevant = false;
}
+
+ table_id = rtm->rtm_table;
+ if (attrs[RTA_TABLE]) {
+ table_id = nl_attr_get_u32(attrs[RTA_TABLE]);
+ }
+ /* Do not consider changes in non-standard routing tables. */
+ if (table_id
+ && table_id != RT_TABLE_DEFAULT
+ && table_id != RT_TABLE_MAIN
+ && table_id != RT_TABLE_LOCAL) {
+ change->relevant = false;
+ }
+
change->nlmsg_type = nlmsg->nlmsg_type;
change->rd.rtm_dst_len = rtm->rtm_dst_len + (ipv4 ? 96 : 0);
change->rd.local = rtm->rtm_type == RTN_LOCAL;
@@ -312,7 +358,9 @@ static void
route_table_change(const struct route_table_msg *change OVS_UNUSED,
void *aux OVS_UNUSED)
{
- route_table_valid = false;
+ if (!change || change->relevant) {
+ route_table_valid = false;
+ }
}
static void
diff --git a/tests/system-route.at b/tests/system-route.at
index 114aaebc7..c0ecad6cf 100644
--- a/tests/system-route.at
+++ b/tests/system-route.at
@@ -64,3 +64,67 @@ Cached: fc00:db8:beef::13/128 dev br0 GW fc00:db8:cafe::1
SRC fc00:db8:cafe::2])
OVS_TRAFFIC_VSWITCHD_STOP
AT_CLEANUP
+
+dnl Checks that OVS doesn't use routes from non-standard tables.
+AT_SETUP([ovs-route - route tables])
+AT_KEYWORDS([route])
+OVS_TRAFFIC_VSWITCHD_START()
+
+dnl Create tap port.
+on_exit 'ip link del p1-route'
+AT_CHECK([ip tuntap add name p1-route mode tap])
+AT_CHECK([ip link set p1-route up])
+
+dnl Add ip address.
+AT_CHECK([ip addr add 10.0.0.17/24 dev p1-route], [0], [stdout])
+
+dnl Check that OVS catches route updates.
+OVS_WAIT_UNTIL_EQUAL([ovs-appctl ovs/route/show | grep 'p1-route' | sort], [dnl
+Cached: 10.0.0.0/24 dev p1-route SRC 10.0.0.17
+Cached: 10.0.0.17/32 dev p1-route SRC 10.0.0.17 local])
+
+dnl Add a route to the main routing table and check that OVS caches
+dnl this new route.
+AT_CHECK([ip route add 10.0.0.18/32 dev p1-route])
+OVS_WAIT_UNTIL_EQUAL([ovs-appctl ovs/route/show | grep 'p1-route' | sort], [dnl
+Cached: 10.0.0.0/24 dev p1-route SRC 10.0.0.17
+Cached: 10.0.0.17/32 dev p1-route SRC 10.0.0.17 local
+Cached: 10.0.0.18/32 dev p1-route SRC 10.0.0.17])
+
+dnl Add a route to a custom routing table and check that OVS doesn't cache it.
+AT_CHECK([ip route add 10.0.0.19/32 dev p1-route table 42])
+AT_CHECK([ip route show table 42 | grep 'p1-route' | grep -q '10.0.0.19'])
+dnl Give the main thread a chance to act.
+AT_CHECK([ovs-appctl revalidator/wait])
+dnl Check that OVS didn't learn this route.
+AT_CHECK([ovs-appctl ovs/route/show | grep 'p1-route' | sort], [0], [dnl
+Cached: 10.0.0.0/24 dev p1-route SRC 10.0.0.17
+Cached: 10.0.0.17/32 dev p1-route SRC 10.0.0.17 local
+Cached: 10.0.0.18/32 dev p1-route SRC 10.0.0.17
+])
+
+dnl Delete a route from the main table and check that OVS removes the route
+dnl from the cache.
+AT_CHECK([ip route del 10.0.0.18/32 dev p1-route])
+OVS_WAIT_UNTIL_EQUAL([ovs-appctl ovs/route/show | grep 'p1-route' | sort], [dnl
+Cached: 10.0.0.0/24 dev p1-route SRC 10.0.0.17
+Cached: 10.0.0.17/32 dev p1-route SRC 10.0.0.17 local])
+
+dnl Delete a route from a custom routing table and check that the cache
+dnl dosn't change.
+AT_CHECK([ip route del 10.0.0.19/32 dev p1-route table 42])
+dnl Give the main thread a chance to act.
+AT_CHECK([ovs-appctl revalidator/wait])
+dnl Check that the cache is still the same.
+AT_CHECK([ovs-appctl ovs/route/show | grep 'p1-route' | sort], [0], [dnl
+Cached: 10.0.0.0/24 dev p1-route SRC 10.0.0.17
+Cached: 10.0.0.17/32 dev p1-route SRC 10.0.0.17 local
+])
+
+dnl Delete ip address.
+AT_CHECK([ip addr del 10.0.0.17/24 dev p1-route], [0], [stdout])
+dnl Check that routes were removed from OVS.
+OVS_WAIT_UNTIL([test $(ovs-appctl ovs/route/show | grep -c 'p1-route') -eq 0 ])
+
+OVS_TRAFFIC_VSWITCHD_STOP
+AT_CLEANUP
--
2.43.0
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