diff --git a/FAQ.md b/FAQ.md
index 5a09d1344..01e2648c1 100644
--- a/FAQ.md
+++ b/FAQ.md
@@ -1065,6 +1065,33 @@ A: This is expected behavior on virtual switches. RFC2544 tests were
ovs-vsctl --no-wait set Open_vSwitch . other_config:max-idle=50000
+### Q: How can I configure the bridge internal interface MTU? Why does Open
+ vSwitch keep changing internal ports MTU?
+
+A: By default Open vSwitch overrides the internal interfaces (e.g. br0) MTU.
+ If you have just an internal interface (e.g. br0) and a physical interface
+ (e.g. eth0), then every change in MTU to eth0 will be reflected to br0.
+ Any manual MTU configuration using `ip` or `ifconfig` on internal interfaces
+ is going to be overridden by Open vSwitch to match the current bridge
+ minimum.
+
+ Sometimes this behavior is not desirable, for example with tunnels. The
+ MTU of an internal interface can be explicitly set using the following
+ command:
+
+ ovs-vsctl set int br0 mtu_request=1450
+
+ After this, Open vSwitch will configure br0 MTU to 1450. Since this
+ setting is in the database it will be persistent (compared to what
+ happens with `ip` or `ifconfig`).
+
+ The MTU configuration can be removed to restore the default behavior with
+
+ ovs-vsctl set int br0 mtu_request=[]
+
+ The mtu_request column can be used to configure MTU even for physical
+ interfaces (e.g. eth0).
+
## QOS
### Q: Does OVS support Quality of Service (QoS)?
diff --git a/NEWS b/NEWS
index 143915136..8c78b3676 100644
--- a/NEWS
+++ b/NEWS
@@ -122,7 +122,7 @@ v2.6.0 - xx xxx xxxx
SHA-1 is no longer secure and some operating systems have started to
disable it in OpenSSL.
- Add 'mtu_request' column to the Interface table. It can be used to
- configure the MTU of non-internal ports.
+ configure the MTU of the ports.
v2.5.0 - 26 Feb 2016
diff --git a/lib/netdev-provider.h b/lib/netdev-provider.h
index cd04ae9e6..c8507a56b 100644
--- a/lib/netdev-provider.h
+++ b/lib/netdev-provider.h
@@ -63,6 +63,10 @@ struct netdev {
struct seq *reconfigure_seq;
uint64_t last_reconfigure_seq;
+ /* If this is 'true', the user explicitly specified an MTU for this
+ * netdev. Otherwise, Open vSwitch is allowed to override it. */
+ bool mtu_user_config;
+
/* The core netdev code initializes these at netdev construction and only
* provide read-only access to its client. Netdev implementations may
* modify them. */
diff --git a/lib/netdev.c b/lib/netdev.c
index 10f2d0f03..ddf2a34ac 100644
--- a/lib/netdev.c
+++ b/lib/netdev.c
@@ -877,6 +877,27 @@ netdev_set_mtu(struct netdev *netdev, int mtu)
return error;
}
+/* If 'user_config' is true, the user wants to control 'netdev''s MTU and we
+ * should not override it. If 'user_config' is false, we may adjust
+ * 'netdev''s MTU (e.g., if 'netdev' is internal). */
+void
+netdev_mtu_user_config(struct netdev *netdev, bool user_config)
+{
+ if (netdev->mtu_user_config != user_config) {
+ netdev_change_seq_changed(netdev);
+ netdev->mtu_user_config = user_config;
+ }
+}
+
+/* Returns 'true' if the user explicitly specified an MTU value for 'netdev'.
+ * Otherwise, returns 'false', in which case we are allowed to adjust the
+ * device MTU. */
+bool
+netdev_mtu_is_user_config(struct netdev *netdev)
+{
+ return netdev->mtu_user_config;
+}
+
/* Returns the ifindex of 'netdev', if successful, as a positive number. On
* failure, returns a negative errno value.
*
diff --git a/lib/netdev.h b/lib/netdev.h
index d8ec62798..634c665f3 100644
--- a/lib/netdev.h
+++ b/lib/netdev.h
@@ -133,6 +133,8 @@ const char *netdev_get_type(const struct netdev *);
const char *netdev_get_type_from_name(const char *);
int netdev_get_mtu(const struct netdev *, int *mtup);
int netdev_set_mtu(struct netdev *, int mtu);
+void netdev_mtu_user_config(struct netdev *, bool);
+bool netdev_mtu_is_user_config(struct netdev *);
int netdev_get_ifindex(const struct netdev *);
int netdev_set_tx_multiq(struct netdev *, unsigned int n_txq);
diff --git a/ofproto/ofproto.c b/ofproto/ofproto.c
index da7372de0..f813c0b1a 100644
--- a/ofproto/ofproto.c
+++ b/ofproto/ofproto.c
@@ -175,8 +175,8 @@ static void learned_cookies_flush(struct ofproto *, struct ovs_list *dead_cookie
/* ofport. */
static void ofport_destroy__(struct ofport *) OVS_EXCLUDED(ofproto_mutex);
static void ofport_destroy(struct ofport *, bool del);
-static inline bool ofport_is_internal(const struct ofproto *,
- const struct ofport *);
+static bool ofport_is_mtu_overridden(const struct ofproto *,
+ const struct ofport *);
static int update_port(struct ofproto *, const char *devname);
static int init_ports(struct ofproto *);
@@ -2416,12 +2416,12 @@ static void
ofport_remove(struct ofport *ofport)
{
struct ofproto *p = ofport->ofproto;
- bool is_internal = ofport_is_internal(p, ofport);
+ bool is_mtu_overridden = ofport_is_mtu_overridden(p, ofport);
connmgr_send_port_status(ofport->ofproto->connmgr, NULL, &ofport->pp,
OFPPR_DELETE);
ofport_destroy(ofport, true);
- if (!is_internal) {
+ if (!is_mtu_overridden) {
update_mtu_ofproto(p);
}
}
@@ -2701,14 +2701,23 @@ init_ports(struct ofproto *p)
return 0;
}
-static inline bool
+static bool
ofport_is_internal(const struct ofproto *p, const struct ofport *port)
{
return !strcmp(netdev_get_type(port->netdev),
ofproto_port_open_type(p->type, "internal"));
}
-/* Find the minimum MTU of all non-datapath devices attached to 'p'.
+/* If 'port' is internal and if the user didn't explicitly specify an mtu
+ * through the database, we have to override it. */
+static bool
+ofport_is_mtu_overridden(const struct ofproto *p, const struct ofport *port)
+{
+ return ofport_is_internal(p, port)
+ && !netdev_mtu_is_user_config(port->netdev);
+}
+
+/* Find the minimum MTU of all non-overridden devices attached to 'p'.
* Returns ETH_PAYLOAD_MAX or the minimum of the ports. */
static int
find_min_mtu(struct ofproto *p)
@@ -2720,9 +2729,8 @@ find_min_mtu(struct ofproto *p)
struct netdev *netdev = ofport->netdev;
int dev_mtu;
- /* Skip any internal ports, since that's what we're trying to
- * set. */
- if (ofport_is_internal(p, ofport)) {
+ /* Skip any overridden port, since that's what we're trying to set. */
+ if (ofport_is_mtu_overridden(p, ofport)) {
continue;
}
@@ -2737,8 +2745,8 @@ find_min_mtu(struct ofproto *p)
return mtu ? mtu: ETH_PAYLOAD_MAX;
}
-/* Update MTU of all datapath devices on 'p' to the minimum of the
- * non-datapath ports in event of 'port' added or changed. */
+/* Update MTU of all overridden devices on 'p' to the minimum of the
+ * non-overridden ports in event of 'port' added or changed. */
static void
update_mtu(struct ofproto *p, struct ofport *port)
{
@@ -2749,25 +2757,25 @@ update_mtu(struct ofproto *p, struct ofport *port)
port->mtu = 0;
return;
}
- if (ofport_is_internal(p, port)) {
+ if (ofport_is_mtu_overridden(p, port)) {
if (dev_mtu > p->min_mtu) {
- if (!netdev_set_mtu(port->netdev, p->min_mtu)) {
- dev_mtu = p->min_mtu;
- }
+ if (!netdev_set_mtu(port->netdev, p->min_mtu)) {
+ dev_mtu = p->min_mtu;
+ }
}
port->mtu = dev_mtu;
return;
}
port->mtu = dev_mtu;
- /* For non-internal port find new min mtu. */
+ /* For non-overridden port find new min mtu. */
+
update_mtu_ofproto(p);
}
static void
update_mtu_ofproto(struct ofproto *p)
{
- /* For non-internal port find new min mtu. */
struct ofport *ofport;
int old_min = p->min_mtu;
@@ -2779,7 +2787,7 @@ update_mtu_ofproto(struct ofproto *p)
HMAP_FOR_EACH (ofport, hmap_node, &p->ports) {
struct netdev *netdev = ofport->netdev;
- if (ofport_is_internal(p, ofport)) {
+ if (ofport_is_mtu_overridden(p, ofport)) {
if (!netdev_set_mtu(netdev, p->min_mtu)) {
ofport->mtu = p->min_mtu;
}
diff --git a/tests/ofproto-dpif.at b/tests/ofproto-dpif.at
index d7705da87..0295a99ef 100644
--- a/tests/ofproto-dpif.at
+++ b/tests/ofproto-dpif.at
@@ -8892,5 +8892,20 @@ AT_CHECK([ovs-vsctl add-port br0 p2 -- set int p2 type=dummy mtu_request=1600])
AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface p2 mtu=1600])
AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface br0 mtu=1600])
+# Explicitly set mtu_request on the internal interface. This should prevent
+# the MTU from being overriden.
+AT_CHECK([ovs-vsctl set int br0 mtu_request=1700])
+AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface br0 mtu=1700])
+
+# The new MTU on p2 should not affect br0.
+AT_CHECK([ovs-vsctl set int p2 mtu_request=1400])
+AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface p2 mtu=1400])
+AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface br0 mtu=1700])
+
+# Remove explicit mtu_request from br0. Now it should track the bridge
+# minimum again.
+AT_CHECK([ovs-vsctl set int br0 mtu_request=[[]]])
+AT_CHECK([ovs-vsctl --timeout=10 wait-until Interface br0 mtu=1400])
+
OVS_VSWITCHD_STOP
AT_CLEANUP
diff --git a/vswitchd/bridge.c b/vswitchd/bridge.c
index a7a12ecfe..61cb96633 100644
--- a/vswitchd/bridge.c
+++ b/vswitchd/bridge.c
@@ -722,20 +722,20 @@ add_ofp_port(ofp_port_t port, ofp_port_t *ports, size_t *n, size_t *allocated)
}
/* Configures the MTU of 'netdev' based on the "mtu_request" column
- * in 'iface_cfg'. 'br_type' must be the datapath_type of the bridge
- * which contains 'netdev'. */
+ * in 'iface_cfg'. */
static int
iface_set_netdev_mtu(const struct ovsrec_interface *iface_cfg,
- const char *br_type, struct netdev *netdev)
+ struct netdev *netdev)
{
- if (iface_cfg->n_mtu_request == 1
- && strcmp(netdev_get_type(netdev),
- ofproto_port_open_type(br_type, "internal"))) {
- /* Try to set the MTU to the requested value. This is not done
- * for internal interfaces, since their MTU is decided by the
- * ofproto module, based on other ports in the bridge. */
+ if (iface_cfg->n_mtu_request == 1) {
+ /* The user explicitly asked for this MTU. */
+ netdev_mtu_user_config(netdev, true);
+ /* Try to set the MTU to the requested value. */
return netdev_set_mtu(netdev, *iface_cfg->mtu_request);
}
+
+ /* The user didn't explicitly asked for any MTU. */
+ netdev_mtu_user_config(netdev, false);
return 0;
}
@@ -793,7 +793,7 @@ bridge_delete_or_reconfigure_ports(struct bridge *br)
goto delete;
}
- iface_set_netdev_mtu(iface->cfg, br->type, iface->netdev);
+ iface_set_netdev_mtu(iface->cfg, iface->netdev);
/* If the requested OpenFlow port for 'iface' changed, and it's not
* already the correct port, then we might want to temporarily delete
@@ -1736,7 +1736,7 @@ iface_do_create(const struct bridge *br,
goto error;
}
- iface_set_netdev_mtu(iface_cfg, br->type, netdev);
+ iface_set_netdev_mtu(iface_cfg, netdev);
*ofp_portp = iface_pick_ofport(iface_cfg);
error = ofproto_port_add(br->ofproto, netdev, ofp_portp);
diff --git a/vswitchd/vswitch.xml b/vswitchd/vswitch.xml
index 69b559202..f64c18acb 100644
--- a/vswitchd/vswitch.xml
+++ b/vswitchd/vswitch.xml
@@ -2388,14 +2388,16 @@
- A client may change a non-internal interface MTU by filling in
-
+
+ The currently configured MTU for the interface.
+
+
This column will be empty for an interface that does not
have an MTU as, for example, some kinds of tunnels do not.
@@ -2411,7 +2413,13 @@
type='{"type": "integer", "minInteger": 1}'>
Requested MTU (Maximum Transmission Unit) for the interface. A client
- can fill this column to change the MTU of a non-internal interface.
+ can fill this column to change the MTU of an interface.
+
+
+
+ If this is not set and if the interface has internal
+ type, Open vSwitch will change the MTU to match the minimum of the
+ other interfaces in the bridge.