From f40aa23339e2d06b1a8daaece5a511bb1c4f704c Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Fri, 30 Mar 2018 13:46:18 +0300 Subject: [PATCH 1/2] net: bridge: set min MTU on port events and allow user to set max Recently the bridge was changed to automatically set maximum MTU on port events (add/del/changemtu) when vlan filtering is enabled, but that actually changes behaviour in a way which breaks some setups and can lead to packet drops. In order to still allow that maximum to be set while being compatible, we add the ability for the user to tune the bridge MTU up to the maximum when vlan filtering is enabled, but that has to be done explicitly and all port events (add/del/changemtu) lead to resetting that MTU to the minimum as before. Suggested-by: Roopa Prabhu Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/bridge/br.c | 2 +- net/bridge/br_device.c | 3 ++- net/bridge/br_if.c | 43 ++++++++++++++--------------------------- net/bridge/br_private.h | 2 +- 4 files changed, 18 insertions(+), 32 deletions(-) diff --git a/net/bridge/br.c b/net/bridge/br.c index 26e1616b2c905..565ff055813b3 100644 --- a/net/bridge/br.c +++ b/net/bridge/br.c @@ -52,7 +52,7 @@ static int br_device_event(struct notifier_block *unused, unsigned long event, v switch (event) { case NETDEV_CHANGEMTU: - dev_set_mtu(br->dev, br_mtu(br)); + dev_set_mtu(br->dev, br_mtu(br, false)); break; case NETDEV_CHANGEADDR: diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index 278fc999d3550..edb9967eb165c 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -224,7 +224,8 @@ static void br_get_stats64(struct net_device *dev, static int br_change_mtu(struct net_device *dev, int new_mtu) { struct net_bridge *br = netdev_priv(dev); - if (new_mtu > br_mtu(br)) + + if (new_mtu > br_mtu(br, br_vlan_enabled(dev))) return -EINVAL; dev->mtu = new_mtu; diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index 87b2afd455c7f..7d5dc5a910840 100644 --- a/net/bridge/br_if.c +++ b/net/bridge/br_if.c @@ -424,41 +424,26 @@ int br_del_bridge(struct net *net, const char *name) return ret; } -static bool min_mtu(int a, int b) -{ - return a < b ? 1 : 0; -} - -static bool max_mtu(int a, int b) -{ - return a > b ? 1 : 0; -} - -/* MTU of the bridge pseudo-device: ETH_DATA_LEN or the minimum of the ports */ -static int __br_mtu(const struct net_bridge *br, bool (compare_fn)(int, int)) +/* MTU of the bridge pseudo-device: ETH_DATA_LEN if there are no ports, the + * minimum of the ports if @max is false or the maximum if it's true + */ +int br_mtu(const struct net_bridge *br, bool max) { const struct net_bridge_port *p; - int mtu = 0; + int ret_mtu = 0; ASSERT_RTNL(); - if (list_empty(&br->port_list)) - mtu = ETH_DATA_LEN; - else { - list_for_each_entry(p, &br->port_list, list) { - if (!mtu || compare_fn(p->dev->mtu, mtu)) - mtu = p->dev->mtu; + list_for_each_entry(p, &br->port_list, list) { + if (!max) { + if (!ret_mtu || ret_mtu > p->dev->mtu) + ret_mtu = p->dev->mtu; + } else if (p->dev->mtu > ret_mtu) { + ret_mtu = p->dev->mtu; } } - return mtu; -} -int br_mtu(const struct net_bridge *br) -{ - if (br_vlan_enabled(br->dev)) - return __br_mtu(br, max_mtu); - else - return __br_mtu(br, min_mtu); + return ret_mtu ? ret_mtu : ETH_DATA_LEN; } static void br_set_gso_limits(struct net_bridge *br) @@ -612,7 +597,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev, if (changed_addr) call_netdevice_notifiers(NETDEV_CHANGEADDR, br->dev); - dev_set_mtu(br->dev, br_mtu(br)); + dev_set_mtu(br->dev, br_mtu(br, false)); br_set_gso_limits(br); kobject_uevent(&p->kobj, KOBJ_ADD); @@ -659,7 +644,7 @@ int br_del_if(struct net_bridge *br, struct net_device *dev) */ del_nbp(p); - dev_set_mtu(br->dev, br_mtu(br)); + dev_set_mtu(br->dev, br_mtu(br, false)); br_set_gso_limits(br); spin_lock_bh(&br->lock); diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 048d5b51813ba..586f84b9670d9 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -578,7 +578,7 @@ int br_del_bridge(struct net *net, const char *name); int br_add_if(struct net_bridge *br, struct net_device *dev, struct netlink_ext_ack *extack); int br_del_if(struct net_bridge *br, struct net_device *dev); -int br_mtu(const struct net_bridge *br); +int br_mtu(const struct net_bridge *br, bool max); netdev_features_t br_features_recompute(struct net_bridge *br, netdev_features_t features); void br_port_flags_change(struct net_bridge_port *port, unsigned long mask); From 804b854d374e39f5f8bff9638fd274b9a9ca7d33 Mon Sep 17 00:00:00 2001 From: Nikolay Aleksandrov Date: Fri, 30 Mar 2018 13:46:19 +0300 Subject: [PATCH 2/2] net: bridge: disable bridge MTU auto tuning if it was set manually As Roopa noted today the biggest source of problems when configuring bridge and ports is that the bridge MTU keeps changing automatically on port events (add/del/changemtu). That leads to inconsistent behaviour and network config software needs to chase the MTU and fix it on each such event. Let's improve on that situation and allow for the user to set any MTU within ETH_MIN/MAX limits, but once manually configured it is the user's responsibility to keep it correct afterwards. In case the MTU isn't manually set - the behaviour reverts to the previous and the bridge follows the minimum MTU. Signed-off-by: Nikolay Aleksandrov Signed-off-by: David S. Miller --- net/bridge/br.c | 2 +- net/bridge/br_device.c | 5 ++--- net/bridge/br_if.c | 36 +++++++++++++++++++++--------------- net/bridge/br_private.h | 3 ++- 4 files changed, 26 insertions(+), 20 deletions(-) diff --git a/net/bridge/br.c b/net/bridge/br.c index 565ff055813b3..671d13c10f6f4 100644 --- a/net/bridge/br.c +++ b/net/bridge/br.c @@ -52,7 +52,7 @@ static int br_device_event(struct notifier_block *unused, unsigned long event, v switch (event) { case NETDEV_CHANGEMTU: - dev_set_mtu(br->dev, br_mtu(br, false)); + br_mtu_auto_adjust(br); break; case NETDEV_CHANGEADDR: diff --git a/net/bridge/br_device.c b/net/bridge/br_device.c index edb9967eb165c..e682a668ce57c 100644 --- a/net/bridge/br_device.c +++ b/net/bridge/br_device.c @@ -225,11 +225,10 @@ static int br_change_mtu(struct net_device *dev, int new_mtu) { struct net_bridge *br = netdev_priv(dev); - if (new_mtu > br_mtu(br, br_vlan_enabled(dev))) - return -EINVAL; - dev->mtu = new_mtu; + /* this flag will be cleared if the MTU was automatically adjusted */ + br->mtu_set_by_user = true; #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) /* remember the MTU in the rtable for PMTU */ dst_metric_set(&br->fake_rtable.dst, RTAX_MTU, new_mtu); diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c index 7d5dc5a910840..82c1a6f430b37 100644 --- a/net/bridge/br_if.c +++ b/net/bridge/br_if.c @@ -424,28 +424,34 @@ int br_del_bridge(struct net *net, const char *name) return ret; } -/* MTU of the bridge pseudo-device: ETH_DATA_LEN if there are no ports, the - * minimum of the ports if @max is false or the maximum if it's true - */ -int br_mtu(const struct net_bridge *br, bool max) +/* MTU of the bridge pseudo-device: ETH_DATA_LEN or the minimum of the ports */ +static int br_mtu_min(const struct net_bridge *br) { const struct net_bridge_port *p; int ret_mtu = 0; - ASSERT_RTNL(); - - list_for_each_entry(p, &br->port_list, list) { - if (!max) { - if (!ret_mtu || ret_mtu > p->dev->mtu) - ret_mtu = p->dev->mtu; - } else if (p->dev->mtu > ret_mtu) { + list_for_each_entry(p, &br->port_list, list) + if (!ret_mtu || ret_mtu > p->dev->mtu) ret_mtu = p->dev->mtu; - } - } return ret_mtu ? ret_mtu : ETH_DATA_LEN; } +void br_mtu_auto_adjust(struct net_bridge *br) +{ + ASSERT_RTNL(); + + /* if the bridge MTU was manually configured don't mess with it */ + if (br->mtu_set_by_user) + return; + + /* change to the minimum MTU and clear the flag which was set by + * the bridge ndo_change_mtu callback + */ + dev_set_mtu(br->dev, br_mtu_min(br)); + br->mtu_set_by_user = false; +} + static void br_set_gso_limits(struct net_bridge *br) { unsigned int gso_max_size = GSO_MAX_SIZE; @@ -597,7 +603,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev, if (changed_addr) call_netdevice_notifiers(NETDEV_CHANGEADDR, br->dev); - dev_set_mtu(br->dev, br_mtu(br, false)); + br_mtu_auto_adjust(br); br_set_gso_limits(br); kobject_uevent(&p->kobj, KOBJ_ADD); @@ -644,7 +650,7 @@ int br_del_if(struct net_bridge *br, struct net_device *dev) */ del_nbp(p); - dev_set_mtu(br->dev, br_mtu(br, false)); + br_mtu_auto_adjust(br); br_set_gso_limits(br); spin_lock_bh(&br->lock); diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h index 586f84b9670d9..a7cb3ece50310 100644 --- a/net/bridge/br_private.h +++ b/net/bridge/br_private.h @@ -410,6 +410,7 @@ struct net_bridge { int offload_fwd_mark; #endif bool neigh_suppress_enabled; + bool mtu_set_by_user; struct hlist_head fdb_list; }; @@ -578,7 +579,7 @@ int br_del_bridge(struct net *net, const char *name); int br_add_if(struct net_bridge *br, struct net_device *dev, struct netlink_ext_ack *extack); int br_del_if(struct net_bridge *br, struct net_device *dev); -int br_mtu(const struct net_bridge *br, bool max); +void br_mtu_auto_adjust(struct net_bridge *br); netdev_features_t br_features_recompute(struct net_bridge *br, netdev_features_t features); void br_port_flags_change(struct net_bridge_port *port, unsigned long mask);