The maximum MTU is defined via the slave devices of an batman-adv interface. Thus it is not possible to calculate the max_mtu during the creation of the batman-adv device when no slave devices are attached. Doing so would for example break non-fragmentation setups which then (incorrectly) allow an MTU of 1500 even when underlying device cannot transport 1500 bytes + batman-adv headers.
Checking the dynamically calculated max_mtu via the minimum of the slave devices MTU during .ndo_change_mtu is also used by the bridge interface.
Cc: Jarod Wilson jarod@redhat.com Fixes: b3e3893e1253 ("net: use core MTU range checking in misc drivers") Signed-off-by: Sven Eckelmann sven@narfation.org --- Original patch + my comment: https://patchwork.ozlabs.org/patch/684722/
I just got informed about this patch when it was already applied in net-next. So I can only ask for an revet of the batman-adv parts
net/batman-adv/soft-interface.c | 13 ++++++++++++- 1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index 112679d..49e16b6 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -158,6 +158,17 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p) return 0; }
+static int batadv_interface_change_mtu(struct net_device *dev, int new_mtu) +{ + /* check ranges */ + if ((new_mtu < 68) || (new_mtu > batadv_hardif_min_mtu(dev))) + return -EINVAL; + + dev->mtu = new_mtu; + + return 0; +} + /** * batadv_interface_set_rx_mode - set the rx mode of a device * @dev: registered network device to modify @@ -909,6 +920,7 @@ static const struct net_device_ops batadv_netdev_ops = { .ndo_vlan_rx_add_vid = batadv_interface_add_vid, .ndo_vlan_rx_kill_vid = batadv_interface_kill_vid, .ndo_set_mac_address = batadv_interface_set_mac_addr, + .ndo_change_mtu = batadv_interface_change_mtu, .ndo_set_rx_mode = batadv_interface_set_rx_mode, .ndo_start_xmit = batadv_interface_tx, .ndo_validate_addr = eth_validate_addr, @@ -975,7 +987,6 @@ struct net_device *batadv_softif_create(struct net *net, const char *name) dev_net_set(soft_iface, net);
soft_iface->rtnl_link_ops = &batadv_link_ops; - soft_iface->max_mtu = batadv_hardif_min_mtu(soft_iface);
ret = register_netdevice(soft_iface); if (ret < 0) {