The following commit has been merged in the batadv/net-next branch: commit e189b7b3ce6f3091f33882f928558ab899b8ec83 Author: Sven Eckelmann sven@narfation.org Date: Thu Jul 27 10:13:43 2023 +0200

batman-adv: Check hardif MTU against runtime MTU

If the MTU of the soft/mesh interface was already reduced (enough), it is not necessary to print a warning about a hard interface not having a MTU to transport ethernet payloads of 1500 bytes.

Signed-off-by: Sven Eckelmann sven@narfation.org Signed-off-by: Simon Wunderlich sw@simonwunderlich.de

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 41c1ad33d009..5a4ff9a81e74 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -9,6 +9,7 @@

#include <linux/atomic.h> #include <linux/byteorder/generic.h> +#include <linux/compiler.h> #include <linux/container_of.h> #include <linux/errno.h> #include <linux/gfp.h> @@ -699,9 +700,14 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface, struct batadv_priv *bat_priv; __be16 ethertype = htons(ETH_P_BATMAN); int max_header_len = batadv_max_header_len(); + unsigned int required_mtu; + unsigned int hardif_mtu; int ret;

- if (hard_iface->net_dev->mtu < ETH_MIN_MTU + max_header_len) + hardif_mtu = READ_ONCE(hard_iface->net_dev->mtu); + required_mtu = READ_ONCE(soft_iface->mtu) + max_header_len; + + if (hardif_mtu < ETH_MIN_MTU + max_header_len) return -EINVAL;

if (hard_iface->if_status != BATADV_IF_NOT_IN_USE) @@ -734,18 +740,18 @@ int batadv_hardif_enable_interface(struct batadv_hard_iface *hard_iface, hard_iface->net_dev->name);

if (atomic_read(&bat_priv->fragmentation) && - hard_iface->net_dev->mtu < ETH_DATA_LEN + max_header_len) + hardif_mtu < required_mtu) batadv_info(hard_iface->soft_iface, "The MTU of interface %s is too small (%i) to handle the transport of batman-adv packets. Packets going over this interface will be fragmented on layer2 which could impact the performance. Setting the MTU to %i would solve the problem.\n", - hard_iface->net_dev->name, hard_iface->net_dev->mtu, - ETH_DATA_LEN + max_header_len); + hard_iface->net_dev->name, hardif_mtu, + required_mtu);

if (!atomic_read(&bat_priv->fragmentation) && - hard_iface->net_dev->mtu < ETH_DATA_LEN + max_header_len) + hardif_mtu < required_mtu) batadv_info(hard_iface->soft_iface, "The MTU of interface %s is too small (%i) to handle the transport of batman-adv packets. If you experience problems getting traffic through try increasing the MTU to %i.\n", - hard_iface->net_dev->name, hard_iface->net_dev->mtu, - ETH_DATA_LEN + max_header_len); + hard_iface->net_dev->name, hardif_mtu, + required_mtu);

if (batadv_hardif_is_iface_up(hard_iface)) batadv_hardif_activate_interface(hard_iface);