There are from time to time discussions about supporting jumbo frames with batman-adv. While the changes were known since a longe time [1], no actual tests were performed and no actual reviews were gathered.
Maybe some more interest can be stirred up by this RFC and some Tested-by/Reviewed-by [2] can be collected - or some fixes.
[1] https://www.open-mesh.org/issues/365 [2] https://www.kernel.org/doc/html/v6.4/process/submitting-patches.html#using-r...
Signed-off-by: Sven Eckelmann sven@narfation.org --- Sven Eckelmann (3): batman-adv: Avoid magic value for minimum MTU batman-adv: Check hardif MTU against runtime MTU batman-adv: Add support for jumbo frames
net/batman-adv/hard-interface.c | 24 ++++++++++++++---------- net/batman-adv/main.h | 2 ++ net/batman-adv/soft-interface.c | 5 +++-- 3 files changed, 19 insertions(+), 12 deletions(-) --- base-commit: f779cdaf7782ee765dbddd31f6d9a89abf0c52f9 change-id: 20230727-jumbo-mtu-13d736059c84
Best regards,
The header linux/if_ether.h already defines a constant for the minimum MTU. So simply use it instead of having a magic constant in the code.
Signed-off-by: Sven Eckelmann sven@narfation.org --- net/batman-adv/soft-interface.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index d3fdf822..f7947fad 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -154,7 +154,7 @@ static int batadv_interface_set_mac_addr(struct net_device *dev, void *p) 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)) + if (new_mtu < ETH_MIN_MTU || new_mtu > batadv_hardif_min_mtu(dev)) return -EINVAL;
dev->mtu = new_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 --- net/batman-adv/hard-interface.c | 20 +++++++++++++------- 1 file changed, 13 insertions(+), 7 deletions(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 41c1ad33..5a4ff9a8 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);
Since batman-adv is not actually depending on hardware capabilities, it has no limit on the MTU. Only the lower hard interfaces can limit it. In case these have an high enough MTU or fragmentation is enabled, a higher MTU than 1500 can be enabled.
Signed-off-by: Sven Eckelmann sven@narfation.org --- net/batman-adv/hard-interface.c | 4 +--- net/batman-adv/main.h | 2 ++ net/batman-adv/soft-interface.c | 3 ++- 3 files changed, 5 insertions(+), 4 deletions(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 5a4ff9a8..4fbb6339 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -618,10 +618,8 @@ int batadv_hardif_min_mtu(struct net_device *soft_iface)
/* the real soft-interface MTU is computed by removing the payload * overhead from the maximum amount of bytes that was just computed. - * - * However batman-adv does not support MTUs bigger than ETH_DATA_LEN */ - return min_t(int, min_mtu - batadv_max_header_len(), ETH_DATA_LEN); + return min_t(int, min_mtu - batadv_max_header_len(), BATADV_MAX_MTU); }
/** diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h index e0d53273..4dc81ddb 100644 --- a/net/batman-adv/main.h +++ b/net/batman-adv/main.h @@ -22,6 +22,8 @@ #define BATADV_THROUGHPUT_MAX_VALUE 0xFFFFFFFF #define BATADV_JITTER 20
+#define BATADV_MAX_MTU (ETH_MAX_MTU - batadv_max_header_len()) + /* Time To Live of broadcast messages */ #define BATADV_TTL 50
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index f7947fad..13d5f993 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -769,7 +769,7 @@ static int batadv_softif_init_late(struct net_device *dev) atomic_set(&bat_priv->log_level, 0); #endif atomic_set(&bat_priv->fragmentation, 1); - atomic_set(&bat_priv->packet_size_max, ETH_DATA_LEN); + atomic_set(&bat_priv->packet_size_max, BATADV_MAX_MTU); atomic_set(&bat_priv->bcast_queue_left, BATADV_BCAST_QUEUE_LEN); atomic_set(&bat_priv->batman_queue_left, BATADV_BATMAN_QUEUE_LEN);
@@ -1009,6 +1009,7 @@ static void batadv_softif_init_early(struct net_device *dev) * have not been initialized yet */ dev->mtu = ETH_DATA_LEN; + dev->max_mtu = BATADV_MAX_MTU;
/* generate random address */ eth_hw_addr_random(dev);
b.a.t.m.a.n@lists.open-mesh.org
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Sven Eckelmann