It was noticed (while proposing a starting point/patch for https://www.open-mesh.org/issues/365 ) that the auto-adjusting MTU handling in batman-adv looks rather odd.
* events for pre-MTU change and (post) MTU change were not triggered for an auto-adjust * user set (lower) MTUs were always overwritten when a hard-interface became active
Signed-off-by: Sven Eckelmann sven@narfation.org --- Sven Eckelmann (2): batman-adv: Trigger events for auto adjusted MTU batman-adv: Don't increase MTU when set by user
net/batman-adv/hard-interface.c | 14 +++++++++++++- net/batman-adv/soft-interface.c | 3 +++ net/batman-adv/types.h | 6 ++++++ 3 files changed, 22 insertions(+), 1 deletion(-) --- base-commit: 8924adbdf993cd0521f9d0024b43e3b23af5114f change-id: 20230719-mtu-e5ff71c6dd77
Best regards,
If an interface changes the MTU, it is expected that an NETDEV_PRECHANGEMTU and NETDEV_CHANGEMTU notification events is triggered. This worked fine for .ndo_change_mtu based changes because core networking code took care of it. But for auto-adjustments after hard-interfaces changes, these events were simply missing.
Due to this problem, non-batman-adv components weren't aware of MTU changes and thus couldn't perform their own tasks correctly.
Fixes: 8009e9f7ac4f ("set bat0 MTU according to the MTUs of the hard interfaces") Signed-off-by: Sven Eckelmann sven@narfation.org --- net/batman-adv/hard-interface.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index 41c1ad33..ae5762af 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -630,7 +630,7 @@ int batadv_hardif_min_mtu(struct net_device *soft_iface) */ void batadv_update_min_mtu(struct net_device *soft_iface) { - soft_iface->mtu = batadv_hardif_min_mtu(soft_iface); + dev_set_mtu(soft_iface, batadv_hardif_min_mtu(soft_iface));
/* Check if the local translate table should be cleaned up to match a * new (and smaller) MTU.
If the user set an MTU value, it usually means that there are special requirements for the MTU. But if an interface gots activated, the MTU was always recalculated and then the user set value was overwritten.
The only reason why this user set value has to be overwritten, is when the MTU has to be decreased because batman-adv is not able to transfer packets with the user specified size.
Fixes: 88861ea9acb7 ("[batman-adv] replacing if up/down timer with kernel notifications") Signed-off-by: Sven Eckelmann sven@narfation.org --- net/batman-adv/hard-interface.c | 14 +++++++++++++- net/batman-adv/soft-interface.c | 3 +++ net/batman-adv/types.h | 6 ++++++ 3 files changed, 22 insertions(+), 1 deletion(-)
diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c index ae5762af..24c9c0c3 100644 --- a/net/batman-adv/hard-interface.c +++ b/net/batman-adv/hard-interface.c @@ -630,7 +630,19 @@ int batadv_hardif_min_mtu(struct net_device *soft_iface) */ void batadv_update_min_mtu(struct net_device *soft_iface) { - dev_set_mtu(soft_iface, batadv_hardif_min_mtu(soft_iface)); + struct batadv_priv *bat_priv = netdev_priv(soft_iface); + int limit_mtu; + int mtu; + + mtu = batadv_hardif_min_mtu(soft_iface); + + if (bat_priv->mtu_set_by_user) + limit_mtu = bat_priv->mtu_set_by_user; + else + limit_mtu = ETH_DATA_LEN; + + mtu = min(mtu, limit_mtu); + dev_set_mtu(soft_iface, mtu);
/* Check if the local translate table should be cleaned up to match a * new (and smaller) MTU. diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c index d3fdf822..85d00dc9 100644 --- a/net/batman-adv/soft-interface.c +++ b/net/batman-adv/soft-interface.c @@ -153,11 +153,14 @@ 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) { + struct batadv_priv *bat_priv = netdev_priv(dev); + /* check ranges */ if (new_mtu < 68 || new_mtu > batadv_hardif_min_mtu(dev)) return -EINVAL;
dev->mtu = new_mtu; + bat_priv->mtu_set_by_user = new_mtu;
return 0; } diff --git a/net/batman-adv/types.h b/net/batman-adv/types.h index ca9449ec..cf1a0eaf 100644 --- a/net/batman-adv/types.h +++ b/net/batman-adv/types.h @@ -1546,6 +1546,12 @@ struct batadv_priv { /** @soft_iface: net device which holds this struct as private data */ struct net_device *soft_iface;
+ /** + * @mtu_set_by_user: MTU was set once by user + * protected by rtnl_lock + */ + int mtu_set_by_user; + /** * @bat_counters: mesh internal traffic statistic counters (see * batadv_counters)
b.a.t.m.a.n@lists.open-mesh.org
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Sven Eckelmann