Messages in this thread | | | Date | Wed, 23 Feb 2022 08:03:42 -0800 | From | Jakub Kicinski <> | Subject | Re: [PATCH net] net: vlan: allow vlan device MTU change follow real device from smaller to bigger |
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On Wed, 23 Feb 2022 12:26:18 +0100 Guillaume Nault wrote: > Do you mean something like: > > ip link set dev eth0 vlan-mtu-policy <policy-name> > > that'd affect all existing (and future) vlans of eth0?
I meant
ip link set dev vlan0 mtu-policy blah
but also
ip link set dev bond0 mtu-policy blah
and
ip link set dev macsec0 mtu-policy blah2 ip link set dev vxlan0 mtu-policy blah2
etc.
> Then I think that for non-ethernet devices, we should reject this > option and skip it when dumping config. But yes, that's another > possibility. > > I personnaly don't really mind, as long as we keep a clear behaviour. > > What I'd really like to avoid is something like: > - By default it behaves this way. > - If you modified the MTU it behaves in another way > - But if you modified the MTU but later restored the > original MTU, then you're back to the default behaviour > (or not?), unless the MTU of the upper device was also > changed meanwhile, in which case ... to be continued ... > - BTW, you might not be able to tell how the VLAN's MTU is going to > behave by simply looking at its configuration, because that also > depends on past configurations. > - Well, and if your kernel is older than xxx, then you always get the > default behaviour. > - ... and we might modify the heuristics again in the future to > accomodate with situations or use cases we failed to consider.
To be honest I'm still not clear if this is a real problem. The patch does not specify what the use case is.
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