ofp_mtu_set() function doesn't set interface MTU value properly

[ViktorTikkanen]

There are currently some problems in ofp_mtu_set() function:

1. Used odp_pktio_mtu() function is deprecated in the latest ODP API (new ones are odp_pktin_maxlen() and odp_pktout_maxlen()).

2. The value returned by odp_pktio_mtu() is (should be) the link frame size (which includes ethernet header). ofp_mtu_set() assumes wrongly that this value doesn't include ethernet header size. As a result fragmentation doesn't work in OFP with linux-generic ODP for DPDK interfaces.

3. The overall logic of MTU size checking/setting is not consistent inside ofp_mtu_set() (uses e.g. hardcoded value 9000).

[sovu]

TSC meeting 16.01.18

Janne comment:
minimum fix is to report 1500 by default
advanced: configurable with card capability
ultimate: configure per interface

[sovu]

TSC meeting 23.01.2018

There is a patch that resolves the minimal requirement above. Sorin has reviewed the patch. This can be pushed after we update the Travis to support latest tagged ODP master. --enable-deprecate-option.

There are ongoing discussions about configurable MTU per interface.

[sovu]

Only the minimum fix was submitted. We should keep this issue open to not loose sight of "ultimate" functionality goal.

[sovu]

TSC meeting 30.01.2018

We agree to use Jere proposal on the mailing list.