On 2016/11/30 15:36, Nikita Yushchenko wrote: >> But I think it is not necessary since the driver don't support jumbo frame. > > Hardcoded 1522 raises two separate issues. > > (1) When DSA is in use, frames processed by FEC chip contain DSA tag and > thus can be larger than hardcoded limit of 1522. This issue is not > FEC-specific, any driver that hardcodes maximum frame size to 1522 (many > do) will have this issue if used with DSA. > > Clean solution for this must take into account that difference between > MTU and max frame size is no longer known at compile time. Actually this > is the case even without DSA, due to VLANs: max frame size is (MTU + 18) > without VLANs, but (MTU + 22) with VLANs. However currently drivers tend > to ignore this and hardcode 22. With DSA, 22 is not enough, need to add > switch-specific tag size to that. > > Not yet sure how to handle this. DSA-specific API to find out tag size > could be added, but generic solution should handle all cases of dynamic > difference between MTU and max frame size, not only DSA.
BTW I'm trying to introduce envelope frames to solve this kind of problems. http://marc.info/?t=147496691500005&r=1&w=2 http://marc.info/?t=147496691500003&r=1&w=2 http://marc.info/?t=147496691500002&r=1&w=2 http://marc.info/?t=147496691500004&r=1&w=2 http://marc.info/?t=147496691500001&r=1&w=2 It needs jumbo frame support of NICs though. Regards, Toshiaki Makita
