Re: [RFC PATCH v2] Initial Implementation For Jumbo Frames Test Suite

[Stephen Hemminger <stephen@networkplumber.org>]

On Fri, 21 Jun 2024 17:19:21 -0400
Nicholas Pratte <npratte@iol.unh.edu> wrote:

> +The test suite ensures the consistency of jumbo frames transmission within
> +Poll Mode Drivers using a series of individual test cases. If a Poll Mode
> +Driver receives a packet that is greater than its assigned MTU length, then
> +that packet will be dropped, and thus not received. Likewise, if a Poll Mode Driver
> +receives a packet that is less than or equal to a its designated MTU length, then the
> +packet should be transmitted by the Poll Mode Driver, completing a cycle within the
> +testbed and getting received by the traffic generator. Thus, the following test suite
> +evaluates the behavior within all possible edge cases, ensuring that a test Poll
> +Mode Driver strictly abides by the above implications.

There are some weird drivers where MRU and MTU are not the same thing.
I believe the e1000 HW only allowed setting buffer size to a power of 2.
At least on Linux, that meant that with 1500 byte MTU it would receive an up to 2K packet.
This never caused any problem for upper layer protocols, just some picky conformance tests.