Packets are gso'ed only if their size match the mtu

[pjalaber]

Problem:

At first this test prevents building a gso train of packets if they are smaller than the mtu:

s2n-quic/quic/s2n-quic-transport/src/connection/transmission.rs

Line 98 in f5d9d74

segment_len

A similar issue has been recently fixed in Quinn:
quinn-rs/quinn#1837

Solution:

Lower the restriction on the mtu size and try to build a train of packets of smaller size.

Requirements / Acceptance Criteria:

Out of scope:

[camshaft]

Generally packets are assembled to fit the max datagram size. So this logic would only apply to the final tail packet. Also keep in mind we have a burst rate of 10 packets so GSO should usually be under 15,000 bytes on public Internet links.

As such, I'm inclined to say it's fine as is.

[WesleyRosenblum]

Closing, feel free to reopen if you have further questions