netinet6: In tcp_lro_rx_ipv6(), check for IPv6 flow ID.
Submitted by: Neel Chauhan <neel AT neelc DOT org>
nc on May 31 2020, 7:58 PM.Authored by
In RFC 6437 there is no rule, that flow labels are immutable for a given TCP session. It only notes in section 6.1, that changing the flow label within a TCP stream might be suspicious.
Given, that LRO handling is on the recipient end of the session -- there are no routing, forwarding or QoS behind this point -- the flow label is irrelevant by definition.
If I'm wrong, the change can be passed.
We don't throw away the packet. We just refuse to merge it with the packet in the LRO buffer. This causes us to send both packets up the stack separately, so that the flow label is properly preserved.