Merge branch 'TCP_INFO-RTO'

Merge branch 'TCP_INFO-RTO'

Aananth V says:

====================
tcp: new TCP_INFO stats for RTO events

The 2023 SIGCOMM paper "Improving Network Availability with Protective
ReRoute" has indicated Linux TCP's RTO-triggered txhash rehashing can
effectively reduce application disruption during outages. To better
measure the efficacy of this feature, this patch set adds three more
detailed stats during RTO recovery and exports via TCP_INFO.
Applications and monitoring systems can leverage this data to measure
the network path diversity and end-to-end repair latency during network
outages to improve their network infrastructure.

Patch 1 fixes a bug in TFO SYNACK that we encountered while testing
these new metrics.

Patch 2 adds the new metrics to tcp_sock and tcp_info.

v2: Addressed feedback from a check bot in patch 2 by removing the
inline keyword from the tcp_update_rto_time and tcp_update_rto_stats
functions. Changed a comment in include/net/tcp.h to fit under 80 words.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>