Previously we had two maps keyed on a direction-specific tuple, with
distinct values containing the data (action) for that direction.
Values pointed at each other across maps to ensure they were removed
at the same time in the case of tuple overwrite, but LRU eviction
was per-map. So if LRU was turned on, it was possible for one
direction's data (action) to be evicted and leave the other direction
dangling.
NewFlow replaces the two direction-specific flow constructors, and
lookups return the direction-specific PacketAction directly.
Now the values in each map point to the same element, with data for both
directions in the element. A linked list also points to the elements to
implement LRU. The previous flowtrack.Cache is removed.
The single LRU structure will allow us to implement idle time expiration
by walking the list backward starting with the least recently used flow, and
stopping after a fixed number of flows, or at the first non-expired flow.
We add commented-out unused placeholder fields for tracking the
"last seen" timestamp, and an on-removal hook, to document the intent for
the follow-up expiry work.
Updates tailscale/corp#38630
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Introduce a datapathHandler that implements hooks that will
receive packets from the tstun.Wrapper. This commit does not wire
those up just yet.
Perform DNAT from Magic IP to Transit IP on outbound flows on clients,
and reverse SNAT in the reverse direction.
Perform DNAT from Transit IP to final destination IP on outbound flows
on connectors, and reverse SNAT in the reverse direction.
Introduce FlowTable to cache validated flows by 5-tuple for fast lookups
after the first packet.
Flow expiration is not covered, and is intended as future work before
the feature is officially released.
Fixestailscale/corp#34249Fixestailscale/corp#35995
Co-authored-by: Fran Bull <fran@tailscale.com>
Signed-off-by: Michael Ben-Ami <mzb@tailscale.com>
Michael Ben-Amiandmzbenami
