Commit Graph

253 Commits

Author SHA1 Message Date
Brad Fitzpatrick
7a62dddeac net/netcheck, wgengine/magicsock: make netmon.Monitor required
This has been a TODO for ages. Time to do it.

The goal is to move more network state accessors to netmon.Monitor
where they can be cheaper/cached.

Updates tailscale/corp#10910
Updates tailscale/corp#18960
Updates #7967
Updates #3299

Change-Id: I60fc6508cd2d8d079260bda371fc08b6318bcaf1
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-26 20:23:43 -07:00
Brad Fitzpatrick
6d69fc137f ipn/{ipnlocal,localapi},wgengine{,/magicsock}: plumb health.Tracker
Down to 25 health.Global users. After this remains controlclient &
net/dns & wgengine/router.

Updates #11874
Updates #4136

Change-Id: I6dd1856e3d9bf523bdd44b60fb3b8f7501d5dc0d
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-26 09:43:28 -07:00
Brad Fitzpatrick
ebc552d2e0 health: add Tracker type, in prep for removing global variables
This moves most of the health package global variables to a new
`health.Tracker` type.

But then rather than plumbing the Tracker in tsd.System everywhere,
this only goes halfway and makes one new global Tracker
(`health.Global`) that all the existing callers now use.

A future change will eliminate that global.

Updates #11874
Updates #4136

Change-Id: I6ee27e0b2e35f68cb38fecdb3b2dc4c3f2e09d68
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-25 13:46:22 -07:00
Brad Fitzpatrick
03d5d1f0f9 wgengine/magicsock: disable portmapper in tunchan-faked tests
Most of the magicsock tests fake the network, simulating packets going
out and coming in. There's no reason to actually hit your router to do
UPnP/NAT-PMP/PCP during in tests. But while debugging thousands of
iterations of tests to deflake some things, I saw it slamming my
router. This stops that.

Updates #11762

Change-Id: I59b9f48f8f5aff1fa16b4935753d786342e87744
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-17 21:47:38 -07:00
Brad Fitzpatrick
7c1d6e35a5 all: use Go 1.22 range-over-int
Updates #11058

Change-Id: I35e7ef9b90e83cac04ca93fd964ad00ed5b48430
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-16 15:32:38 -07:00
Brad Fitzpatrick
0fba9e7570 cmd/tailscale/cli: prevent concurrent Start calls in 'up'
Seems to deflake tstest/integration tests. I can't reproduce it
anymore on one of my VMs that was consistently flaking after a dozen
runs before. Now I can run hundreds of times.

Updates #11649
Fixes #7036

Change-Id: I2f7d4ae97500d507bdd78af9e92cd1242e8e44b8
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2024-04-16 10:03:53 -07:00
Charlotte Brandhorst-Satzkorn
449f46c207
wgengine/magicsock: rebind/restun if a syscall.EPERM error is returned (#11711)
We have seen in macOS client logs that the "operation not permitted", a
syscall.EPERM error, is being returned when traffic is attempted to be
sent. This may be caused by security software on the client.

This change will perform a rebind and restun if we receive a
syscall.EPERM error on clients running darwin. Rebinds will only be
called if we haven't performed one specifically for an EPERM error in
the past 5 seconds.

Updates #11710

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>
2024-04-15 13:57:55 -07:00
Andrew Dunham
f072d017bd wgengine/magicsock: don't change DERP home when not connected to control
This pretty much always results in an outage because peers won't
discover our new home region and thus won't be able to establish
connectivity.

Updates tailscale/corp#18095

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Ic0d09133f198b528dd40c6383b16d7663d9d37a7
2024-03-08 14:15:13 -05:00
Andrew Dunham
4338db28f7 wgengine/magicsock: prefer link-local addresses to private ones
Since link-local addresses are definitionally more likely to be a direct
(lower-latency, more reliable) connection than a non-link-local private
address, give those a bit of a boost when selecting endpoints.

Updates #8097

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I93fdeb07de55ba39ba5fcee0834b579ca05c2a4e
2024-03-05 20:32:45 -05:00
Jordan Whited
8b47322acc
wgengine/magicsock: implement probing of UDP path lifetime (#10844)
This commit implements probing of UDP path lifetime on the tail end of
an active direct connection. Probing configuration has two parts -
Cliffs, which are various timeout cliffs of interest, and
CycleCanStartEvery, which limits how often a probing cycle can start,
per-endpoint. Initially a statically defined default configuration will
be used. The default configuration has cliffs of 10s, 30s, and 60s,
with a CycleCanStartEvery of 24h. Probing results are communicated via
clientmetric counters. Probing is off by default, and can be enabled
via control knob. Probing is purely informational and does not yet
drive any magicsock behaviors.

Updates #540

Signed-off-by: Jordan Whited <jordan@tailscale.com>
2024-01-23 09:37:32 -08:00
Maisem Ali
5297bd2cff cmd/tailscaled,net/tstun: fix data race on start-up in TUN mode
Fixes #7894

Change-Id: Ice3f8019405714dd69d02bc07694f3872bb598b8

Co-authored-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Signed-off-by: Maisem Ali <maisem@tailscale.com>
2023-10-14 08:54:30 -07:00
Val
893bdd729c disco,net/tstun,wgengine/magicsock: probe peer MTU
Automatically probe the path MTU to a peer when peer MTU is enabled, but do not
use the MTU information for anything yet.

Updates #311

Signed-off-by: Val <valerie@tailscale.com>
2023-10-09 01:57:12 -07:00
Brad Fitzpatrick
f991c8a61f tstest: make ResourceCheck panic on parallel tests
To find potential flakes earlier.

Updates #deflake-effort

Change-Id: I52add6111d660821c3a23d4b1dd032821344bc48
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-10-06 19:12:34 -07:00
Val
4130851f12 wgengine/magicsock: probe but don't use path MTU from CLI ping
When sending a CLI ping with a specific size, continue to probe all possible UDP
paths to the peer until we find one with a large enough MTU to accommodate the
ping. Record any peer path MTU information we discover (but don't use it for
anything other than CLI pings).

Updates #311

Signed-off-by: Val <valerie@tailscale.com>
2023-10-02 03:52:02 -07:00
Val
67926ede39 wgengine/magicsock: add MTU to addrLatency and rename to addrQuality
Add a field to record the wire MTU of the path to this address to the
addrLatency struct and rename it addrQuality.

Updates #311

Signed-off-by: Val <valerie@tailscale.com>
2023-10-02 03:52:02 -07:00
Brad Fitzpatrick
425cf9aa9d tailcfg, all: use []netip.AddrPort instead of []string for Endpoints
It's JSON wire compatible.

Updates #cleanup

Change-Id: Ifa5c17768fec35b305b06d75eb5f0611c8a135a6
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-10-01 18:23:02 -07:00
Brad Fitzpatrick
0d991249e1 types/netmap: remove NetworkMap.{Addresses,MachineStatus}
And convert all callers over to the methods that check SelfNode.

Now we don't have multiple ways to express things in tests (setting
fields on SelfNode vs NetworkMap, sometimes inconsistently) and don't
have multiple ways to check those two fields (often only checking one
or the other).

Updates #9443

Change-Id: I2d7ba1cf6556142d219fae2be6f484f528756e3c
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-09-18 17:08:11 +01:00
Brad Fitzpatrick
ff6fadddb6 wgengine/magicsock: stop retaining *netmap.NetworkMap
We're trying to start using that monster type less and eventually get
rid of it.

Updates #1909

Change-Id: I8e1e725bce5324fb820a9be6c7952767863e6542
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-09-11 20:07:30 -07:00
Brad Fitzpatrick
d050700a3b wgengine/magicsock: make peerMap also keyed by NodeID
In prep for incremental netmap update plumbing (#1909), make peerMap
also keyed by NodeID, as all the netmap node mutations passed around
later will be keyed by NodeID.

In the process, also:

* add envknob.InDevMode, as a signal that we can panic more aggressively
  in unexpected cases.
* pull two moderately large blocks of code in Conn.SetNetworkMap out
  into their own methods
* convert a few more sets from maps to set.Set

Updates #1909

Change-Id: I7acdd64452ba58e9d554140ee7a8760f9043f961
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-09-11 12:43:47 -07:00
Brad Fitzpatrick
dc7aa98b76 all: use set.Set consistently instead of map[T]struct{}
I didn't clean up the more idiomatic map[T]bool with true values, at
least yet.  I just converted the relatively awkward struct{}-valued
maps.

Updates #cleanup

Change-Id: I758abebd2bb1f64bc7a9d0f25c32298f4679c14f
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-09-09 10:59:19 -07:00
Brad Fitzpatrick
ea4425d8a9 ipn/ipnlocal, wgengine/magicsock: move UpdateStatus stuff around
Upcoming work on incremental netmap change handling will require some
replumbing of which subsystems get notified about what. Done naively,
it could break "tailscale status --json" visibility later. To make sure
I understood the flow of all the updates I was rereading the status code
and realized parts of ipnstate.Status were being populated by the wrong
subsystems.

The engine (wireguard) and magicsock (data plane, NAT traveral) should
only populate the stuff that they uniquely know. The WireGuard bits
were fine but magicsock was populating stuff stuff that LocalBackend
could've better handled, so move it there.

Updates #1909

Change-Id: I6d1b95d19a2d1b70fbb3c875fac8ea1e169e8cb0
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-08-23 13:35:47 -07:00
James Tucker
e1c7e9b736 wgengine/magicsock: improve endpoint selection for WireGuard peers with rx time
If we don't have the ICMP hint available, such as on Android, we can use
the signal of rx traffic to bias toward a particular endpoint.

We don't want to stick to a particular endpoint for a very long time
without any signals, so the sticky time is reduced to 1 second, which is
large enough to avoid excessive packet reordering in the common case,
but should be small enough that either rx provides a strong signal, or
we rotate in a user-interactive schedule to another endpoint, improving
the feel of failover to other endpoints.

Updates #8999

Co-authored-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>

Signed-off-by: James Tucker <james@tailscale.com>
Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>
2023-08-22 15:39:08 -07:00
Brad Fitzpatrick
58a4fd43d8 types/netmap, all: use read-only tailcfg.NodeView in NetworkMap
Updates #8948

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-08-18 20:04:35 -07:00
Brad Fitzpatrick
bc0eb6b914 all: import x/exp/maps as xmaps to distinguish from Go 1.21 "maps"
Updates #8419

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-08-17 09:54:18 -07:00
Andrew Dunham
95d776bd8c wgengine/magicsock: only cache N most recent endpoints per-Addr
If a node is flapping or otherwise generating lots of STUN endpoints, we
can end up caching a ton of useless values and sending them to peers.
Instead, let's apply a fixed per-Addr limit of endpoints that we cache,
so that we're only sending peers up to the N most recent.

Updates tailscale/corp#13890

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I8079a05b44220c46da55016c0e5fc96dd2135ef8
2023-08-15 14:06:42 -07:00
David Anderson
52212f4323 all: update exp/slices and fix call sites
slices.SortFunc suffered a late-in-cycle API breakage.

Updates #cleanup

Signed-off-by: David Anderson <danderson@tailscale.com>
2023-07-28 13:11:53 -07:00
Charlotte Brandhorst-Satzkorn
339397ab74 wgengine/magicsock: remove noV4/noV6 check in addrForSendWireGuardLocked
This change removes the noV4/noV6 check from addrForSendWireGuardLocked.

On Android, the client panics when reaching	`rand.Intn()`, likely due to
the candidates list being containing no candidates. The suspicion is
that the `noV4` and the `noV6` are both being triggered causing the
loop to continue.

Updates tailscale/corp#12938
Updates #7826

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>
2023-07-07 18:59:19 -07:00
Andrew Dunham
2a9d46c38f wgengine/magicsock: prefer private endpoints to public ones
Switch our best address selection to use a scoring-based approach, where
we boost each address based on whether it's a private IP or IPv6.

For users in cloud environments, this biases endpoint selection towards
using an endpoint that is less likely to cost the user money, and should
be less surprising to users.

This also involves updating the tests to not use private IPv4 addresses;
other than that change, the behaviour should be identical for existing
endpoints.

Updates #8097

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I069e3b399daea28be66b81f7e44fc27b2943d8af
2023-06-08 12:23:28 -04:00
Brad Fitzpatrick
4d7927047c wgengine/magicsock: annotate, skip flaky TestIsWireGuardOnlyPickEndpointByPing
Updates #8037
Updates #7826

Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-05-03 14:58:28 -07:00
Charlotte Brandhorst-Satzkorn
ddb4040aa0
wgengine/magicsock: add address selection for wireguard only endpoints (#7979)
This change introduces address selection for wireguard only endpoints.
If a endpoint has not been used before, an address is randomly selected
to be used based on information we know about, such as if they are able
to use IPv4 or IPv6. When an address is initially selected, we also
initiate a new ICMP ping to the endpoints addresses to determine which
endpoint offers the best latency. This information is then used to
update which endpoint we should be using based on the best possible
route. If the latency is the same for a IPv4 and an IPv6 address, IPv6
will be used.

Updates #7826

Signed-off-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>
2023-05-02 17:49:56 -07:00
Andrew Dunham
bcf7b63d7e wgengine/magicsock: add hysteresis to endpoint selection
Avoid selecting an endpoint as "better" than the current endpoint if the
total latency improvement is less than 1%. This adds some hysteresis to
avoid flapping between endpoints for a minimal improvement in latency.

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: If8312e1768ea65c4b4d4e13d8de284b3825d7a73
2023-05-02 08:56:16 -07:00
Andrew Dunham
80b138f0df wgengine/magicsock: keep advertising endpoints after we stop discovering them
Previously, when updating endpoints we would immediately stop
advertising any endpoint that wasn't discovered during
determineEndpoints. This could result in, for example, a case where we
performed an incremental netcheck, didn't get any of our three STUN
packets back, and then dropped our STUN endpoint from the set of
advertised endpoints... which would result in clients falling back to a
DERP connection until the next call to determineEndpoints.

Instead, let's cache endpoints that we've discovered and continue
reporting them to clients until a timeout expires. In the above case
where we temporarily don't have a discovered STUN endpoint, we would
continue reporting the old value, then re-discover the STUN endpoint
again and continue reporting it as normal, so clients never see a
withdrawal.

Updates tailscale/coral#108

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: I42de72e7418ab328a6c732bdefc74549708cf8b9
2023-04-17 11:26:02 -04:00
Brad Fitzpatrick
10f1c90f4d wgengine/magicsock, types/nettype, etc: finish ReadFromUDPAddrPort netip migration
So we're staying within the netip.Addr/AddrPort consistently and
avoiding allocs/conversions to the legacy net addr types.

Updates #5162

Change-Id: I59feba60d3de39f773e68292d759766bac98c917
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-04-15 13:40:15 -07:00
James Tucker
20f17d6e7b wgengine/magicsock: reenable magicsock tests on Windows
These tests are passing locally and on CI. They had failed earlier in
the day when first fixing up CI, and it is not immediately clear why. I
have cycled IPv6 support locally, but this should not have a substantial
effect.

Updates #7876

Signed-off-by: James Tucker <jftucker@gmail.com>
2023-04-14 22:53:53 -07:00
James Tucker
8dec1a8724 .github/workflows: reenable Windows CI, disable broken tests
We accidentally switched to ./tool/go in
4022796484 which resulted in no longer
running Windows builds, as this is attempting to run a bash script.

I was unable to quickly fix the various tests that have regressed, so
instead I've added skips referencing #7876, which we need to back and
fix.

Updates #7262
Updates #7876

Signed-off-by: James Tucker <james@tailscale.com>
2023-04-14 14:13:53 -07:00
Brad Fitzpatrick
6866aaeab3 wgengine/magicsock: factor out receiveIPv4 & receiveIPv6 common code
Updates #2331

Change-Id: I801df38b217f5d17203e8dc3b8654f44747e0f4b
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-04-14 10:40:42 -07:00
Maisem Ali
64bbf1738e tailcfg: make SelfNodeV4MasqAddrForThisPeer a pointer
This makes `omitempty` actually work, and saves bytes in each map response.

Updates tailscale/corp#8020

Signed-off-by: Maisem Ali <maisem@tailscale.com>
2023-04-13 11:28:33 -07:00
Charlotte Brandhorst-Satzkorn
c573bef0aa tailcfg,wgengine: add initial support for WireGuard only peers
A peer can have IsWireGuardOnly, which means it will not support DERP or
Disco, and it must have Endpoints filled in order to be usable.

In the present implementation only the first Endpoint will be used as
the bestAddr.

Updates tailscale/corp#10351

Co-authored-by: Charlotte Brandhorst-Satzkorn <charlotte@tailscale.com>
Co-authored-by: James Tucker <james@tailscale.com>
Signed-off-by: James Tucker <james@tailscale.com>
2023-04-08 22:08:25 -07:00
James Tucker
6cfcb3cae4 wgengine/magicsock: fix synchronization of endpoint disco fields
Identified in review in #7821 endpoint.discoKey and endpoint.discoShort
are often accessed without first taking endpoint.mu. The arrangement
with endpoint.mu is inconvenient for a good number of those call-sites,
so it is instead replaced with an atomic pointer to carry both pieces of
disco info. This will also help with #7821 that wants to add explicit
checks/guards to disable disco behaviors when disco keys are missing
which is necessarily implicitly mostly covered by this change.

Updates #7821

Signed-off-by: James Tucker <james@tailscale.com>
2023-04-08 17:15:54 -07:00
Jordan Whited
f475e5550c
net/neterror, wgengine/magicsock: use UDP GSO and GRO on Linux (#7791)
This commit implements UDP offloading for Linux. GSO size is passed to
and from the kernel via socket control messages. Support is probed at
runtime.

UDP GSO is dependent on checksum offload support on the egress netdev.
UDP GSO will be disabled in the event sendmmsg() returns EIO, which is
a strong signal that the egress netdev does not support checksum
offload.

Updates tailscale/corp#8734

Signed-off-by: Jordan Whited <jordan@tailscale.com>
2023-04-04 16:32:16 -07:00
Andrew Dunham
8d3acc9235 util/sysresources, magicsock: scale DERP buffer based on system memory
This adds the util/sysresources package, which currently only contains a
function to return the total memory size of the current system.

Then, we modify magicsock to scale the number of buffered DERP messages
based on the system's available memory, ensuring that we never use a
value lower than the previous constant of 32.

Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Ib763c877de4d0d4ee88869078e7d512f6a3a148d
2023-04-03 17:14:14 -04:00
Will Norris
71029cea2d all: update copyright and license headers
This updates all source files to use a new standard header for copyright
and license declaration.  Notably, copyright no longer includes a date,
and we now use the standard SPDX-License-Identifier header.

This commit was done almost entirely mechanically with perl, and then
some minimal manual fixes.

Updates #6865

Signed-off-by: Will Norris <will@tailscale.com>
2023-01-27 15:36:29 -08:00
Brad Fitzpatrick
d8feeeee4c wgengine/magicsock: fix buggy fast path in Conn.SetNetworkMap
Spotted by Maisem.

Fixes #6680

Change-Id: I5fdc01de8b006a1c43a2a4848f69397f54b4453a
Co-authored-By: Maisem Ali <maisem@tailscale.com>
Co-authored-By: Andrew Dunham <andrew@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2023-01-24 14:19:15 -08:00
Andrew Dunham
aea251d42a cmd/testwrapper: move from corp; mark magicsock test as flaky
Signed-off-by: Andrew Dunham <andrew@du.nham.ca>
Change-Id: Ibab5860f5797b3db151d3c27855333e43a9088a4
2023-01-18 12:08:23 -05:00
Brad Fitzpatrick
0f604923d3 ipn/ipnlocal: fix StatusWithoutPeers not populating parts of Status
Fixes #4311

Change-Id: Iaae0615148fa7154f4ef8f66b455e3a6c2fa9df3
Co-authored-by: Claire Wang <claire@tailscale.com>
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
2022-12-19 13:15:28 -08:00
Joe Tsai
d9df023e6f
net/connstats: enforce maximum number of connections (#6760)
The Tailscale logging service has a hard limit on the maximum
log message size that can be accepted.
We want to ensure that netlog messages never exceed
this limit otherwise a client cannot transmit logs.

Move the goroutine for periodically dumping netlog messages
from wgengine/netlog to net/connstats.
This allows net/connstats to manage when it dumps messages,
either based on time or by size.

Updates tailscale/corp#8427

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
2022-12-16 10:14:00 -08:00
Jordan Whited
ea5ee6f87c
all: update golang.zx2c4.com/wireguard to github.com/tailscale/wireguard-go (#6692)
This is temporary while we work to upstream performance work in
https://github.com/WireGuard/wireguard-go/pull/64. A replace directive
is less ideal as it breaks dependent code without duplication of the
directive.

Signed-off-by: Jordan Whited <jordan@tailscale.com>
2022-12-09 15:12:20 -08:00
Jordan Whited
76389d8baf
net/tstun, wgengine/magicsock: enable vectorized I/O on Linux (#6663)
This commit updates the wireguard-go dependency and implements the
necessary changes to the tun.Device and conn.Bind implementations to
support passing vectors of packets in tailscaled. This significantly
improves throughput performance on Linux.

Updates #414

Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: James Tucker <james@tailscale.com>
Co-authored-by: James Tucker <james@tailscale.com>
2022-12-08 17:58:14 -08:00
Mihai Parparita
bdc45b9066 wgengine/magicsock: fix panic when rebinding fails
We would replace the existing real implementation of nettype.PacketConn
with a blockForeverConn, but that violates the contract of atomic.Value
(where the type cannot change). Fix by switching to a pointer value
(atomic.Pointer[nettype.PacketConn]).

A longstanding issue, but became more prevalent when we started binding
connections to interfaces on macOS and iOS (#6566), which could lead to
the bind call failing if the interface was no longer available.

Fixes #6641

Signed-off-by: Mihai Parparita <mihai@tailscale.com>
2022-12-08 16:34:14 -08:00
Joe Tsai
2e5d08ec4f
net/connstats: invert network logging data flow (#6272)
Previously, tstun.Wrapper and magicsock.Conn managed their
own statistics data structure and relied on an external call to
Extract to extract (and reset) the statistics.
This makes it difficult to ensure a maximum size on the statistics
as the caller has no introspection into whether the number
of unique connections is getting too large.

Invert the control flow such that a *connstats.Statistics
is registered with tstun.Wrapper and magicsock.Conn.
Methods on non-nil *connstats.Statistics are called for every packet.
This allows the implementation of connstats.Statistics (in the future)
to better control when it needs to flush to ensure
bounds on maximum sizes.

The value registered into tstun.Wrapper and magicsock.Conn could
be an interface, but that has two performance detriments:

1. Method calls on interface values are more expensive since
they must go through a virtual method dispatch.

2. The implementation would need a sync.Mutex to protect the
statistics value instead of using an atomic.Pointer.

Given that methods on constats.Statistics are called for every packet,
we want reduce the CPU cost on this hot path.

Signed-off-by: Joe Tsai <joetsai@digital-static.net>
2022-11-28 15:59:33 -08:00