One of the first rules of WaitGroups is that you call wg.Add
outside of a goroutine, not inside it. Fix this embarrassing mistake.
This prevents an extremely rare race condition (2 per 100,000 runs)
which could occur when attempting to start a new peer
concurrently with shutting down a device.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This is particularly problematic on mobile,
where there is a fixed number of elements.
If most of them leak, it'll impact performance;
if all of them leak, the device will permanently deadlock.
I have a test that detects element leaks, which is how I found this one.
There are some remaining leaks that I have not yet tracked down,
but this is the most prominent by far.
I will commit the test when it passes reliably.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
bufio is not required.
strings.Builder is cheaper than bytes.Buffer for constructing strings.
io.Writer is more flexible than io.StringWriter,
and just as cheap (when used with io.WriteString).
Run gofmt.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This was shifted by 2 bytes when making persistent keepalive into a u32.
Fix it by placing it after the aligned region.
Fixes: e739ff7 ("device: fix persistent_keepalive_interval data races")
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
People are actually hitting this condition, so make it uniform. Also,
change a printf into a println, to match the other conventions.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Found by the race detector and existing tests.
To avoid introducing a lock into this hot path,
calculate and cache whether any peers exist.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Access keypair.sendNonce atomically.
Eliminate one unnecessary initialization to zero.
Mutate handshake.lastSentHandshake with the mutex held.
Co-authored-by: David Anderson <danderson@tailscale.com>
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
They're called elem in most places.
Rename a few local variables to make it consistent.
This makes it easier to grep the code for things like elem.Drop.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This is a similar treatment to the handling of the encryption
channel found a few commits ago: Use the closing of the channel
to manage goroutine lifetime and shutdown.
It is considerably simpler because there is only a single writer.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
The new test introduced in this commit used to deadlock about 1% of the time.
I believe that the deadlock occurs as follows:
* The test completes, calling device.Close.
* device.Close closes device.signals.stop.
* RoutineEncryption stops.
* The deferred function in RoutineEncryption drains device.queue.encryption.
* RoutineEncryption exits.
* A peer's RoutineNonce processes an element queued in peer.queue.nonce.
* RoutineNonce puts that element into the outbound and encryption queues.
* RoutineSequentialSender reads that elements from the outbound queue.
* It waits for that element to get Unlocked by RoutineEncryption.
* RoutineEncryption has already exited, so RoutineSequentialSender blocks forever.
* device.RemoveAllPeers calls peer.Stop on all peers.
* peer.Stop waits for peer.routines.stopping, which blocks forever.
Rather than attempt to add even more ordering to the already complex
centralized shutdown orchestration, this commit moves towards a
data-flow-oriented shutdown.
The device.queue.encryption gets closed when there will be no more writes to it.
All device.queue.encryption readers always read until the channel is closed and then exit.
We thus guarantee that any element that enters the encryption queue also exits it.
This removes the need for central control of the lifetime of RoutineEncryption,
removes the need to drain the encryption queue on shutdown, and simplifies RoutineEncryption.
This commit also fixes a data race. When RoutineSequentialSender
drains its queue on shutdown, it needs to lock the elem before operating on it,
just as the main body does.
The new test in this commit passed 50k iterations with the race detector enabled
and 150k iterations with the race detector disabled, with no failures.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Since we already have it packed into a uint64
in a known byte order, write it back out again
the same byte order instead of copying byte by byte.
This should also generate more efficient code,
because the compiler can do a single uint64 write,
instead of eight bounds checks and eight byte writes.
Due to a missed optimization, it actually generates a mishmash
of smaller writes: 1 byte, 4 bytes, 2 bytes, 1 byte.
This is https://golang.org/issue/41663.
The code is still better than before, and will get better yet
once that compiler bug gets fixed.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This makes it easier to work with configs in tests.
It'll see heavier use over upcoming commits;
this commit only adds the infrastructure.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Any io.Reader will do, and there are no performance concerns here.
This is technically backwards incompatible,
but it is very unlikely to break any existing code.
It is compatible with the existing uses in wireguard-{windows,android,apple}
and also will allow us to slightly simplify it if desired.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
When running many concurrent test processing using
https://godoc.org/golang.org/x/tools/cmd/stress
the processing sometimes cannot complete a ping in under 300ms.
Increase the timeout to 5s to reduce the rate of false positives.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
When closing a device, packets that are in flight
can make it to SendBuffer, which then returns an error.
Those errors add noise but no light;
they do not reflect an actual problem.
Adding the synchronization required to prevent
this from occurring is currently expensive and error-prone.
Instead, quietly drop such packets instead of
returning an error.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
In each case, the starting waitgroup did nothing but ensure
that the goroutine has launched.
Nothing downstream depends on the order in which goroutines launch,
and if the Go runtime scheduler is so broken that goroutines
don't get launched reasonably promptly, we have much deeper problems.
Given all that, simplify the code.
Passed a race-enabled stress test 25,000 times without failure.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
Picking two free ports to use for a test is difficult.
The free port we selected might no longer be free when we reach
for it a second time.
On my machine, this failure mode led to failures approximately
once per thousand test runs.
Since failures are rare, and threading through and checking for
all possible errors is complicated, fix this with a big hammer:
Retry if either device fails to come up.
Also, if you accidentally pick the same port twice, delightful confusion ensues.
The handshake failures manifest as crypto errors, which look scary.
Again, fix with retries.
To make these retries easier to implement, use testing.T.Cleanup
instead of defer to close devices. This requires Go 1.14.
Update go.mod accordingly. Go 1.13 is no longer supported anyway.
With these fixes, 'go test -race' ran 100,000 times without failure.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
This doesn't cause any practical problems as it is,
but vet (rightly) flags this code as copying a mutex.
It is easy to fix, so do so.
Signed-off-by: Josh Bleecher Snyder <josh@tailscale.com>
fix panic: send on closed channel when remove peer
Signed-off-by: Haichao Liu <liuhaichao@bytedance.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Both wireguard-windows and wireguard-android access Bind
directly for these methods now.
Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Use the RTMGRP_IPV4_ROUTE const from x/sys/unix instead of using the
corresponding RTNLGRP_IPV4_ROUTE const to create the multicast groups
mask.
Signed-off-by: Tobias Klauser <tklauser@distanz.ch>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Peers are currently removed after Device's goroutines are signaled to stop,
but without waiting for them to actually do so, which is racy.
For example, RoutineHandshake may be in Peer.SendKeepalive
when the corresponding peer is removed, which closes its nonce channel.
This causes a send on a closed channel, as observed in tailscale/tailscale#487.
This patch seems to be the correct synchronizing action:
Peer's goroutines are receivers and handle channel closure gracefully,
so Device's goroutines are the ones that should be fully stopped first.
Signed-Off-By: Dmytro Shynkevych <dmytro@tailscale.com>
Go's GC semantics might not always guarantee the safety of this, and the
race detector gets upset too, so instead we wrap this all in atomic
accessors.
Reported-by: David Anderson <danderson@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
The sticky socket code stays in the device package for now,
as it reaches deeply into the peer list.
This is the first step in an effort to split some code out of
the very busy device package.
Signed-off-by: David Crawshaw <crawshaw@tailscale.com>
