In tailscale/wireguard-go#65, @lkosewsk reproduced a memory leak seen
in prod with lots of wireguard-go instances being created and
destroyed, where they were still being retained forever due to cycles
in the runtime.SetFinalizer reference graph.
Really we shouldn't be using runtime.SetFinalizer anywhere. But we
still use it on mobile platforms in WaitPool. But those platforms
don't have thousands of tsnet.Server instances coming & going, so this
is a half fix: avoid the finalizer registration on Linux, etc where
the queue doesn't need to be drained and there's no WaitPool
accounting. Just let GC handle it, without adding finalizer cycle
complexity.
Updates tailscale/corp#42776
Signed-off-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Outbound element buffers now come from the sing allocator sized to the
actual packet instead of the bounded MaxMessageSize pool, element and
container pools become plain sync.Pools, and the bounded message buffer
pool serves only the receive path. Packets injected via
InputPacket/InputPackets are dropped before they are copied once a peer
has 2048 packets queued: injection runs on the caller's read loop, which
must never block on pool exhaustion, and the queues are bounded in
containers, so a flood was buffered instead of dropped.
The sync.Locker used with a sync.Cond must be acquired when changing
the associated condition, otherwise there is a window within
sync.Cond.Wait() where a wake-up may be missed.
Fixes: 4846070 ("device: use a waiting sync.Pool instead of a channel")
Reviewed-by: Brad Fitzpatrick <bradfitz@tailscale.com>
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Queue{In,Out}boundElement locking can contribute to significant
overhead via sync.Mutex.lockSlow() in some environments. These types
are passed throughout the device package as elements in a slice, so
move the per-element Mutex to a container around the slice.
Reviewed-by: Maisem Ali <maisem@tailscale.com>
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Accept packet vectors for reading and writing in the tun.Device and
conn.Bind interfaces, so that the internal plumbing between these
interfaces now passes a vector of packets. Vectors move untouched
between these interfaces, i.e. if 128 packets are received from
conn.Bind.Read(), 128 packets are passed to tun.Device.Write(). There is
no internal buffering.
Currently, existing implementations are only adjusted to have vectors
of length one. Subsequent patches will improve that.
Also, as a related fixup, use the unix and windows packages rather than
the syscall package when possible.
Co-authored-by: James Tucker <james@tailscale.com>
Signed-off-by: James Tucker <james@tailscale.com>
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.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>
