There is a possible deadlock in `device.Close()` when you try to close
the device very soon after its start. The problem is that two different
methods acquire the same locks in different order:
1. device.Close()
- device.ipcMutex.Lock()
- device.state.Lock()
2. device.changeState(deviceState)
- device.state.Lock()
- device.ipcMutex.Lock()
Reproducer:
func TestDevice_deadlock(t *testing.T) {
d := randDevice(t)
d.Close()
}
Problem:
$ go clean -testcache && go test -race -timeout 3s -run TestDevice_deadlock ./device | grep -A 10 sync.runtime_SemacquireMutex
sync.runtime_SemacquireMutex(0xc000117d20?, 0x94?, 0x0?)
/usr/local/opt/go/libexec/src/runtime/sema.go:77 +0x25
sync.(*Mutex).lockSlow(0xc000130518)
/usr/local/opt/go/libexec/src/sync/mutex.go:171 +0x213
sync.(*Mutex).Lock(0xc000130518)
/usr/local/opt/go/libexec/src/sync/mutex.go:90 +0x55
golang.zx2c4.com/wireguard/device.(*Device).Close(0xc000130500)
/Users/martin.basovnik/git/basovnik/wireguard-go/device/device.go:373 +0xb6
golang.zx2c4.com/wireguard/device.TestDevice_deadlock(0x0?)
/Users/martin.basovnik/git/basovnik/wireguard-go/device/device_test.go:480 +0x2c
testing.tRunner(0xc00014c000, 0x131d7b0)
--
sync.runtime_SemacquireMutex(0xc000130564?, 0x60?, 0xc000130548?)
/usr/local/opt/go/libexec/src/runtime/sema.go:77 +0x25
sync.(*Mutex).lockSlow(0xc000130750)
/usr/local/opt/go/libexec/src/sync/mutex.go:171 +0x213
sync.(*Mutex).Lock(0xc000130750)
/usr/local/opt/go/libexec/src/sync/mutex.go:90 +0x55
sync.(*RWMutex).Lock(0xc000130750)
/usr/local/opt/go/libexec/src/sync/rwmutex.go:147 +0x45
golang.zx2c4.com/wireguard/device.(*Device).upLocked(0xc000130500)
/Users/martin.basovnik/git/basovnik/wireguard-go/device/device.go:179 +0x72
golang.zx2c4.com/wireguard/device.(*Device).changeState(0xc000130500, 0x1)
Signed-off-by: Martin Basovnik <martin.basovnik@gmail.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Only bother updating the rxBytes counter once we've processed a whole
vector, since additions are atomic.
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Peer.RoutineSequentialReceiver() deals with packet vectors and does not
need to perform timer and endpoint operations for every packet in a
given vector. Changing these per-packet operations to per-vector
improves throughput by as much as 10% in some environments.
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
Access to Peer.endpoint was previously synchronized by Peer.RWMutex.
This has now moved to Peer.endpoint.Mutex. Peer.SendBuffers() is now the
sole caller of Endpoint.ClearSrc(), which is signaled via a new bool,
Peer.endpoint.clearSrcOnTx. Previous Callers of Endpoint.ClearSrc() now
set this bool, primarily via peer.markEndpointSrcForClearing().
Peer.SetEndpointFromPacket() clears Peer.endpoint.clearSrcOnTx when an
updated conn.Endpoint is stored. This maintains the same event order as
before, i.e. a conn.Endpoint received after peer.endpoint.clearSrcOnTx
is set, but before the next Peer.SendBuffers() call results in the
latest conn.Endpoint source being used for the next packet transmission.
These changes result in throughput improvements for single flow,
parallel (-P n) flow, and bidirectional (--bidir) flow iperf3 TCP/UDP
tests as measured on both Linux and Windows. Latency under load improves
especially for high throughput Linux scenarios. These improvements are
likely realized on all platforms to some degree, as the changes are not
platform-specific.
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>
Implement UDP GSO and GRO for the Linux tun.Device, which is made
possible by virtio extensions in the kernel's TUN driver starting in
v6.2.
secnetperf, a QUIC benchmark utility from microsoft/msquic@8e1eb1a, is
used to demonstrate the effect of this commit between two Linux
computers with i5-12400 CPUs. There is roughly ~13us of round trip
latency between them. secnetperf was invoked with the following command
line options:
-stats:1 -exec:maxtput -test:tput -download:10000 -timed:1 -encrypt:0
The first result is from commit 2e0774f without UDP GSO/GRO on the TUN.
[conn][0x55739a144980] STATS: EcnCapable=0 RTT=3973 us
SendTotalPackets=55859 SendSuspectedLostPackets=61
SendSpuriousLostPackets=59 SendCongestionCount=27
SendEcnCongestionCount=0 RecvTotalPackets=2779122
RecvReorderedPackets=0 RecvDroppedPackets=0
RecvDuplicatePackets=0 RecvDecryptionFailures=0
Result: 3654977571 bytes @ 2922821 kbps (10003.972 ms).
The second result is with UDP GSO/GRO on the TUN.
[conn][0x56493dfd09a0] STATS: EcnCapable=0 RTT=1216 us
SendTotalPackets=165033 SendSuspectedLostPackets=64
SendSpuriousLostPackets=61 SendCongestionCount=53
SendEcnCongestionCount=0 RecvTotalPackets=11845268
RecvReorderedPackets=25267 RecvDroppedPackets=0
RecvDuplicatePackets=0 RecvDecryptionFailures=0
Result: 15574671184 bytes @ 12458214 kbps (10001.222 ms).
Signed-off-by: Jordan Whited <jordan@tailscale.com>
Signed-off-by: Jason A. Donenfeld <Jason@zx2c4.com>
