diff options
Diffstat (limited to 'pkg/flipcall')
| -rw-r--r-- | pkg/flipcall/BUILD | 33 | ||||
| -rw-r--r-- | pkg/flipcall/ctrl_futex.go | 176 | ||||
| -rw-r--r-- | pkg/flipcall/flipcall.go | 255 | ||||
| -rw-r--r-- | pkg/flipcall/flipcall_example_test.go | 112 | ||||
| -rw-r--r-- | pkg/flipcall/flipcall_test.go | 404 | ||||
| -rw-r--r-- | pkg/flipcall/flipcall_unsafe.go | 87 | ||||
| -rw-r--r-- | pkg/flipcall/futex_linux.go | 118 | ||||
| -rw-r--r-- | pkg/flipcall/io.go | 113 | ||||
| -rw-r--r-- | pkg/flipcall/packet_window_allocator.go | 166 |
9 files changed, 0 insertions, 1464 deletions
diff --git a/pkg/flipcall/BUILD b/pkg/flipcall/BUILD deleted file mode 100644 index c1e078c7c..000000000 --- a/pkg/flipcall/BUILD +++ /dev/null @@ -1,33 +0,0 @@ -load("//tools/go_stateify:defs.bzl", "go_library", "go_test") - -package(licenses = ["notice"]) - -go_library( - name = "flipcall", - srcs = [ - "ctrl_futex.go", - "flipcall.go", - "flipcall_unsafe.go", - "futex_linux.go", - "io.go", - "packet_window_allocator.go", - ], - importpath = "gvisor.dev/gvisor/pkg/flipcall", - visibility = ["//visibility:public"], - deps = [ - "//pkg/abi/linux", - "//pkg/log", - "//pkg/memutil", - "//third_party/gvsync", - ], -) - -go_test( - name = "flipcall_test", - size = "small", - srcs = [ - "flipcall_example_test.go", - "flipcall_test.go", - ], - embed = [":flipcall"], -) diff --git a/pkg/flipcall/ctrl_futex.go b/pkg/flipcall/ctrl_futex.go deleted file mode 100644 index 8390915a2..000000000 --- a/pkg/flipcall/ctrl_futex.go +++ /dev/null @@ -1,176 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "encoding/json" - "fmt" - "math" - "sync/atomic" - - "gvisor.dev/gvisor/pkg/log" -) - -type endpointControlImpl struct { - state int32 -} - -// Bits in endpointControlImpl.state. -const ( - epsBlocked = 1 << iota - epsShutdown -) - -func (ep *Endpoint) ctrlInit(opts ...EndpointOption) error { - if len(opts) != 0 { - return fmt.Errorf("unknown EndpointOption: %T", opts[0]) - } - return nil -} - -type ctrlHandshakeRequest struct{} - -type ctrlHandshakeResponse struct{} - -func (ep *Endpoint) ctrlConnect() error { - if err := ep.enterFutexWait(); err != nil { - return err - } - _, err := ep.futexConnect(&ctrlHandshakeRequest{}) - ep.exitFutexWait() - return err -} - -func (ep *Endpoint) ctrlWaitFirst() error { - if err := ep.enterFutexWait(); err != nil { - return err - } - defer ep.exitFutexWait() - - // Wait for the handshake request. - if err := ep.futexSwitchFromPeer(); err != nil { - return err - } - - // Read the handshake request. - reqLen := atomic.LoadUint32(ep.dataLen()) - if reqLen > ep.dataCap { - return fmt.Errorf("invalid handshake request length %d (maximum %d)", reqLen, ep.dataCap) - } - var req ctrlHandshakeRequest - if err := json.NewDecoder(ep.NewReader(reqLen)).Decode(&req); err != nil { - return fmt.Errorf("error reading handshake request: %v", err) - } - - // Write the handshake response. - w := ep.NewWriter() - if err := json.NewEncoder(w).Encode(ctrlHandshakeResponse{}); err != nil { - return fmt.Errorf("error writing handshake response: %v", err) - } - *ep.dataLen() = w.Len() - - // Return control to the client. - raceBecomeInactive() - if err := ep.futexSwitchToPeer(); err != nil { - return err - } - - // Wait for the first non-handshake message. - return ep.futexSwitchFromPeer() -} - -func (ep *Endpoint) ctrlRoundTrip() error { - if err := ep.futexSwitchToPeer(); err != nil { - return err - } - if err := ep.enterFutexWait(); err != nil { - return err - } - err := ep.futexSwitchFromPeer() - ep.exitFutexWait() - return err -} - -func (ep *Endpoint) ctrlWakeLast() error { - return ep.futexSwitchToPeer() -} - -func (ep *Endpoint) enterFutexWait() error { - switch eps := atomic.AddInt32(&ep.ctrl.state, epsBlocked); eps { - case epsBlocked: - return nil - case epsBlocked | epsShutdown: - atomic.AddInt32(&ep.ctrl.state, -epsBlocked) - return shutdownError{} - default: - // Most likely due to ep.enterFutexWait() being called concurrently - // from multiple goroutines. - panic(fmt.Sprintf("invalid flipcall.Endpoint.ctrl.state before flipcall.Endpoint.enterFutexWait(): %v", eps-epsBlocked)) - } -} - -func (ep *Endpoint) exitFutexWait() { - switch eps := atomic.AddInt32(&ep.ctrl.state, -epsBlocked); eps { - case 0: - return - case epsShutdown: - // ep.ctrlShutdown() was called while we were blocked, so we are - // repsonsible for indicating connection shutdown. - ep.shutdownConn() - default: - panic(fmt.Sprintf("invalid flipcall.Endpoint.ctrl.state after flipcall.Endpoint.exitFutexWait(): %v", eps+epsBlocked)) - } -} - -func (ep *Endpoint) ctrlShutdown() { - // Set epsShutdown to ensure that future calls to ep.enterFutexWait() fail. - if atomic.AddInt32(&ep.ctrl.state, epsShutdown)&epsBlocked != 0 { - // Wake the blocked thread. This must loop because it's possible that - // FUTEX_WAKE occurs after the waiter sets epsBlocked, but before it - // blocks in FUTEX_WAIT. - for { - // Wake MaxInt32 threads to prevent a broken or malicious peer from - // swallowing our wakeup by FUTEX_WAITing from multiple threads. - if err := ep.futexWakeConnState(math.MaxInt32); err != nil { - log.Warningf("failed to FUTEX_WAKE Endpoints: %v", err) - break - } - yieldThread() - if atomic.LoadInt32(&ep.ctrl.state)&epsBlocked == 0 { - break - } - } - } else { - // There is no blocked thread, so we are responsible for indicating - // connection shutdown. - ep.shutdownConn() - } -} - -func (ep *Endpoint) shutdownConn() { - switch cs := atomic.SwapUint32(ep.connState(), csShutdown); cs { - case ep.activeState: - if err := ep.futexWakeConnState(1); err != nil { - log.Warningf("failed to FUTEX_WAKE peer Endpoint for shutdown: %v", err) - } - case ep.inactiveState: - // The peer is currently active and will detect shutdown when it tries - // to update the connection state. - case csShutdown: - // The peer also called Endpoint.Shutdown(). - default: - log.Warningf("unexpected connection state before Endpoint.shutdownConn(): %v", cs) - } -} diff --git a/pkg/flipcall/flipcall.go b/pkg/flipcall/flipcall.go deleted file mode 100644 index 386cee42c..000000000 --- a/pkg/flipcall/flipcall.go +++ /dev/null @@ -1,255 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// Package flipcall implements a protocol providing Fast Local Interprocess -// Procedure Calls between mutually-distrusting processes. -package flipcall - -import ( - "fmt" - "math" - "sync/atomic" - "syscall" -) - -// An Endpoint provides the ability to synchronously transfer data and control -// to a connected peer Endpoint, which may be in another process. -// -// Since the Endpoint control transfer model is synchronous, at any given time -// one Endpoint "has control" (designated the active Endpoint), and the other -// is "waiting for control" (designated the inactive Endpoint). Users of the -// flipcall package designate one Endpoint as the client, which is initially -// active, and the other as the server, which is initially inactive. See -// flipcall_example_test.go for usage. -type Endpoint struct { - // packet is a pointer to the beginning of the packet window. (Since this - // is a raw OS memory mapping and not a Go object, it does not need to be - // represented as an unsafe.Pointer.) packet is immutable. - packet uintptr - - // dataCap is the size of the datagram part of the packet window in bytes. - // dataCap is immutable. - dataCap uint32 - - // activeState is csClientActive if this is a client Endpoint and - // csServerActive if this is a server Endpoint. - activeState uint32 - - // inactiveState is csServerActive if this is a client Endpoint and - // csClientActive if this is a server Endpoint. - inactiveState uint32 - - // shutdown is non-zero if Endpoint.Shutdown() has been called, or if the - // Endpoint has acknowledged shutdown initiated by the peer. shutdown is - // accessed using atomic memory operations. - shutdown uint32 - - ctrl endpointControlImpl -} - -// EndpointSide indicates which side of a connection an Endpoint belongs to. -type EndpointSide int - -const ( - // ClientSide indicates that an Endpoint is a client (initially-active; - // first method call should be Connect). - ClientSide EndpointSide = iota - - // ServerSide indicates that an Endpoint is a server (initially-inactive; - // first method call should be RecvFirst.) - ServerSide -) - -// Init must be called on zero-value Endpoints before first use. If it -// succeeds, ep.Destroy() must be called once the Endpoint is no longer in use. -// -// pwd represents the packet window used to exchange data with the peer -// Endpoint. FD may differ between Endpoints if they are in different -// processes, but must represent the same file. The packet window must -// initially be filled with zero bytes. -func (ep *Endpoint) Init(side EndpointSide, pwd PacketWindowDescriptor, opts ...EndpointOption) error { - switch side { - case ClientSide: - ep.activeState = csClientActive - ep.inactiveState = csServerActive - case ServerSide: - ep.activeState = csServerActive - ep.inactiveState = csClientActive - default: - return fmt.Errorf("invalid EndpointSide: %v", side) - } - if pwd.Length < pageSize { - return fmt.Errorf("packet window size (%d) less than minimum (%d)", pwd.Length, pageSize) - } - if pwd.Length > math.MaxUint32 { - return fmt.Errorf("packet window size (%d) exceeds maximum (%d)", pwd.Length, math.MaxUint32) - } - m, _, e := syscall.RawSyscall6(syscall.SYS_MMAP, 0, uintptr(pwd.Length), syscall.PROT_READ|syscall.PROT_WRITE, syscall.MAP_SHARED, uintptr(pwd.FD), uintptr(pwd.Offset)) - if e != 0 { - return fmt.Errorf("failed to mmap packet window: %v", e) - } - ep.packet = m - ep.dataCap = uint32(pwd.Length) - uint32(PacketHeaderBytes) - if err := ep.ctrlInit(opts...); err != nil { - ep.unmapPacket() - return err - } - return nil -} - -// NewEndpoint is a convenience function that returns an initialized Endpoint -// allocated on the heap. -func NewEndpoint(side EndpointSide, pwd PacketWindowDescriptor, opts ...EndpointOption) (*Endpoint, error) { - var ep Endpoint - if err := ep.Init(side, pwd, opts...); err != nil { - return nil, err - } - return &ep, nil -} - -// An EndpointOption configures an Endpoint. -type EndpointOption interface { - isEndpointOption() -} - -// Destroy releases resources owned by ep. No other Endpoint methods may be -// called after Destroy. -func (ep *Endpoint) Destroy() { - ep.unmapPacket() -} - -func (ep *Endpoint) unmapPacket() { - syscall.RawSyscall(syscall.SYS_MUNMAP, ep.packet, uintptr(ep.dataCap)+PacketHeaderBytes, 0) - ep.packet = 0 -} - -// Shutdown causes concurrent and future calls to ep.Connect(), ep.SendRecv(), -// ep.RecvFirst(), and ep.SendLast(), as well as the same calls in the peer -// Endpoint, to unblock and return errors. It does not wait for concurrent -// calls to return. Successive calls to Shutdown have no effect. -// -// Shutdown is the only Endpoint method that may be called concurrently with -// other methods on the same Endpoint. -func (ep *Endpoint) Shutdown() { - if atomic.SwapUint32(&ep.shutdown, 1) != 0 { - // ep.Shutdown() has previously been called. - return - } - ep.ctrlShutdown() -} - -// isShutdownLocally returns true if ep.Shutdown() has been called. -func (ep *Endpoint) isShutdownLocally() bool { - return atomic.LoadUint32(&ep.shutdown) != 0 -} - -type shutdownError struct{} - -// Error implements error.Error. -func (shutdownError) Error() string { - return "flipcall connection shutdown" -} - -// DataCap returns the maximum datagram size supported by ep. Equivalently, -// DataCap returns len(ep.Data()). -func (ep *Endpoint) DataCap() uint32 { - return ep.dataCap -} - -// Connection state. -const ( - // The client is, by definition, initially active, so this must be 0. - csClientActive = 0 - csServerActive = 1 - csShutdown = 2 -) - -// Connect blocks until the peer Endpoint has called Endpoint.RecvFirst(). -// -// Preconditions: ep is a client Endpoint. ep.Connect(), ep.RecvFirst(), -// ep.SendRecv(), and ep.SendLast() have never been called. -func (ep *Endpoint) Connect() error { - err := ep.ctrlConnect() - if err == nil { - raceBecomeActive() - } - return err -} - -// RecvFirst blocks until the peer Endpoint calls Endpoint.SendRecv(), then -// returns the datagram length specified by that call. -// -// Preconditions: ep is a server Endpoint. ep.SendRecv(), ep.RecvFirst(), and -// ep.SendLast() have never been called. -func (ep *Endpoint) RecvFirst() (uint32, error) { - if err := ep.ctrlWaitFirst(); err != nil { - return 0, err - } - raceBecomeActive() - recvDataLen := atomic.LoadUint32(ep.dataLen()) - if recvDataLen > ep.dataCap { - return 0, fmt.Errorf("received packet with invalid datagram length %d (maximum %d)", recvDataLen, ep.dataCap) - } - return recvDataLen, nil -} - -// SendRecv transfers control to the peer Endpoint, causing its call to -// Endpoint.SendRecv() or Endpoint.RecvFirst() to return with the given -// datagram length, then blocks until the peer Endpoint calls -// Endpoint.SendRecv() or Endpoint.SendLast(). -// -// Preconditions: dataLen <= ep.DataCap(). No previous call to ep.SendRecv() or -// ep.RecvFirst() has returned an error. ep.SendLast() has never been called. -// If ep is a client Endpoint, ep.Connect() has previously been called and -// returned nil. -func (ep *Endpoint) SendRecv(dataLen uint32) (uint32, error) { - if dataLen > ep.dataCap { - panic(fmt.Sprintf("attempting to send packet with datagram length %d (maximum %d)", dataLen, ep.dataCap)) - } - // This store can safely be non-atomic: Under correct operation we should - // be the only thread writing ep.dataLen(), and ep.ctrlRoundTrip() will - // synchronize with the receiver. We will not read from ep.dataLen() until - // after ep.ctrlRoundTrip(), so if the peer is mutating it concurrently then - // they can only shoot themselves in the foot. - *ep.dataLen() = dataLen - raceBecomeInactive() - if err := ep.ctrlRoundTrip(); err != nil { - return 0, err - } - raceBecomeActive() - recvDataLen := atomic.LoadUint32(ep.dataLen()) - if recvDataLen > ep.dataCap { - return 0, fmt.Errorf("received packet with invalid datagram length %d (maximum %d)", recvDataLen, ep.dataCap) - } - return recvDataLen, nil -} - -// SendLast causes the peer Endpoint's call to Endpoint.SendRecv() or -// Endpoint.RecvFirst() to return with the given datagram length. -// -// Preconditions: dataLen <= ep.DataCap(). No previous call to ep.SendRecv() or -// ep.RecvFirst() has returned an error. ep.SendLast() has never been called. -// If ep is a client Endpoint, ep.Connect() has previously been called and -// returned nil. -func (ep *Endpoint) SendLast(dataLen uint32) error { - if dataLen > ep.dataCap { - panic(fmt.Sprintf("attempting to send packet with datagram length %d (maximum %d)", dataLen, ep.dataCap)) - } - *ep.dataLen() = dataLen - raceBecomeInactive() - if err := ep.ctrlWakeLast(); err != nil { - return err - } - return nil -} diff --git a/pkg/flipcall/flipcall_example_test.go b/pkg/flipcall/flipcall_example_test.go deleted file mode 100644 index 8d88b845d..000000000 --- a/pkg/flipcall/flipcall_example_test.go +++ /dev/null @@ -1,112 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "bytes" - "fmt" - "sync" -) - -func Example() { - const ( - reqPrefix = "request " - respPrefix = "response " - count = 3 - maxMessageLen = len(respPrefix) + 1 // 1 digit - ) - - pwa, err := NewPacketWindowAllocator() - if err != nil { - panic(err) - } - defer pwa.Destroy() - pwd, err := pwa.Allocate(PacketWindowLengthForDataCap(uint32(maxMessageLen))) - if err != nil { - panic(err) - } - var clientEP Endpoint - if err := clientEP.Init(ClientSide, pwd); err != nil { - panic(err) - } - defer clientEP.Destroy() - var serverEP Endpoint - if err := serverEP.Init(ServerSide, pwd); err != nil { - panic(err) - } - defer serverEP.Destroy() - - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - i := 0 - var buf bytes.Buffer - // wait for first request - n, err := serverEP.RecvFirst() - if err != nil { - return - } - for { - // read request - buf.Reset() - buf.Write(serverEP.Data()[:n]) - fmt.Println(buf.String()) - // write response - buf.Reset() - fmt.Fprintf(&buf, "%s%d", respPrefix, i) - copy(serverEP.Data(), buf.Bytes()) - // send response and wait for next request - n, err = serverEP.SendRecv(uint32(buf.Len())) - if err != nil { - return - } - i++ - } - }() - defer func() { - serverEP.Shutdown() - serverRun.Wait() - }() - - // establish connection as client - if err := clientEP.Connect(); err != nil { - panic(err) - } - var buf bytes.Buffer - for i := 0; i < count; i++ { - // write request - buf.Reset() - fmt.Fprintf(&buf, "%s%d", reqPrefix, i) - copy(clientEP.Data(), buf.Bytes()) - // send request and wait for response - n, err := clientEP.SendRecv(uint32(buf.Len())) - if err != nil { - panic(err) - } - // read response - buf.Reset() - buf.Write(clientEP.Data()[:n]) - fmt.Println(buf.String()) - } - - // Output: - // request 0 - // response 0 - // request 1 - // response 1 - // request 2 - // response 2 -} diff --git a/pkg/flipcall/flipcall_test.go b/pkg/flipcall/flipcall_test.go deleted file mode 100644 index 168a487ec..000000000 --- a/pkg/flipcall/flipcall_test.go +++ /dev/null @@ -1,404 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "runtime" - "sync" - "testing" - "time" -) - -var testPacketWindowSize = pageSize - -type testConnection struct { - pwa PacketWindowAllocator - clientEP Endpoint - serverEP Endpoint -} - -func newTestConnectionWithOptions(tb testing.TB, clientOpts, serverOpts []EndpointOption) *testConnection { - c := &testConnection{} - if err := c.pwa.Init(); err != nil { - tb.Fatalf("failed to create PacketWindowAllocator: %v", err) - } - pwd, err := c.pwa.Allocate(testPacketWindowSize) - if err != nil { - c.pwa.Destroy() - tb.Fatalf("PacketWindowAllocator.Allocate() failed: %v", err) - } - if err := c.clientEP.Init(ClientSide, pwd, clientOpts...); err != nil { - c.pwa.Destroy() - tb.Fatalf("failed to create client Endpoint: %v", err) - } - if err := c.serverEP.Init(ServerSide, pwd, serverOpts...); err != nil { - c.pwa.Destroy() - c.clientEP.Destroy() - tb.Fatalf("failed to create server Endpoint: %v", err) - } - return c -} - -func newTestConnection(tb testing.TB) *testConnection { - return newTestConnectionWithOptions(tb, nil, nil) -} - -func (c *testConnection) destroy() { - c.pwa.Destroy() - c.clientEP.Destroy() - c.serverEP.Destroy() -} - -func testSendRecv(t *testing.T, c *testConnection) { - // This shared variable is used to confirm that synchronization between - // flipcall endpoints is visible to the Go race detector. - state := 0 - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - t.Logf("server Endpoint waiting for packet 1") - if _, err := c.serverEP.RecvFirst(); err != nil { - t.Errorf("server Endpoint.RecvFirst() failed: %v", err) - return - } - state++ - if state != 2 { - t.Errorf("shared state counter: got %d, wanted 2", state) - } - t.Logf("server Endpoint got packet 1, sending packet 2 and waiting for packet 3") - if _, err := c.serverEP.SendRecv(0); err != nil { - t.Errorf("server Endpoint.SendRecv() failed: %v", err) - return - } - state++ - if state != 4 { - t.Errorf("shared state counter: got %d, wanted 4", state) - } - t.Logf("server Endpoint got packet 3") - }() - defer func() { - // Ensure that the server goroutine is cleaned up before - // c.serverEP.Destroy(), even if the test fails. - c.serverEP.Shutdown() - serverRun.Wait() - }() - - t.Logf("client Endpoint establishing connection") - if err := c.clientEP.Connect(); err != nil { - t.Fatalf("client Endpoint.Connect() failed: %v", err) - } - state++ - if state != 1 { - t.Errorf("shared state counter: got %d, wanted 1", state) - } - t.Logf("client Endpoint sending packet 1 and waiting for packet 2") - if _, err := c.clientEP.SendRecv(0); err != nil { - t.Fatalf("client Endpoint.SendRecv() failed: %v", err) - } - state++ - if state != 3 { - t.Errorf("shared state counter: got %d, wanted 3", state) - } - t.Logf("client Endpoint got packet 2, sending packet 3") - if err := c.clientEP.SendLast(0); err != nil { - t.Fatalf("client Endpoint.SendLast() failed: %v", err) - } - t.Logf("waiting for server goroutine to complete") - serverRun.Wait() -} - -func TestSendRecv(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testSendRecv(t, c) -} - -func testShutdownBeforeConnect(t *testing.T, c *testConnection, remoteShutdown bool) { - if remoteShutdown { - c.serverEP.Shutdown() - } else { - c.clientEP.Shutdown() - } - if err := c.clientEP.Connect(); err == nil { - t.Errorf("client Endpoint.Connect() succeeded unexpectedly") - } -} - -func TestShutdownBeforeConnectLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownBeforeConnect(t, c, false) -} - -func TestShutdownBeforeConnectRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownBeforeConnect(t, c, true) -} - -func testShutdownDuringConnect(t *testing.T, c *testConnection, remoteShutdown bool) { - var clientRun sync.WaitGroup - clientRun.Add(1) - go func() { - defer clientRun.Done() - if err := c.clientEP.Connect(); err == nil { - t.Errorf("client Endpoint.Connect() succeeded unexpectedly") - } - }() - time.Sleep(time.Second) // to allow c.clientEP.Connect() to block - if remoteShutdown { - c.serverEP.Shutdown() - } else { - c.clientEP.Shutdown() - } - clientRun.Wait() -} - -func TestShutdownDuringConnectLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringConnect(t, c, false) -} - -func TestShutdownDuringConnectRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringConnect(t, c, true) -} - -func testShutdownBeforeRecvFirst(t *testing.T, c *testConnection, remoteShutdown bool) { - if remoteShutdown { - c.clientEP.Shutdown() - } else { - c.serverEP.Shutdown() - } - if _, err := c.serverEP.RecvFirst(); err == nil { - t.Errorf("server Endpoint.RecvFirst() succeeded unexpectedly") - } -} - -func TestShutdownBeforeRecvFirstLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownBeforeRecvFirst(t, c, false) -} - -func TestShutdownBeforeRecvFirstRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownBeforeRecvFirst(t, c, true) -} - -func testShutdownDuringRecvFirstBeforeConnect(t *testing.T, c *testConnection, remoteShutdown bool) { - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - if _, err := c.serverEP.RecvFirst(); err == nil { - t.Errorf("server Endpoint.RecvFirst() succeeded unexpectedly") - } - }() - time.Sleep(time.Second) // to allow c.serverEP.RecvFirst() to block - if remoteShutdown { - c.clientEP.Shutdown() - } else { - c.serverEP.Shutdown() - } - serverRun.Wait() -} - -func TestShutdownDuringRecvFirstBeforeConnectLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringRecvFirstBeforeConnect(t, c, false) -} - -func TestShutdownDuringRecvFirstBeforeConnectRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringRecvFirstBeforeConnect(t, c, true) -} - -func testShutdownDuringRecvFirstAfterConnect(t *testing.T, c *testConnection, remoteShutdown bool) { - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - if _, err := c.serverEP.RecvFirst(); err == nil { - t.Errorf("server Endpoint.RecvFirst() succeeded unexpectedly") - } - }() - defer func() { - // Ensure that the server goroutine is cleaned up before - // c.serverEP.Destroy(), even if the test fails. - c.serverEP.Shutdown() - serverRun.Wait() - }() - if err := c.clientEP.Connect(); err != nil { - t.Fatalf("client Endpoint.Connect() failed: %v", err) - } - if remoteShutdown { - c.clientEP.Shutdown() - } else { - c.serverEP.Shutdown() - } - serverRun.Wait() -} - -func TestShutdownDuringRecvFirstAfterConnectLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringRecvFirstAfterConnect(t, c, false) -} - -func TestShutdownDuringRecvFirstAfterConnectRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringRecvFirstAfterConnect(t, c, true) -} - -func testShutdownDuringClientSendRecv(t *testing.T, c *testConnection, remoteShutdown bool) { - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - if _, err := c.serverEP.RecvFirst(); err != nil { - t.Errorf("server Endpoint.RecvFirst() failed: %v", err) - } - // At this point, the client must be blocked in c.clientEP.SendRecv(). - if remoteShutdown { - c.serverEP.Shutdown() - } else { - c.clientEP.Shutdown() - } - }() - defer func() { - // Ensure that the server goroutine is cleaned up before - // c.serverEP.Destroy(), even if the test fails. - c.serverEP.Shutdown() - serverRun.Wait() - }() - if err := c.clientEP.Connect(); err != nil { - t.Fatalf("client Endpoint.Connect() failed: %v", err) - } - if _, err := c.clientEP.SendRecv(0); err == nil { - t.Errorf("client Endpoint.SendRecv() succeeded unexpectedly") - } -} - -func TestShutdownDuringClientSendRecvLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringClientSendRecv(t, c, false) -} - -func TestShutdownDuringClientSendRecvRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringClientSendRecv(t, c, true) -} - -func testShutdownDuringServerSendRecv(t *testing.T, c *testConnection, remoteShutdown bool) { - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - if _, err := c.serverEP.RecvFirst(); err != nil { - t.Errorf("server Endpoint.RecvFirst() failed: %v", err) - return - } - if _, err := c.serverEP.SendRecv(0); err == nil { - t.Errorf("server Endpoint.SendRecv() succeeded unexpectedly") - } - }() - defer func() { - // Ensure that the server goroutine is cleaned up before - // c.serverEP.Destroy(), even if the test fails. - c.serverEP.Shutdown() - serverRun.Wait() - }() - if err := c.clientEP.Connect(); err != nil { - t.Fatalf("client Endpoint.Connect() failed: %v", err) - } - if _, err := c.clientEP.SendRecv(0); err != nil { - t.Fatalf("client Endpoint.SendRecv() failed: %v", err) - } - time.Sleep(time.Second) // to allow serverEP.SendRecv() to block - if remoteShutdown { - c.clientEP.Shutdown() - } else { - c.serverEP.Shutdown() - } - serverRun.Wait() -} - -func TestShutdownDuringServerSendRecvLocal(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringServerSendRecv(t, c, false) -} - -func TestShutdownDuringServerSendRecvRemote(t *testing.T) { - c := newTestConnection(t) - defer c.destroy() - testShutdownDuringServerSendRecv(t, c, true) -} - -func benchmarkSendRecv(b *testing.B, c *testConnection) { - var serverRun sync.WaitGroup - serverRun.Add(1) - go func() { - defer serverRun.Done() - if b.N == 0 { - return - } - if _, err := c.serverEP.RecvFirst(); err != nil { - b.Errorf("server Endpoint.RecvFirst() failed: %v", err) - return - } - for i := 1; i < b.N; i++ { - if _, err := c.serverEP.SendRecv(0); err != nil { - b.Errorf("server Endpoint.SendRecv() failed: %v", err) - return - } - } - if err := c.serverEP.SendLast(0); err != nil { - b.Errorf("server Endpoint.SendLast() failed: %v", err) - } - }() - defer func() { - c.serverEP.Shutdown() - serverRun.Wait() - }() - - if err := c.clientEP.Connect(); err != nil { - b.Fatalf("client Endpoint.Connect() failed: %v", err) - } - runtime.GC() - b.ResetTimer() - for i := 0; i < b.N; i++ { - if _, err := c.clientEP.SendRecv(0); err != nil { - b.Fatalf("client Endpoint.SendRecv() failed: %v", err) - } - } - b.StopTimer() -} - -func BenchmarkSendRecv(b *testing.B) { - c := newTestConnection(b) - defer c.destroy() - benchmarkSendRecv(b, c) -} diff --git a/pkg/flipcall/flipcall_unsafe.go b/pkg/flipcall/flipcall_unsafe.go deleted file mode 100644 index a37952637..000000000 --- a/pkg/flipcall/flipcall_unsafe.go +++ /dev/null @@ -1,87 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "reflect" - "unsafe" - - "gvisor.dev/gvisor/third_party/gvsync" -) - -// Packets consist of a 16-byte header followed by an arbitrarily-sized -// datagram. The header consists of: -// -// - A 4-byte native-endian connection state. -// -// - A 4-byte native-endian datagram length in bytes. -// -// - 8 reserved bytes. -const ( - // PacketHeaderBytes is the size of a flipcall packet header in bytes. The - // maximum datagram size supported by a flipcall connection is equal to the - // length of the packet window minus PacketHeaderBytes. - // - // PacketHeaderBytes is exported to support its use in constant - // expressions. Non-constant expressions may prefer to use - // PacketWindowLengthForDataCap(). - PacketHeaderBytes = 16 -) - -func (ep *Endpoint) connState() *uint32 { - return (*uint32)((unsafe.Pointer)(ep.packet)) -} - -func (ep *Endpoint) dataLen() *uint32 { - return (*uint32)((unsafe.Pointer)(ep.packet + 4)) -} - -// Data returns the datagram part of ep's packet window as a byte slice. -// -// Note that the packet window is shared with the potentially-untrusted peer -// Endpoint, which may concurrently mutate the contents of the packet window. -// Thus: -// -// - Readers must not assume that two reads of the same byte in Data() will -// return the same result. In other words, readers should read any given byte -// in Data() at most once. -// -// - Writers must not assume that they will read back the same data that they -// have written. In other words, writers should avoid reading from Data() at -// all. -func (ep *Endpoint) Data() []byte { - var bs []byte - bsReflect := (*reflect.SliceHeader)((unsafe.Pointer)(&bs)) - bsReflect.Data = ep.packet + PacketHeaderBytes - bsReflect.Len = int(ep.dataCap) - bsReflect.Cap = int(ep.dataCap) - return bs -} - -// ioSync is a dummy variable used to indicate synchronization to the Go race -// detector. Compare syscall.ioSync. -var ioSync int64 - -func raceBecomeActive() { - if gvsync.RaceEnabled { - gvsync.RaceAcquire((unsafe.Pointer)(&ioSync)) - } -} - -func raceBecomeInactive() { - if gvsync.RaceEnabled { - gvsync.RaceReleaseMerge((unsafe.Pointer)(&ioSync)) - } -} diff --git a/pkg/flipcall/futex_linux.go b/pkg/flipcall/futex_linux.go deleted file mode 100644 index b127a2bbb..000000000 --- a/pkg/flipcall/futex_linux.go +++ /dev/null @@ -1,118 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -// +build linux - -package flipcall - -import ( - "encoding/json" - "fmt" - "runtime" - "sync/atomic" - "syscall" - - "gvisor.dev/gvisor/pkg/abi/linux" -) - -func (ep *Endpoint) futexConnect(req *ctrlHandshakeRequest) (ctrlHandshakeResponse, error) { - var resp ctrlHandshakeResponse - - // Write the handshake request. - w := ep.NewWriter() - if err := json.NewEncoder(w).Encode(req); err != nil { - return resp, fmt.Errorf("error writing handshake request: %v", err) - } - *ep.dataLen() = w.Len() - - // Exchange control with the server. - if err := ep.futexSwitchToPeer(); err != nil { - return resp, err - } - if err := ep.futexSwitchFromPeer(); err != nil { - return resp, err - } - - // Read the handshake response. - respLen := atomic.LoadUint32(ep.dataLen()) - if respLen > ep.dataCap { - return resp, fmt.Errorf("invalid handshake response length %d (maximum %d)", respLen, ep.dataCap) - } - if err := json.NewDecoder(ep.NewReader(respLen)).Decode(&resp); err != nil { - return resp, fmt.Errorf("error reading handshake response: %v", err) - } - - return resp, nil -} - -func (ep *Endpoint) futexSwitchToPeer() error { - // Update connection state to indicate that the peer should be active. - if !atomic.CompareAndSwapUint32(ep.connState(), ep.activeState, ep.inactiveState) { - switch cs := atomic.LoadUint32(ep.connState()); cs { - case csShutdown: - return shutdownError{} - default: - return fmt.Errorf("unexpected connection state before FUTEX_WAKE: %v", cs) - } - } - - // Wake the peer's Endpoint.futexSwitchFromPeer(). - if err := ep.futexWakeConnState(1); err != nil { - return fmt.Errorf("failed to FUTEX_WAKE peer Endpoint: %v", err) - } - return nil -} - -func (ep *Endpoint) futexSwitchFromPeer() error { - for { - switch cs := atomic.LoadUint32(ep.connState()); cs { - case ep.activeState: - return nil - case ep.inactiveState: - if ep.isShutdownLocally() { - return shutdownError{} - } - if err := ep.futexWaitConnState(ep.inactiveState); err != nil { - return fmt.Errorf("failed to FUTEX_WAIT for peer Endpoint: %v", err) - } - continue - case csShutdown: - return shutdownError{} - default: - return fmt.Errorf("unexpected connection state before FUTEX_WAIT: %v", cs) - } - } -} - -func (ep *Endpoint) futexWakeConnState(numThreads int32) error { - if _, _, e := syscall.RawSyscall(syscall.SYS_FUTEX, ep.packet, linux.FUTEX_WAKE, uintptr(numThreads)); e != 0 { - return e - } - return nil -} - -func (ep *Endpoint) futexWaitConnState(curState uint32) error { - _, _, e := syscall.Syscall6(syscall.SYS_FUTEX, ep.packet, linux.FUTEX_WAIT, uintptr(curState), 0, 0, 0) - if e != 0 && e != syscall.EAGAIN && e != syscall.EINTR { - return e - } - return nil -} - -func yieldThread() { - syscall.Syscall(syscall.SYS_SCHED_YIELD, 0, 0, 0) - // The thread we're trying to yield to may be waiting for a Go runtime P. - // runtime.Gosched() will hand off ours if necessary. - runtime.Gosched() -} diff --git a/pkg/flipcall/io.go b/pkg/flipcall/io.go deleted file mode 100644 index 85e40b932..000000000 --- a/pkg/flipcall/io.go +++ /dev/null @@ -1,113 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "fmt" - "io" -) - -// DatagramReader implements io.Reader by reading a datagram from an Endpoint's -// packet window. Its use is optional; users that can use Endpoint.Data() more -// efficiently are advised to do so. -type DatagramReader struct { - ep *Endpoint - off uint32 - end uint32 -} - -// Init must be called on zero-value DatagramReaders before first use. -// -// Preconditions: dataLen is 0, or was returned by a previous call to -// ep.RecvFirst() or ep.SendRecv(). -func (r *DatagramReader) Init(ep *Endpoint, dataLen uint32) { - r.ep = ep - r.Reset(dataLen) -} - -// Reset causes r to begin reading a new datagram of the given length from the -// associated Endpoint. -// -// Preconditions: dataLen is 0, or was returned by a previous call to the -// associated Endpoint's RecvFirst() or SendRecv() methods. -func (r *DatagramReader) Reset(dataLen uint32) { - if dataLen > r.ep.dataCap { - panic(fmt.Sprintf("invalid dataLen (%d) > ep.dataCap (%d)", dataLen, r.ep.dataCap)) - } - r.off = 0 - r.end = dataLen -} - -// NewReader is a convenience function that returns an initialized -// DatagramReader allocated on the heap. -// -// Preconditions: dataLen was returned by a previous call to ep.RecvFirst() or -// ep.SendRecv(). -func (ep *Endpoint) NewReader(dataLen uint32) *DatagramReader { - r := &DatagramReader{} - r.Init(ep, dataLen) - return r -} - -// Read implements io.Reader.Read. -func (r *DatagramReader) Read(dst []byte) (int, error) { - n := copy(dst, r.ep.Data()[r.off:r.end]) - r.off += uint32(n) - if r.off == r.end { - return n, io.EOF - } - return n, nil -} - -// DatagramWriter implements io.Writer by writing a datagram to an Endpoint's -// packet window. Its use is optional; users that can use Endpoint.Data() more -// efficiently are advised to do so. -type DatagramWriter struct { - ep *Endpoint - off uint32 -} - -// Init must be called on zero-value DatagramWriters before first use. -func (w *DatagramWriter) Init(ep *Endpoint) { - w.ep = ep -} - -// Reset causes w to begin writing a new datagram to the associated Endpoint. -func (w *DatagramWriter) Reset() { - w.off = 0 -} - -// NewWriter is a convenience function that returns an initialized -// DatagramWriter allocated on the heap. -func (ep *Endpoint) NewWriter() *DatagramWriter { - w := &DatagramWriter{} - w.Init(ep) - return w -} - -// Write implements io.Writer.Write. -func (w *DatagramWriter) Write(src []byte) (int, error) { - n := copy(w.ep.Data()[w.off:w.ep.dataCap], src) - w.off += uint32(n) - if n != len(src) { - return n, fmt.Errorf("datagram would exceed maximum size of %d bytes", w.ep.dataCap) - } - return n, nil -} - -// Len returns the length of the written datagram. -func (w *DatagramWriter) Len() uint32 { - return w.off -} diff --git a/pkg/flipcall/packet_window_allocator.go b/pkg/flipcall/packet_window_allocator.go deleted file mode 100644 index ccb918fab..000000000 --- a/pkg/flipcall/packet_window_allocator.go +++ /dev/null @@ -1,166 +0,0 @@ -// Copyright 2019 The gVisor Authors. -// -// Licensed under the Apache License, Version 2.0 (the "License"); -// you may not use this file except in compliance with the License. -// You may obtain a copy of the License at -// -// http://www.apache.org/licenses/LICENSE-2.0 -// -// Unless required by applicable law or agreed to in writing, software -// distributed under the License is distributed on an "AS IS" BASIS, -// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. -// See the License for the specific language governing permissions and -// limitations under the License. - -package flipcall - -import ( - "fmt" - "math/bits" - "os" - "syscall" - - "gvisor.dev/gvisor/pkg/abi/linux" - "gvisor.dev/gvisor/pkg/memutil" -) - -var ( - pageSize = os.Getpagesize() - pageMask = pageSize - 1 -) - -func init() { - if bits.OnesCount(uint(pageSize)) != 1 { - // This is depended on by roundUpToPage(). - panic(fmt.Sprintf("system page size (%d) is not a power of 2", pageSize)) - } - if uintptr(pageSize) < PacketHeaderBytes { - // This is required since Endpoint.Init() imposes a minimum packet - // window size of 1 page. - panic(fmt.Sprintf("system page size (%d) is less than packet header size (%d)", pageSize, PacketHeaderBytes)) - } -} - -// PacketWindowDescriptor represents a packet window, a range of pages in a -// shared memory file that is used to exchange packets between partner -// Endpoints. -type PacketWindowDescriptor struct { - // FD is the file descriptor representing the shared memory file. - FD int - - // Offset is the offset into the shared memory file at which the packet - // window begins. - Offset int64 - - // Length is the size of the packet window in bytes. - Length int -} - -// PacketWindowLengthForDataCap returns the minimum packet window size required -// to accommodate datagrams of the given size in bytes. -func PacketWindowLengthForDataCap(dataCap uint32) int { - return roundUpToPage(int(dataCap) + int(PacketHeaderBytes)) -} - -func roundUpToPage(x int) int { - return (x + pageMask) &^ pageMask -} - -// A PacketWindowAllocator owns a shared memory file, and allocates packet -// windows from it. -type PacketWindowAllocator struct { - fd int - nextAlloc int64 - fileSize int64 -} - -// Init must be called on zero-value PacketWindowAllocators before first use. -// If it succeeds, Destroy() must be called once the PacketWindowAllocator is -// no longer in use. -func (pwa *PacketWindowAllocator) Init() error { - fd, err := memutil.CreateMemFD("flipcall_packet_windows", linux.MFD_CLOEXEC|linux.MFD_ALLOW_SEALING) - if err != nil { - return fmt.Errorf("failed to create memfd: %v", err) - } - // Apply F_SEAL_SHRINK to prevent either party from causing SIGBUS in the - // other by truncating the file, and F_SEAL_SEAL to prevent either party - // from applying F_SEAL_GROW or F_SEAL_WRITE. - if _, _, e := syscall.RawSyscall(syscall.SYS_FCNTL, uintptr(fd), linux.F_ADD_SEALS, linux.F_SEAL_SHRINK|linux.F_SEAL_SEAL); e != 0 { - syscall.Close(fd) - return fmt.Errorf("failed to apply memfd seals: %v", e) - } - pwa.fd = fd - return nil -} - -// NewPacketWindowAllocator is a convenience function that returns an -// initialized PacketWindowAllocator allocated on the heap. -func NewPacketWindowAllocator() (*PacketWindowAllocator, error) { - var pwa PacketWindowAllocator - if err := pwa.Init(); err != nil { - return nil, err - } - return &pwa, nil -} - -// Destroy releases resources owned by pwa. This invalidates file descriptors -// previously returned by pwa.FD() and pwd.Allocate(). -func (pwa *PacketWindowAllocator) Destroy() { - syscall.Close(pwa.fd) -} - -// FD represents the file descriptor of the shared memory file backing pwa. -func (pwa *PacketWindowAllocator) FD() int { - return pwa.fd -} - -// Allocate allocates a new packet window of at least the given size and -// returns a PacketWindowDescriptor representing it. -// -// Preconditions: size > 0. -func (pwa *PacketWindowAllocator) Allocate(size int) (PacketWindowDescriptor, error) { - if size <= 0 { - return PacketWindowDescriptor{}, fmt.Errorf("invalid size: %d", size) - } - // Page-align size to ensure that pwa.nextAlloc remains page-aligned. - size = roundUpToPage(size) - if size <= 0 { - return PacketWindowDescriptor{}, fmt.Errorf("size %d overflows after rounding up to page size", size) - } - end := pwa.nextAlloc + int64(size) // overflow checked by ensureFileSize - if err := pwa.ensureFileSize(end); err != nil { - return PacketWindowDescriptor{}, err - } - start := pwa.nextAlloc - pwa.nextAlloc = end - return PacketWindowDescriptor{ - FD: pwa.fd, - Offset: start, - Length: size, - }, nil -} - -func (pwa *PacketWindowAllocator) ensureFileSize(min int64) error { - if min <= 0 { - return fmt.Errorf("file size would overflow") - } - if pwa.fileSize >= min { - return nil - } - newSize := 2 * pwa.fileSize - if newSize == 0 { - newSize = int64(pageSize) - } - for newSize < min { - newNewSize := newSize * 2 - if newNewSize <= 0 { - return fmt.Errorf("file size would overflow") - } - newSize = newNewSize - } - if err := syscall.Ftruncate(pwa.fd, newSize); err != nil { - return fmt.Errorf("ftruncate failed: %v", err) - } - pwa.fileSize = newSize - return nil -} |