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authorJason A. Donenfeld <Jason@zx2c4.com>2018-05-14 00:28:30 +0200
committerJason A. Donenfeld <Jason@zx2c4.com>2018-05-14 00:30:52 +0200
commit7e10ebe1010898c48e3f1cfc12ad42d0bb5c0fa1 (patch)
treec0a43be046bf87808ab7dd8839b8a3cd650cacde /rwcancel/rwcancel_unix.go
parentPrettier abbreviation (diff)
downloadwireguard-go-7e10ebe1010898c48e3f1cfc12ad42d0bb5c0fa1.tar.xz
wireguard-go-7e10ebe1010898c48e3f1cfc12ad42d0bb5c0fa1.zip
Introduce rwcancel
Diffstat (limited to 'rwcancel/rwcancel_unix.go')
-rw-r--r--rwcancel/rwcancel_unix.go132
1 files changed, 132 insertions, 0 deletions
diff --git a/rwcancel/rwcancel_unix.go b/rwcancel/rwcancel_unix.go
new file mode 100644
index 0000000..cd3661f
--- /dev/null
+++ b/rwcancel/rwcancel_unix.go
@@ -0,0 +1,132 @@
+/* SPDX-License-Identifier: GPL-2.0
+ *
+ * Copyright (C) 2017-2018 Jason A. Donenfeld <Jason@zx2c4.com>. All Rights Reserved.
+ */
+
+package rwcancel
+
+import (
+ "errors"
+ "golang.org/x/sys/unix"
+ "os"
+ "runtime"
+ "syscall"
+)
+
+type RWCancel struct {
+ fd int
+ closingReader *os.File
+ closingWriter *os.File
+}
+
+type fdSet struct {
+ fdset unix.FdSet
+}
+
+func (fdset *fdSet) set(i int) {
+ bits := 32 << (^uint(0) >> 63)
+ fdset.fdset.Bits[i/bits] |= 1 << uint(i%bits)
+}
+
+func (fdset *fdSet) check(i int) bool {
+ bits := 32 << (^uint(0) >> 63)
+ return (fdset.fdset.Bits[i/bits] & (1 << uint(i%bits))) != 0
+}
+
+func max(a, b int) int {
+ if a > b {
+ return a
+ }
+ return b
+}
+
+func NewRWCancel(fd int) (*RWCancel, error) {
+ err := unix.SetNonblock(fd, true)
+ if err != nil {
+ return nil, err
+ }
+ rwcancel := RWCancel{fd: fd}
+
+ rwcancel.closingReader, rwcancel.closingWriter, err = os.Pipe()
+ if err != nil {
+ return nil, err
+ }
+
+ runtime.SetFinalizer(&rwcancel, func(rw *RWCancel) {
+ rw.Cancel()
+ })
+
+ return &rwcancel, nil
+}
+
+/* https://golang.org/src/crypto/rand/eagain.go */
+func ErrorIsEAGAIN(err error) bool {
+ if pe, ok := err.(*os.PathError); ok {
+ if errno, ok := pe.Err.(syscall.Errno); ok && errno == syscall.EAGAIN {
+ return true
+ }
+ }
+ if errno, ok := err.(syscall.Errno); ok && errno == syscall.EAGAIN {
+ return true
+ }
+ return false
+}
+
+func (rw *RWCancel) ReadyRead() bool {
+ closeFd := int(rw.closingReader.Fd())
+ fdset := fdSet{}
+ fdset.set(rw.fd)
+ fdset.set(closeFd)
+ _, err := unix.Select(max(rw.fd, closeFd)+1, &fdset.fdset, nil, nil, nil)
+ if err != nil {
+ return false
+ }
+ if fdset.check(closeFd) {
+ return false
+ }
+ return fdset.check(rw.fd)
+}
+
+func (rw *RWCancel) ReadyWrite() bool {
+ closeFd := int(rw.closingReader.Fd())
+ fdset := fdSet{}
+ fdset.set(rw.fd)
+ fdset.set(closeFd)
+ _, err := unix.Select(max(rw.fd, closeFd)+1, nil, &fdset.fdset, nil, nil)
+ if err != nil {
+ return false
+ }
+ if fdset.check(closeFd) {
+ return false
+ }
+ return fdset.check(rw.fd)
+}
+
+func (rw *RWCancel) Read(p []byte) (n int, err error) {
+ for {
+ n, err := unix.Read(rw.fd, p)
+ if err == nil || !ErrorIsEAGAIN(err) {
+ return n, err
+ }
+ if !rw.ReadyRead() {
+ return 0, errors.New("fd closed")
+ }
+ }
+}
+
+func (rw *RWCancel) Write(p []byte) (n int, err error) {
+ for {
+ n, err := unix.Write(rw.fd, p)
+ if err == nil || !ErrorIsEAGAIN(err) {
+ return n, err
+ }
+ if !rw.ReadyWrite() {
+ return 0, errors.New("fd closed")
+ }
+ }
+}
+
+func (rw *RWCancel) Cancel() (err error) {
+ _, err = rw.closingWriter.Write([]byte{0})
+ return
+}