keksvpn/vendor/github.com/mdlayher/socket/conn.go

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Go
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2022-02-27 03:22:11 +00:00
package socket
import (
"os"
"sync/atomic"
"syscall"
"time"
"golang.org/x/sys/unix"
)
// A Conn is a low-level network connection which integrates with Go's runtime
// network poller to provide asynchronous I/O and deadline support.
type Conn struct {
// Indicates whether or not Conn.Close has been called. Must be accessed
// atomically. Atomics definitions must come first in the Conn struct.
closed uint32
// A unique name for the Conn which is also associated with derived file
// descriptors such as those created by accept(2).
name string
// Provides access to the underlying file registered with the runtime
// network poller, and arbitrary raw I/O calls.
fd *os.File
rc syscall.RawConn
}
// A Config contains options for a Conn.
type Config struct {
// NetNS specifies the Linux network namespace the Conn will operate in.
// This option is unsupported on other operating systems.
//
// If set (non-zero), Conn will enter the specified network namespace and an
// error will occur in Socket if the operation fails.
//
// If not set (zero), a best-effort attempt will be made to enter the
// network namespace of the calling thread: this means that any changes made
// to the calling thread's network namespace will also be reflected in Conn.
// If this operation fails (due to lack of permissions or because network
// namespaces are disabled by kernel configuration), Socket will not return
// an error, and the Conn will operate in the default network namespace of
// the process. This enables non-privileged use of Conn in applications
// which do not require elevated privileges.
//
// Entering a network namespace is a privileged operation (root or
// CAP_SYS_ADMIN are required), and most applications should leave this set
// to 0.
NetNS int
}
// High-level methods which provide convenience over raw system calls.
// Close closes the underlying file descriptor for the Conn, which also causes
// all in-flight I/O operations to immediately unblock and return errors. Any
// subsequent uses of Conn will result in EBADF.
func (c *Conn) Close() error {
// The caller has expressed an intent to close the socket, so immediately
// increment s.closed to force further calls to result in EBADF before also
// closing the file descriptor to unblock any outstanding operations.
//
// Because other operations simply check for s.closed != 0, we will permit
// double Close, which would increment s.closed beyond 1.
if atomic.AddUint32(&c.closed, 1) != 1 {
// Multiple Close calls.
return nil
}
return os.NewSyscallError("close", c.fd.Close())
}
// CloseRead shuts down the reading side of the Conn. Most callers should just
// use Close.
func (c *Conn) CloseRead() error { return c.Shutdown(unix.SHUT_RD) }
// CloseWrite shuts down the writing side of the Conn. Most callers should just
// use Close.
func (c *Conn) CloseWrite() error { return c.Shutdown(unix.SHUT_WR) }
// Read implements io.Reader by reading directly from the underlying file
// descriptor.
func (c *Conn) Read(b []byte) (int, error) { return c.fd.Read(b) }
// Write implements io.Writer by writing directly to the underlying file
// descriptor.
func (c *Conn) Write(b []byte) (int, error) { return c.fd.Write(b) }
// SetDeadline sets both the read and write deadlines associated with the Conn.
func (c *Conn) SetDeadline(t time.Time) error { return c.fd.SetDeadline(t) }
// SetReadDeadline sets the read deadline associated with the Conn.
func (c *Conn) SetReadDeadline(t time.Time) error { return c.fd.SetReadDeadline(t) }
// SetWriteDeadline sets the write deadline associated with the Conn.
func (c *Conn) SetWriteDeadline(t time.Time) error { return c.fd.SetWriteDeadline(t) }
// ReadBuffer gets the size of the operating system's receive buffer associated
// with the Conn.
func (c *Conn) ReadBuffer() (int, error) {
return c.GetsockoptInt(unix.SOL_SOCKET, unix.SO_RCVBUF)
}
// WriteBuffer gets the size of the operating system's transmit buffer
// associated with the Conn.
func (c *Conn) WriteBuffer() (int, error) {
return c.GetsockoptInt(unix.SOL_SOCKET, unix.SO_SNDBUF)
}
// SetReadBuffer sets the size of the operating system's receive buffer
// associated with the Conn.
//
// When called with elevated privileges on Linux, the SO_RCVBUFFORCE option will
// be used to override operating system limits. Otherwise SO_RCVBUF is used
// (which obeys operating system limits).
func (c *Conn) SetReadBuffer(bytes int) error { return c.setReadBuffer(bytes) }
// SetWriteBuffer sets the size of the operating system's transmit buffer
// associated with the Conn.
//
// When called with elevated privileges on Linux, the SO_SNDBUFFORCE option will
// be used to override operating system limits. Otherwise SO_SNDBUF is used
// (which obeys operating system limits).
func (c *Conn) SetWriteBuffer(bytes int) error { return c.setWriteBuffer(bytes) }
// SyscallConn returns a raw network connection. This implements the
// syscall.Conn interface.
//
// SyscallConn is intended for advanced use cases, such as getting and setting
// arbitrary socket options using the socket's file descriptor. If possible,
// those operations should be performed using methods on Conn instead.
//
// Once invoked, it is the caller's responsibility to ensure that operations
// performed using Conn and the syscall.RawConn do not conflict with each other.
func (c *Conn) SyscallConn() (syscall.RawConn, error) {
if atomic.LoadUint32(&c.closed) != 0 {
return nil, os.NewSyscallError("syscallconn", unix.EBADF)
}
// TODO(mdlayher): mutex or similar to enforce syscall.RawConn contract of
// FD remaining valid for duration of calls?
return c.rc, nil
}
// Socket wraps the socket(2) system call to produce a Conn. domain, typ, and
// proto are passed directly to socket(2), and name should be a unique name for
// the socket type such as "netlink" or "vsock".
//
// The cfg parameter specifies optional configuration for the Conn. If nil, no
// additional configuration will be applied.
//
// If the operating system supports SOCK_CLOEXEC and SOCK_NONBLOCK, they are
// automatically applied to typ to mirror the standard library's socket flag
// behaviors.
func Socket(domain, typ, proto int, name string, cfg *Config) (*Conn, error) {
if cfg == nil {
cfg = &Config{}
}
if cfg.NetNS == 0 {
// Non-Linux or no network namespace.
return socket(domain, typ, proto, name)
}
// Linux only: create Conn in the specified network namespace.
return withNetNS(cfg.NetNS, func() (*Conn, error) {
return socket(domain, typ, proto, name)
})
}
// socket is the internal, cross-platform entry point for socket(2).
func socket(domain, typ, proto int, name string) (*Conn, error) {
var (
fd int
err error
)
for {
fd, err = unix.Socket(domain, typ|socketFlags, proto)
switch {
case err == nil:
// Some OSes already set CLOEXEC with typ.
if !flagCLOEXEC {
unix.CloseOnExec(fd)
}
// No error, prepare the Conn.
return newConn(fd, name)
case !ready(err):
// System call interrupted or not ready, try again.
continue
case err == unix.EINVAL, err == unix.EPROTONOSUPPORT:
// On Linux, SOCK_NONBLOCK and SOCK_CLOEXEC were introduced in
// 2.6.27. On FreeBSD, both flags were introduced in FreeBSD 10.
// EINVAL and EPROTONOSUPPORT check for earlier versions of these
// OSes respectively.
//
// Mirror what the standard library does when creating file
// descriptors: avoid racing a fork/exec with the creation of new
// file descriptors, so that child processes do not inherit socket
// file descriptors unexpectedly.
//
// For a more thorough explanation, see similar work in the Go tree:
// func sysSocket in net/sock_cloexec.go, as well as the detailed
// comment in syscall/exec_unix.go.
syscall.ForkLock.RLock()
fd, err = unix.Socket(domain, typ, proto)
if err != nil {
syscall.ForkLock.RUnlock()
return nil, os.NewSyscallError("socket", err)
}
unix.CloseOnExec(fd)
syscall.ForkLock.RUnlock()
return newConn(fd, name)
default:
// Unhandled error.
return nil, os.NewSyscallError("socket", err)
}
}
}
// TODO(mdlayher): consider exporting newConn as New?
// newConn wraps an existing file descriptor to create a Conn. name should be a
// unique name for the socket type such as "netlink" or "vsock".
func newConn(fd int, name string) (*Conn, error) {
// All Conn I/O is nonblocking for integration with Go's runtime network
// poller. Depending on the OS this might already be set but it can't hurt
// to set it again.
if err := unix.SetNonblock(fd, true); err != nil {
return nil, os.NewSyscallError("setnonblock", err)
}
// os.NewFile registers the non-blocking file descriptor with the runtime
// poller, which is then used for most subsequent operations except those
// that require raw I/O via SyscallConn.
//
// See also: https://golang.org/pkg/os/#NewFile
f := os.NewFile(uintptr(fd), name)
rc, err := f.SyscallConn()
if err != nil {
return nil, err
}
return &Conn{
name: name,
fd: f,
rc: rc,
}, nil
}
// Low-level methods which provide raw system call access.
// Accept wraps accept(2) or accept4(2) depending on the operating system, but
// returns a Conn for the accepted connection rather than a raw file descriptor.
//
// If the operating system supports accept4(2) (which allows flags),
// SOCK_CLOEXEC and SOCK_NONBLOCK are automatically applied to flags to mirror
// the standard library's socket flag behaviors.
//
// If the operating system only supports accept(2) (which does not allow flags)
// and flags is not zero, an error will be returned.
func (c *Conn) Accept(flags int) (*Conn, unix.Sockaddr, error) {
var (
nfd int
sa unix.Sockaddr
err error
)
doErr := c.read(sysAccept, func(fd int) error {
// Either accept(2) or accept4(2) depending on the OS.
nfd, sa, err = accept(fd, flags|socketFlags)
return err
})
if doErr != nil {
return nil, nil, doErr
}
if err != nil {
// sysAccept is either "accept" or "accept4" depending on the OS.
return nil, nil, os.NewSyscallError(sysAccept, err)
}
// Successfully accepted a connection, wrap it in a Conn for use by the
// caller.
ac, err := newConn(nfd, c.name)
if err != nil {
return nil, nil, err
}
return ac, sa, nil
}
// Bind wraps bind(2).
func (c *Conn) Bind(sa unix.Sockaddr) error {
const op = "bind"
var err error
doErr := c.control(op, func(fd int) error {
err = unix.Bind(fd, sa)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// Connect wraps connect(2).
func (c *Conn) Connect(sa unix.Sockaddr) error {
const op = "connect"
var err error
doErr := c.write(op, func(fd int) error {
err = unix.Connect(fd, sa)
return err
})
if doErr != nil {
return doErr
}
if err == unix.EISCONN {
// EISCONN is reported if the socket is already established and should
// not be treated as an error.
// - Darwin reports this for at least TCP sockets
// - Linux reports this for at least AF_VSOCK sockets
return nil
}
return os.NewSyscallError(op, err)
}
// Getsockname wraps getsockname(2).
func (c *Conn) Getsockname() (unix.Sockaddr, error) {
const op = "getsockname"
var (
sa unix.Sockaddr
err error
)
doErr := c.control(op, func(fd int) error {
sa, err = unix.Getsockname(fd)
return err
})
if doErr != nil {
return nil, doErr
}
return sa, os.NewSyscallError(op, err)
}
// GetsockoptInt wraps getsockopt(2) for integer values.
func (c *Conn) GetsockoptInt(level, opt int) (int, error) {
const op = "getsockopt"
var (
value int
err error
)
doErr := c.control(op, func(fd int) error {
value, err = unix.GetsockoptInt(fd, level, opt)
return err
})
if doErr != nil {
return 0, doErr
}
return value, os.NewSyscallError(op, err)
}
// Listen wraps listen(2).
func (c *Conn) Listen(n int) error {
const op = "listen"
var err error
doErr := c.control(op, func(fd int) error {
err = unix.Listen(fd, n)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// Recvmsg wraps recvmsg(2).
func (c *Conn) Recvmsg(p, oob []byte, flags int) (int, int, int, unix.Sockaddr, error) {
const op = "recvmsg"
var (
n, oobn, recvflags int
from unix.Sockaddr
err error
)
doErr := c.read(op, func(fd int) error {
n, oobn, recvflags, from, err = unix.Recvmsg(fd, p, oob, flags)
return err
})
if doErr != nil {
return 0, 0, 0, nil, doErr
}
return n, oobn, recvflags, from, os.NewSyscallError(op, err)
}
// Recvfrom wraps recvfrom(2)
func (c *Conn) Recvfrom(p []byte, flags int) (int, unix.Sockaddr, error) {
const op = "recvfrom"
var (
n int
addr unix.Sockaddr
err error
)
doErr := c.read(op, func(fd int) error {
n, addr, err = unix.Recvfrom(fd, p, flags)
return err
})
if doErr != nil {
return 0, nil, doErr
}
return n, addr, os.NewSyscallError(op, err)
}
// Sendmsg wraps sendmsg(2).
func (c *Conn) Sendmsg(p, oob []byte, to unix.Sockaddr, flags int) error {
const op = "sendmsg"
var err error
doErr := c.write(op, func(fd int) error {
err = unix.Sendmsg(fd, p, oob, to, flags)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// Sendto wraps sendto(2).
func (c *Conn) Sendto(b []byte, to unix.Sockaddr, flags int) error {
const op = "sendto"
var err error
doErr := c.write(op, func(fd int) error {
err = unix.Sendto(fd, b, flags, to)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// SetsockoptInt wraps setsockopt(2) for integer values.
func (c *Conn) SetsockoptInt(level, opt, value int) error {
const op = "setsockopt"
var err error
doErr := c.control(op, func(fd int) error {
err = unix.SetsockoptInt(fd, level, opt, value)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// Shutdown wraps shutdown(2).
func (c *Conn) Shutdown(how int) error {
const op = "shutdown"
var err error
doErr := c.control(op, func(fd int) error {
err = unix.Shutdown(fd, how)
return err
})
if doErr != nil {
return doErr
}
return os.NewSyscallError(op, err)
}
// Conn low-level read/write/control functions. These functions mirror the
// syscall.RawConn APIs but the input closures return errors rather than
// booleans. Any syscalls invoked within f should return their error to allow
// the Conn to check for readiness with the runtime network poller, or to retry
// operations which may have been interrupted by EINTR or similar.
//
// Note that errors from the input closure functions are not propagated to the
// error return values of read/write/control, and the caller is still
// responsible for error handling.
// read executes f, a read function, against the associated file descriptor.
// op is used to create an *os.SyscallError if the file descriptor is closed.
func (c *Conn) read(op string, f func(fd int) error) error {
if atomic.LoadUint32(&c.closed) != 0 {
return os.NewSyscallError(op, unix.EBADF)
}
return c.rc.Read(func(fd uintptr) bool {
return ready(f(int(fd)))
})
}
// write executes f, a write function, against the associated file descriptor.
// op is used to create an *os.SyscallError if the file descriptor is closed.
func (c *Conn) write(op string, f func(fd int) error) error {
if atomic.LoadUint32(&c.closed) != 0 {
return os.NewSyscallError(op, unix.EBADF)
}
return c.rc.Write(func(fd uintptr) bool {
return ready(f(int(fd)))
})
}
// control executes f, a control function, against the associated file
// descriptor. op is used to create an *os.SyscallError if the file descriptor
// is closed.
func (c *Conn) control(op string, f func(fd int) error) error {
if atomic.LoadUint32(&c.closed) != 0 {
return os.NewSyscallError(op, unix.EBADF)
}
return c.rc.Control(func(fd uintptr) {
// Repeatedly attempt the syscall(s) invoked by f until completion is
// indicated by the return value of ready.
for {
if ready(f(int(fd))) {
return
}
}
})
}
// ready indicates readiness based on the value of err.
func ready(err error) bool {
// When a socket is in non-blocking mode, we might see a variety of errors:
// - EAGAIN: most common case for a socket read not being ready
// - EALREADY: reported on connect after EINPROGRESS for AF_VSOCK at least
// - EINPROGRESS: reported by some sockets when first calling connect
// - EINTR: system call interrupted, more frequently occurs in Go 1.14+
// because goroutines can be asynchronously preempted
//
// Return false to let the poller wait for readiness. See the source code
// for internal/poll.FD.RawRead for more details.
switch err {
case unix.EAGAIN, unix.EALREADY, unix.EINPROGRESS, unix.EINTR:
// Not ready.
return false
default:
// Ready regardless of whether there was an error or no error.
return true
}
}