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// Copyright 2009 The Go Authors.  All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

// +build darwin freebsd linux netbsd openbsd windows

// Unix domain sockets

package net

import (
        "os"
        "syscall"
        "time"
)

func unixSocket(net string, laddr, raddr *UnixAddr, mode string) (fd *netFD, err error) {
        var sotype int
        switch net {
        default:
                return nil, UnknownNetworkError(net)
        case "unix":
                sotype = syscall.SOCK_STREAM
        case "unixgram":
                sotype = syscall.SOCK_DGRAM
        case "unixpacket":
                sotype = syscall.SOCK_SEQPACKET
        }

        var la, ra syscall.Sockaddr
        switch mode {
        default:
                panic("unixSocket mode " + mode)

        case "dial":
                if laddr != nil {
                        la = &syscall.SockaddrUnix{Name: laddr.Name}
                }
                if raddr != nil {
                        ra = &syscall.SockaddrUnix{Name: raddr.Name}
                } else if sotype != syscall.SOCK_DGRAM || laddr == nil {
                        return nil, &OpError{Op: mode, Net: net, Err: errMissingAddress}
                }

        case "listen":
                if laddr == nil {
                        return nil, &OpError{mode, net, nil, errMissingAddress}
                }
                la = &syscall.SockaddrUnix{Name: laddr.Name}
                if raddr != nil {
                        return nil, &OpError{Op: mode, Net: net, Addr: raddr, Err: &AddrError{Err: "unexpected remote address", Addr: raddr.String()}}
                }
        }

        f := sockaddrToUnix
        if sotype == syscall.SOCK_DGRAM {
                f = sockaddrToUnixgram
        } else if sotype == syscall.SOCK_SEQPACKET {
                f = sockaddrToUnixpacket
        }

        fd, oserr := socket(net, syscall.AF_UNIX, sotype, 0, la, ra, f)
        if oserr != nil {
                goto Error
        }
        return fd, nil

Error:
        addr := raddr
        if mode == "listen" {
                addr = laddr
        }
        return nil, &OpError{Op: mode, Net: net, Addr: addr, Err: oserr}
}

func sockaddrToUnix(sa syscall.Sockaddr) Addr {
        if s, ok := sa.(*syscall.SockaddrUnix); ok {
                return &UnixAddr{s.Name, "unix"}
        }
        return nil
}

func sockaddrToUnixgram(sa syscall.Sockaddr) Addr {
        if s, ok := sa.(*syscall.SockaddrUnix); ok {
                return &UnixAddr{s.Name, "unixgram"}
        }
        return nil
}

func sockaddrToUnixpacket(sa syscall.Sockaddr) Addr {
        if s, ok := sa.(*syscall.SockaddrUnix); ok {
                return &UnixAddr{s.Name, "unixpacket"}
        }
        return nil
}

func sotypeToNet(sotype int) string {
        switch sotype {
        case syscall.SOCK_STREAM:
                return "unix"
        case syscall.SOCK_SEQPACKET:
                return "unixpacket"
        case syscall.SOCK_DGRAM:
                return "unixgram"
        default:
                panic("sotypeToNet unknown socket type")
        }
        return ""
}

// UnixConn is an implementation of the Conn interface
// for connections to Unix domain sockets.
type UnixConn struct {
        fd *netFD
}

func newUnixConn(fd *netFD) *UnixConn { return &UnixConn{fd} }

func (c *UnixConn) ok() bool { return c != nil && c.fd != nil }

// Implementation of the Conn interface - see Conn for documentation.

// Read implements the Conn Read method.
func (c *UnixConn) Read(b []byte) (n int, err error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        return c.fd.Read(b)
}

// Write implements the Conn Write method.
func (c *UnixConn) Write(b []byte) (n int, err error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        return c.fd.Write(b)
}

// Close closes the Unix domain connection.
func (c *UnixConn) Close() error {
        if !c.ok() {
                return os.EINVAL
        }
        err := c.fd.Close()
        c.fd = nil
        return err
}

// LocalAddr returns the local network address, a *UnixAddr.
// Unlike in other protocols, LocalAddr is usually nil for dialed connections.
func (c *UnixConn) LocalAddr() Addr {
        if !c.ok() {
                return nil
        }
        return c.fd.laddr
}

// RemoteAddr returns the remote network address, a *UnixAddr.
// Unlike in other protocols, RemoteAddr is usually nil for connections
// accepted by a listener.
func (c *UnixConn) RemoteAddr() Addr {
        if !c.ok() {
                return nil
        }
        return c.fd.raddr
}

// SetDeadline implements the Conn SetDeadline method.
func (c *UnixConn) SetDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setDeadline(c.fd, t)
}

// SetReadDeadline implements the Conn SetReadDeadline method.
func (c *UnixConn) SetReadDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setReadDeadline(c.fd, t)
}

// SetWriteDeadline implements the Conn SetWriteDeadline method.
func (c *UnixConn) SetWriteDeadline(t time.Time) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setWriteDeadline(c.fd, t)
}

// SetReadBuffer sets the size of the operating system's
// receive buffer associated with the connection.
func (c *UnixConn) SetReadBuffer(bytes int) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setReadBuffer(c.fd, bytes)
}

// SetWriteBuffer sets the size of the operating system's
// transmit buffer associated with the connection.
func (c *UnixConn) SetWriteBuffer(bytes int) error {
        if !c.ok() {
                return os.EINVAL
        }
        return setWriteBuffer(c.fd, bytes)
}

// ReadFromUnix reads a packet from c, copying the payload into b.
// It returns the number of bytes copied into b and the return address
// that was on the packet.
//
// ReadFromUnix can be made to time out and return
// an error with Timeout() == true after a fixed time limit;
// see SetDeadline and SetReadDeadline.
func (c *UnixConn) ReadFromUnix(b []byte) (n int, addr *UnixAddr, err error) {
        if !c.ok() {
                return 0, nil, os.EINVAL
        }
        n, sa, err := c.fd.ReadFrom(b)
        switch sa := sa.(type) {
        case *syscall.SockaddrUnix:
                addr = &UnixAddr{sa.Name, sotypeToNet(c.fd.sotype)}
        }
        return
}

// ReadFrom implements the PacketConn ReadFrom method.
func (c *UnixConn) ReadFrom(b []byte) (n int, addr Addr, err error) {
        if !c.ok() {
                return 0, nil, os.EINVAL
        }
        n, uaddr, err := c.ReadFromUnix(b)
        return n, uaddr.toAddr(), err
}

// WriteToUnix writes a packet to addr via c, copying the payload from b.
//
// WriteToUnix can be made to time out and return
// an error with Timeout() == true after a fixed time limit;
// see SetDeadline and SetWriteDeadline.
// On packet-oriented connections, write timeouts are rare.
func (c *UnixConn) WriteToUnix(b []byte, addr *UnixAddr) (n int, err error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        if addr.Net != sotypeToNet(c.fd.sotype) {
                return 0, os.EAFNOSUPPORT
        }
        sa := &syscall.SockaddrUnix{Name: addr.Name}
        return c.fd.WriteTo(b, sa)
}

// WriteTo implements the PacketConn WriteTo method.
func (c *UnixConn) WriteTo(b []byte, addr Addr) (n int, err error) {
        if !c.ok() {
                return 0, os.EINVAL
        }
        a, ok := addr.(*UnixAddr)
        if !ok {
                return 0, &OpError{"write", c.fd.net, addr, os.EINVAL}
        }
        return c.WriteToUnix(b, a)
}

func (c *UnixConn) ReadMsgUnix(b, oob []byte) (n, oobn, flags int, addr *UnixAddr, err error) {
        if !c.ok() {
                return 0, 0, 0, nil, os.EINVAL
        }
        n, oobn, flags, sa, err := c.fd.ReadMsg(b, oob)
        switch sa := sa.(type) {
        case *syscall.SockaddrUnix:
                addr = &UnixAddr{sa.Name, sotypeToNet(c.fd.sotype)}
        }
        return
}

func (c *UnixConn) WriteMsgUnix(b, oob []byte, addr *UnixAddr) (n, oobn int, err error) {
        if !c.ok() {
                return 0, 0, os.EINVAL
        }
        if addr != nil {
                if addr.Net != sotypeToNet(c.fd.sotype) {
                        return 0, 0, os.EAFNOSUPPORT
                }
                sa := &syscall.SockaddrUnix{Name: addr.Name}
                return c.fd.WriteMsg(b, oob, sa)
        }
        return c.fd.WriteMsg(b, oob, nil)
}

// File returns a copy of the underlying os.File, set to blocking mode.
// It is the caller's responsibility to close f when finished.
// Closing c does not affect f, and closing f does not affect c.
func (c *UnixConn) File() (f *os.File, err error) { return c.fd.dup() }

// DialUnix connects to the remote address raddr on the network net,
// which must be "unix" or "unixgram".  If laddr is not nil, it is used
// as the local address for the connection.
func DialUnix(net string, laddr, raddr *UnixAddr) (*UnixConn, error) {
        fd, err := unixSocket(net, laddr, raddr, "dial")
        if err != nil {
                return nil, err
        }
        return newUnixConn(fd), nil
}

// UnixListener is a Unix domain socket listener.
// Clients should typically use variables of type Listener
// instead of assuming Unix domain sockets.
type UnixListener struct {
        fd   *netFD
        path string
}

// ListenUnix announces on the Unix domain socket laddr and returns a Unix listener.
// Net must be "unix" (stream sockets).
func ListenUnix(net string, laddr *UnixAddr) (*UnixListener, error) {
        if net != "unix" && net != "unixgram" && net != "unixpacket" {
                return nil, UnknownNetworkError(net)
        }
        if laddr != nil {
                laddr = &UnixAddr{laddr.Name, net} // make our own copy
        }
        fd, err := unixSocket(net, laddr, nil, "listen")
        if err != nil {
                return nil, err
        }
        err = syscall.Listen(fd.sysfd, listenerBacklog)
        if err != nil {
                closesocket(fd.sysfd)
                return nil, &OpError{Op: "listen", Net: net, Addr: laddr, Err: err}
        }
        return &UnixListener{fd, laddr.Name}, nil
}

// AcceptUnix accepts the next incoming call and returns the new connection
// and the remote address.
func (l *UnixListener) AcceptUnix() (*UnixConn, error) {
        if l == nil || l.fd == nil {
                return nil, os.EINVAL
        }
        fd, err := l.fd.accept(sockaddrToUnix)
        if err != nil {
                return nil, err
        }
        c := newUnixConn(fd)
        return c, nil
}

// Accept implements the Accept method in the Listener interface;
// it waits for the next call and returns a generic Conn.
func (l *UnixListener) Accept() (c Conn, err error) {
        c1, err := l.AcceptUnix()
        if err != nil {
                return nil, err
        }
        return c1, nil
}

// Close stops listening on the Unix address.
// Already accepted connections are not closed.
func (l *UnixListener) Close() error {
        if l == nil || l.fd == nil {
                return os.EINVAL
        }

        // The operating system doesn't clean up
        // the file that announcing created, so
        // we have to clean it up ourselves.
        // There's a race here--we can't know for
        // sure whether someone else has come along
        // and replaced our socket name already--
        // but this sequence (remove then close)
        // is at least compatible with the auto-remove
        // sequence in ListenUnix.  It's only non-Go
        // programs that can mess us up.
        if l.path[0] != '@' {
                syscall.Unlink(l.path)
        }
        err := l.fd.Close()
        l.fd = nil
        return err
}

// Addr returns the listener's network address.
func (l *UnixListener) Addr() Addr { return l.fd.laddr }

// SetDeadline sets the deadline associated with the listener.
// A zero time value disables the deadline.
func (l *UnixListener) SetDeadline(t time.Time) (err error) {
        if l == nil || l.fd == nil {
                return os.EINVAL
        }
        return setDeadline(l.fd, t)
}

// File returns a copy of the underlying os.File, set to blocking mode.
// It is the caller's responsibility to close f when finished.
// Closing c does not affect f, and closing f does not affect c.
func (l *UnixListener) File() (f *os.File, err error) { return l.fd.dup() }

// ListenUnixgram listens for incoming Unix datagram packets addressed to the
// local address laddr.  The returned connection c's ReadFrom
// and WriteTo methods can be used to receive and send UDP
// packets with per-packet addressing.  The network net must be "unixgram".
func ListenUnixgram(net string, laddr *UnixAddr) (*UDPConn, error) {
        switch net {
        case "unixgram":
        default:
                return nil, UnknownNetworkError(net)
        }
        if laddr == nil {
                return nil, &OpError{"listen", net, nil, errMissingAddress}
        }
        fd, err := unixSocket(net, laddr, nil, "listen")
        if err != nil {
                return nil, err
        }
        return newUDPConn(fd), nil
}