tailscale/safesocket/unixsocket.go

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// Copyright (c) 2020 Tailscale Inc & 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 !windows
package safesocket
import (
"fmt"
"net"
"os"
)
func path(vendor, name string) string {
return fmt.Sprintf("%s-%s.sock", vendor, name)
}
func ConnCloseRead(c net.Conn) error {
return c.(*net.UnixConn).CloseRead()
}
func ConnCloseWrite(c net.Conn) error {
return c.(*net.UnixConn).CloseWrite()
}
// TODO(apenwarr): handle magic cookie auth
func Connect(cookie, vendor, name string, port uint16) (net.Conn, error) {
pipe, err := net.Dial("unix", path(vendor, name))
if err != nil {
return nil, err
}
return pipe, err
}
// TODO(apenwarr): handle magic cookie auth
func Listen(cookie, vendor, name string, port uint16) (net.Listener, uint16, error) {
// Unix sockets hang around in the filesystem even after nobody
// is listening on them. (Which is really unfortunate but long-
// entrenched semantics.) Try connecting first; if it works, then
// the socket is still live, so let's not replace it. If it doesn't
// work, then replace it.
//
// Note that there's a race condition between these two steps. A
// "proper" daemon usually uses a dance involving pidfiles to first
// ensure that no other instances of itself are running, but that's
// beyond the scope of our simple socket library.
p := path(vendor, name)
c, err := net.Dial("unix", p)
if err == nil {
c.Close()
return nil, 0, fmt.Errorf("%v: address already in use", p)
}
_ = os.Remove(p)
pipe, err := net.Listen("unix", p)
if err != nil {
return nil, 0, err
}
os.Chmod(p, 0666)
return pipe, 0, err
}