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|
// +build !windows
/*
Package sockets is a simple unix domain socket wrapper.
Usage
For example:
import(
"fmt"
"net"
"os"
"github.com/docker/go-connections/sockets"
)
func main() {
l, err := sockets.NewUnixSocketWithOpts("/path/to/sockets",
sockets.WithChown(0,0),sockets.WithChmod(0660))
if err != nil {
panic(err)
}
echoStr := "hello"
go func() {
for {
conn, err := l.Accept()
if err != nil {
return
}
conn.Write([]byte(echoStr))
conn.Close()
}
}()
conn, err := net.Dial("unix", path)
if err != nil {
t.Fatal(err)
}
buf := make([]byte, 5)
if _, err := conn.Read(buf); err != nil {
panic(err)
} else if string(buf) != echoStr {
panic(fmt.Errorf("Msg may lost"))
}
}
*/
package sockets
import (
"net"
"os"
"syscall"
)
// SockOption sets up socket file's creating option
type SockOption func(string) error
// WithChown modifies the socket file's uid and gid
func WithChown(uid, gid int) SockOption {
return func(path string) error {
if err := os.Chown(path, uid, gid); err != nil {
return err
}
return nil
}
}
// WithChmod modifies socket file's access mode.
func WithChmod(mask os.FileMode) SockOption {
return func(path string) error {
if err := os.Chmod(path, mask); err != nil {
return err
}
return nil
}
}
// NewUnixSocketWithOpts creates a unix socket with the specified options.
// By default, socket permissions are 0000 (i.e.: no access for anyone); pass
// WithChmod() and WithChown() to set the desired ownership and permissions.
//
// This function temporarily changes the system's "umask" to 0777 to work around
// a race condition between creating the socket and setting its permissions. While
// this should only be for a short duration, it may affect other processes that
// create files/directories during that period.
func NewUnixSocketWithOpts(path string, opts ...SockOption) (net.Listener, error) {
if err := syscall.Unlink(path); err != nil && !os.IsNotExist(err) {
return nil, err
}
// net.Listen does not allow for permissions to be set. As a result, when
// specifying custom permissions ("WithChmod()"), there is a short time
// between creating the socket and applying the permissions, during which
// the socket permissions are Less restrictive than desired.
//
// To work around this limitation of net.Listen(), we temporarily set the
// umask to 0777, which forces the socket to be created with 000 permissions
// (i.e.: no access for anyone). After that, WithChmod() must be used to set
// the desired permissions.
//
// We don't use "defer" here, to reset the umask to its original value as soon
// as possible. Ideally we'd be able to detect if WithChmod() was passed as
// an option, and skip changing umask if default permissions are used.
origUmask := syscall.Umask(0777)
l, err := net.Listen("unix", path)
syscall.Umask(origUmask)
if err != nil {
return nil, err
}
for _, op := range opts {
if err := op(path); err != nil {
_ = l.Close()
return nil, err
}
}
return l, nil
}
// NewUnixSocket creates a unix socket with the specified path and group.
func NewUnixSocket(path string, gid int) (net.Listener, error) {
return NewUnixSocketWithOpts(path, WithChown(0, gid), WithChmod(0660))
}
|
