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//go:build darwin
package quic
import (
"errors"
"fmt"
"strconv"
"strings"
"syscall"
"golang.org/x/sys/unix"
)
// for macOS versions, see https://en.wikipedia.org/wiki/Darwin_(operating_system)#Darwin_20_onwards
const (
macOSVersion11 = 20
macOSVersion15 = 24
)
func setDF(rawConn syscall.RawConn) (bool, error) {
// Setting DF bit is only supported from macOS 11.
// https://github.com/chromium/chromium/blob/117.0.5881.2/net/socket/udp_socket_posix.cc#L555
version, err := getMacOSVersion()
if err != nil || version < macOSVersion11 {
return false, err
}
var controlErr error
var disableDF bool
if err := rawConn.Control(func(fd uintptr) {
addr, err := unix.Getsockname(int(fd))
if err != nil {
controlErr = fmt.Errorf("getsockname: %w", err)
return
}
// Dual-stack sockets are effectively IPv6 sockets (with IPV6_ONLY set to 0).
// On macOS, the DF bit on dual-stack sockets is controlled by the IPV6_DONTFRAG option.
// See https://datatracker.ietf.org/doc/draft-seemann-tsvwg-udp-fragmentation/ for details.
switch addr.(type) {
case *unix.SockaddrInet4:
controlErr = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_DONTFRAG, 1)
case *unix.SockaddrInet6:
controlErr = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_DONTFRAG, 1)
// Setting the DF bit on dual-stack sockets works since macOS Sequoia.
// Disable DF on dual-stack sockets before Sequoia.
if version < macOSVersion15 {
// check if this is a dual-stack socket by reading the IPV6_V6ONLY flag
v6only, err := unix.GetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_V6ONLY)
if err != nil {
controlErr = fmt.Errorf("getting IPV6_V6ONLY: %w", err)
return
}
disableDF = v6only == 0
}
default:
controlErr = fmt.Errorf("unknown address type: %T", addr)
}
}); err != nil {
return false, err
}
if controlErr != nil {
return false, controlErr
}
return !disableDF, nil
}
func isSendMsgSizeErr(err error) bool {
return errors.Is(err, unix.EMSGSIZE)
}
func isRecvMsgSizeErr(error) bool { return false }
func getMacOSVersion() (int, error) {
uname := &unix.Utsname{}
if err := unix.Uname(uname); err != nil {
return 0, err
}
release := string(uname.Release[:])
idx := strings.Index(release, ".")
if idx == -1 {
return 0, nil
}
version, err := strconv.Atoi(release[:idx])
if err != nil {
return 0, err
}
return version, nil
}
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