github.com/sagernet/quic-go@v0.43.1-beta.1/sys_conn_df_darwin.go (about)

     1  //go:build darwin
     2  
     3  package quic
     4  
     5  import (
     6  	"errors"
     7  	"strconv"
     8  	"strings"
     9  	"syscall"
    10  
    11  	"github.com/sagernet/quic-go/internal/utils"
    12  	"golang.org/x/sys/unix"
    13  )
    14  
    15  func setDF(rawConn syscall.RawConn) (bool, error) {
    16  	// Setting DF bit is only supported from macOS11
    17  	// https://github.com/chromium/chromium/blob/117.0.5881.2/net/socket/udp_socket_posix.cc#L555
    18  	if supportsDF, err := isAtLeastMacOS11(); !supportsDF || err != nil {
    19  		return false, err
    20  	}
    21  
    22  	// Enabling IP_DONTFRAG will force the kernel to return "sendto: message too long"
    23  	// and the datagram will not be fragmented
    24  	var errDFIPv4, errDFIPv6 error
    25  	if err := rawConn.Control(func(fd uintptr) {
    26  		errDFIPv4 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_DONTFRAG, 1)
    27  		errDFIPv6 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_DONTFRAG, 1)
    28  	}); err != nil {
    29  		return false, err
    30  	}
    31  	switch {
    32  	case errDFIPv4 == nil && errDFIPv6 == nil:
    33  		utils.DefaultLogger.Debugf("Setting DF for IPv4 and IPv6.")
    34  	case errDFIPv4 == nil && errDFIPv6 != nil:
    35  		utils.DefaultLogger.Debugf("Setting DF for IPv4.")
    36  	case errDFIPv4 != nil && errDFIPv6 == nil:
    37  		utils.DefaultLogger.Debugf("Setting DF for IPv6.")
    38  		// On macOS, the syscall for setting DF bit for IPv4 fails on dual-stack listeners.
    39  		// Treat the connection as not having DF enabled, even though the DF bit will be set
    40  		// when used for IPv6.
    41  		// See https://github.com/sagernet/quic-go/issues/3793 for details.
    42  		return false, nil
    43  	case errDFIPv4 != nil && errDFIPv6 != nil:
    44  		return false, errors.New("setting DF failed for both IPv4 and IPv6")
    45  	}
    46  	return true, nil
    47  }
    48  
    49  func isSendMsgSizeErr(err error) bool {
    50  	return errors.Is(err, unix.EMSGSIZE)
    51  }
    52  
    53  func isRecvMsgSizeErr(error) bool { return false }
    54  
    55  func isAtLeastMacOS11() (bool, error) {
    56  	uname := &unix.Utsname{}
    57  	err := unix.Uname(uname)
    58  	if err != nil {
    59  		return false, err
    60  	}
    61  
    62  	release := string(uname.Release[:])
    63  	if idx := strings.Index(release, "."); idx != -1 {
    64  		version, err := strconv.Atoi(release[:idx])
    65  		if err != nil {
    66  			return false, err
    67  		}
    68  		// Darwin version 20 is macOS version 11
    69  		// https://en.wikipedia.org/wiki/Darwin_(operating_system)#Darwin_20_onwards
    70  		return version >= 20, nil
    71  	}
    72  	return false, nil
    73  }