github.com/quic-go/quic-go@v0.44.0/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  	"golang.org/x/sys/unix"
    12  
    13  	"github.com/quic-go/quic-go/internal/utils"
    14  )
    15  
    16  func setDF(rawConn syscall.RawConn) (bool, error) {
    17  	// Setting DF bit is only supported from macOS11
    18  	// https://github.com/chromium/chromium/blob/117.0.5881.2/net/socket/udp_socket_posix.cc#L555
    19  	if supportsDF, err := isAtLeastMacOS11(); !supportsDF || err != nil {
    20  		return false, err
    21  	}
    22  
    23  	// Enabling IP_DONTFRAG will force the kernel to return "sendto: message too long"
    24  	// and the datagram will not be fragmented
    25  	var errDFIPv4, errDFIPv6 error
    26  	if err := rawConn.Control(func(fd uintptr) {
    27  		errDFIPv4 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_DONTFRAG, 1)
    28  		errDFIPv6 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_DONTFRAG, 1)
    29  	}); err != nil {
    30  		return false, err
    31  	}
    32  	switch {
    33  	case errDFIPv4 == nil && errDFIPv6 == nil:
    34  		utils.DefaultLogger.Debugf("Setting DF for IPv4 and IPv6.")
    35  	case errDFIPv4 == nil && errDFIPv6 != nil:
    36  		utils.DefaultLogger.Debugf("Setting DF for IPv4.")
    37  	case errDFIPv4 != nil && errDFIPv6 == nil:
    38  		utils.DefaultLogger.Debugf("Setting DF for IPv6.")
    39  		// On macOS, the syscall for setting DF bit for IPv4 fails on dual-stack listeners.
    40  		// Treat the connection as not having DF enabled, even though the DF bit will be set
    41  		// when used for IPv6.
    42  		// See https://github.com/quic-go/quic-go/issues/3793 for details.
    43  		return false, nil
    44  	case errDFIPv4 != nil && errDFIPv6 != nil:
    45  		return false, errors.New("setting DF failed for both IPv4 and IPv6")
    46  	}
    47  	return true, nil
    48  }
    49  
    50  func isSendMsgSizeErr(err error) bool {
    51  	return errors.Is(err, unix.EMSGSIZE)
    52  }
    53  
    54  func isRecvMsgSizeErr(error) bool { return false }
    55  
    56  func isAtLeastMacOS11() (bool, error) {
    57  	uname := &unix.Utsname{}
    58  	err := unix.Uname(uname)
    59  	if err != nil {
    60  		return false, err
    61  	}
    62  
    63  	release := string(uname.Release[:])
    64  	if idx := strings.Index(release, "."); idx != -1 {
    65  		version, err := strconv.Atoi(release[:idx])
    66  		if err != nil {
    67  			return false, err
    68  		}
    69  		// Darwin version 20 is macOS version 11
    70  		// https://en.wikipedia.org/wiki/Darwin_(operating_system)#Darwin_20_onwards
    71  		return version >= 20, nil
    72  	}
    73  	return false, nil
    74  }