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

     1  //go:build linux
     2  
     3  package quic
     4  
     5  import (
     6  	"errors"
     7  	"syscall"
     8  
     9  	"github.com/sagernet/quic-go/internal/utils"
    10  	"golang.org/x/sys/unix"
    11  )
    12  
    13  func setDF(rawConn syscall.RawConn) (bool, error) {
    14  	// Enabling IP_MTU_DISCOVER will force the kernel to return "sendto: message too long"
    15  	// and the datagram will not be fragmented
    16  	var errDFIPv4, errDFIPv6 error
    17  	if err := rawConn.Control(func(fd uintptr) {
    18  		errDFIPv4 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IP, unix.IP_MTU_DISCOVER, unix.IP_PMTUDISC_DO)
    19  		errDFIPv6 = unix.SetsockoptInt(int(fd), unix.IPPROTO_IPV6, unix.IPV6_MTU_DISCOVER, unix.IPV6_PMTUDISC_DO)
    20  	}); err != nil {
    21  		return false, err
    22  	}
    23  	switch {
    24  	case errDFIPv4 == nil && errDFIPv6 == nil:
    25  		utils.DefaultLogger.Debugf("Setting DF for IPv4 and IPv6.")
    26  	case errDFIPv4 == nil && errDFIPv6 != nil:
    27  		utils.DefaultLogger.Debugf("Setting DF for IPv4.")
    28  	case errDFIPv4 != nil && errDFIPv6 == nil:
    29  		utils.DefaultLogger.Debugf("Setting DF for IPv6.")
    30  	case errDFIPv4 != nil && errDFIPv6 != nil:
    31  		utils.DefaultLogger.Debugf("Setting DF failed for both IPv4 and IPv6.")
    32  	}
    33  	return true, nil
    34  }
    35  
    36  func isSendMsgSizeErr(err error) bool {
    37  	// https://man7.org/linux/man-pages/man7/udp.7.html
    38  	return errors.Is(err, unix.EMSGSIZE)
    39  }
    40  
    41  func isRecvMsgSizeErr(error) bool { return false }