github.com/ooni/psiphon/tunnel-core@v0.0.0-20230105123940-fe12a24c96ee/oovendor/quic-go/conn_df_linux.go (about)

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