cloudflared-mirror/ingress/icmp_posix.go

146 lines
3.4 KiB
Go

//go:build darwin || linux
package ingress
// This file extracts logic shared by Linux and Darwin implementation if ICMPProxy.
import (
"fmt"
"net"
"net/netip"
"github.com/google/gopacket/layers"
"golang.org/x/net/icmp"
"github.com/cloudflare/cloudflared/packet"
)
// Opens a non-privileged ICMP socket on Linux and Darwin
func newICMPConn(listenIP netip.Addr) (*icmp.PacketConn, error) {
network := "udp6"
if listenIP.Is4() {
network = "udp4"
}
return icmp.ListenPacket(network, listenIP.String())
}
func netipAddr(addr net.Addr) (netip.Addr, bool) {
udpAddr, ok := addr.(*net.UDPAddr)
if !ok {
return netip.Addr{}, false
}
return netip.AddrFromSlice(udpAddr.IP)
}
type flowID struct {
srcIP netip.Addr
echoID int
}
func (fi *flowID) Type() string {
return "srcIP_echoID"
}
func (fi *flowID) String() string {
return fmt.Sprintf("%s:%d", fi.srcIP, fi.echoID)
}
// icmpEchoFlow implements the packet.Funnel interface.
type icmpEchoFlow struct {
*packet.RawPacketFunnel
assignedEchoID int
originalEchoID int
// it's up to the user to ensure respEncoder is not used concurrently
respEncoder *packet.Encoder
}
func newICMPEchoFlow(src netip.Addr, sendPipe, returnPipe packet.FunnelUniPipe, assignedEchoID, originalEchoID int, respEncoder *packet.Encoder) *icmpEchoFlow {
return &icmpEchoFlow{
RawPacketFunnel: packet.NewRawPacketFunnel(src, sendPipe, returnPipe),
assignedEchoID: assignedEchoID,
originalEchoID: originalEchoID,
respEncoder: respEncoder,
}
}
// sendToDst rewrites the echo ID to the one assigned to this flow
func (ief *icmpEchoFlow) sendToDst(dst netip.Addr, msg *icmp.Message) error {
originalEcho, err := getICMPEcho(msg)
if err != nil {
return err
}
sendMsg := icmp.Message{
Type: msg.Type,
Code: msg.Code,
Body: &icmp.Echo{
ID: ief.assignedEchoID,
Seq: originalEcho.Seq,
Data: originalEcho.Data,
},
}
// For IPv4, the pseudoHeader is not used because the checksum is always calculated
var pseudoHeader []byte = nil
serializedPacket, err := sendMsg.Marshal(pseudoHeader)
if err != nil {
return err
}
return ief.SendToDst(dst, packet.RawPacket{Data: serializedPacket})
}
// returnToSrc rewrites the echo ID to the original echo ID from the eyeball
func (ief *icmpEchoFlow) returnToSrc(reply *echoReply) error {
reply.echo.ID = ief.originalEchoID
reply.msg.Body = reply.echo
pk := packet.ICMP{
IP: &packet.IP{
Src: reply.from,
Dst: ief.Src,
Protocol: layers.IPProtocol(reply.msg.Type.Protocol()),
},
Message: reply.msg,
}
serializedPacket, err := ief.respEncoder.Encode(&pk)
if err != nil {
return err
}
return ief.ReturnToSrc(serializedPacket)
}
type echoReply struct {
from netip.Addr
msg *icmp.Message
echo *icmp.Echo
}
func parseReply(from net.Addr, rawMsg []byte) (*echoReply, error) {
fromAddr, ok := netipAddr(from)
if !ok {
return nil, fmt.Errorf("cannot convert %s to netip.Addr", from)
}
proto := layers.IPProtocolICMPv4
if fromAddr.Is6() {
proto = layers.IPProtocolICMPv6
}
msg, err := icmp.ParseMessage(int(proto), rawMsg)
if err != nil {
return nil, err
}
echo, err := getICMPEcho(msg)
if err != nil {
return nil, err
}
return &echoReply{
from: fromAddr,
msg: msg,
echo: echo,
}, nil
}
func toICMPEchoFlow(funnel packet.Funnel) (*icmpEchoFlow, error) {
icmpFlow, ok := funnel.(*icmpEchoFlow)
if !ok {
return nil, fmt.Errorf("%v is not *ICMPEchoFunnel", funnel)
}
return icmpFlow, nil
}