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icmp.go
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icmp.go
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// Copyright 2016 The Prometheus Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package prober
import (
"bytes"
"context"
"net"
"os"
"sync"
"time"
"github.com/go-kit/kit/log"
"github.com/go-kit/kit/log/level"
"github.com/prometheus/client_golang/prometheus"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
"github.com/prometheus/blackbox_exporter/config"
)
var (
icmpSequence uint16
icmpSequenceMutex sync.Mutex
)
func getICMPSequence() uint16 {
icmpSequenceMutex.Lock()
defer icmpSequenceMutex.Unlock()
icmpSequence++
return icmpSequence
}
func ProbeICMP(ctx context.Context, target string, module config.Module, registry *prometheus.Registry, logger log.Logger) (success bool) {
var (
socket *icmp.PacketConn
requestType icmp.Type
replyType icmp.Type
)
timeoutDeadline, _ := ctx.Deadline()
deadline := time.Now().Add(timeoutDeadline.Sub(time.Now()))
ip, err := chooseProtocol(module.ICMP.PreferredIPProtocol, target, registry, logger)
if err != nil {
level.Warn(logger).Log("msg", "Error resolving address", "err", err)
return false
}
level.Info(logger).Log("msg", "Creating socket")
if ip.IP.To4() == nil {
requestType = ipv6.ICMPTypeEchoRequest
replyType = ipv6.ICMPTypeEchoReply
socket, err = icmp.ListenPacket("ip6:ipv6-icmp", "::")
} else {
requestType = ipv4.ICMPTypeEcho
replyType = ipv4.ICMPTypeEchoReply
socket, err = icmp.ListenPacket("ip4:icmp", "0.0.0.0")
}
if err != nil {
level.Error(logger).Log("msg", "Error listening to socket", "err", err)
return
}
defer socket.Close()
body := &icmp.Echo{
ID: os.Getpid() & 0xffff,
Seq: int(getICMPSequence()),
Data: []byte("Prometheus Blackbox Exporter"),
}
level.Info(logger).Log("msg", "Creating ICMP packet", "seq", body.Seq, "id", body.ID)
wm := icmp.Message{
Type: requestType,
Code: 0,
Body: body,
}
wb, err := wm.Marshal(nil)
if err != nil {
level.Error(logger).Log("msg", "Error marshalling packet", "err", err)
return
}
level.Info(logger).Log("msg", "Writing out packet")
if _, err = socket.WriteTo(wb, ip); err != nil {
level.Warn(logger).Log("msg", "Error writing to socket", "err", err)
return
}
// Reply should be the same except for the message type.
wm.Type = replyType
wb, err = wm.Marshal(nil)
if err != nil {
level.Error(logger).Log("msg", "Error marshalling packet", "err", err)
return
}
rb := make([]byte, 1500)
if err := socket.SetReadDeadline(deadline); err != nil {
level.Error(logger).Log("msg", "Error setting socket deadline", "err", err)
return
}
level.Info(logger).Log("msg", "Waiting for reply packets")
for {
n, peer, err := socket.ReadFrom(rb)
if err != nil {
if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
level.Warn(logger).Log("msg", "Timeout reading from socket", "err", err)
return
}
level.Error(logger).Log("msg", "Error reading from socket", "err", err)
continue
}
if peer.String() != ip.String() {
continue
}
if replyType == ipv6.ICMPTypeEchoReply {
// Clear checksum to make comparison succeed.
rb[2] = 0
rb[3] = 0
}
if bytes.Compare(rb[:n], wb) == 0 {
level.Info(logger).Log("msg", "Found matching reply packet")
return true
}
}
}