forked from prometheus/blackbox_exporter
/
icmp.go
95 lines (85 loc) · 2.18 KB
/
icmp.go
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package main
import (
"net"
"net/http"
"os"
"sync"
"time"
"golang.org/x/net/internal/iana"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv4"
"github.com/prometheus/log"
)
var (
icmpSequence uint16
icmpSequenceMutex sync.Mutex
)
func getICMPSequence() uint16 {
icmpSequenceMutex.Lock()
defer icmpSequenceMutex.Unlock()
icmpSequence+=1
return icmpSequence
}
func probeICMP(target string, w http.ResponseWriter, module Module) (success bool) {
deadline := time.Now().Add(module.Timeout)
socket, err := icmp.ListenPacket("ip4:icmp", "0.0.0.0")
if err != nil {
log.Errorf("Error listening to socket: %s", err)
return
}
defer socket.Close()
ip, err := net.ResolveIPAddr("ip4", target)
if err != nil {
log.Errorf("Error resolving address %s: %s", target, err)
return
}
seq := getICMPSequence()
pid := os.Getpid() & 0xffff
wm := icmp.Message{
Type: ipv4.ICMPTypeEcho, Code: 0,
Body: &icmp.Echo{
ID: pid, Seq: int(seq),
Data: []byte("Prometheus Blackbox Exporter"),
},
}
wb, err := wm.Marshal(nil)
if err != nil {
log.Errorf("Error marshalling packet for %s: %s", target, err)
return
}
if _, err := socket.WriteTo(wb, ip); err != nil {
log.Errorf("Error writing to socker for %s: %s", target, err)
return
}
rb := make([]byte, 1500)
if err := socket.SetReadDeadline(deadline); err != nil {
log.Errorf("Error setting socket deadline for %s: %s", target, err)
return
}
for {
n, peer, err := socket.ReadFrom(rb)
if err != nil {
if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
log.Infof("Timeout reading from socket for %s: %s", target, err)
return
}
log.Errorf("Error reading from socket for %s: %s", target, err)
continue
}
if peer.String() != ip.String() {
continue
}
rm, err := icmp.ParseMessage(iana.ProtocolICMP, rb[:n])
if err != nil {
log.Warnf("Error parsing ICMP message for %s: %s", target, err)
continue
}
if rm.Type == ipv4.ICMPTypeEchoReply {
// The ICMP package does not support unmarshalling
// messages, so assume this is the right sequence number.
success = true
return
}
}
return
}