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loop.go
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loop.go
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package icmp
import (
"bytes"
"encoding/binary"
"fmt"
"math/rand"
"net"
"sync"
"time"
"golang.org/x/net/icmp"
"golang.org/x/net/ipv4"
"golang.org/x/net/ipv6"
)
type icmpLoop struct {
conn4, conn6 *icmp.PacketConn
recv chan packet
mutex sync.Mutex
requests map[requestID]*requestContext
}
type timeoutError struct {
}
const (
// iana types
protocolICMP = 1
protocolIPv6ICMP = 58
)
type packet struct {
ts time.Time
addr net.Addr
Type icmp.Type // type, either ipv4.ICMPType or ipv6.ICMPType
Code int // code
Checksum int // checksum
Echo icmp.Echo
}
type requestID struct {
addr string
proto int
id int
seq int
}
type requestContext struct {
l *icmpLoop
id requestID
ts time.Time
result chan requestResult
}
type requestResult struct {
packet packet
err error
}
var (
loopInit sync.Once
loop *icmpLoop
)
func newICMPLoop() (*icmpLoop, error) {
conn4, err := icmp.ListenPacket("ip4:icmp", "")
if err != nil {
return nil, err
}
conn6, err := icmp.ListenPacket("ip6:ipv6-icmp", "")
if err != nil {
conn4.Close()
return nil, err
}
l := &icmpLoop{
conn4: conn4,
conn6: conn6,
recv: make(chan packet, 16),
requests: map[requestID]*requestContext{},
}
go l.runICMPRecv(conn4, protocolICMP)
go l.runICMPRecv(conn6, protocolIPv6ICMP)
return l, nil
}
func (l *icmpLoop) runICMPRecv(conn *icmp.PacketConn, proto int) {
for {
bytes := make([]byte, 512)
conn.SetReadDeadline(time.Now().Add(1 * time.Second))
_, addr, err := conn.ReadFrom(bytes)
if err != nil {
if neterr, ok := err.(*net.OpError); ok {
if neterr.Timeout() {
continue
} else {
// TODO: report error and quit loop
return
}
}
}
ts := time.Now()
m, err := icmp.ParseMessage(proto, bytes)
if err != nil {
continue
}
// process echo reply only
if m.Type != ipv4.ICMPTypeEchoReply && m.Type != ipv6.ICMPTypeEchoReply {
continue
}
echo, ok := m.Body.(*icmp.Echo)
if !ok {
continue
}
id := requestID{
addr: addr.String(),
proto: proto,
id: echo.ID,
seq: echo.Seq,
}
l.mutex.Lock()
ctx := l.requests[id]
if ctx != nil {
delete(l.requests, id)
}
l.mutex.Unlock()
// no return context available for echo reply -> handle next message
if ctx == nil {
continue
}
ctx.result <- requestResult{
packet: packet{
ts: ts,
addr: addr,
Type: m.Type,
Code: m.Code,
Checksum: m.Checksum,
Echo: *echo,
},
}
}
}
func (l *icmpLoop) ping(
addr *net.IPAddr,
timeout time.Duration,
interval time.Duration,
) (time.Duration, int, error) {
var err error
toTimer := time.NewTimer(timeout)
defer toTimer.Stop()
ticker := time.NewTicker(interval)
defer ticker.Stop()
done := false
doneSignal := make(chan struct{})
success := false
var rtt time.Duration
// results accepts first response received only
results := make(chan time.Duration, 1)
requests := 0
awaitResponse := func(ctx *requestContext) {
select {
case <-doneSignal:
ctx.Stop()
case r := <-ctx.result:
// ctx is removed from request tables automatically a response is
// received. No need to stop it.
// try to push RTT. The first result available will be reported
select {
case results <- r.packet.ts.Sub(ctx.ts):
default:
}
}
}
for !done {
var ctx *requestContext
ctx, err = l.sendEchoRequest(addr)
if err != nil {
close(doneSignal)
break
}
go awaitResponse(ctx)
requests++
select {
case <-toTimer.C:
// no response for any active request received. Finish loop
// and remove all requests from request table.
done = true
close(doneSignal)
case <-ticker.C:
// No response yet. Send another request with every tick
case rtt = <-results:
success = true
done = true
close(doneSignal)
}
}
if err != nil {
return 0, 0, err
}
if !success {
return 0, 0, timeoutError{}
}
return rtt, requests, nil
}
func (l *icmpLoop) sendEchoRequest(addr *net.IPAddr) (*requestContext, error) {
var conn *icmp.PacketConn
var proto int
var typ icmp.Type
if l == nil {
panic("icmp loop not initialized")
}
if isIPv4(addr.IP) {
conn = l.conn4
proto = protocolICMP
typ = ipv4.ICMPTypeEcho
} else if isIPv6(addr.IP) {
conn = l.conn6
proto = protocolIPv6ICMP
typ = ipv6.ICMPTypeEchoRequest
} else {
return nil, fmt.Errorf("%v is unknown ip address", addr)
}
id := requestID{
addr: addr.String(),
proto: proto,
id: rand.Intn(0xffff),
seq: rand.Intn(0xffff),
}
ctx := &requestContext{
l: l,
id: id,
result: make(chan requestResult, 1),
}
l.mutex.Lock()
l.requests[id] = ctx
l.mutex.Unlock()
payloadBuf := make([]byte, 0, 8)
payload := bytes.NewBuffer(payloadBuf)
ts := time.Now()
binary.Write(payload, binary.BigEndian, ts.UnixNano())
msg := &icmp.Message{
Type: typ,
Body: &icmp.Echo{
ID: id.id,
Seq: id.seq,
Data: payload.Bytes(),
},
}
encoded, _ := msg.Marshal(nil)
_, err := conn.WriteTo(encoded, addr)
if err != nil {
return nil, err
}
ctx.ts = ts
return ctx, nil
}
// timeoutError implements net.Error interface
func (timeoutError) Error() string { return "ping timeout" }
func (timeoutError) Timeout() bool { return true }
func (timeoutError) Temporary() bool { return true }
func (r *requestContext) Stop() {
r.l.mutex.Lock()
delete(r.l.requests, r.id)
r.l.mutex.Unlock()
}