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|
package ndpcmd
import (
"context"
"errors"
"fmt"
"log"
"net"
"net/netip"
"time"
"github.com/mdlayher/ndp"
)
func sendReceiveLoop(
ctx context.Context,
c *ndp.Conn,
ll *log.Logger,
m ndp.Message,
dst netip.Addr,
check func(m ndp.Message) bool,
) error {
for i := 0; ; i++ {
msg, from, err := sendReceive(ctx, c, m, dst, check)
switch err {
case context.Canceled:
fmt.Println()
ll.Printf("canceled, sent %d message(s)", i+1)
return err
case errRetry:
fmt.Print(".")
continue
case nil:
fmt.Println()
printMessage(ll, msg, from)
return nil
default:
return err
}
}
}
func receiveLoop(
ctx context.Context,
c *ndp.Conn,
ll *log.Logger,
check func(m ndp.Message) bool,
recv func(ll *log.Logger, msg ndp.Message, from netip.Addr),
) error {
if recv == nil {
recv = printMessage
}
var count int
for {
msg, from, err := receive(ctx, c, check)
switch err {
case context.Canceled:
ll.Printf("received %d message(s)", count)
return nil
case errRetry:
continue
case nil:
count++
recv(ll, msg, from)
default:
return err
}
}
}
var errRetry = errors.New("retry")
func sendReceive(
ctx context.Context,
c *ndp.Conn,
m ndp.Message,
dst netip.Addr,
check func(m ndp.Message) bool,
) (ndp.Message, netip.Addr, error) {
if err := c.WriteTo(m, nil, dst); err != nil {
return nil, netip.Addr{}, fmt.Errorf("failed to write message: %v", err)
}
return receive(ctx, c, check)
}
func receive(
ctx context.Context,
c *ndp.Conn,
check func(m ndp.Message) bool,
) (ndp.Message, netip.Addr, error) {
if err := c.SetReadDeadline(time.Now().Add(1 * time.Second)); err != nil {
return nil, netip.Addr{}, fmt.Errorf("failed to set deadline: %v", err)
}
msg, _, from, err := c.ReadFrom()
if err == nil {
if check != nil && !check(msg) {
// Read a message, but it isn't the one we want. Keep trying.
return nil, netip.Addr{}, errRetry
}
// Got a message that passed the check, if check was not nil.
return msg, from, nil
}
// Was the context canceled already?
select {
case <-ctx.Done():
return nil, netip.Addr{}, ctx.Err()
default:
}
// Was the error caused by a read timeout, and should the loop continue?
if nerr, ok := err.(net.Error); ok && nerr.Timeout() {
return nil, netip.Addr{}, errRetry
}
return nil, netip.Addr{}, fmt.Errorf("failed to read message: %v", err)
}
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