ctr: move signals to commands package

Signed-off-by: Jess Valarezo <valarezo.jessica@gmail.com>

cmd/ctr/commands/signals.go

@@ -0,0 +1,59 @@
+package commands
+
+import (
+	gocontext "context"
+	"fmt"
+	"os"
+	"os/signal"
+	"strconv"
+	"strings"
+	"syscall"
+
+	"github.com/containerd/containerd"
+	"github.com/sirupsen/logrus"
+)
+
+type killer interface {
+	Kill(gocontext.Context, syscall.Signal, ...containerd.KillOpts) error
+}
+
+// ForwardAllSignals forwards signals
+func ForwardAllSignals(ctx gocontext.Context, task killer) chan os.Signal {
+	sigc := make(chan os.Signal, 128)
+	signal.Notify(sigc)
+	go func() {
+		for s := range sigc {
+			logrus.Debug("forwarding signal ", s)
+			if err := task.Kill(ctx, s.(syscall.Signal)); err != nil {
+				logrus.WithError(err).Errorf("forward signal %s", s)
+			}
+		}
+	}()
+	return sigc
+}
+
+// StopCatch stops and closes a channel
+func StopCatch(sigc chan os.Signal) {
+	signal.Stop(sigc)
+	close(sigc)
+}
+
+// ParseSignal parses a given string into a syscall.Signal
+// it checks that the signal exists in the platform-appropriate signalMap
+func ParseSignal(rawSignal string) (syscall.Signal, error) {
+	s, err := strconv.Atoi(rawSignal)
+	if err == nil {
+		sig := syscall.Signal(s)
+		for _, msig := range signalMap {
+			if sig == msig {
+				return sig, nil
+			}
+		}
+		return -1, fmt.Errorf("unknown signal %q", rawSignal)
+	}
+	signal, ok := signalMap[strings.TrimPrefix(strings.ToUpper(rawSignal), "SIG")]
+	if !ok {
+		return -1, fmt.Errorf("unknown signal %q", rawSignal)
+	}
+	return signal, nil
+}