add kubernetes pause

Add the k8s pause binary to `pause/pause.c` and do the plumbing in the
Makefile to install it in $libexec/podman/pause/pause.  It is intended to
replace the k8s pause image and hence the need for network connectivity
when creating pods.

[NO NEW TESTS NEEDED] since it will be tested in a following commit.

Signed-off-by: Valentin Rothberg <rothberg@redhat.com>

1 files changed, 69 insertions, 0 deletions

diff --git a/pause/pause.c b/pause/pause.c
new file mode 100644
index 000000000..1e363bd7a
--- /dev/null
+++ b/pause/pause.c
@@ -0,0 +1,69 @@
+/*
+Copyright 2016 The Kubernetes Authors.
+Copyright 2021 The Podman 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.
+*/
+
+#include <signal.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+#include <unistd.h>
+
+#define STRINGIFY(x) #x
+#define VERSION_STRING(x) STRINGIFY(x)
+
+#ifndef VERSION
+#define VERSION HEAD
+#endif
+
+static void sigdown(int signo) {
+  psignal(signo, "Shutting down, got signal");
+  exit(0);
+}
+
+static void sigreap(int signo) {
+  while (waitpid(-1, NULL, WNOHANG) > 0)
+    ;
+}
+
+int main(int argc, char **argv) {
+  int i;
+  for (i = 1; i < argc; ++i) {
+    if (!strcasecmp(argv[i], "-v")) {
+      printf("pause.c %s\n", VERSION_STRING(VERSION));
+      return 0;
+    }
+  }
+
+  if (getpid() != 1)
+    /* Not an error because pause sees use outside of infra containers. */
+    fprintf(stderr, "Warning: pause should be the first process\n");
+
+  if (sigaction(SIGINT, &(struct sigaction){.sa_handler = sigdown}, NULL) < 0)
+    return 1;
+  if (sigaction(SIGTERM, &(struct sigaction){.sa_handler = sigdown}, NULL) < 0)
+    return 2;
+  if (sigaction(SIGCHLD, &(struct sigaction){.sa_handler = sigreap,
+                                             .sa_flags = SA_NOCLDSTOP},
+                NULL) < 0)
+    return 3;
+
+  for (;;)
+    pause();
+  fprintf(stderr, "Error: infinite loop terminated\n");
+  return 42;
+}