feat: add spin handler

Signed-off-by: Sven Pfennig <[email protected]>

Makefile.am

@@ -51,6 +51,7 @@ libcrun_SOURCES = src/libcrun/utils.c \
 		src/libcrun/handlers/handler-utils.c \
 		src/libcrun/handlers/krun.c \
 		src/libcrun/handlers/mono.c \
+		src/libcrun/handlers/spin.c \
 		src/libcrun/handlers/wasmedge.c \
 		src/libcrun/handlers/wasmer.c \
 		src/libcrun/handlers/wasmtime.c \

configure.ac

@@ -132,6 +132,10 @@ AS_IF([test "x$with_libkrun" = "xyes"], AC_CHECK_HEADERS([libkrun.h], AC_DEFINE(
 
 AM_CONDITIONAL([ENABLE_KRUN], [test "x$with_libkrun" = xyes])
 
+dnl include support for spin (EXPERIMENTAL)
+AC_ARG_WITH([spin], AS_HELP_STRING([--with-spin], [build with spin support]))
+AS_IF([test "x$with_spin" = "xyes"], AC_DEFINE([HAVE_SPIN], 1, [Define if spin is available]))
+
 
 dnl libseccomp
 AC_ARG_ENABLE([seccomp],

src/libcrun/custom-handler.c

@@ -48,6 +48,9 @@ extern struct custom_handler_s handler_wasmer;
 #if HAVE_DLOPEN && HAVE_MONO
 extern struct custom_handler_s handler_mono;
 #endif
+#if HAVE_DLOPEN && HAVE_SPIN
+extern struct custom_handler_s handler_spin;
+#endif
 
 static struct custom_handler_s *static_handlers[] = {
 #if HAVE_DLOPEN && HAVE_LIBKRUN
@@ -64,6 +67,9 @@ static struct custom_handler_s *static_handlers[] = {
 #endif
 #if HAVE_DLOPEN && HAVE_MONO
   &handler_mono,
+#endif
+#if HAVE_DLOPEN && HAVE_SPIN
+  &handler_spin,
 #endif
   NULL,
 };

src/libcrun/handlers/spin.c

@@ -0,0 +1,116 @@
+/*
+ * crun - OCI runtime written in C
+ *
+ * Copyright (C) 2023 Sven Pfennig <[email protected]>
+ * crun is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License as published by
+ * the Free Software Foundation; either version 2.1 of the License, or
+ * (at your option) any later version.
+ *
+ * crun is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public License
+ * along with crun.  If not, see <http://www.gnu.org/licenses/>.
+ */
+#define _GNU_SOURCE
+
+#include <config.h>
+#include "../custom-handler.h"
+#include "../linux.h"
+#include <sys/stat.h>
+
+#ifdef HAVE_DLOPEN
+#  include <dlfcn.h>
+#endif
+
+#ifdef HAVE_SPIN
+
+#endif
+
+#if HAVE_DLOPEN && HAVE_SPIN
+static int
+spin_exec (void *cookie arg_unused, libcrun_container_t *container arg_unused,
+           const char *pathname arg_unused, char *const argv[] arg_unused)
+{
+  // wasmtime fails to determine default config path if $HOME is not set
+  char *newenviron[] = { "HOME=/root", NULL };
+  char *newargv[] = { "/bin/spin", "up", "--listen", "0.0.0.0:80", NULL };
+
+  // spin up needs a /tmp folder
+  int dir_result = mkdir ("/tmp", 0777);
+  if (dir_result != 0 && errno != EEXIST)
+    {
+      error (EXIT_FAILURE, errno, "failed to execute mkdir `/tmp`");
+    }
+
+  execve (newargv[0], newargv, newenviron);
+  perror ("execve");
+  exit (EXIT_FAILURE);
+}
+
+static int
+spin_load (void **cookie, libcrun_error_t *err)
+{
+  return 0;
+}
+
+static int
+spin_configure_container (void *cookie arg_unused, enum handler_configure_phase phase,
+                          libcrun_context_t *context arg_unused, libcrun_container_t *container,
+                          const char *rootfs arg_unused, libcrun_error_t *err)
+{
+  int ret;
+  if (phase != HANDLER_CONFIGURE_MOUNTS)
+    return 0;
+
+  char *options[] = {
+    "ro",
+    "rprivate",
+    "nosuid",
+    "nodev",
+    "rbind"
+  };
+
+  ret = libcrun_container_do_bind_mount (container, "/usr/local/bin/spin", "/bin/spin", options, 5, err);
+  if (ret != 0)
+    return ret;
+
+  /* release any error if set since we are going to be returning from here */
+  crun_error_release (err);
+
+  return 0;
+}
+
+static int
+spin_unload (void *cookie, libcrun_error_t *err)
+{
+  return 0;
+}
+
+static int
+spin_can_handle_container (libcrun_container_t *container, libcrun_error_t *err arg_unused)
+{
+  const char *entrypoint_executable;
+
+  if (container->container_def->process == NULL || container->container_def->process->args == NULL)
+    return 0;
+
+  entrypoint_executable = container->container_def->process->args[0];
+  return strcmp (entrypoint_executable, "/") ? 0 : 1;
+}
+
+struct custom_handler_s handler_spin = {
+  .name = "spin",
+  .alias = NULL,
+  .feature_string = "WASM:spin",
+  .load = spin_load,
+  .unload = spin_unload,
+  .run_func = spin_exec,
+  .can_handle_container = spin_can_handle_container,
+  .configure_container = spin_configure_container,
+};
+
+#endif