#define _GNU_SOURCE

#include <sys/wait.h>

#include <sched.h>

#include <sys/mount.h>

#include "duckerscript.h"

#define Usage(code) ({printf("Usage: ducker run duckerfile\n"); exit(code);})

#define Module "ducker"

#define Container_StackSize (1<<13)

#define Default_Hostname "ducker_container"

#define Default_Root "/"

#define Proc_Path_Capacity 1024

int CloneFn(void *);

static void run(DuckerScript_Table *);

int CloneFn(void *arg) {

DuckerScript_Table *table = (DuckerScript_Table *)arg;

char *hostname = DuckerScript_TableFindDefault(table, "hostname", Default_Hostname);

if (sethostname(hostname, strlen(hostname)) == -1) Error(Module, "sethostname failed");

printf("[INF] %s: hostname set to `%s`\n", Module, hostname);

char *root = DuckerScript_TableFindDefault(table, "root", Default_Root);

Ducker_RemoveTrailing(&root, '/');

char *proc = (char *)malloc(sizeof(char)*Proc_Path_Capacity);

snprintf(proc, Proc_Path_Capacity, "%s/proc", root);

if (unshare(CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWUTS) != 0) Error(Module, "unshare failed");

printf("[INF] %s: isolated namespace from host\n", Module);

if (mount("/proc", proc, "proc", 0, NULL) != 0) Error(Module, "mount failed");

printf("[INF] %s: /proc mounted to `%s`\n", Module, proc);

root = DuckerScript_TableFindDefault(table, "root", Default_Root);

if (chroot(root) != 0) Error(Module, "chroot failed");

printf("[INF] %s: root set to `%s`\n", Module, root);

DuckerScript_TableCmdExecute(table);

if (umount(proc) != 0) Error(Module, "umount failed");

printf("[INF] %s: /proc `%s` unmounted\n", Module, proc);

exit(EXIT_SUCCESS);

}

static void run(DuckerScript_Table *table) {

char *stack = (char *)malloc(sizeof(char)*Container_StackSize);

if (!stack) Error(Module, "malloc failed");

int flags = CLONE_NEWNS | CLONE_NEWPID | CLONE_NEWUTS | SIGCHLD;

int pid = clone(&CloneFn, stack+Container_StackSize, flags, (void *)table);

if (pid == -1) {

free(stack);

Error(Module, "clone failed");

}

int status;

if (waitpid(pid, &status, 0) == -1) {

free(stack);

Error(Module, "waitpid failed");

}

free(stack);

if (WIFEXITED(status)) exit(WEXITSTATUS(status));

else Error(Module, "child process did not terminate normally");

}

int main(int argc, char *argv[], char *envp[]) {

if (argc != 3) Usage(EXIT_FAILURE);

DuckerScript_Table *table = NULL;

DuckerScript_ParseFile(argv[2], &table);

if (strcmp(argv[1], "run") == 0) run(table);

Usage(EXIT_FAILURE);

}