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#define _GNU_SOURCE
#include <stdio.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/un.h>
#include <sys/prctl.h>
#include "utils.h"
#define ERROR(f_, ...) fprintf(stderr, (f_), ##__VA_ARGS__)
#define UNUSED(x) (void)(x)
#define ERROR_EXIT(f_, ...) { \
fprintf(stderr, (f_), ##__VA_ARGS__); \
return 1; \
}
volatile sig_atomic_t term_caught = 0;
void onterm(int sig)
{
printf("sigterm caught\n");
UNUSED(sig);
term_caught = 1;
}
int main()
{
int result;
int sock_fd, sock_conn;
int nsfd;
/* Get current namespace's file descriptor. */
nsfd = open("/proc/self/ns/mnt", O_RDONLY);
if (nsfd == -1)
ERROR_EXIT("error: failed to acquire mount namespace's fd.%s\n",
strerror(errno));
/* Fork. */
pid_t ppid_before_fork = getpid();
pid_t pid = fork();
if (pid == -1)
ERROR_EXIT("fork: %s\n", strerror(errno));
if (pid == 0) {
/* Catch SIGTERM. */
struct sigaction sa = {0};
sa.sa_handler = onterm;
sigaction(SIGTERM, &sa, NULL);
/* Ignore SIGINT. */
signal(SIGINT, SIG_IGN);
/* Set the child to die when parent thread dies. */
int r = prctl(PR_SET_PDEATHSIG, SIGTERM);
if (r == -1)
ERROR_EXIT("prctl: %s\n", strerror(errno));
if (getppid() != ppid_before_fork)
ERROR_EXIT("error: parent has died already.\n");
/* Create unix socket. */
sock_fd = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock_fd == -1)
ERROR_EXIT("socket: %s.\n", strerror(errno));
struct sockaddr_un sock_addr = {0};
sock_addr.sun_family = AF_UNIX;
strcpy(&sock_addr.sun_path[1], "/tmp/voidnsrun-test.sock");
if (bind(sock_fd, (struct sockaddr *)&sock_addr, sizeof(sock_addr)) == -1)
ERROR_EXIT("bind: %s\n", strerror(errno));
listen(sock_fd, 1);
while (!term_caught) {
sock_conn = accept(sock_fd, NULL, 0);
if (sock_conn == -1) {
ERROR("accept: %s\n", strerror(errno));
continue;
}
printf("accepted\n");
send_fd(sock_conn, nsfd);
}
printf("exiting\n");
} else {
/* This is parent. Launch a program. */
char *argv[2] = {"/bin/sh", NULL};
result = execvp(argv[0], (char *const *)argv);
if (result == -1)
ERROR_EXIT("execvp: %s\n", strerror(errno));
}
return 0;
}
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