pingpong.c

#include <linux/init.h>
#include <linux/module.h>
#include <linux/kernel.h>

#include <linux/kthread.h>
#include <net/net_namespace.h>
#include <linux/socket.h>
#include <linux/in.h>

#include <linux/delay.h>

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Ryoga Saito (proelbtn)");
MODULE_DESCRIPTION("");
MODULE_VERSION("");

struct socket *sock;
struct task_struct *handler;

int listen_fn(void *data) {
  int err;
  struct socket *newsock;

  unsigned char buf[1024];
  struct kvec vec;
  struct msghdr msg;

  while (1) {
    if (kthread_should_stop()) break;
    err = kernel_accept(sock, &newsock, SOCK_NONBLOCK);
    if (err) continue;

    memset(&vec, 0, sizeof(vec));
    memset(&msg, 0, sizeof(msg));
    vec.iov_base = buf;
    vec.iov_len = 1024;

    kernel_recvmsg(newsock, &msg, &vec, 1, 1024, 0);

    memset(&vec, 0, sizeof(vec));
    memset(&msg, 0, sizeof(msg));
    vec.iov_base = buf;
    vec.iov_len = 1024;
    
    kernel_sendmsg(newsock, &msg, &vec, 1, 1024);

    sock_release(newsock);
  }
  do_exit(0);
  schedule();
  return 0;
}

static int __init http_init(void) {
  int err;
  struct sockaddr_in addr;

  err = sock_create_kern(&init_net, AF_INET, SOCK_STREAM, 0, &sock);
  if (err) {
    pr_err("sock_create (%d)\n", err);
    goto err1;
  }
  pr_info("sock created (0x%p)\n", sock);

  memset(&addr, 0, sizeof(addr));
  addr.sin_family = AF_INET;
  addr.sin_port = htons(80);

  err = kernel_bind(sock, (struct sockaddr *)&addr, sizeof(addr));
  if (err) {
    pr_err("bind (%d)\n", err);
    goto err2;
  }
  pr_info("sock binded\n");

  err = kernel_listen(sock, 1);
  if (err) {
    pr_err("listen (%d)\n", err);
    goto err2;
  }
  pr_info("sock listened\n");

  handler = kthread_create(listen_fn, NULL, "http-handler");
  if (!handler) {
    pr_err("kthread_create\n");
    goto err2;
  }
  pr_info("kthread created (0x%p)\n", handler);

  wake_up_process(handler);
  pr_info("wake_up_process\n");

  return err;

err2:
  sock_release(sock);
  pr_info("sock released\n");
err1:
  return err;
}

static void __exit http_exit(void) {
  pr_info("kthread %p\n", handler);
  
  kthread_stop(handler);
  pr_info("kthread stopped\n");

  sock_release(sock);
  pr_info("sock released\n");
}

module_init(http_init);
module_exit(http_exit);