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echo_server.c
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echo_server.c
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#include <linux/kernel.h>
#include <linux/kthread.h>
#include <linux/sched/signal.h>
#include <linux/tcp.h>
#include <linux/types.h>
#include "echo_server.h"
#define BUF_SIZE 4096
struct echo_service daemon = {.is_stopped = false};
struct runtime_state states = {0};
extern struct workqueue_struct *kecho_wq;
static int get_request(struct socket *sock, unsigned char *buf, size_t size)
{
struct msghdr msg;
struct kvec vec;
int length;
/* kvec setting */
vec.iov_len = size;
vec.iov_base = buf;
/* msghdr setting */
msg.msg_name = 0;
msg.msg_namelen = 0;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = 0;
/* get msg */
length = kernel_recvmsg(sock, &msg, &vec, size, size, msg.msg_flags);
if (likely(length)) /* Not EOF */
TRACE(recvmsg);
return length;
}
static int send_request(struct socket *sock, unsigned char *buf, size_t size)
{
int length;
struct kvec vec;
struct msghdr msg;
msg.msg_name = NULL;
msg.msg_namelen = 0;
msg.msg_control = NULL;
msg.msg_controllen = 0;
msg.msg_flags = 0;
vec.iov_base = buf;
vec.iov_len = strlen(buf);
length = kernel_sendmsg(sock, &msg, &vec, 1, size);
TRACE(sendmsg);
return length;
}
static void echo_server_worker(struct work_struct *work)
{
struct kecho *worker = container_of(work, struct kecho, kecho_work);
unsigned char *buf;
// 取得 buffer 空間
rekzalloc:
buf = kzalloc(BUF_SIZE, GFP_KERNEL);
if (!buf) {
TRACE(kzalloc_err);
goto rekzalloc;
}
// 當程式還沒有要中斷前,執行無限迴圈
while (!daemon.is_stopped) {
// 取得資料
int res = get_request(worker->sock, buf, BUF_SIZE - 1);
if (res <= 0) {
if (res)
TRACE(get_err);
break;
}
// 回傳資料
res = send_request(worker->sock, buf, res);
if (res < 0) {
TRACE(send_err);
break;
}
// 重置 buffer
memset(buf, 0, res);
}
kernel_sock_shutdown(worker->sock, SHUT_RDWR);
TRACE(shutdown);
kfree(buf);
}
static struct work_struct *create_work(struct socket *sk)
{
struct kecho *work;
// 分配 kecho 結構大小的空間
// GFP_KERNEL: 正常配置記憶體
if (!(work = kmalloc(sizeof(struct kecho), GFP_KERNEL)))
return NULL;
work->sock = sk;
// 初始化已經建立的 work ,並運行函式 echo_server_worker
INIT_WORK(&work->kecho_work, echo_server_worker);
list_add(&work->list, &daemon.worker);
return &work->kecho_work;
}
/* it would be better if we do this dynamically */
static void free_work(void)
{
struct kecho *l, *tar;
/* cppcheck-suppress uninitvar */
list_for_each_entry_safe (tar, l, &daemon.worker, list) {
kernel_sock_shutdown(tar->sock, SHUT_RDWR);
flush_work(&tar->kecho_work);
sock_release(tar->sock);
kfree(tar);
}
}
static void do_analysis(void)
{
__atomic_thread_fence(__ATOMIC_SEQ_CST);
#define TRACE_PRINT(ops) \
printk(MODULE_NAME ": %s : %d\n", #ops, atomic_read(&states.ops));
TRACE_PRINT(recvmsg);
TRACE_PRINT(sendmsg);
TRACE_PRINT(shutdown);
TRACE_PRINT(kzalloc_err);
TRACE_PRINT(get_err);
TRACE_PRINT(send_err);
TRACE_PRINT(accept_err);
TRACE_PRINT(work_err);
}
int echo_server_daemon(void *arg)
{
struct echo_server_param *param = arg;
struct socket *sock;
struct work_struct *work;
// 登記要接收的 Signal
allow_signal(SIGKILL);
allow_signal(SIGTERM);
INIT_LIST_HEAD(&daemon.worker);
// 判斷執行緒是否該被中止
while (!kthread_should_stop()) {
/* using blocking I/O */
int error = kernel_accept(param->listen_sock, &sock, 0);
if (error < 0) {
// 檢查當前執行緒是否有 signal 處理
if (signal_pending(current))
break;
TRACE(accept_err);
continue;
}
if (unlikely(!(work = create_work(sock)))) {
TRACE(work_err);
kernel_sock_shutdown(sock, SHUT_RDWR);
sock_release(sock);
continue;
}
/* start server worker */
queue_work(kecho_wq, work);
}
printk(MODULE_NAME ": daemon shutdown in progress...\n");
daemon.is_stopped = true;
do_analysis();
free_work();
return 0;
}