實作 Linux Kernel-space 的 UDP Server
2011-06-26 22:03
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http://fred-zone.blogspot.com/2008/02/linux-kernel-space-udp-server.html
今天在『Linux Kernel Newbies』閒逛,看近期 Kernel 的動態和變化,心中不時贊歎 Linux 發展的複雜和快速,每次去都令人驚奇。該網站上除了有 kernel 的最新資訊,也有一些相關的文件和教學手冊,而其中一篇文獻『Simple UDP Server in Kernel-space』簡單示範了 kernel thread 的使用以及 Module 的撰寫,相當值得推薦參考。
由於完整程式碼不長,在這裡摘錄:
如果以上程式碼有什麼遺漏,敬請見諒,一切還是以原文為準。另外,該網站除了 UDP Server 之外,還有 Web Server in kernel-space 的範例,有興趣的人可以自行去閱讀研究:
http://br.kernelnewbies.org/docs/modulos_guia.html#threads
今天在『Linux Kernel Newbies』閒逛,看近期 Kernel 的動態和變化,心中不時贊歎 Linux 發展的複雜和快速,每次去都令人驚奇。該網站上除了有 kernel 的最新資訊,也有一些相關的文件和教學手冊,而其中一篇文獻『Simple UDP Server in Kernel-space』簡單示範了 kernel thread 的使用以及 Module 的撰寫,相當值得推薦參考。
由於完整程式碼不長,在這裡摘錄:
#include <linux/kernel.h> #include <linux/module.h> #include <linux/init.h> #include <linux/kthread.h> #include <linux/errno.h> #include <linux/types.h> #include <linux/netdevice.h> #include <linux/ip.h> #include <linux/in.h> #include <linux/delay.h> #define DEFAULT_PORT 2325 #define CONNECT_PORT 23 #define MODULE_NAME "ksocket" //#define INADDR_SEND ((unsigned long int)0x7f000001) /* 127.0.0.1 */ #define INADDR_SEND INADDR_LOOPBACK /* 2006/06/27 - Added ksocket_send, so, after receive a packet, the kernel send another back to the CONNECT_PORT - Rodrigo Rubira Branco <rodrigo@kernelhacking.com> 2006/05/14 - Initial version - Toni Garcia-Navarro <topi@phreaker.net> */ struct kthread_t { struct task_struct *thread; struct socket *sock; struct sockaddr_in addr; struct socket *sock_send; struct sockaddr_in addr_send; int running; }; struct kthread_t *kthread = NULL; /* function prototypes */ int ksocket_receive(struct socket *sock, struct sockaddr_in *addr, unsigned char *buf, int len); int ksocket_send(struct socket *sock, struct sockaddr_in *addr, unsigned char *buf, int len); static void ksocket_start(void) { int size, err; int bufsize = 10; unsigned char buf[bufsize+1]; /* kernel thread initialization */ lock_kernel(); kthread->running = 1; current->flags |= PF_NOFREEZE; /* daemonize (take care with signals, after daemonize() they are disabled) */ daemonize(MODULE_NAME); allow_signal(SIGKILL); unlock_kernel(); /* create a socket */ if ( ( (err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_UDP, &kthread->sock)) < 0) || ( (err = sock_create(AF_INET, SOCK_DGRAM, IPPROTO_UDP, &kthread->sock_send)) < 0 )) { printk(KERN_INFO MODULE_NAME": Could not create a datagram socket, error = %d\n", -ENXIO); goto out; } memset(&kthread->addr, 0, sizeof(struct sockaddr)); memset(&kthread->addr_send, 0, sizeof(struct sockaddr)); kthread->addr.sin_family = AF_INET; kthread->addr_send.sin_family = AF_INET; kthread->addr.sin_addr.s_addr = htonl(INADDR_ANY); kthread->addr_send.sin_addr.s_addr = htonl(INADDR_SEND); kthread->addr.sin_port = htons(DEFAULT_PORT); kthread->addr_send.sin_port = htons(CONNECT_PORT); if ( ( (err = kthread->sock->ops->bind(kthread->sock, (struct sockaddr *)&kthread->addr, sizeof(struct sockaddr) ) ) < 0) || (err = kthread->sock_send->ops->connect(kthread->sock_send, (struct sockaddr *)&kthread->addr_send, sizeof(struct sockaddr), 0) < 0 )) { printk(KERN_INFO MODULE_NAME": Could not bind or connect to socket, error = %d\n", -err); goto close_and_out; } printk(KERN_INFO MODULE_NAME": listening on port %d\n", DEFAULT_PORT); /* main loop */ for (;;) { memset(&buf, 0, bufsize+1); size = ksocket_receive(kthread->sock, &kthread->addr, buf, bufsize); if (signal_pending(current)) break; if (size < 0) printk(KERN_INFO MODULE_NAME": error getting datagram, sock_recvmsg error = %d\n", size); else { printk(KERN_INFO MODULE_NAME": received %d bytes\n", size); /* data processing */ printk("\n data: %s\n", buf); /* sending */ memset(&buf, 0, bufsize+1); strcat(buf, "testing..."); ksocket_send(kthread->sock_send, &kthread->addr_send, buf, strlen(buf)); } } close_and_out: sock_release(kthread->sock); sock_release(kthread->sock_send); kthread->sock = NULL; kthread->sock_send = NULL; out: kthread->thread = NULL; kthread->running = 0; } int ksocket_send(struct socket *sock, struct sockaddr_in *addr, unsigned char *buf, int len) { struct msghdr msg; struct iovec iov; mm_segment_t oldfs; int size = 0; if (sock->sk==NULL) return 0; iov.iov_base = buf; iov.iov_len = len; msg.msg_flags = 0; msg.msg_name = addr; msg.msg_namelen = sizeof(struct sockaddr_in); msg.msg_control = NULL; msg.msg_controllen = 0; msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = NULL; oldfs = get_fs(); set_fs(KERNEL_DS); size = sock_sendmsg(sock,&msg,len); set_fs(oldfs); return size; } int ksocket_receive(struct socket* sock, struct sockaddr_in* addr, unsigned char* buf, int len) { struct msghdr msg; struct iovec iov; mm_segment_t oldfs; int size = 0; if (sock->sk==NULL) return 0; iov.iov_base = buf; iov.iov_len = len; msg.msg_flags = 0; msg.msg_name = addr; msg.msg_namelen = sizeof(struct sockaddr_in); msg.msg_control = NULL; msg.msg_controllen = 0; msg.msg_iov = &iov; msg.msg_iovlen = 1; msg.msg_control = NULL; oldfs = get_fs(); set_fs(KERNEL_DS); size = sock_recvmsg(sock,&msg,len,msg.msg_flags); set_fs(oldfs); return size; } int __init ksocket_init(void) { kthread = kmalloc(sizeof(struct kthread_t), GFP_KERNEL); memset(kthread, 0, sizeof(struct kthread_t)); /* start kernel thread */ kthread->thread = kthread_run((void *)ksocket_start, NULL, MODULE_NAME); if (IS_ERR(kthread->thread)) { printk(KERN_INFO MODULE_NAME": unable to start kernel thread\n"); kfree(kthread); kthread = NULL; return -ENOMEM; } return 0; } void __exit ksocket_exit(void) { int err; if (kthread->thread==NULL) printk(KERN_INFO MODULE_NAME": no kernel thread to kill\n"); else { lock_kernel(); err = kill_proc(kthread->thread->pid, SIGKILL, 1); unlock_kernel(); /* wait for kernel thread to die */ if (err < 0) printk(KERN_INFO MODULE_NAME": unknown error %d while trying to terminate kernel thread\n",-err); else { while (kthread->running == 1) msleep(10); printk(KERN_INFO MODULE_NAME": succesfully killed kernel thread!\n"); } } /* free allocated resources before exit */ if (kthread->sock != NULL) { sock_release(kthread->sock); kthread->sock = NULL; } kfree(kthread); kthread = NULL; printk(KERN_INFO MODULE_NAME": module unloaded\n"); } /* init and cleanup functions */ module_init(ksocket_init); module_exit(ksocket_exit); /* module information */ MODULE_DESCRIPTION("kernel thread listening on a UDP socket (code example)"); MODULE_AUTHOR("Toni Garcia-Navarro <topi@phreaker.net>"); MODULE_LICENSE("GPL");
如果以上程式碼有什麼遺漏,敬請見諒,一切還是以原文為準。另外,該網站除了 UDP Server 之外,還有 Web Server in kernel-space 的範例,有興趣的人可以自行去閱讀研究:
http://br.kernelnewbies.org/docs/modulos_guia.html#threads
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