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昨天CU论坛有人问到如何在内核模块发送数据包,于是找到了之前写的代码,跟大家分享一下。
该代码SLES 11 sp2内核3.0.13上编译运行通过。
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/*
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* Kernel Send Udp packet Module
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License as published by
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* the Free Software Foundation; either version 2 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program; if not, write to the Free Software
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* Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
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*
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* Copyright(C) Tony <tingw.liu@gmail.com> 2007-2013
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*
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*/
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#include <linux/module.h>
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#include <linux/moduleparam.h>
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#include <linux/netfilter.h>
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#include <linux/ip.h>
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#include <net/tcp.h>
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#include <net/udp.h>
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#include <net/icmp.h>
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#include <linux/skbuff.h>
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#include <net/sock.h>
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#include <linux/net.h>
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#include <linux/inetdevice.h>
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#include <linux/in.h>
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#include <linux/kernel.h>
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#include <linux/types.h>
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#include <asm/unaligned.h>
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#include <linux/kthread.h>
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MODULE_LICENSE("GPL");
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MODULE_AUTHOR("Tony ");
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char *ifname = "eth0";
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module_param(ifname, charp, 0644);
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MODULE_PARM_DESC(ifname, "Send packets from which net device");
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char *buffer = "Tony test from kernel!\n";
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module_param(buffer, charp, 0644);
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MODULE_PARM_DESC(buffer, "Packet content");
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__u32 dstip = 0xc0a80056;
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module_param(dstip, uint, 0644);
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__s16 dstport = 8000;
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module_param(dstport, short, 0644);
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long timeout = 1;
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module_param(timeout, long, 0644);
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MODULE_PARM_DESC(timeout, "Interval between send packets, default 1(unit second)");
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static struct task_struct *kthreadtask = NULL;
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static int bind_to_device(struct socket *sock, char *ifname)
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{
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struct net *net;
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struct net_device *dev;
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__be32 addr;
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struct sockaddr_in sin;
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int err;
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net = sock_net(sock->sk);
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dev = __dev_get_by_name(net, ifname);
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if (!dev) {
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printk(KERN_ALERT "No such device named %s\n", ifname);
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return -ENODEV;
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}
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addr = inet_select_addr(dev, 0, RT_SCOPE_UNIVERSE);
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sin.sin_family = AF_INET;
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sin.sin_addr.s_addr = addr;
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sin.sin_port = 0;
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err = sock->ops->bind(sock, (struct sockaddr*)&sin, sizeof(sin));
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if (err < 0) {
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printk(KERN_ALERT "sock bind err, err=%d\n", err);
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return err;
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}
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return 0;
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}
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static int connect_to_addr(struct socket *sock)
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{
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struct sockaddr_in daddr;
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int err;
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daddr.sin_family = AF_INET;
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daddr.sin_addr.s_addr = cpu_to_be32(dstip);
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daddr.sin_port = cpu_to_be16(dstport);
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err = sock->ops->connect(sock, (struct sockaddr*)&daddr,
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sizeof(struct sockaddr), 0);
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if (err < 0) {
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printk(KERN_ALERT "sock connect err, err=%d\n", err);
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return err;
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}
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return 0;
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}
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struct threadinfo{
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struct socket *sock;
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char *buffer;
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};
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static int sendthread(void *data)
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{
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struct kvec iov;
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struct threadinfo *tinfo = data;
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struct msghdr msg = {.msg_flags = MSG_DONTWAIT|MSG_NOSIGNAL};
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int len;
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while (!kthread_should_stop()) {
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iov.iov_base = (void *)tinfo->buffer;
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iov.iov_len = strlen(tinfo->buffer);
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len = kernel_sendmsg(tinfo->sock, &msg, &iov, 1, strlen(tinfo->buffer));
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if (len != strlen(buffer)) {
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printk(KERN_ALERT "kernel_sendmsg err, len=%d, buffer=%d\n",
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len, (int)strlen(buffer));
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if (len == -ECONNREFUSED) {
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printk(KERN_ALERT "Receive Port Unreachable packet!\n");
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}
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break;
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}
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schedule_timeout_interruptible(timeout * HZ);
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}
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kthreadtask = NULL;
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sk_release_kernel(tinfo->sock->sk);
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kfree(tinfo);
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return 0;
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}
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static int __init udp_send_init(void)
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{
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int err = 0;
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struct socket *sock;
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struct threadinfo *tinfo;
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err = sock_create_kern(PF_INET, SOCK_DGRAM, IPPROTO_UDP, &sock);
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if (err < 0) {
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printk(KERN_ALERT "UDP create sock err, err=%d\n", err);
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goto create_error;
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}
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sock->sk->sk_reuse = 1;
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err = bind_to_device(sock, ifname);
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if (err < 0) {
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printk(KERN_ALERT "Bind to %s err, err=%d\n", ifname, err);
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goto bind_error;
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}
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err = connect_to_addr(sock);
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if (err < 0) {
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printk(KERN_ALERT "sock connect err, err=%d\n", err);
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goto connect_error;
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}
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tinfo = kmalloc(sizeof(struct threadinfo), GFP_KERNEL);
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if (!tinfo) {
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printk(KERN_ALERT "kmalloc threadinfo err\n");
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goto kmalloc_error;
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}
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tinfo->sock = sock;
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tinfo->buffer = buffer;
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kthreadtask = kthread_run(sendthread, tinfo, "Tony-sendmsg");
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if (IS_ERR(kthreadtask)) {
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printk(KERN_ALERT "create sendmsg thread err, err=%ld\n",
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PTR_ERR(kthreadtask));
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goto thread_error;
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}
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return 0;
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thread_error:
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kfree(tinfo);
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kmalloc_error:
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bind_error:
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connect_error:
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sk_release_kernel(sock->sk);
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kthreadtask = NULL;
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create_error:
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return -1;
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}
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static void __exit udp_send_exit(void)
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{
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if (kthreadtask) {
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kthread_stop(kthreadtask);
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}
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printk(KERN_ALERT "UDP send quit\n");
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return;
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}
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module_init(udp_send_init);
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module_exit(udp_send_exit);
下面是测试效果:
在192.168.0.86机器上开启netcat从8000端口接收数据包:
在192.168.0.3机器上加载该内核模块:
这个时候,在192.168.0.86机器上就可以每隔1秒钟接收到一个数据包:
在192.168.0.3的机器上可以看到发送数据包的内核线程“Tony-sendmsg":
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