如何使用netlink套接字与内核模块通信?

也请不要告诉我看内核代码.我已经在做，但是要花很多时间，而且我还剩很多. 更新:经过大量的试验和错误后，我有以下代码将消息从用户程序发送到内核，但是消息从内核到用户程序，即使用netlink_unicast()无法正常工作.它不仅不起作用，而且调用使系统挂起，然后我必须重新启动计算机.可以请一个人看看并告诉我我在做什么错.在以下代码中注释了netlink_unicast()调用.对于内核到用户程序的消息，应该不加注释.用户程序#include <sys/socket.h>#include <linux/netlink.h>#define NETLINK_USER 31#define MAX_PAYLOAD 1024 /* maximum payload size*/struct sockaddr_nl src_addr, dest_addr;struct nlmsghdr *nlh = NULL;struct iovec iov;int sock_fd;struct msghdr msg;void main(){ sock_fd=socket(PF_NETLINK, SOCK_RAW, NETLINK_USER); if(sock_fd<0) return -1; memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = AF_NETLINK; src_addr.nl_pid = getpid(); /* self pid */ /* interested in group 1<<0 */ bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); dest_addr.nl_family = AF_NETLINK; dest_addr.nl_pid = 0; /* For Linux Kernel */ dest_addr.nl_groups = 0; /* unicast */ nlh = (struct nlmsghdr *)malloc( NLMSG_SPACE(MAX_PAYLOAD)); memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD)); nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD); nlh->nlmsg_pid = getpid(); nlh->nlmsg_flags = 0; strcpy(NLMSG_DATA(nlh), "Hello"); iov.iov_base = (void *)nlh; iov.iov_len = nlh->nlmsg_len; msg.msg_name = (void *)&dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = &iov; msg.msg_iovlen = 1; printf("Sending message to kernel\n"); sendmsg(sock_fd,&msg,0); printf("Waiting for message from kernel\n"); /* Read message from kernel */ recvmsg(sock_fd, &msg, 0); printf(" Received message payload: %s\n", NLMSG_DATA(nlh)); close(sock_fd);}内核代码#include <linux/module.h>#include <linux/kernel.h>#include <linux/init.h>#include <net/sock.h>#include <linux/socket.h>#include <linux/net.h>#include <asm/types.h>#include <linux/netlink.h>#include <linux/skbuff.h>#define NETLINK_USER 31struct sock *nl_sk = NULL;static void hello_nl_recv_msg(struct sk_buff *skb){ struct nlmsghdr *nlh; int pid; printk(KERN_INFO "Entering: %s\n", __FUNCTION__); nlh=(struct nlmsghdr*)skb->data; printk(KERN_INFO "Netlink received msg payload: %s\n", (char*)NLMSG_DATA(nlh)); pid = nlh->nlmsg_pid; /*pid of sending process */ NETLINK_CB(skb).dst_group = 0; /* not in mcast group */ NETLINK_CB(skb).pid = 0; /* from kernel */ //NETLINK_CB(skb).groups = 0; /* not in mcast group */ //NETLINK_CB(skb).dst_pid = pid; printk("About to send msg bak:\n"); //netlink_unicast(nl_sk,skb,pid,MSG_DONTWAIT);}static int __init hello_init(void){ printk("Entering: %s\n",__FUNCTION__); nl_sk=netlink_kernel_create(&init_net, NETLINK_USER, 0, hello_nl_recv_msg, NULL, THIS_MODULE); if(!nl_sk) { printk(KERN_ALERT "Error creating socket.\n"); return -10; } return 0;}static void __exit hello_exit(void){ printk(KERN_INFO "exiting hello module\n"); netlink_kernel_release(nl_sk);}module_init(hello_init);module_exit(hello_exit);解决方案阅读内核源代码之后，我终于设法使netlink套接字对我有用.以下是Netlink套接字基础知识的示例，即打开一个Netlink套接字，对其进行读写，然后将其关闭.内核模块 #include <linux/module.h>#include <net/sock.h>#include <linux/netlink.h>#include <linux/skbuff.h>#define NETLINK_USER 31struct sock *nl_sk = NULL;static void hello_nl_recv_msg(struct sk_buff *skb){ struct nlmsghdr *nlh; int pid; struct sk_buff *skb_out; int msg_size; char *msg = "Hello from kernel"; int res; printk(KERN_INFO "Entering: %s\n", __FUNCTION__); msg_size = strlen(msg); nlh = (struct nlmsghdr *)skb->data; printk(KERN_INFO "Netlink received msg payload:%s\n", (char *)nlmsg_data(nlh)); pid = nlh->nlmsg_pid; /*pid of sending process */ skb_out = nlmsg_new(msg_size, 0); if (!skb_out) { printk(KERN_ERR "Failed to allocate new skb\n"); return; } nlh = nlmsg_put(skb_out, 0, 0, NLMSG_DONE, msg_size, 0); NETLINK_CB(skb_out).dst_group = 0; /* not in mcast group */ strncpy(nlmsg_data(nlh), msg, msg_size); res = nlmsg_unicast(nl_sk, skb_out, pid); if (res < 0) printk(KERN_INFO "Error while sending bak to user\n");}static int __init hello_init(void){ printk("Entering: %s\n", __FUNCTION__); //nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, 0, hello_nl_recv_msg, NULL, THIS_MODULE); struct netlink_kernel_cfg cfg = { .input = hello_nl_recv_msg, }; nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, &cfg); if (!nl_sk) { printk(KERN_ALERT "Error creating socket.\n"); return -10; } return 0;}static void __exit hello_exit(void){ printk(KERN_INFO "exiting hello module\n"); netlink_kernel_release(nl_sk);}module_init(hello_init); module_exit(hello_exit);MODULE_LICENSE("GPL");用户程序 #include <linux/netlink.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/socket.h>#include <unistd.h>#define NETLINK_USER 31#define MAX_PAYLOAD 1024 /* maximum payload size*/struct sockaddr_nl src_addr, dest_addr;struct nlmsghdr *nlh = NULL;struct iovec iov;int sock_fd;struct msghdr msg;int main(){ sock_fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_USER); if (sock_fd < 0) return -1; memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = AF_NETLINK; src_addr.nl_pid = getpid(); /* self pid */ bind(sock_fd, (struct sockaddr *)&src_addr, sizeof(src_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); dest_addr.nl_family = AF_NETLINK; dest_addr.nl_pid = 0; /* For Linux Kernel */ dest_addr.nl_groups = 0; /* unicast */ nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD)); memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD)); nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD); nlh->nlmsg_pid = getpid(); nlh->nlmsg_flags = 0; strcpy(NLMSG_DATA(nlh), "Hello"); iov.iov_base = (void *)nlh; iov.iov_len = nlh->nlmsg_len; msg.msg_name = (void *)&dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = &iov; msg.msg_iovlen = 1; printf("Sending message to kernel\n"); sendmsg(sock_fd, &msg, 0); printf("Waiting for message from kernel\n"); /* Read message from kernel */ recvmsg(sock_fd, &msg, 0); printf("Received message payload: %s\n", NLMSG_DATA(nlh)); close(sock_fd);} 有关魔术常数NETLINK_USER 31的相关主题:内核空间中可以有32个以上的netlink套接字吗? I am trying to write a linux kernel module that communicates with user process using netlink. I am using netlink because the user program I want to communicate to communicates only using sockets and I cant change that to add ioctl() or anything.Problem is that I cant figure out how to do that. I have googled but all examples I found are for old like this one and no longer valid for current kernel versions. I have also looked at this SO question but the sample here uses libnl for socket operations but I want to stick to standard socket functions (defined by sys/socket.h). So can some one plz guide me here to some tutorial or guide or some thing that can help me understand the interface and usage of netlink. I would highly appreciate a working example, nothing fancy, just a very basic example of how to establish a connection from a socket in user program to a socket in kernel and then send data from user process to kernel and receive back from kernel.Also please do not tell me to look at kernel code. I am already doing it but it will take a lot of time and I dont have lot of it left.Update:After lot of trial and error I have following code which sends message from user program to kernel but the message from kernel to user program i.e using netlink_unicast() is not working. Its not only not working, the call hangs the systems and then I have to restart the machine. Can some one plz take a look and tell me what wrong I am doing. The netlink_unicast() call is commented in the following code. It should be uncommented for kernel to user program message.User Program#include <sys/socket.h>#include <linux/netlink.h>#define NETLINK_USER 31#define MAX_PAYLOAD 1024 /* maximum payload size*/struct sockaddr_nl src_addr, dest_addr;struct nlmsghdr *nlh = NULL;struct iovec iov;int sock_fd;struct msghdr msg;void main(){ sock_fd=socket(PF_NETLINK, SOCK_RAW, NETLINK_USER); if(sock_fd<0) return -1; memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = AF_NETLINK; src_addr.nl_pid = getpid(); /* self pid */ /* interested in group 1<<0 */ bind(sock_fd, (struct sockaddr*)&src_addr, sizeof(src_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); dest_addr.nl_family = AF_NETLINK; dest_addr.nl_pid = 0; /* For Linux Kernel */ dest_addr.nl_groups = 0; /* unicast */ nlh = (struct nlmsghdr *)malloc( NLMSG_SPACE(MAX_PAYLOAD)); memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD)); nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD); nlh->nlmsg_pid = getpid(); nlh->nlmsg_flags = 0; strcpy(NLMSG_DATA(nlh), "Hello"); iov.iov_base = (void *)nlh; iov.iov_len = nlh->nlmsg_len; msg.msg_name = (void *)&dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = &iov; msg.msg_iovlen = 1; printf("Sending message to kernel\n"); sendmsg(sock_fd,&msg,0); printf("Waiting for message from kernel\n"); /* Read message from kernel */ recvmsg(sock_fd, &msg, 0); printf(" Received message payload: %s\n", NLMSG_DATA(nlh)); close(sock_fd);}Kernel Code#include <linux/module.h>#include <linux/kernel.h>#include <linux/init.h>#include <net/sock.h>#include <linux/socket.h>#include <linux/net.h>#include <asm/types.h>#include <linux/netlink.h>#include <linux/skbuff.h>#define NETLINK_USER 31struct sock *nl_sk = NULL;static void hello_nl_recv_msg(struct sk_buff *skb){ struct nlmsghdr *nlh; int pid; printk(KERN_INFO "Entering: %s\n", __FUNCTION__); nlh=(struct nlmsghdr*)skb->data; printk(KERN_INFO "Netlink received msg payload: %s\n", (char*)NLMSG_DATA(nlh)); pid = nlh->nlmsg_pid; /*pid of sending process */ NETLINK_CB(skb).dst_group = 0; /* not in mcast group */ NETLINK_CB(skb).pid = 0; /* from kernel */ //NETLINK_CB(skb).groups = 0; /* not in mcast group */ //NETLINK_CB(skb).dst_pid = pid; printk("About to send msg bak:\n"); //netlink_unicast(nl_sk,skb,pid,MSG_DONTWAIT);}static int __init hello_init(void){ printk("Entering: %s\n",__FUNCTION__); nl_sk=netlink_kernel_create(&init_net, NETLINK_USER, 0, hello_nl_recv_msg, NULL, THIS_MODULE); if(!nl_sk) { printk(KERN_ALERT "Error creating socket.\n"); return -10; } return 0;}static void __exit hello_exit(void){ printk(KERN_INFO "exiting hello module\n"); netlink_kernel_release(nl_sk);}module_init(hello_init);module_exit(hello_exit); 解决方案 After reading kernel source I finally managed to make netlink sockets work for me. Below is an example of Netlink socket basics i.e opening a netlink socket, reading and writing to it and closing it.Kernel Module#include <linux/module.h>#include <net/sock.h>#include <linux/netlink.h>#include <linux/skbuff.h>#define NETLINK_USER 31struct sock *nl_sk = NULL;static void hello_nl_recv_msg(struct sk_buff *skb){ struct nlmsghdr *nlh; int pid; struct sk_buff *skb_out; int msg_size; char *msg = "Hello from kernel"; int res; printk(KERN_INFO "Entering: %s\n", __FUNCTION__); msg_size = strlen(msg); nlh = (struct nlmsghdr *)skb->data; printk(KERN_INFO "Netlink received msg payload:%s\n", (char *)nlmsg_data(nlh)); pid = nlh->nlmsg_pid; /*pid of sending process */ skb_out = nlmsg_new(msg_size, 0); if (!skb_out) { printk(KERN_ERR "Failed to allocate new skb\n"); return; } nlh = nlmsg_put(skb_out, 0, 0, NLMSG_DONE, msg_size, 0); NETLINK_CB(skb_out).dst_group = 0; /* not in mcast group */ strncpy(nlmsg_data(nlh), msg, msg_size); res = nlmsg_unicast(nl_sk, skb_out, pid); if (res < 0) printk(KERN_INFO "Error while sending bak to user\n");}static int __init hello_init(void){ printk("Entering: %s\n", __FUNCTION__); //nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, 0, hello_nl_recv_msg, NULL, THIS_MODULE); struct netlink_kernel_cfg cfg = { .input = hello_nl_recv_msg, }; nl_sk = netlink_kernel_create(&init_net, NETLINK_USER, &cfg); if (!nl_sk) { printk(KERN_ALERT "Error creating socket.\n"); return -10; } return 0;}static void __exit hello_exit(void){ printk(KERN_INFO "exiting hello module\n"); netlink_kernel_release(nl_sk);}module_init(hello_init); module_exit(hello_exit);MODULE_LICENSE("GPL");User Program#include <linux/netlink.h>#include <stdio.h>#include <stdlib.h>#include <string.h>#include <sys/socket.h>#include <unistd.h>#define NETLINK_USER 31#define MAX_PAYLOAD 1024 /* maximum payload size*/struct sockaddr_nl src_addr, dest_addr;struct nlmsghdr *nlh = NULL;struct iovec iov;int sock_fd;struct msghdr msg;int main(){ sock_fd = socket(PF_NETLINK, SOCK_RAW, NETLINK_USER); if (sock_fd < 0) return -1; memset(&src_addr, 0, sizeof(src_addr)); src_addr.nl_family = AF_NETLINK; src_addr.nl_pid = getpid(); /* self pid */ bind(sock_fd, (struct sockaddr *)&src_addr, sizeof(src_addr)); memset(&dest_addr, 0, sizeof(dest_addr)); dest_addr.nl_family = AF_NETLINK; dest_addr.nl_pid = 0; /* For Linux Kernel */ dest_addr.nl_groups = 0; /* unicast */ nlh = (struct nlmsghdr *)malloc(NLMSG_SPACE(MAX_PAYLOAD)); memset(nlh, 0, NLMSG_SPACE(MAX_PAYLOAD)); nlh->nlmsg_len = NLMSG_SPACE(MAX_PAYLOAD); nlh->nlmsg_pid = getpid(); nlh->nlmsg_flags = 0; strcpy(NLMSG_DATA(nlh), "Hello"); iov.iov_base = (void *)nlh; iov.iov_len = nlh->nlmsg_len; msg.msg_name = (void *)&dest_addr; msg.msg_namelen = sizeof(dest_addr); msg.msg_iov = &iov; msg.msg_iovlen = 1; printf("Sending message to kernel\n"); sendmsg(sock_fd, &msg, 0); printf("Waiting for message from kernel\n"); /* Read message from kernel */ recvmsg(sock_fd, &msg, 0); printf("Received message payload: %s\n", NLMSG_DATA(nlh)); close(sock_fd);}Related thread about the magic constant NETLINK_USER 31: Can I have more than 32 netlink sockets in kernelspace? 这篇关于如何使用netlink套接字与内核模块通信?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 上岸，阿里云！