最近在學習netlink，用來實作用戶層和內核的通信，在寫內核部分代碼時，遇到一個奇怪的問題：
每次卸載完模塊后，必須修改協議號（NETLINK_TEST）,netlink_kernel_create(&init_net,NETLINK_TEST,&cfg);才能成功，不修改協議號，一直創建內核sock失敗，
哪位大佬幫幫忙！！！
所用平臺Ubuntu16.04+linux內核4.15.0-46-generic
內核代碼如下
#include<linux/module.h>
#include<linux/netlink.h>
#include<linux/skbuff.h>
#include<net/sock.h>
#define MAX_MSG_LEN 1024
//#define USER_PID 66666
#define NETLINK_TEST 21 //proto number
static struct sock* g_sk_nl_k = NULL;
static struct nlmsghdr *g_nlh = NULL; //will contain user's pid,data and so on
//static int g_nlmsg_pid = USER_PID;
//static void revFromApp(struct sk_buff* skb);
//send msg to app
int sendToApp(char *pmsg){
struct nlmsghdr *nlh = NULL;
struct sk_buff *nl_skb_out = NULL;
int ret;
ret= -1;
if(!pmsg){
printk("Msg is null,send msg failed!\n");
return -1;
}
if(!g_sk_nl_k){
printk("User's pid is'n known,send msg failed!\n");
return -1;
}
nl_skb_out = nlmsg_new(MAX_MSG_LEN,0);//Allocate a new skb to send a new netlink message to nl_APP
//nl_skb_out = alloc_skb(NLMSG_SPACE(MAX_MSG_LEN), GFP_ATOMIC);
if(!nl_skb_out){
printk("Allocate new skb failed,send msg failed!\n");
return -1;
}
nlh = nlmsg_put(nl_skb_out,0,0,0,MAX_MSG_LEN,0);
if(nlh == NULL){
printk("nlmsg_put failaure!\n");
nlmsg_free(nl_skb_out);
return -1;
}
NETLINK_CB(nl_skb_out).creds.pid = 0;
//NETLINK_CB(nl_skb_out).dst_group = 0;
memcpy(NLMSG_DATA(nlh), pmsg, strlen(pmsg));
//ret = nlmsg;
ret = netlink_unicast(g_sk_nl_k, nl_skb_out,g_nlh->nlmsg_pid, MSG_DONTWAIT);//USER_PID
if(ret < 0){
printk("nlmsg_unicast failaure!\n");
nlmsg_free(nl_skb_out);
return -1;
}
nlmsg_free(nl_skb_out);
return 0;
}
//receive msg from app(only run one time if no loop)
static void revFromApp(struct sk_buff* skb){
char * msgFromApp = NULL;
char * str0 = "msg from kernel";
//struct nlmsghdr *nlh; turn to gloabe
g_nlh=(struct nlmsghdr*)(skb->data); //nlh message from shb's data...(sk_buff:unsigned char *data)
//nlh = nlmsg_hdr(skb);
msgFromApp = nlmsg_data(g_nlh);//get data from struct nlmsghdr *nlh;
//test
printk("msg:%s\n",msgFromApp);
sendToApp(str0);
}
struct netlink_kernel_cfg cfg = {
.input=revFromApp,
};
//create socket
int netlinkCreate(void){
g_sk_nl_k = netlink_kernel_create(&init_net,NETLINK_TEST,&cfg);
if(!g_sk_nl_k){
printk("Error creating socket!\n");
return -1;
}
return 0;
}
//close socket
void netlinkClose(struct sock* sk_nl_k){
if(!sk_nl_k){
//sock_release(sk_nl_k->sk_socket);
netlink_kernel_release(sk_nl_k);
//sk_nl_k = NULL;
}
}
//netlink open
static int __init netlink_init(void){
int ret = -1;
ret = netlinkCreate();//get struct sock* g_sk_nl_k
if(ret < 0){
printk("Netlink open failed!\n");
return -1;
}
printk("Netlink open !\n");
return 0;
}
//netlink close
static void __exit netlink_exit(void){
//netlink_kernel_release(g_sk_nl_k);
//printk("Netlink close0!\n");
netlinkClose(g_sk_nl_k);
printk("Netlink close1!\n");
}
module_init(netlink_init);
module_exit(netlink_exit);
MODULE_LICENSE("GPL");
MODULE_AUTHOR("ysx");
makefile如下：
ifneq ($(KERNELRELEASE),)
obj-m :=nldrv.o
#obj-m += hello.o
else
KDIR :=/lib/modules/$(shell uname -r)/build
all:
make -C $(KDIR) M=$(PWD) modules
clean:
rm -f *.ko *.o *.mod.o *.mod.c *.symvers *.order
endif
uj5u.com熱心網友回復：
可以嘗試下創建完socket后，設定這兩個屬性：setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &state, sizeof(state));
setsockopt(sock, SOL_SOCKET, SO_REUSEPORT, &state, sizeof(state));
引數：
int state = 1;
uj5u.com熱心網友回復：
謝謝大佬，我找到問題了，netlinkclose函式里的判斷錯了轉載請註明出處，本文鏈接：https://www.uj5u.com/caozuo/110333.html
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