Seaworth / hello-netlink

Netlink communication between kernel and userspace.

简介

genetlink-with-libnl

genetlink-with-libnl文件夹包含kernel-module和userspace-module。实现了userspace-module向kernel-module发送消息，同时userspace-module可以监听kernel-module的multicast消息。

testgenl用户程序

• 参数-c：表示作为client，testgenel向kernel发送msg，testgenl将用户输入的字符和数字（日期）通过netlink传到testgenl.ko内核模块，并在kernel中将字符打印出来，testgenl.ko模块也会将字符串和数字（日期加一）返回给testgenl。
• 参数-s：表示作为server，testgenel接收kernel netlink multicast的msg，并打印接收到的msg。

testgenl.ko内核模块

• 当insmod testgenl.ko时，创建并注册family和multicast group；
• 启动timer，每隔10s发送multicast消息，testgenl用户程序绑定了对应的family和multicast gourp，就会收到消息；
• 可以接收testgenl用户程序发送的netlink消息；

netlink-with-socket

Netlink是一种userspace和kernel通信的机制。netlink-with-socket文件夹包含kernel-module和userspace-module，分别编译hello_netlink.ko内核模块和netlink_client用户程序。netlink_client将用户输入的字符通过netlink传到hello_netlink内核模块，并在kernel中将字符打印出来。

步骤

运行环境：VMware Linux ubuntu 4.15.0-142-generic

genetlink-with-libnl

进入genetlink-with-libnl目录执行下面命令：

sudo make

在根目录下面会产生testgenl.ko内核模块和testgenl用户程序。 在终端1中输入：

sudo insmod testgenl.ko
dmesg -Hw

ps:dmesg -Hw显示kernel log。 在终端2中输入：

./testgenl -c -s

netlink-with-socket

进入netlink-with-socket目录执行下面命令：

sudo make

在根目录下面会产生hello_netlink.ko内核模块和netlink_client用户程序。 在终端1中输入：

sudo insmod hello_netlink.ko
dmesg -Hw

ps:dmesg -Hw显示kernel log。 在终端2中输入：

./netlink_client

输入文本和kernel通信！

结果

genetlink-with-libnl

testgenl log:

root@ubuntu:~# ./testgenl -c -s
[INFO] [main.c:213] (main) - client mode:

[INFO] [main.c:128] (run_client) - start to send message
[INFO] [main.c:137] (run_client) - msg=Hello, I am userspace!, data=20220917
[INFO] [main.c:138] (run_client) - start to recv message
[INFO] [main.c:56] (recv_genl_msg) - reply from kernel
[INFO] [main.c:44] (recv_genl) - receive from kernel: message=I am message from kernel!, data=20220918
[INFO] [main.c:217] (main) - server mode:

[INFO] [main.c:183] (run_server) - The group is 4.

[INFO] [main.c:59] (recv_genl_msg) - multicast from kernel
[INFO] [main.c:44] (recv_genl) - receive from kernel: message=MULTICAST TEST, data=12345

kernel log:

[  +5.081569] receive from user: message=Hello, I am userspace!, data=20220917.
[  +0.000004] send to user: message=I am message from kernel!, data=20220918
[4月21 11:15] ----- Running timer -----
[  +0.000063] Newing message.
[  +0.000011] Adding Generic Netlink header to the message.
[  +0.000008] Nla_putting MSG(string) attribute.
[  +0.000005] Nla_putting DATA(u32) attribute.
[  +0.000005] Ending message.
[  +0.000005] Multicasting message.
[  +0.000006] The group ID is 4.
[  +0.000026] Success.

netlink-with-socket

netlink_client log:

root@ubuntu:~# ./netlink_client 
Sending message to kernel
Sendmsg ret: 1040
Waiting for message from kernel
Received message payload: hello, I am from kernel
Input your msg for sending to kernel: 123456              
Sending msg "123456" to kernel
send ret: 1040
Received message payload: hello, I am from kernel
Input your msg for sending to kernel: netlink
Sending msg "netlink" to kernel
send ret: 1040
Received message payload: hello, I am from kernel
Input your msg for sending to kernel: 

kernel log:

[  +1.072065] genetlink module exit successful
[4月21 11:22] Entering: hello_netlink_init, protocol family = 30 
[  +0.000001] hello_netlink_init ok
[ +14.754175] kernel recv msg from userspace: hello kernel, I am from userspace
[4月21 11:23] kernel recv msg from userspace: 123456
[ +21.328643] kernel recv msg from userspace: netlink