chen172/nl80211

for kernel 4.19

Goal:

analyse when kernel receive generical netlink message, how kernel processing it.

file description:

1. nl80211.c: interface for wireless generic netlink programming, in /net/wireless dir, is cfg80211 module
2. nl80211.h: the data structure for nl80211.c, in /net/wireless dir, is cfg80211 module
3. genetlink.h: genl data structure, in your system /usr/src/linux-head-xxx/include/net dir
4. genetlink.c: genl operation, the interface for nl80211.c, in linux-source/net/netlink dir, is netlink_diag module
5. netlink.h: netlink operation, in your system /usr/src/linux-head-xxx/include/net dir
6. nlattr.c: netlink attribute operation, in linux-source/lib dir

Ongoing:

1. kernel received message put into genl_info, how kernel put it?
2. use nl80211.c's function process it, for example, nl80211_get_wiphy
3. and then put the processed message into struct sk_buf

编译cfg80211模块

进入内核的源码目录net/wireless

1.修改trace.h文件中的最后的路径为当前目录的路径

2.把Makefile删掉

添加这个Kbuild文件,然后执行下面的命令

make -C /lib/modules/$(uname -r)/build/ M=$PWD

TO DO

how the kernel get struct genl_info

Info:

Data structure

File	Data structure/Function	Description	Link
include/net/mac802.11.h	struct ieee80211_tx_info
include/linux/skbuff.h	skb_put_data	copy data to skb
include/linux/netdevice.h	struct net_device_ops	This structure defines the management hooks for network devices	link
include/linux/skbuff.h	struct sk_buff	a metadata structure and does not hold any packet data(?)	link
uapi/linux/if_ether.h	skb->protocol	struct sk_buff protocol filed(only ethernet frame type?)	link
include/uapi/linux/nl80211.h	enum nl80211_iftype	(virtual) interface types	link
/net/core/dev.c	netif_rx	send buffer to network stack	link

Ubuntu linux header

/usr/src

Download your system kernel

1. get your kernel release

uname -r

2. find the kernel source

• https://kernel.ubuntu.com/git/ubuntu/ubuntu-focal.git/refs/tags (Ubuntu)
• https://gitlab.com/kalilinux/packages/linux (Kali linux)

3. download specific directory

• https://github.com/chen172/ruby_script/tree/main/download_cgit_directory (Ubuntu)
• diret download from web ui, gitlab support download directory (Kali linux)

reference

https://elixir.bootlin.com/linux/v4.13/ident/skb_put_data