Kernel compatibility for Linux kernel module development

Because the Linux kernel changes very quickly, each iteration between the data structure, the interface is likely to change, so for our write kernel module compatibility brings some problems, often in a version of the module can be compiled normally, the other module on the compilation failed, this time we need to do the kernel version compatible, Here's how to fix it:

In the kernel, there is a linux/version.h header file, there are two macros Linux_version_code and kernel_version, you can use these two macros to help complete the compatibility process, the example code is as follows:

static struct Nf_hook_ops Mrs_ops_forward = {     . Hook    = Mrs_hook_forward,     . Owner   = this_module,     . PF      = Pf_inet, #if (Linux_version_code >= kernel_version (2,6,25))     . Hooknum = Nf_inet_forward, #else     . Hooknum = Nf_ip_forward, #endif. Priority = Nf_ip_pri_first,//nf_ip_pri_raw,};

You can also nest multiple layers of # if else to support more kernel versions and get the truth out of it in practice.

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Kernel compatibility for Linux kernel module development