Convert source IP address from struct iphdr* to string equivalent using Linux netfilter

Question

I want to convert the source & destination IP addresses from a packet captured using netfilter to char *.

In my netfilter hook function, I have:

Answer 1

The kernel's family of printf() functions has a special format specifier for IP-addresses (%pI4 for IPv4-addresses, %pI6 for IPv6).

So with IPv4, you could use something like:

char source[16];
snprintf(source, 16, "%pI4", &ip_header->saddr); // Mind the &!

Or write to dynamically allocated memory.

If you simply want to print debug-output, you can also use printk(). For the many other features of %p, see this document.