Question

I wanted to know how I can parse an IPv6 address in C and convert it to a 128 bit value?

So a hex address like 1:22:333:aaaa:b:c:d:e needs to be converted to its 128 bit equivalent binary. The problem is the IP address could be of the type ::2 and its variant since they are valid IPv6 address.

The input is from the keyboard and hence is in ASCII format.

Answer 1

You can use POSIX inet_pton to convert a string to a struct in6_addr.

#include <arpa/inet.h>

  ...

const char *ip6str = "::2";
struct in6_addr result;

if (inet_pton(AF_INET6, ip6str, &result) == 1) // success!
{
    //successfully parsed string into "result"
}
else
{
    //failed, perhaps not a valid representation of IPv6?
}