How to convert IP address to byte array using D?

One way to do this is to get a pointer to the core.sys.posix.sys.socket.sockaddr structure using the Address.name. Something like auto saddr_ptr = results[0].address.name; would do. Then you can extract the data you need by casting this pointer to a pointer of appropriate type (depending on the address family).

Here is a modified example from getAddress() documentation which uses sockaddr* to give you addresses as uint32_t values and conver them to ubyte[4] arrays:

module main;

import std.stdio;
import std.socket;
import std.c.linux.socket: sockaddr_in, in_addr;

void main(string[] args) {
    // auto results = getAddressInfo("www.digitalmars.com");

    try {
        Address[] addresses = getAddress("dlang.org", 80);
        writefln("  %d addresses found.", addresses.length);
        foreach (int i, Address a; addresses) {

            writefln("  Address %d:", i+1);
            writefln("    IP address: %s", a.toAddrString());
            writefln("    Hostname: %s", a.toHostNameString());
            writefln("    Port: %s", a.toPortString());
            writefln("    Service name: %s", a.toServiceNameString());
            auto saddr_ptr = a.name;
            auto in_ptr = *(cast(sockaddr_in*) saddr_ptr);
            // let's convert it to ubyte[4] so we can access individual
            // parts  of the IPv4 address.
            writeln(cast(ubyte[4])(in_ptr.sin_addr));
        }
    } catch (SocketException e) {
        writefln("  Lookup error: %s", e.msg);
    }

    // Lets the user press <Return> before program returns
    stdin.readln();
}

Output:

  3 addresses found.
  Address 1:
    IP address: 162.217.114.56
    Hostname: digitalmars.com
    Port: 80
    Service name: http
[162, 217, 114, 56]
  Address 2:
    IP address: 162.217.114.56
    Hostname: digitalmars.com
    Port: 80
    Service name: http
[162, 217, 114, 56]
  Address 3:
    IP address: 162.217.114.56
    Hostname: digitalmars.com
    Port: 80
    Service name: http
[162, 217, 114, 56]