Our project uses a bunch of open source packages. I’ve been looking through them and this seems to be the current state:

• Linux Kernel: Good to go in both 2.4 and 2.6
• OpenPegasus CIM Broker: IPV6 support is underway, but not yet implemented.
• SBLIM SFCBD IPV6 Support is built in, based on a compile time switch
• OpenIPMI: IPMI Tool won’t accept a valid IPv6 address. This is a slightly different code source than the rest of the project, so it doesn’t mean that the rest of it won’t support IPv6.
• OpenWSMAN
• OpenSSL: Claims to be agnostic of the IP level. Since Open SSH is build on OpenSSL, and OpenSSH works, it works for at least a subset of it’s functionality.
• OpenSSH: Connecting via IPv6 Works Confirmed for both ssh and scp.  scp is a pain.
• OpenSLP: Seems to have IPv6 support, but it isvery recent.  It requires IPv6 multicast support.  Multicast has often been an after thought in switch implementations, so IPv6 multicast may have issues in the future.

This is probably the simplest solution to the switch code I discussed yesterday:
union sockaddress{
struct sockaddr addr;
struct sockaddr_in in;
struct sockaddr_in6 in6;
} sockaddress;

union sockaddress sa;

To find the type:

switch (sa.addr. sa_family){

case AF_INET:

…

case AF_INET6;

…

}

Although our product needs to support IPv6, it will be used by people in IPv4 mode for the near future. Since a call to the socket or bind system calls will fail if the underlying interface is not IPv6 enabled, we have to fall back to IPv6. So I am currently thinking we’ll have code like this:

int af_inet_version = AF_INET;

With code that can set that to AF_INET6 either read out of a config file or a command line argument.

Then later…

int rc = socket( af_inet_version, …);

And when calling bind, use af_inet_version to switch

Part of getting our product converted to IPv6 is project for reliable messaging. This code is no longer actively maintained. I’ve done a few simple greps through the code and agree with my co-worker who warned me that it is going to be quite tricky. Aside from the obvious calls to socket and bind, ISIS records addresses to be reused later. For example, In include/cl_inter.h the ioq structure contains

saddr io_address; /* Destination address */
saddr io_rcvaddr; /* Receive address (for statistics) */

where saddrs is a typedef in include/cl_typedefs.h

typedef struct sockaddr_in saddr;

I am thinking of an approach that would be to use a union:

struct sockaddress{
union{
struct sockaddr_in in;
struct sockaddr_in6 in6;
}addr;
};
struct sockaddress sin;
struct sockaddress pin;

switch(af_inet_version){
case AF_INET:
addrsize = sizeof(struct sockaddr_in);
sin.addr.in.sin_addr.s_addr = INADDR_ANY;
sin.addr.in.sin_port = htons(port);
sin.addr.in.sin_family = af_inet_version;
break;

case AF_INET6:
addrsize = sizeof(struct sockaddr_in6);
sin.addr.in6.sin6_addr = in6addr_any;
sin.addr.in6.sin6_port = htons(port);
sin.addr.in6.sin6_family = af_inet_version;
break;
}

I put the union inside a struct because I originally was going to put the AF_INET to AF_INET6 field into struct sockaddress. I may go back to that for the real code, and then I can support both IPv6 and IPv4 in a single system.

Language standard library support for IPv6.

What follows is an attempt to view the support for IPv6 in various
languages.

Java

Java has clean support for IPV6, and makes it easy to go between
IPv4 and IPv6 addresses. Example:

import java.net.*;public class IPTest{

private static void displayClasses(String host){
 		System.out.print("looking up host" +host+"tt");
 		try{
 			InetAddress[] address =	InetAddress.getAllByName(host);
 			System.out.print("[Success]:");
 			for (int i =0; i < address.length;i++){
 				System.out.println(address[i].getClass().getName());
 			}
 		}catch(UnknownHostException e){

System.out.println("[Unknown]");
 		}

}

public static void main(String[] args) {

displayClasses("fe80::218:8bff:fec4:284b");
 		displayClasses("fe80::218:8bff:fec4:284b/64");
 		displayClasses("00:18:8B:C4:28:4B");
 		displayClasses("::10.17.126.126");
 		displayClasses("10.17.126.126");
 		displayClasses("vmware.com");
 		displayClasses("adyoung-laptop");

}
 }

This code produces the following output

adyoung@adyoung-laptop$ java IPTest
 looking up hostfe80::218:8bff:fec4:284b         [Success]:java.net.Inet6Address
 looking up hostfe80::218:8bff:fec4:284b/64              [Unknown]
 looking up host00:18:8B:C4:28:4B                [Unknown]
 looking up host::10.17.126.126          [Success]:java.net.Inet6Address
 looking up host10.17.126.126            [Success]:java.net.Inet4Address
 looking up hostvmware.com               [Success]:java.net.Inet4Address
 looking up hostadyoung-laptop           [Success]:java.net.Inet4Address

C++

While C++ can always default to C for network support, I wanted to
see what existed in the C++ way of doing things. There is nothing in
the standard library for network support, and nothing pending in TR1.
The third party libary for Asynchronous I/O (asio) does support
IPv6. Boost has not accepted this package yet, but the acceptance
process appears to be underway. This package has a class for ip
address abstraction: asio::ip::address.

#include <iostream>
 #include <boost/array.hpp>
 #include <asio.hpp>using asio::ip::address;
 using namespace std;

void displayAddr(char * addr){
 	cout << "parsing addr " << addr;
 	try{
 		address::from_string(addr) ;
 		cout << "t[success]" ;
 	}catch(...){
 		cout << "t[Failed]";
 	}
 	cout << endl;
 }

int main(int argc, char* argv[]){
 	displayAddr("fe80::218:8bff:fec4:284b");
 	displayAddr("fe80::218:8bff:fec4:284b/64");
 	displayAddr("00:18:8B:C4:28:4B");
 	displayAddr("::10.17.126.126");
 	displayAddr("10.17.126.126");
 	displayAddr("vmware.com");
 	displayAddr("adyoung-laptop");
 	return 0;
 }

This produces the following output:

parsing addr fe80::218:8bff:fec4:284b   [success]
 parsing addr fe80::218:8bff:fec4:284b/64        [Failed]
 parsing addr 00:18:8B:C4:28:4B  [Failed]
 parsing addr ::10.17.126.126    [success]
 parsing addr 10.17.126.126      [success]
 parsing addr vmware.com [Failed]
 parsing addr adyoung-laptop     [Failed]

So the major distinction between this and the Java code is that the
Java code accepts hostnames, this only accepts well formed IP
Addresses.

Python

Python has IPv6 support built in to recent version.

#!/usr/bin/pythonimport socket

def displayAddr(addr):
 	try :
 		addr_info = socket.getaddrinfo(addr,"");
 		print "Parsing ", addr , "t[Succeeded]"
 	except socket.gaierror :
 		print "Parsing ", addr, "t[Failed]"

def main():
 	displayAddr("fe80::218:8bff:fec4:284b");
 	displayAddr("fe80::218:8bff:fec4:284b/64");
 	displayAddr("00:18:8B:C4:28:4B");
 	displayAddr("::10.17.126.126");
 	displayAddr("10.17.126.126");
 	displayAddr("vmware.com");
 	displayAddr("adyoung-laptop");

if __name__ == '__main__':
 	main()

This Code produces the following output

 adyoung@adyoung-laptop$ ./SockTest.py
 Parsing  fe80::218:8bff:fec4:284b       [Succeeded]
 Parsing  fe80::218:8bff:fec4:284b/64    [Failed]
 Parsing  00:18:8B:C4:28:4B      [Failed]
 Parsing  ::10.17.126.126        [Succeeded]
 Parsing  10.17.126.126  [Succeeded]
 Parsing  vmware.com     [Succeeded]
 Parsing  adyoung-laptop         [Succeeded]

So, like Java, hostnames are correctly parsed the same as IP
addressed.

PERL

Perl has two APIs that look promising: Socket and Net::IP.

#!/usr/bin/perl
 use strict;
 use Socket;
 sub displayAddr{
 	my ($addr) = @_;
 	my $host = gethostbyname ($addr);
 	if ($host){
 		print ("parsed ".$addr."n");
 	}else{
 		print ("Unable to parse ".$addr."n");
 	}
 }
 displayAddr("fec0::218:8bff:fe81:f81e");
 displayAddr("fe80::218:8bff:fe81:f81e");
 displayAddr("fe80::218:8bff:fec4:284b");
 displayAddr("fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b");
 displayAddr("fe80::218:8bff:fec4:284b/64");
 displayAddr("00:18:8B:C4:28:4B");
 displayAddr("::10.17.126.126");
 displayAddr("10.17.126.126");
 displayAddr("vmware.com");
 displayAddr("adyoung-laptop");
 displayAddr("ip6-allhosts");
 displayAddr("ip6-localnet");

This produces:

adyoung@adyoung-laptop$ less ip-test.pl
 adyoung@adyoung-laptop$ ./ip-test.pl
 IP  : fec0:0000:0000:0000:0218:8bff:fe81:f81e Type: RESERVED
 IP  : fe80:0000:0000:0000:0218:8bff:fe81:f81e Type: LINK-LOCAL-UNICAST
 IP  : fe80:0000:0000:0000:0218:8bff:fec4:284b Type: LINK-LOCAL-UNICAST
 cannot parse fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b
 cannot parse fe80::218:8bff:fec4:284b/64
 cannot parse 00:18:8B:C4:28:4B
 IP  : 0000:0000:0000:0000:0000:0000:0a11:7e7e Type: IPV4COMP
 IP  : 10.17.126.126 Type: PRIVATE
 cannot parse vmware.com
 cannot parse adyoung-laptop
 cannot parse ip6-allhosts
 cannot parse ip6-localnet

So it handles IPv4 and IPv6., but not host names.
The alternate API, Socket, is older. It doesn ot seem to have the
new Posix function getaddrinfo, so I treid the old gethostbyname:

#!/usr/bin/perl

use strict;
 use Socket;
 sub displayAddr{
 	my ($addr) = @_;
 	my $host = gethostbyname ($addr);
 	if ($host){
 		print ("parsed ".$addr."n");
 	}else{
 		print ("Unable to parse ".$addr."n");
 	}
 }
 displayAddr("fec0::218:8bff:fe81:f81e");
 displayAddr("fe80::218:8bff:fe81:f81e");
 displayAddr("fe80::218:8bff:fec4:284b");
 displayAddr("fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b");
 displayAddr("fe80::218:8bff:fec4:284b/64");
 displayAddr("00:18:8B:C4:28:4B");
 displayAddr("::10.17.126.126");
 displayAddr("10.17.126.126");
 displayAddr("vmware.com");
 displayAddr("adyoung-laptop");
 displayAddr("ip6-allhosts");
 displayAddr("ip6-localnet");

This produced the following output:

Unable to parse fec0::218:8bff:fe81:f81e
 Unable to parse fe80::218:8bff:fe81:f81e
 Unable to parse fe80::218:8bff:fec4:284b
 Unable to parse fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b
 Unable to parse fe80::218:8bff:fec4:284b/64
 Unable to parse 00:18:8B:C4:28:4B
 Unable to parse ::10.17.126.126
 parsed 10.17.126.126
 parsed vmware.com
 parsed adyoung-laptop
 Unable to parse ip6-allhosts
 Unable to parse ip6-localnet

It was able to handle IPv4 and domain names, but not IPv6. This was
on a system that had an IPv6 interface, so it was not the problem
shown in the straight C section

C#

This code exercizes the IPAddress and Dns classes.

using System;
 using System.Net;public class NetTest
 {
 	public static void Main(string[] args){
 		DisplayAddr("fec0::218:8bff:fe81:f81e");
 		DisplayAddr("fe80::218:8bff:fe81:f81e");
 		DisplayAddr("fe80::218:8bff:fec4:284b");
 		DisplayAddr("fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b");
 		DisplayAddr("fe80::218:8bff:fec4:284b/64");
 		DisplayAddr("00:18:8B:C4:28:4B");
 		DisplayAddr("::10.17.126.126");
 		DisplayAddr("10.17.126.126");
 		DisplayAddr("vmware.com");
 		DisplayAddr("adyoung-laptop");
 		DisplayAddr("ip6-allhosts");
 		DisplayAddr("ip6-localnet");
 	}

public static void DisplayAddr(string host){
 		try{
 			IPAddress addr = IPAddress.Parse(host);
 			Console.WriteLine("addr has address:"
 					+ addr.ToString());
 		}catch(Exception ){
 			Console.WriteLine("unable to parse :" + host);
 			try{
 				IPHostEntry hostEntry = Dns.GetHostByName(host);

Console.WriteLine("addr has address:"
 						+ hostEntry.AddressList[0]
 						.ToString());
 			}catch(Exception ){
 				Console.WriteLine("Cannot get host from DNS:",host);
 			}
 		}
 	}
 }

This code produces the following output.

addr has address:fec0::218:8bff:fe81:f81e
 addr has address:fe80::218:8bff:fe81:f81e
 addr has address:fe80::218:8bff:fec4:284b
 unable to parse :fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b
 Cannot get host from DNS:
 addr has address:fe80::218:8bff:fec4:284b
 unable to parse :00:18:8B:C4:28:4B
 Cannot get host from DNS:
 addr has address:::10.17.126.126
 addr has address:10.17.126.126
 unable to parse :vmware.com
 addr has address:10.19.249.99
 unable to parse :adyoung-laptop
 addr has address:10.17.124.70
 unable to parse :ip6-allhosts
 Cannot get host from DNS:
 unable to parse :ip6-localnet
 Cannot get host from DNS:

C# Handles both IPv4 and IPv6 address equally well. The IPAddress
class does not handle host names. The Dns service does an explicit
DNS lookup, not a call via the NSSwitch functions. This leaves a
hole for hosts declared via YP, /etc/hosts, LDAP, or other naming
services. I ran this under both Mono and Microsoft Visual Studio.
On MSVS, it called out that GetHostByName was deprecated, but the
replacement call, GetHostEntry, had the same behavior.

Straight C
(Posix)

The obvious method does not work:

#include <sys/types.h>
 #include <sys/socket.h>
 #include <netdb.h>
 #include <stdio.h>void displayAddr(char *addr){
         struct hostent * hostent;

hostent =gethostbyname(addr);
         if (hostent){
                 printf( "Parsing %s t[Succeeded]n", addr);
         }else{

printf( "Parsing %s t[Failed]n", addr);
         }
 }

int main(){
         displayAddr("fe80::218:8bff:fec4:284b");
         displayAddr("fe80::218:8bff:fec4:284b/64");
         displayAddr("00:18:8B:C4:28:4B");
         displayAddr("::10.17.126.126");
         displayAddr("10.17.126.126");
         displayAddr("vmware.com");
         displayAddr("adyoung-laptop");
         return 0;
 }

This code produces the following output:

adyoung@adyoung-laptop$ ./socktest
 Parsing fe80::218:8bff:fec4:284b        [Failed]
 Parsing fe80::218:8bff:fec4:284b/64     [Failed]
 Parsing 00:18:8B:C4:28:4B       [Failed]
 Parsing ::10.17.126.126         [Failed]
 Parsing 10.17.126.126   [Succeeded]
 Parsing vmware.com      [Succeeded]
 Parsing adyoung-laptop  [Succeeded]

Thus it does not deal with IPv6 addresses correctly. This seems to
be at odds with the man page which states:

The gethostbyname() function returns a structure of type hostent for the given  host  name.   Here name  is  either  a  host name, or an IPv4 address in standard dot notation, or an IPv6 address in colon (and possibly dot) notation.

The next attempt is to using the call specified in the porting
doc:getaddrinfo

#include <sys/types.h>
 #include <sys/socket.h>
 #include <netdb.h>
 #include <stdio.h>void displayAddr(char *addr){
 	struct addrinfo * addrinfo;
 	int rc = getaddrinfo(addr,NULL,NULL,&addrinfo);
 	if (0 ==  rc ){
 		printf( "Parsing %s t[Succeeded]n", addr);
 		freeaddrinfo(addrinfo);
 	}else{

printf( "Parsing %s t[Failed]n", addr);
 	}
 }

int main(){
 	displayAddr("fec0::218:8bff:fe81:f81e");
 	displayAddr("fe80::218:8bff:fe81:f81e");
 	displayAddr("fe80::218:8bff:fec4:284b");
 	displayAddr("fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b");
 	displayAddr("fe80::218:8bff:fec4:284b/64");
 	displayAddr("00:18:8B:C4:28:4B");
 	displayAddr("::10.17.126.126");
 	displayAddr("10.17.126.126");
 	displayAddr("vmware.com");
 	displayAddr("adyoung-laptop");
 	return 0;
 }

This Code Worked differently Depending on whether the machine had an
IPv6 interface configured. Without and IPv6 Interface:

adyoung@adyoung-laptop$ ./getaddrinfo-test
 Parsing fec0::218:8bff:fe81:f81e        [Failed]
 Parsing fe80::218:8bff:fe81:f81e        [Failed]
 Parsing fe80::218:8bff:fec4:284b        [Failed]
 Parsing fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b   [Failed]
 Parsing fe80::218:8bff:fec4:284b/64     [Failed]
 Parsing 00:18:8B:C4:28:4B       [Failed]
 Parsing ::10.17.126.126         [Failed]
 Parsing 10.17.126.126   [Succeeded]
 Parsing vmware.com      [Succeeded]
 Parsing adyoung-laptop  [Succeeded]

With an IPv6 interface.

-bash-3.00$ ./getaddrinfo-test
 Parsing fec0::218:8bff:fe81:f81e        [Succeeded]
 Parsing fe80::218:8bff:fe81:f81e        [Succeeded]
 Parsing fe80::218:8bff:fec4:284b        [Succeeded]
 Parsing fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b   [Failed]
 Parsing fe80::218:8bff:fec4:284b/64     [Failed]
 Parsing 00:18:8B:C4:28:4B       [Failed]
 Parsing ::10.17.126.126         [Succeeded]
 Parsing 10.17.126.126   [Succeeded]
 Parsing vmware.com      [Succeeded]
 Parsing adyoung-laptop  [Failed]

The getaddrinfo function call gives us a way to determine the
correct family to use to connect to the host. If we add this to the
displayAddr function:

		switch( addrinfo->ai_family){
 			case AF_INET6:
 				printf( "socket family = AF_INET6n");
 				break;			case AF_INET:
 				printf( "socket family = AF_INETn");
 				break;
 		}

and request the resolution of a few more hosts:

	displayAddr("ip6-allhosts");
 	displayAddr("ip6-localnet");

We get:

Parsing fec0::218:8bff:fe81:f81e        [Succeeded]socket family = AF_INET6
 Parsing fe80::218:8bff:fe81:f81e        [Succeeded]socket family = AF_INET6
 Parsing fe80::218:8bff:fec4:284b        [Succeeded]socket family = AF_INET6
 Parsing fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b   [Failed]
 Name or service not known
 Parsing fe80::218:8bff:fec4:284b/64     [Failed]
 Name or service not known
 Parsing 00:18:8B:C4:28:4B       [Failed]
 Name or service not known
 Parsing ::10.17.126.126         [Succeeded]socket family = AF_INET6
 Parsing 10.17.126.126   [Succeeded]socket family = AF_INET
 Parsing vmware.com      [Succeeded]socket family = AF_INET
 Parsing adyoung-laptop  [Succeeded]socket family = AF_INET
 Parsing ip6-allhosts    [Succeeded]socket family = AF_INET6
 Parsing ip6-localnet    [Succeeded]socket family = AF_INET6

So we can take the approach where the applications store hosts in a
free string format, presumably by host names, but perhaps by IPv4 or
IPv6 addresses, and we will use gethostinfo to decide how to connect.
For example, (without error handling)

void connectTo(char * host){
 	struct addrinfo * addrinfo;
 	struct protoent * protoent;
 	protoent = getprotobyname("tcp");
 	int rc = getaddrinfo(host,NULL,NULL,&addrinfo);
 	int sockfd = socket( addrinfo->ai_family,SOCK_STREAM,protoent->p_proto);
 }

Visual C++

The code for VC++ is very similar to posix, with slightly
different build requirments. Note the addition of the winsock
initialization code.

// nettest.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include <stdio.h>
void displayAddr(char *addr){
        struct addrinfo * addrinfo;
        int rc = getaddrinfo(addr,NULL,NULL,&addrinfo);
        if (0 ==  rc ){
                printf( "Parsing %s t[Succeeded]", addr);
                switch( addrinfo->ai_family){
                                                case AF_INET6:
                                                        printf( "socket family = AF_INET6n");
                                                        break;

                                                case AF_INET:
                                                        printf( "socket family = AF_INETn");
                                                        break;
                }
                freeaddrinfo(addrinfo);
        }else{
                printf( "Parsing %s t[Failed]n", addr);
                printf("%sn",gai_strerror(rc));
        }
}

void connectTo(char * host){
        struct addrinfo * addrinfo;
        struct protoent * protoent;
        protoent = getprotobyname("tcp");
        int rc = getaddrinfo(host,NULL,NULL,&addrinfo);
        int sockfd = socket( addrinfo->ai_family,SOCK_STREAM,protoent->p_proto);
}
WSAData wsaData;
int _tmain(int argc, _TCHAR* argv[])
{
        int iResult;

        // Initialize Winsock
        iResult = WSAStartup(MAKEWORD(2,2), &wsaData);
        if (iResult != 0) {
                printf("WSAStartup failed: %dn", iResult);
                return 1;
        }

        displayAddr("fec0::218:8bff:fe81:f81e");
        displayAddr("fe80::218:8bff:fe81:f81e");
        displayAddr("fe80::218:8bff:fec4:284b");
        displayAddr("fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b");
        displayAddr("fe80::218:8bff:fec4:284b/64");
        displayAddr("00:18:8B:C4:28:4B");
        displayAddr("::10.17.126.126");
        displayAddr("10.17.126.126");
        displayAddr("vmware.com");
        displayAddr("adyoung-laptop");
        displayAddr("ip6-allhosts");
        displayAddr("ip6-localnet");

        return 0;
}

The file stdafx.h contains the includes

#include <winsock2.h>
#include <ws2tcpip.h>

This produced the output:

Parsing fec0::218:8bff:fe81:f81e        [Succeeded]socket family = AF_INET6
Parsing fe80::218:8bff:fe81:f81e        [Succeeded]socket family = AF_INET6
Parsing fe80::218:8bff:fec4:284b        [Succeeded]socket family = AF_INET6
Parsing fe80:0:0:0:0:0:0:0:0:0:0:0:218:8bff:fec4:284b   [Failed]
N
Parsing fe80::218:8bff:fec4:284b/64     [Failed]
N
Parsing 00:18:8B:C4:28:4B       [Failed]
N
Parsing ::10.17.126.126         [Succeeded]socket family = AF_INET6
Parsing 10.17.126.126   [Succeeded]socket family = AF_INET
Parsing vmware.com      [Succeeded]socket family = AF_INET
Parsing adyoung-laptop  [Failed]
N
Parsing ip6-allhosts    [Succeeded]socket family = AF_INET6
Parsing ip6-localnet    [Succeeded]socket family = AF_INET6

Again, this only worked if there was an IPv6 interface configured on
the system. Also, the default localhost, allhosts, and localnet
names from Linux were not supported on Windows. These had been
declared in /etc/hosts. Once these entries were added to
c:\windows\system32\drivers\etc\hosts it worked correctly. The error
reporting function does not work, but it does resolve and link. It
merely prints out the letter ‘N’.

I am looking at some code that is IPv4 specific. It stores network addresses as a tuple of a uin32 for the address, a uin16 for the port, and a uin16 type code. I suspect the reason for the type code being a uint16 as opposed to enum is that enums are 32bits in C, and they wanted to pack a everything into 64 bits total.

How would this be stored in IPv6? Ports and types could stay the same, but the address needs to handle 128 bits, not 32. In /usr/include/netinet/ip6.h We see that the ipv6 header is defined with source and destinations of type struct in6_addr. This has the interesting definition of:

I am looking at some code that is IPv4 specific. It stores network addresses as a tuple of a uin32 for the address, a uin16 for the port, and a uin16 type code. I suspect the reason for the type code being a uint16 as opposed to enum is that enums are 32bits in C, and they wanted to packa everything into 64 bits total.

How would this be stored in IPv6? Ports and types could stay the same, but the address needs to handle 128 bits, not 32. In /usr/include/netinet/ip6.h We see that the ipv6 header is defined with source and destinations of type struct in6_addr. This can be found in /usr/include/netinet/in.h and is defined as:

struct in6_addr
{
union
{
uint8_t u6_addr8[16];
uint16_t u6_addr16[8];
uint32_t u6_addr32[4];
} in6_u;
#define s6_addr in6_u.u6_addr8
#define s6_addr16 in6_u.u6_addr16
#define s6_addr32 in6_u.u6_addr32
};

So you have choices. All these fields are arrays, and they are all the same size. One issues is endian-ness. To me, it makes the most sense to work with the array of bytes (or octets) as defined uint8_t u6_addr8[16] as it avoids the endian issues, but using the structure means that the programmer has choices.

The code in question is written to be non-os specific, which is perhaps why they define their own data type for addresses. To make this code IPv6 compliant, I would start with a typedef for netaddress uint32. Then everywhere that used a network address, I would replace the uin32 definition with netaddress. Some people like to use the _t suffix for type names, but I am a little more resistant to anything that smells like Hungarian notation. Once everything used netaddress it would be easier to switch the ipv4 specfic calls to ipv6.