IPv6 Support for the OpenBSD Apache HTTP Server

### Apache HTTP Server

# IPv6 Support for the OpenBSD Apache HTTP Server

This document explains how OpenBSD Apache makes use of IPv6.

To support IPv6 the apache module API/ABI had to be changed, to avoid IPv4-dependent structure member variables (like use of u_long to hold an IPv4 address, or whatever). Keep this in mind when writing new modules or adding modules to the ports collection.

Basically you can write IPv6 address where IPv4 address fits.

## extra command-line argument

-4
  Assume IPv4 address on ambiguous directives (default)
-6
  Assume IPv6 address on ambiguous directives
-U
  Don't assume a specific address family on ambiguous directives

The above options can be used to remove ambiguities in directives, for example "BindAddress *".

## base commands

### Listen

Listen is expanded to take one or two arguments.

    	Listen port
    	Listen address:port
    	Listen address port

This is to let you specify "Listen :: 80", since "Listen :::80" won't work.

If you want httpd to listen on port 80 of all IPv4 and IPv6 addresses simultaneously, you would specify this using the following commands in your main server configuration:

    	Listen 0.0.0.0 80
    	Listen :: 80

## mod_access

deny from
allow from

"deny from" and "allow from" supports IPv6 addresses, under the following forms:

    	{deny,allow} from v6addr
    	{deny,allow} from v6addr/v6mask
    	{deny,allow} from v6addr/prefixlen

Also, wildcard ("*") and string hostname matches IPv6 hosts as well.

## mod_proxy

ProxyRequests on

http/ftp proxying for both IPv4 and IPv6 is possible. Access control functions (NoProxy) are not updated yet.

NOTE: for security reasons, we recommend you to filter out outsider's access to your proxy, by directives like below:

    	order deny,allow
    	deny from all
    	allow from 10.0.0.0/8
    	allow from 3ffe:9999:8888:7777::/64

## virtual host

If you would like to this feature, you must describe 'Listen' part on configuration file explicitly. like below:

    	Listen :: 80
    	Listen 0.0.0.0 80

NameVirtualHost

NameVirtualHost is expanded to take one or two arguments.

    	NameVirtualHost address
    	NameVirtualHost address:port
    	NameVirtualHost address port

This is to let you specify IPv6 address into address part.

Note that, if a colon is found in the specified address string, the code will try to resolve the address in the following way:

1. try to resolve as address:port (most of IPv6 address fails)
2. if (1) is failed, try to resolve as address only

If there's ambiguity, i.e. 3ffe:0501::1:2, the address may not be parsed as you expect (3ffe:0501::1 with port 2, or 3ffe:0501::1:2 with default port). To get the right effect you are encouraged to specify it without ambiguity. In IPv6 case "address port" (specify address and port separated by a space) is the safest way.

    <VirtualHost host:port [host:port ...]>

If you would like to specify IPv6 numeric address in host part, use bracketed format like below:

    	<VirtualHost [::1]:80>

Note: Now we DO NOT handle old non-bracketed format,

    	<VirtualHost 0:0:0:0:0:0:0:1:80>

so configuration file must be updated.

Note: The following is bad example to specify host ::1 port 80. This will treated as host ::1:80.

    	<VirtualHost ::1:80>

## logresolve (src/support)

error statistics in nameserver cache code is omitted.

## mod_unique_id

Originally mod_unique_id used IPv4 address as a seed for UNIQUE_ID, and took IPv4 address registered onto DNS for the hostname (UNIX hostname taken by gethostname(3)). Therefore, this does not work for IPv6-only hosts as they do not have IPv4 address for them.

Now, UNIQUE_ID can be generated using IPv6 address. IPv6 address can be used as the seed for UNIQUE_ID. Because of this, UNIQUE_ID will be longer than normal apache. This may cause problem with some of the CGI scripts. The preference of the addresses is based on the order returned by getaddrinfo(). If your getaddrinfo() returns IPv4 address, IPv4 adderss will be used as a seed.

Note that some of IPv6 addresses are "scoped"; If you happened to use link-local or site-local address as a seed, the UNIQUE_ID may not be worldwide unique.

If longer UNIQUE_ID causes a problem, define SHORT_UNIQUE_ID in mod_unique_id.c. In this case, length of UNIQUE_ID will be kept the same. However, for IPv6 addresses mod_unique_id.c will use the last 32bit (not the whole 128bit) as the seed. Therefore, there can be collision in UNIQUE_ID.

The behavior should be improved in the near future; we welcome your inputs.

## configuration file

We do not support IPv4 mapped addresses (IPv6 address format like ::ffff:10.1.1.1) in configuration file.

### Apache HTTP Server