Mailing List Archive: SPF: Devel

IPv4 to IPv6 convertion

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Igor at ritlabs

Aug 26, 2004, 1:28 AM

Post #1 of 7 (1270 views)
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IPv4 to IPv6 convertion

My server is in IPv4 network. We can get following SPF record:
v=spf1 ip6:0:0:0:0:0:FFFF:192.168.1.128 -all

How to convert sender's IPv4 address to IPv6?

Rfc2373 defines two forms of such convertion:

---< from rfc2373>---
The IPv6 transition mechanisms [TRAN] include a technique for hosts
and routers to dynamically tunnel IPv6 packets over IPv4 routing
infrastructure. IPv6 nodes that utilize this technique are assigned
special IPv6 unicast addresses that carry an IPv4 address in the low-
order 32-bits. This type of address is termed an "IPv4-compatible
IPv6 address" and has the format:

| 80 bits | 16 | 32 bits |
+--------------------------------------+--------------------------+
|0000..............................0000|0000| IPv4 address |
+--------------------------------------+----+---------------------+

A second type of IPv6 address which holds an embedded IPv4 address is
also defined. This address is used to represent the addresses of
IPv4-only nodes (those that *do not* support IPv6) as IPv6 addresses.
This type of address is termed an "IPv4-mapped IPv6 address" and has
the format:

| 80 bits | 16 | 32 bits |
+--------------------------------------+--------------------------+
|0000..............................0000|FFFF| IPv4 address |
+--------------------------------------+----+---------------------+
---< end >---

What form should be used?

- Igor

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Roger.Moser at rama

Aug 27, 2004, 6:20 AM

Post #2 of 7 (1227 views)
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IPv4 to IPv6 convertion [In reply to]

Igor wrote:

> My server is in IPv4 network.

Do you mean the server that is running SPF and receiving the mail?
Or the server publishing the SPF record and sending the mail?

> We can get following SPF record:
> v=spf1 ip6:0:0:0:0:0:FFFF:192.168.1.128 -all

No-one should have such an IPv6 address in the SPF record. IPv6 hosts don't
have such an IP address, and IPv4 hosts should publish "ip4:192.168.1.128".

> How to convert sender's IPv4 address to IPv6?

The SPF implementation should convert client IP addresses that are
IPv4-mapped IPv6 addresses to IPv4 addresses.

For example if the client IP address is for example ::FFFF:192.168.1.128,
then this means that the mail came from an IPv4-only host and the SPF
implementation should treat it as IPv4 address, that means the 'a' and 'mx'
mechanisms should look up A records instead of AAAA records.

Roger

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Igor at ritlabs

Aug 28, 2004, 4:48 AM

Post #3 of 7 (1231 views)
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Re: IPv4 to IPv6 convertion [In reply to]

Hello Roger,

Friday, August 27, 2004, 2:24:00 PM, you wrote:

RM> Do you mean the server that is running SPF and receiving the mail?
RM> Or the server publishing the SPF record and sending the mail?

I'm the author of BatPost mail-server and I'm currently trying to
implement SPF. My server use IPv4 format, but what if it find ip6
mechanism in SPF record?
Should I convert client IPv4 to IPv6?
Or try to determine client's IPv6 address?

This situation can by impossible, but there can be errors in SPF
records and I must interpret such situation somehow.
Maybe in such conditions ip6 mechanism must never match?
Or it can match only if we have IPv4-mapped IPv6 address in
mechanism's argument?

- Igor

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william at elan

Aug 28, 2004, 5:17 AM

Post #4 of 7 (1232 views)
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Re: IPv4 to IPv6 convertion [In reply to]

I have some interest in knowing how widespread ipv6, seeing as you are so
actively discussing it. Could we have a small poll here if possible:
1. Do you have ipv6 installed on your network?
a. If yes, is your ipv6 connection local on the network or global?
b. If global is it by means of local isp (new ip blocks) or 6-bone?
2. Do you have ipv6 installed on your computer (desktop or laptop
computer you regularly use as part of your normal day activities)?
If answered yes to 1 or 2:
3. How long ago have you started using ipv6?:_________
4. Do you use ipv6 for business services or only for testing?
5. Do you have ipv6 enabled mail server?
a. If yes, how many ipv6 connections does your mail server show for
last 30 days?: ______
b. Have you tried publishing SPF ip6 record?
If yes, please provide reference to its dns location: ____________

Please either answer on the list or to me personally. I'll summarize in
one week if there is substantial number of answers that its worth it.

And to be honest I'd be surprised if there is any more then 1 or 2 people
here who are even in position to answer questions 3 and above ...
(I note for myself that I can answer yes up to question 3 with "no" on 5)

On Sat, 28 Aug 2004, Igor wrote:

> Hello Roger,
>
> Friday, August 27, 2004, 2:24:00 PM, you wrote:
>
> RM> Do you mean the server that is running SPF and receiving the mail?
> RM> Or the server publishing the SPF record and sending the mail?
>
> I'm the author of BatPost mail-server and I'm currently trying to
> implement SPF. My server use IPv4 format, but what if it find ip6
> mechanism in SPF record?
> Should I convert client IPv4 to IPv6?
> Or try to determine client's IPv6 address?
>
> This situation can by impossible, but there can be errors in SPF
> records and I must interpret such situation somehow.
> Maybe in such conditions ip6 mechanism must never match?
> Or it can match only if we have IPv4-mapped IPv6 address in
> mechanism's argument?
>
> - Igor
>
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> To unsubscribe, change your address, or temporarily deactivate your subscription,
> please go to http://v2.listbox.com/member/?listname=spf-devel [at] v2

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Roger.Moser at rama

Aug 28, 2004, 8:20 AM

Post #5 of 7 (1242 views)
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IPv4 to IPv6 convertion [In reply to]

Igor wrote:

> I'm the author of BatPost mail-server and I'm currently trying to
> implement SPF. My server use IPv4 format, but what if it find ip6
> mechanism in SPF record?

In this case I would simply ignore the ip6 mechanism.

> Should I convert client IPv4 to IPv6?

You can do that, that means, treat "ip6:::FFFF.1.2.3.4" as "ip4:1.2.3.4".
But SPF records should not have IPv4-mapped IPv6 addresses in ip6
mechanisms.

> Or try to determine client's IPv6 address?

I don't think that this is possible.

Roger

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Roger.Moser at rama

Aug 28, 2004, 8:20 AM

Post #6 of 7 (1228 views)
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IPv4 to IPv6 convertion [In reply to]

William wrote:

> I have some interest in knowing how widespread ipv6, seeing as you are so
> actively discussing it. Could we have a small poll here if possible:

I am running Windows 2000. So all answers to your questions are "no".

Following domains have ip6 in their SPF record:

martin-wimmer.de: "v=spf1 redirect=_spf.eniac.de"
_spf.eniac.de: "v=spf1 +ip4:81.2.179.57 +ip4:213.239.194.211
+ip4:81.92.168.175 +ip6:3ffe:400:950::/48 +ip6:2001:6f8:900:10d::2
+ip6:2001:6f8:9ca::/48 +ip4:212.112.227.130 -all"

imasy.or.jp: "v=spf1 ip4:210.161.150.5 ip6:2001:200:300:1:290:27ff:fe41:f45e
~ip4:210.161.150.0/24 ~ip6:2001:200:300::/48 ~ip6:3ffe:505:0::/48 ~all"

stack.nl: "v=spf1 redirect=spf.stack.nl"
spf.stack.nl: "v=spf1 mx ip4:131.155.0.0/16 ip6:2001:610:1108::/48 ?all"

Roger

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Igor at ritlabs

Aug 29, 2004, 2:14 AM

Post #7 of 7 (1226 views)
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Re[2]: IPv4 to IPv6 convertion [In reply to]

Hello william(at)elan.net,

Saturday, August 28, 2004, 3:17:51 PM, you wrote:

waen> I have some interest in knowing how widespread ipv6, seeing as you are so
waen> actively discussing it. Could we have a small poll here if possible:
waen> 1. Do you have ipv6 installed on your network?
waen> 2. Do you have ipv6 installed on your computer (desktop or laptop
waen> computer you regularly use as part of your normal day activities)?
waen> 3. How long ago have you started using ipv6?:_________
waen> 4. Do you use ipv6 for business services or only for testing?
waen> 5. Do you have ipv6 enabled mail server?

In our network most computers are Windows based. We don't use IPv6.

- Igor

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