DOSemu networking made easy

DOSemu networking made easy

[Mateusz Viste]

Hi all,

I'm happily using DOSemu since a long time now, and the one thing that 
has always been bothering me is the complicated networking settings. 
Playing with bridging and masquerading and transforming the host into a 
routing machine is usually fine on a home desktop PC, but it becomes a 
real pain on a laptop which, by nature, often change it's network 
settings and physical locations.

This is why I wrote a tool to make DOSemu networking much easier (at 
least from my POV): taprouter.
taprouter is a user-mode application that acts like a router for DOSemu, 
and handles the internet access by using the host's networking, using 
SLIRP as a backend (a purist might say that taprouter is more like an 
ethernet-to-SLIP-bridge-with-DHCP-and-ARP-proxy rather than a 'router'). 
It delivers network settings to DOSemu via DHCP, so there's no 
configuration needed on the DOSemu side.

The thing is available for download (along with documentation) at the 
link below:

  http://www.viste-family.net/mateusz/software/taprouter/

I hope it will prove useful to anyone (else than me). :)

cheers,
Mateusz Viste

Re: DOSemu networking made easy

[Stas Sergeev]

24.06.2013 15:36, Mateusz Viste пишет:
> Hi all,
>
> I'm happily using DOSemu since a long time now, and the one thing that
> has always been bothering me is the complicated networking settings.
> Playing with bridging and masquerading and transforming the host into
> a routing machine is usually fine on a home desktop PC, but it becomes
> a real pain on a laptop which, by nature, often change it's network
> settings and physical locations.
>
> This is why I wrote a tool to make DOSemu networking much easier (at
> least from my POV): taprouter.
Hi!

Maybe a naive question, but, what problem does it
actually solve? I can see some advantage of this over
the bridging tap0 with eth0 solution, but what advantage
does it give over the static route with masquerading solution?

You seem to be saying that the dosemu's networking
configuration tends to change when you relocate your
laptop - I can agree with this if we talk about bridging,
but is it still true for the routing case?

I think I can just install a generic DHCP server and dosemu
will be able to reach it. Also, if tap0 is bridged with eth0,
dosemu will be able to reach an outer DHCP server.
Is this not true?

I am not sure what does this mean:
---
taprouter expects you to use the IP address 10.0.2.1 as a default gateway
---
you mean default gateway for dosemu or what?

Why your tool itself need a tap device?

Sorry, I am just a bit lost. :)
Never used dosemu with DHCP, but I haven't expected there
are any problems that need an extra tool to solve.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

Hi Stas!

No, it's not naive at all :). And my descriptions are probably lacking a 
fair amount of clarity.

 > actually solve? I can see some advantage of this over
 > the bridging tap0 with eth0 solution,

Bridging tap0 with eth0 requires that:
  - there is a DHCP server somewhere in the network
  - you are actually using always eth0 (and not wlan0 for instance when 
on the road, and eth0 when at home, etc)
  - you need to have the right to use more than 1 IP

All the conditions above are often unrealistic on a laptop, moving from 
home/office/hotel on the road, etc.

 > but what advantage
 > does it give over the static route with masquerading solution?

Technically - very little. BUT:
  - it's probably much easier to use taprouter
  - you don't need to play with NAT on your own PC
  - you don't need to enable ipforward=1 on your PC (which I am usually 
relunctant to do when being on a foreign network)

 > You seem to be saying that the dosemu's networking
 > configuration tends to change when you relocate your
 > laptop - I can agree with this if we talk about bridging,
 > but is it still true for the routing case?

No, it is not indeed. The only differences are points above.
basically taprouter makes it possible to use DOSemu with networking 
without reconfiguring your host PC to act as a router with NAT & 
possibly DHCP. Plus, taprouter works in usermode (no need to play with 
commands that look obscure to many people using the root account).

in fact, taprouter provides exactly the same service than most 
hypervisors do nowadays (like virtualbox, qemu, bochs..). ie. a 'net 
user' networking mode, where the user don't have to care about 
networking configuration, because as long as his host PC have internet 
access, the virtual machine (or DOSemu in this case) will, too.

 > I think I can just install a generic DHCP server and dosemu
 > will be able to reach it.

Sure. You are also one step away from spoofing any possible DHCP servers 
on whatever network you connect to, if you don't take extra care about 
how you configure your DHCP server. ;)
The solutions you describe are perfectly valid, but they are targeted to 
people that know exactly what they are doing, and why (and able to adapt 
the configuration when needed).
taprouter is targetted to people that don't have in-depth networking 
knowledge, and just want 'internet to work in DOSemu', or simply don't 
have time to wonder if their DOSemu setup will brake whenever they move 
from one network to another.

 > Also, if tap0 is bridged with eth0,
 > dosemu will be able to reach an outer DHCP server.
 > Is this not true?

Totally true. But again, it applies to the situation when there is a 
DHCP server out there, AND you are allowed to use more than 1 IP address 
at a time.

 > I am not sure what does this mean:
 > ---
 > taprouter expects you to use the IP address 10.0.2.1 as a default gateway
 > ---
 > you mean default gateway for dosemu or what?

Yes, that's exactly what I meant. From the point of view of DOSemu, 
DOSemu thinks it's in a 10.0.2.0/24 LAN with a single gateway, and a 
single DNS server - and these won't change, no matter how the 'real' 
network situation of the host looks like.

 > Why your tool itself need a tap device?

because it acts like a tap client. You'd have to imagine that the bridge 
is a L2 switch, and tap interfaces are RJ45 sockets :). You connect both 
your DOSemu and the router to the switch, so they can speak to each 
other. I think this needs to be explained with a drawing - a will do 
such schema and post it on my website.

 > Never used dosemu with DHCP, but I haven't expected there
 > are any problems that need an extra tool to solve.

Because in fact, technically there is no need - you can just as well 
obtain the same result with pure bridging or tap routing + masquerading, 
with optionally a DHCP server running on your PC, and maybe a DNS relay. 
But it's far from being trivial to set up, and additionally you have to 
keep in mind that you need to adapt the whole thing when your network 
settings change, and make sure that nobody can use your machine now as a 
DNS server and/or anonymous router and/or DHCP server.

I hope it's a bit clearer now :) Let me know.

cheers,
Mateusz







On 06/24/2013 03:23 PM, Stas Sergeev wrote:
> 24.06.2013 15:36, Mateusz Viste пишет:
>> Hi all,
>>
>> I'm happily using DOSemu since a long time now, and the one thing that
>> has always been bothering me is the complicated networking settings.
>> Playing with bridging and masquerading and transforming the host into
>> a routing machine is usually fine on a home desktop PC, but it becomes
>> a real pain on a laptop which, by nature, often change it's network
>> settings and physical locations.
>>
>> This is why I wrote a tool to make DOSemu networking much easier (at
>> least from my POV): taprouter.
> Hi!
>
> Maybe a naive question, but, what problem does it
> actually solve? I can see some advantage of this over
> the bridging tap0 with eth0 solution, but what advantage
> does it give over the static route with masquerading solution?
>
> You seem to be saying that the dosemu's networking
> configuration tends to change when you relocate your
> laptop - I can agree with this if we talk about bridging,
> but is it still true for the routing case?
>
> I think I can just install a generic DHCP server and dosemu
> will be able to reach it. Also, if tap0 is bridged with eth0,
> dosemu will be able to reach an outer DHCP server.
> Is this not true?
>
> I am not sure what does this mean:
> ---
> taprouter expects you to use the IP address 10.0.2.1 as a default gateway
> ---
> you mean default gateway for dosemu or what?
>
> Why your tool itself need a tap device?
>
> Sorry, I am just a bit lost. :)
> Never used dosemu with DHCP, but I haven't expected there
> are any problems that need an extra tool to solve.
>

--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Stas Sergeev]

24.06.2013 17:50, Mateusz Viste пишет:
> Hi Stas!
>
> No, it's not naive at all :). And my descriptions are probably lacking
> a fair amount of clarity.
>
> > actually solve? I can see some advantage of this over
> > the bridging tap0 with eth0 solution,
>
> Bridging tap0 with eth0 requires that:
>  - there is a DHCP server somewhere in the network
>  - you are actually using always eth0 (and not wlan0 for instance when
> on the road, and eth0 when at home, etc)
True.
There seem to be the project to solve this:
http://fedoraproject.org/wiki/Features/NetworkManagerBridging

> I hope it's a bit clearer now :) Let me know.
Thanks for the picture you added to the page.
I was actually just writing a mail asking you to do something
like this pict. :)
So basically the static DNS and static gateway are only
needed to allow the configuration without DHCP? Maybe
it is not worth the troubles, and only the DHCP-based
configuration can be left? I mean if you (or anyone else)
is going to port that inside dosemu, that may be easier.
But then, remove the static configuration, and suddenly
not too much is left at all. :)
Could you please explain a little more how NAT+slirp work
in that scenario? What was the task of slirp, is there no
other way to deal with the raw IP packets?
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

On 06/24/2013 05:00 PM, Stas Sergeev wrote:
> So basically the static DNS and static gateway are only
> needed to allow the configuration without DHCP? Maybe
> it is not worth the troubles, and only the DHCP-based
> configuration can be left? I mean if you (or anyone else)
> is going to port that inside dosemu, that may be easier.
> But then, remove the static configuration, and suddenly
> not too much is left at all. :)

The static configuration is the base of the whole solution - that's what 
makes it possible for DOSemu to think that it's in a real network. The 
'fake' DNS address, however, is just a redirection to the DNS server 
used by the host machine (it's not adding complexity at all, since it is 
taken care of by SLIRP, so I had only to implement a virtual ARP proxy 
for the 10.0.2.3 IP to make it work).

The DHCP service is just an additional module I wrote later, to avoid 
having to configure the 10.0.2.x adresses in DOSemu by hand.

> Could you please explain a little more how NAT+slirp work
> in that scenario? What was the task of slirp, is there no
> other way to deal with the raw IP packets?

In fact, it's not real NAT (nor PAT, nor anything similar). SLiRP is an 
astonishing piece of code, that accepts IP packets via a SLIP tunnel, 
and emulates a TCP/UDP/IP stack using normal, unpriviliged sockets on 
the host. In this regard, it acts like a proxy (but at a quite low level 
- TCP/UDP). Initially that's what I wanted taprouter to do, I even 
implemented a functional UDP proxy solution, but TCP is way more 
complicated, so instead of spending months on implementing my own TCP 
stack emulator, I used SLIRP as a backend, who does the job perfectly.

Now, why does SLiRP do such complicated things, instead of performing a 
(seemingly) simple IPsrc/PortSrc substitution on a per-packet basis?
Simply because it's dangerous (SLiRP could reuse a src port that is 
already used by the host's kernel, and thus trash an existing 
connection), and also because it would require the use of 'raw' sockets 
(or alternatively 'packet' sockets), which are not accessible to 
unpriviliged processes (so the user would have to run slirp as root, 
which many users - including me - won't agree too).

The role of taprouter is therefore to handle all the ethernet (L2) 
communication with DOSemu via TAP interfaces, intercept some packets 
(notably ARP requests, as well as UDP datagrams that transport 
BOOTP/DHCP requests), and encapsulate all other packets into SLIP 
messages, handing them to SLiRP, who does all the backend magic. And of 
course, taprouter have to do the work in the opposite direction as well 
- ie. listening for SLIP messages from SLiRP, decapsulating IP packets 
from them, checking who they are targeted to, using its ARP cache to 
encapsulate them into an Ethernet II structure with the correct dst MAC, 
and send them over the bridge. Plus some minor sanitazing stuff like 
dealing with broadcasts, using SLIRP only for non-local destinations, etc.

It would be really cool to have this incorporated into DOSemu, so for 
example a network configuration could be something like:

   $_pktdriver = (on)
   $_vnet = "slirp"
   $_netdev = "/usr/bin/slirp"

And such configuration would provide working network connectivity in any 
situation, without the user having to care about anything (as long as 
the host would have network itself).

I even looked at DOSemu source code, and locating the point where DOSemu 
opens the TAP interface wasn't a big deal, and it would be easy to 
implement any other alternative channel there, but I could not locate 
the code where DOSemu sends/recv ethernet frames into/from the TAP. If 
anybody tells me where in the code this happens, I might try to look 
further.

cheers,
Mateusz

Re: DOSemu networking made easy

[Stas Sergeev]

Aha, thanks for an explanation!
Now I've started to understand what is this all about. :)
Lets add dosemu-devel and Eric Biederman into CC.
The beginning is here:
http://marc.info/?l=linux-msdos&m=137207433306065&w=2

24.06.2013 19:38, Mateusz Viste пишет:
> It would be really cool to have this incorporated into DOSemu, so for
> example a network configuration could be something like:
>
>   $_pktdriver = (on)
>   $_vnet = "slirp"
>   $_netdev = "/usr/bin/slirp"
>
> And such configuration would provide working network connectivity in
> any situation, without the user having to care about anything (as long
> as the host would have network itself).
>
> I even looked at DOSemu source code, and locating the point where
> DOSemu opens the TAP interface wasn't a big deal, and it would be easy
> to implement any other alternative channel there, but I could not
> locate the code where DOSemu sends/recv ethernet frames into/from the
> TAP. If anybody tells me where in the code this happens, I might try
> to look further.
Sure: in pktnew.c please find the following:
---
        if (write(pkt_fd, SEG_ADR((char *), ds, si), LWORD(ecx)) >= 0) {
                    pd_printf("Write to net was ok\n");
                    return 1;
---

and the following:
---
    size = read(fd, pkt_buf, PKT_BUF_SIZE);
    if (size < 0) {
        p_stats->errors_in++;           /* select() somehow lied */
        return 0;
---

and that's it. :)
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Eric W. Biederman]

Stas Sergeev <stsp@list.ru> writes:

> Aha, thanks for an explanation!
> Now I've started to understand what is this all about. :)
> Lets add dosemu-devel and Eric Biederman into CC.
> The beginning is here:
> http://marc.info/?l=linux-msdos&m=137207433306065&w=2

I can see the appeal, of unprivileged NAT.

I don't think I have run any network facing applications in DOS.

Does the slirp code make any pretense of supporting IPv6?  Or is it the
same code I used in college  20 years ago?

Eric

> 24.06.2013 19:38, Mateusz Viste пишет:
>> It would be really cool to have this incorporated into DOSemu, so for
>> example a network configuration could be something like:
>>
>>   $_pktdriver = (on)
>>   $_vnet = "slirp"
>>   $_netdev = "/usr/bin/slirp"
>>
>> And such configuration would provide working network connectivity in
>> any situation, without the user having to care about anything (as long
>> as the host would have network itself).
>>
>> I even looked at DOSemu source code, and locating the point where
>> DOSemu opens the TAP interface wasn't a big deal, and it would be easy
>> to implement any other alternative channel there, but I could not
>> locate the code where DOSemu sends/recv ethernet frames into/from the
>> TAP. If anybody tells me where in the code this happens, I might try
>> to look further.
> Sure: in pktnew.c please find the following:
> ---
>         if (write(pkt_fd, SEG_ADR((char *), ds, si), LWORD(ecx)) >= 0) {
>                     pd_printf("Write to net was ok\n");
>                     return 1;
> ---
>
> and the following:
> ---
>     size = read(fd, pkt_buf, PKT_BUF_SIZE);
>     if (size < 0) {
>         p_stats->errors_in++;           /* select() somehow lied */
>         return 0;
> ---
>
> and that's it. :)
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Stas Sergeev]

24.06.2013 23:58, Eric W. Biederman пишет:
> Stas Sergeev <stsp@list.ru> writes:
>
>> Aha, thanks for an explanation!
>> Now I've started to understand what is this all about. :)
>> Lets add dosemu-devel and Eric Biederman into CC.
>> The beginning is here:
>> http://marc.info/?l=linux-msdos&m=137207433306065&w=2
> I can see the appeal, of unprivileged NAT.
>
> I don't think I have run any network facing applications in DOS.
>
> Does the slirp code make any pretense of supporting IPv6?  Or is it the
> same code I used in college  20 years ago?
You mean proxying the dosemu's IPv4 packets
by the use of IPv6? May be interesting for the
future, but IMHO IPv4 is not going to disappear
any time soon so why do we care at that stage.

My concern is also why there is no slirp packages
in most distros including fedora it seems. Very
few mentioning in google, not to say no docs -
pure nothing, or at least nothing googlable.
Last release like 10 years ago etc... This makes
me really sceptical, may became a maintenance burden.
But, as long as it works...
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

Hello

There is no really any way to translate ipv4 into ipv6.

About slirp - it is a pretty ancient soft indeed, but it is actively maintained by the qemu team. Both Qemu and Bochs use it for their user net service already, so it should be quite stable in time :)



Stas Sergeev <stsp@list.ru> wrote:

>24.06.2013 23:58, Eric W. Biederman пишет:
>> Stas Sergeev <stsp@list.ru> writes:
>>
>>> Aha, thanks for an explanation!
>>> Now I've started to understand what is this all about. :)
>>> Lets add dosemu-devel and Eric Biederman into CC.
>>> The beginning is here:
>>> http://marc.info/?l=linux-msdos&m=137207433306065&w=2
>> I can see the appeal, of unprivileged NAT.
>>
>> I don't think I have run any network facing applications in DOS.
>>
>> Does the slirp code make any pretense of supporting IPv6?  Or is it
>the
>> same code I used in college  20 years ago?
>You mean proxying the dosemu's IPv4 packets
>by the use of IPv6? May be interesting for the
>future, but IMHO IPv4 is not going to disappear
>any time soon so why do we care at that stage.
>
>My concern is also why there is no slirp packages
>in most distros including fedora it seems. Very
>few mentioning in google, not to say no docs -
>pure nothing, or at least nothing googlable.
>Last release like 10 years ago etc... This makes
>me really sceptical, may became a maintenance burden.
>But, as long as it works...
>--
>To unsubscribe from this list: send the line "unsubscribe linux-msdos"
>in
>the body of a message to majordomo@vger.kernel.org
>More majordomo info at  http://vger.kernel.org/majordomo-info.html

Mateusz
-- 
Sent from mobile mail.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Stas Sergeev]

25.06.2013 02:04, Mateusz Viste пишет:
> Hello
>
> There is no really any way to translate ipv4 into ipv6.
Could you please name the exact challenges?
I thought if it does proxying on a transport layer
then all it needs is to map the IPv4 address to IPv6
and then create a TCP connection as usual.
What am I missing?

> About slirp - it is a pretty ancient soft indeed, but it is actively maintained by the qemu team. Both Qemu and Bochs use it for their user net service already, so it should be quite stable in time :)
So for instance on fedora will people have to install
the qemu package to get /usr/bin/slirp? Or is it completely
internal to quemu, so that dosemu will have to import
its sources and re-sync every time?
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

Well, the challenge is simple: let's say that a dos app wants to connect to 1.2.3.4. There is no chance to 'translate' this into an ipv6 address, because both protocols use very different addressing models. Sure there exist some mechanisms that try to solve this by spoofing dns records, providing the client with a fake ip, and then remembering that this ip has to be redirected to the AAAA record of the initially targeted host. But from a network point of view this is total havoc, and I wouldn't expect any sane person to create an actusl implemention :)
It makes much more sense to use a http proxy then, and reach external services via the CONNECT method. This is at least totally transparent at the TCP/IP level, and the client knows that it will receive a bare tcp stream (but it requires the client to support http tunneling).

I dont know how is the availability of slirp on fedora. I had no problem to install it via the package manager of my OpenSuse though. But I guess it was contained in a non-suse repo anyway (packman probably?). Can fedora use outside repos? Otherwise the solution could be to package a slirp executable along with dosemu (eg. as /usr/bin/dosemu-slirp).



Stas Sergeev <stsp@list.ru> wrote:

>25.06.2013 02:04, Mateusz Viste пишет:
>> Hello
>>
>> There is no really any way to translate ipv4 into ipv6.
>Could you please name the exact challenges?
>I thought if it does proxying on a transport layer
>then all it needs is to map the IPv4 address to IPv6
>and then create a TCP connection as usual.
>What am I missing?
>
>> About slirp - it is a pretty ancient soft indeed, but it is actively
>maintained by the qemu team. Both Qemu and Bochs use it for their user
>net service already, so it should be quite stable in time :)
>So for instance on fedora will people have to install
>the qemu package to get /usr/bin/slirp? Or is it completely
>internal to quemu, so that dosemu will have to import
>its sources and re-sync every time?

Mateusz
-- 
Sent from mobile mail.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Eric W. Biederman]

Mateusz Viste <mateusz@viste-family.net> writes:

> Well, the challenge is simple: let's say that a dos app wants to
> connect to 1.2.3.4. There is no chance to 'translate' this into an
> ipv6 address, because both protocols use very different addressing
> models. Sure there exist some mechanisms that try to solve this by
> spoofing dns records, providing the client with a fake ip, and then
> remembering that this ip has to be redirected to the AAAA record of
> the initially targeted host. But from a network point of view this is
> total havoc, and I wouldn't expect any sane person to create an actusl
> implemention :) It makes much more sense to use a http proxy then, and
> reach external services via the CONNECT method. This is at least
> totally transparent at the TCP/IP level, and the client knows that it
> will receive a bare tcp stream (but it requires the client to support
> http tunneling).

For dos applications a http or socks proxy or just running a dedicated
IPv4 network until you no longer need or old crufty dos apps will
probably work for the forseable future.

There is a way to do stateless NAT64 (see RFC6877) with an IPv6 client
and an IPv4 server that isn't too bad at all.  You can pair it with
DNS64 or even better a little proxy on your client device that makes it
IPv4 again and what you effectively have is an IPv4 tunnel over IPv6.
For cell phone networks whose cost double if they offer normal dual
stack that is a very attractive way to go.  Android should include
an implementation of RFC6877 in it's next major release.

With an IPv4 client and IPv6 server the situation sucks because you
don't have enough address bits and you can't look dual stack to your
applictions so something will find a way to break.

> I dont know how is the availability of slirp on fedora. I had no
> problem to install it via the package manager of my OpenSuse
> though. But I guess it was contained in a non-suse repo anyway
> (packman probably?). Can fedora use outside repos?

Fedora can uses outside repos.

>  Otherwise the
> solution could be to package a slirp executable along with dosemu
> (eg. as /usr/bin/dosemu-slirp).

Eric

Re: DOSemu networking made easy

[Stas Sergeev]

25.06.2013 12:27, Eric W. Biederman пишет:
>> I dont know how is the availability of slirp on fedora. I had no
>> problem to install it via the package manager of my OpenSuse
>> though. But I guess it was contained in a non-suse repo anyway
>> (packman probably?). Can fedora use outside repos?
> Fedora can uses outside repos.
But not necessarily the ones intended for another distro like opensuse.
And it doesn't look like slirp is available in any fedora-specific
third party repos.
It seems as if such a functionality is better to have as a lib
rather than the standalone process btw.

------------------------------------------------------------------------------
This SF.net email is sponsored by Windows:

Build for Windows Store.

http://p.sf.net/sfu/windows-dev2dev
_______________________________________________
Dosemu-devel mailing list
Dosemu-devel@lists.sourceforge.net
https://lists.sourceforge.net/lists/listinfo/dosemu-devel

Re: DOSemu networking made easy

[Stas Sergeev]

25.06.2013 11:33, Mateusz Viste пишет:
> Well, the challenge is simple: let's say that a dos app wants to connect to 1.2.3.4. There is no chance to 'translate' this into an ipv6 address, because both protocols use very different addressing models.
How about this:
http://publib.boulder.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ibm.zos.r12.hale001%2Fipv6d0031001726.htm
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Eric W. Biederman]

Stas Sergeev <stsp@list.ru> writes:

> 25.06.2013 11:33, Mateusz Viste пишет:
>> Well, the challenge is simple: let's say that a dos app wants to connect to 1.2.3.4. There is no chance to 'translate' this into an ipv6 address, because both protocols use very different addressing models.
> How about this:
> http://publib.boulder.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ibm.zos.r12.hale001%2Fipv6d0031001726.htm

Those are not on the wire addresses.  Those are just for sockets that
can talk to ipv4 and ipv6 addresses at the same time.  Dual stack
sockets work but can be a little odd sometimes.  To use them would
require upgrading socket calls and literal addresses of slirp and
that is no likely to be worth the effort.

If you happen to have something like NAT64 upstream you can implement
464xlate and get essentialy native IPv4 connectivity and that will
handle connecting to 1.2.3.4.  But at that point you linux box should
already have ipv4 addresses so doing anything in taprouter or dosemu
is pointless.

Another painful example of the problems of trying to NAT between address
families is connecting over ipv6 to an ftp server.  What happens
when the IPv6 ftp server tells the DOS IPv4 ftp client to connect
to 2001:DB8:12:34:::21.  The DOS ftp client doesn't won't have a clue
what to do with that address.

There are lots of protocols with that problem ftp is just the oldest of
them.  Certainly classes of web pages from services such as Akamai (so
no where important) embbed ip address literals into web pages.  Again
defeating attempts to translate names in dns.

Eric
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

That is not really meaningfull to our situation. It is only a way of writing an ipv4 in the ipv6 format, but it has no functional purpose other than simplifying a bit the internal storage of ip addresses inside double stack applications.



Stas Sergeev <stsp@list.ru> wrote:

>25.06.2013 11:33, Mateusz Viste пишет:
>> Well, the challenge is simple: let's say that a dos app wants to
>connect to 1.2.3.4. There is no chance to 'translate' this into an ipv6
>address, because both protocols use very different addressing models.
>How about this:
>http://publib.boulder.ibm.com/infocenter/zos/v1r12/index.jsp?topic=%2Fcom.ibm.zos.r12.hale001%2Fipv6d0031001726.htm

Mateusz
-- 
Sent from mobile mail.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

Hi

I do not think there is any ipv6 support in slirp. But it is not that important I believe, since there is no dos tcp/ip stack with ipv6 support :)


ebiederm@xmission.com wrote:

>Stas Sergeev <stsp@list.ru> writes:
>
>> Aha, thanks for an explanation!
>> Now I've started to understand what is this all about. :)
>> Lets add dosemu-devel and Eric Biederman into CC.
>> The beginning is here:
>> http://marc.info/?l=linux-msdos&m=137207433306065&w=2
>
>I can see the appeal, of unprivileged NAT.
>
>I don't think I have run any network facing applications in DOS.
>
>Does the slirp code make any pretense of supporting IPv6?  Or is it the
>same code I used in college  20 years ago?
>
>Eric
>
>> 24.06.2013 19:38, Mateusz Viste пишет:
>>> It would be really cool to have this incorporated into DOSemu, so
>for
>>> example a network configuration could be something like:
>>>
>>>   $_pktdriver = (on)
>>>   $_vnet = "slirp"
>>>   $_netdev = "/usr/bin/slirp"
>>>
>>> And such configuration would provide working network connectivity in
>>> any situation, without the user having to care about anything (as
>long
>>> as the host would have network itself).
>>>
>>> I even looked at DOSemu source code, and locating the point where
>>> DOSemu opens the TAP interface wasn't a big deal, and it would be
>easy
>>> to implement any other alternative channel there, but I could not
>>> locate the code where DOSemu sends/recv ethernet frames into/from
>the
>>> TAP. If anybody tells me where in the code this happens, I might try
>>> to look further.
>> Sure: in pktnew.c please find the following:
>> ---
>>         if (write(pkt_fd, SEG_ADR((char *), ds, si), LWORD(ecx)) >=
>0) {
>>                     pd_printf("Write to net was ok\n");
>>                     return 1;
>> ---
>>
>> and the following:
>> ---
>>     size = read(fd, pkt_buf, PKT_BUF_SIZE);
>>     if (size < 0) {
>>         p_stats->errors_in++;           /* select() somehow lied */
>>         return 0;
>> ---
>>
>> and that's it. :)

Mateusz
-- 
Sent from mobile mail.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Eric W. Biederman]

Mateusz Viste <mateusz@viste-family.net> writes:

> Hi
>
> I do not think there is any ipv6 support in slirp. But it is not that
> important I believe, since there is no dos tcp/ip stack with ipv6
> support :)

I believe tcp/ip with ipv6 support can be had from one of the etherboot
descendents of gpxe or ipxe.

Ok.  I see what you mean about slirp and qemu.  qemu has forked slirp
and has an internal version.  The standalone slirp package seems only to
be actively maintained by the debian package maintainers at this point.
Of course we are talking old stable code here.  I wonder if it would
make sense for someone to reimport the BSD networking stack into slirp?

At a very basic level I don't know if it is wise to make it easy to
open up old unmaintained dos executables to the public internet.  But
unless it becomes common there are unlikely to be anything except
government level attacks that will target old DOS binaries to break into
your machine so I doubt it is particularly.

With respect to ipv6.  My current swag is 2020 for when ipv6 will have
achieved effectively universal penetration and some ISPs will stop
routing legacy ipv4 from their customers across the internet.

Given that what this is about keeping old software on life support for
a minimal amount of work I don't see any reason to object to the lack of
ipv6 support.  I was mostly curious if this was walking down a
maintenance dead end.  If slirp updates can be pulled from qemu I don't
imagine there will be any maintenance problems.

Eric

Re: DOSemu networking made easy

[Mateusz Viste]

I think there is no point refreshing the bsd stack used in slirp (iirc it uses the stack of a 4.4 bsd), because it is used only between slirp and dosemu anyway. Between slirp and the outside world only 'normal' host's sockets are used.

Anyway, as a 1st step I will transform taprouter into an easy-to-link module. Then, I will look how to integrate it into DOSemu.

cheers
Mateusz


ebiederm@xmission.com wrote:

>Mateusz Viste <mateusz@viste-family.net> writes:
>
>> Hi
>>
>> I do not think there is any ipv6 support in slirp. But it is not that
>> important I believe, since there is no dos tcp/ip stack with ipv6
>> support :)
>
>I believe tcp/ip with ipv6 support can be had from one of the etherboot
>descendents of gpxe or ipxe.
>
>Ok.  I see what you mean about slirp and qemu.  qemu has forked slirp
>and has an internal version.  The standalone slirp package seems only
>to
>be actively maintained by the debian package maintainers at this point.
>Of course we are talking old stable code here.  I wonder if it would
>make sense for someone to reimport the BSD networking stack into slirp?
>
>At a very basic level I don't know if it is wise to make it easy to
>open up old unmaintained dos executables to the public internet.  But
>unless it becomes common there are unlikely to be anything except
>government level attacks that will target old DOS binaries to break
>into
>your machine so I doubt it is particularly.
>
>With respect to ipv6.  My current swag is 2020 for when ipv6 will have
>achieved effectively universal penetration and some ISPs will stop
>routing legacy ipv4 from their customers across the internet.
>
>Given that what this is about keeping old software on life support for
>a minimal amount of work I don't see any reason to object to the lack
>of
>ipv6 support.  I was mostly curious if this was walking down a
>maintenance dead end.  If slirp updates can be pulled from qemu I don't
>imagine there will be any maintenance problems.
>
>Eric


-- 
Sent from mobile mail.

Re: DOSemu networking made easy

[Eric W. Biederman]

Mateusz Viste <mateusz-IMIDigHRhuggabnWlOdIvg@public.gmane.org> writes:

> I think there is no point refreshing the bsd stack used in slirp (iirc
> it uses the stack of a 4.4 bsd), because it is used only between slirp
> and dosemu anyway. Between slirp and the outside world only 'normal'
> host's sockets are used.

I did not mean in the context of dosemu.  I meant more in the context of
qemu and places where applications will start caring.  Depending on the
network stack it should not be too difficult to get ipv6 support in
there as well.

> Anyway, as a 1st step I will transform taprouter into an easy-to-link
> module. Then, I will look how to integrate it into DOSemu.

Sounds good.

I am inclined to look at some of this for the context of lxc so we can
have unprivileged containers that have packets that go out the host
network stack.  ;-)  Now that I know what the trick qemu uses.

Eric

------------------------------------------------------------------------------
This SF.net email is sponsored by Windows:

Build for Windows Store.

http://p.sf.net/sfu/windows-dev2dev

Re: DOSemu networking made easy

[Stas Sergeev]

25.06.2013 03:43, Eric W. Biederman пишет:
> At a very basic level I don't know if it is wise to make it easy to
> open up old unmaintained dos executables to the public internet.
According to wikipedia:
https://en.wikipedia.org/wiki/Slirp#Limitations
slirp cannot accept the incoming connections, and therefore
gives as much of a protection as the NAT does.
But I really can't follow their (wikipedia) logic: at least if the
port is not already in use, why can't slirp open it to listen for
the incoming connections? They claim you need a port forwarding
for that.

> maintenance dead end.  If slirp updates can be pulled from qemu I don't
> imagine there will be any maintenance problems.
Well you probably know how "often" the dosemu releases
are made: not much more frequently than the ones of slirp. :)
So if there be some updates on slirp, even if someone will pull
them into dosemu git quickly, they have zero chances to reach
the user within 10 years or more, so this is not the best solution. :))
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Eric W. Biederman]

Stas Sergeev <stsp@list.ru> writes:

> 25.06.2013 03:43, Eric W. Biederman пишет:
>> At a very basic level I don't know if it is wise to make it easy to
>> open up old unmaintained dos executables to the public internet.
> According to wikipedia:
> https://en.wikipedia.org/wiki/Slirp#Limitations
> slirp cannot accept the incoming connections, and therefore
> gives as much of a protection as the NAT does.
> But I really can't follow their (wikipedia) logic: at least if the
> port is not already in use, why can't slirp open it to listen for
> the incoming connections? They claim you need a port forwarding
> for that.

slirp and qemu can do that.  You can't open a privileged port (because
you don't have permission but it otherwise works).  I do think they call
the feature port forwarding however.

NAT is sufficient to protect your old DOS mail client or to prevent
packet spoofing by the bad guys.  Let alone protect you if your DNS is
compromised or you are otherwise tricked into connecting into a site the
bad guys own.

Applications like chrome and firefox are constantly getting updates to
prevent problems in those kinds of scenarios.  Other network facing
applications are paranoid to one degree or another.

My concern was just that most DOS applications are old enough that if
anyone was serious they could use modern techniques and own your dosemu
without trying hard.

But like you say below these changes don't propogate quickly.

>> maintenance dead end.  If slirp updates can be pulled from qemu I don't
>> imagine there will be any maintenance problems.
> Well you probably know how "often" the dosemu releases
> are made: not much more frequently than the ones of slirp. :)
> So if there be some updates on slirp, even if someone will pull
> them into dosemu git quickly, they have zero chances to reach
> the user within 10 years or more, so this is not the best
> solution. :))

Shrug.  Whatever works.  My networking facing hat is quite paranoid
these days.

I suspect simply having the configuration default to off by default is
enough to protect most existing users of DOS applications.

Eric
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Stas Sergeev]

25.06.2013 11:57, Eric W. Biederman пишет:
> I suspect simply having the configuration default to off by default is
> enough to protect most existing users of DOS applications.
In this case we can keep having TAP the default, which
allows you, but not enabling the ipv4 forwarding, keep
being protected.
But on the other hand, the default config should allow
as much features as possible (users don't like to change
configs), so I dunno.
--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html

Re: DOSemu networking made easy

[Mateusz Viste]

Hi again,

Added a little schema that shows how taprouter interacts with the linux 
bridge, dosemu, tap interfaces and slirp...

http://www.viste-family.net/mateusz/software/taprouter/

Not sure it makes the whole thing looking less of a contraption, though :P

The silver bullet would be to integrate all this mess into DOSemu (ie de 
facto implementing a 'user network' like in qemu/bochs/vbox), but that's 
something I unfortunately don't have enough time for.

Mateusz





On 06/24/2013 03:23 PM, Stas Sergeev wrote:
> 24.06.2013 15:36, Mateusz Viste пишет:
>> Hi all,
>>
>> I'm happily using DOSemu since a long time now, and the one thing that
>> has always been bothering me is the complicated networking settings.
>> Playing with bridging and masquerading and transforming the host into
>> a routing machine is usually fine on a home desktop PC, but it becomes
>> a real pain on a laptop which, by nature, often change it's network
>> settings and physical locations.
>>
>> This is why I wrote a tool to make DOSemu networking much easier (at
>> least from my POV): taprouter.
> Hi!
>
> Maybe a naive question, but, what problem does it
> actually solve? I can see some advantage of this over
> the bridging tap0 with eth0 solution, but what advantage
> does it give over the static route with masquerading solution?
>
> You seem to be saying that the dosemu's networking
> configuration tends to change when you relocate your
> laptop - I can agree with this if we talk about bridging,
> but is it still true for the routing case?
>
> I think I can just install a generic DHCP server and dosemu
> will be able to reach it. Also, if tap0 is bridged with eth0,
> dosemu will be able to reach an outer DHCP server.
> Is this not true?
>
> I am not sure what does this mean:
> ---
> taprouter expects you to use the IP address 10.0.2.1 as a default gateway
> ---
> you mean default gateway for dosemu or what?
>
> Why your tool itself need a tap device?
>
> Sorry, I am just a bit lost. :)
> Never used dosemu with DHCP, but I haven't expected there
> are any problems that need an extra tool to solve.
> --
> To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
>

--
To unsubscribe from this list: send the line "unsubscribe linux-msdos" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html