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Summary: TCP/IP

Abstract

This is a summary of the TCP/IP discussion on aros-dev from December 2001. It covers pro and con points to the bsdsocket API and some ideas to do TCP/IP inside AROS.

This summary contains comments from:

How to add TCP/IP to AROS?

  1. bsdsocket.library as wrapper for the TCP/IP stack of the underlying OS.
  2. Porting AmiTCP 3.0b2
  3. Porting the BSD TCP/IP stack
  4. Writing own stack.

AmiTCP 3.0b2

  • is stable
  • more or less the same as 4.0
  • for the time being it suits our needs
  • SLIP and CSLIP
  • PPP (from third parties)

I've used this package myself over the last seven years or so. From what I understand of the AmiTCP boys, release 3.0b2 is more or less the same as 4.0 (the infamous "demo" release).

By my own, personal experience, I can tell for a fact that 3.0b2 is stable. Over the years, I can't think of one single incident involving AmiTCP 3 (There are, however, a few known issues concerning the "fingerd" service and the "telnet" tool. These have been dealt with and solutions should be accessible from ftp.geekgadgets.org)

No, AmiTCP and the "bsdsocket.library" API isn't an ideal solution for AROS (nor for AmigaOS), but for the time being it suits our needs which is why I'd say you're doing the right thing, Henrik.

BSD socket API

Pro

  • Allow software porting from other platforms (read as: Unix programs)

  • A brand new, clean TCP/IP service would still have to provide some "bsd" wrapper.

  • I think you are all afraid of the Unix code, despite the fact that the BSD implementations are considered to be the premier implementations of the whole thing, at least by some people.

  • The BSD API is unpopular with whom? AT&T tried to reinvent the API, and nobody took that up, so what is wrong with it.

  • Most of the example code in the world uses sockets, all the network programming books.

  • If we don't have POSIX compatibility at some level it'll make porting TCP/IP applications from any other platform a pain.

  • Personally I don't like the ANDI approach... but maybe I'm too used to programming with the BSD socket library. I recently implemented multicast support on a set top box over BSDsockets and without any problem whatsoever. There are many issues that depend on TCP itself rather than on implementations and BSD offer just the instruments useful to avoid or limit those issues. Nobody's perfect, but Cisco IOS stack derived from BSD (it's different in many ways, but it's a direct BSD derivative) and this has a lot of sense and implications for me.

    ... In the document you've indicated I saw several "unique features" and "common problem solutions" that are the same applied on BSD... I think that we should approach this matter without looking beyond the horizon when we have a definitely not so bad solution in front of us.

  • You can argue that "we don't need those stinking applications" & I'd agree, if there was enough interest to write a web server etc.

  • A lot of Amiga applications uses the BSD API.

  • The problem is AFAIK the fact that you cannot wait for AmigaOS signals at the same time you're doing an select(). Say for example you wanted to (all at the same time):

    • Wait for event's from the GUI
    • Wait for timer events
    • Do async file IO
    • Do async network IO

    That why you have SelectSignal() (or what it's called) in AmiTCP (i.e., select() with a time-out + waiting for signals; which in itself suggests that AmiTCP uses them internally somehow).

Contra

  • I think the Amiga "connectivity" would have been a lot better if they would have gone for a more elegant, "Amiga-ish" solution instead.

  • Because it uses the 'everything is a file' philosophy of Unix and not the device philosophy of Amiga. It's not the use of sockets that is a problem it is the way you access them.

  • Part of the "problem" is that the API is linked into the POSIX way of doing things, if you then have a separate POSIX layer for read()/write() calls etc., you get a problem. The only one I can quote from the top of my head is ioctl(). There are workarounds for the problem: winsock uses ioctlsocket() instead, for instance. Having to create another process for blocking calls is also a tad painful at times.

  • > OK, what is the difference between say, ioctl(), or setsockopt() and an > Amiga-like call such as SetObjectA()?

    Not much, really. The real problem comes when trying to be POSIX-compliant, you need an ioctl that can work on files TCP/IP etc. So, you have to avoid using those functions for native support unless you go the whole hog and move ioctl into dos.library somewhere.

  • A brand new API for network services is something that should look and feel like any other OS component. Dealing with network I/O should't be much different from dealing with exec messages (or anything similar).

  • I'm just saying that I think everyone should be aware of the danger relying on some Unix-style API could mean. "Why even bother developing a webserver when there's Apache?" "Why waste time writing a 'finger' utility when I can compile some GNU flavor right out of the box?". If I want to run stuff taken from the Unix world, then I run Linux. If I want to run stuff taken from the AmigaOS world, then I run AROS.

    • The alternative is nobody writing a web server AND we can't use Apache. It's a tough call, but I think we ought to have POSIX compatibility.
  • I don't think we should settle for some simple "bsd" API wrapper; it should rather be the other way around; a network service acting as an integrated piece of the OS core, just like any other runtime component (with an optional "POSIX" wrapper).

  • Functions can be stored within devices. However, as long as the architecture permits it I/O should be done on an asynchronous basis.

  • Now, as I stated in my last e-mail on this thread my standpoint is that whatever solution we go for - no matter what you choose to call it - is that the programming interface should be clean, easy to understand and in cohesion with the rest of the programming environment. "bsd" is anything but this.

Driver

A generic "NE2000" network driver should be sufficient for a start (with PPP for the bandwidth impaired).

Library / Device

  • Library for synchronous calls
  • Device for asynchronous calls
  • An other option would be to implement the library in an asynchronous way. Each opener would get an own task allocated for it (that the library starts up), which handles the asynchronous operations. You would use the library in a similar way as Intuition windows, i.e. creating an messageport / signal that you pass to the library when initializing.

ANDI

http://www.nordicglobal.com/andi.txt.

  • > IIRC, ANDI was designed to replace the SANA-II specifications, nothing

    else.

    Not really. ANDI acts as a protocol independent way of dealing with network I/O using standard Exec asynchronous device processing. Here's a small excerpt from the ANDI technical paper:

  • ANDI was written a few years ago. From what I understand of it, its a draft and work in progress.

ANDI is supposed to...

  • ...follow "typical Amiga programming paradigms" more closely than the existing BSD socket APIs, making it easier for Amiga programmers without previous experience in Unix network programming to develop Amiga network applications.
  • ...be protocol-independent and extensible to support new protocol features in the future.
  • ...not repeat some of the design problems in the BSD socket API, in particular problems related to non-blocking I/O, "half closed connections" in TCP, and problems in the transition to T/TCP, IPV6, SSL, Multicasting and several other new concepts.
  • ...hide as many protocol-specific details as possible from high-level network applications, to allow changes or additions to protocols without requiring changes to applications.
  • ...be implemented and offered for Amiga protocol stacks in addition to the existing BSD socket APIs. The old BSD socket APIs will remain in place for older applications and for future applications ported from Unix, but it is recommended that new Amiga applications use ANDI instead.

Writing own TCP/IP stack

You'd probably ignore TCP to start with and implement some UDP/ICMP features first. To get something that "did something"tm on a network wouldn't be so hard. (Maybe a day, if you had all the RFC's, source code from linux/wattcp etc.)

Hardware drivers would be the major problem, if you can write something that talks to an ne2000 then it's pretty easy to generate the packet headers necessary for something like a ping. However I haven't seen an ne2000 in years & PPP can be used over a null modem cable, but then again PPP is quite complex on the software side.

Once you've got ping working, the next step would be to get a UDP client working ( not sure what client/servers use UDP though ).

Most emulators seem to support NE2000, although if they use NAT to give the emulated machine another IP address you may have troubles with ICMP/UDP.

Then of course you've got the political problem as BSD sockets are unpopular, but as an API it's hard to implement it differently anyway. If all you're going to do is make an API with different names then has the new design been worthwhile? Especially as we'd need a POSIX compatibility layer too.

I do think even implementing our own BSD API would be worthwhile as it's much easier to test something that you're putting together than something you've just managed to recompile, especially as the hardware interface is likely to be completely different & some or all of the AmiTCP code would have been written to run on big-endian hardware. It would be nice if someone understood it all as well.

Miscellaneous

Off-topic & I'll probably be a bit unpopular here too, but it would also be nice if we had support for http://www.rdesktop.org/ (both client and later a server).


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