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Re: Initial SCTP support for the upcoming 1.6.5 release
From: |
Michael Tuexen |
Subject: |
Re: Initial SCTP support for the upcoming 1.6.5 release |
Date: |
Fri, 20 Aug 2004 09:57:28 +0200 |
Kevin,
see my comments in-line.
Best regards
Michael
On Aug 20, 2004, at 3:13 AM, Kevin Ryde wrote:
Michael Tuexen <address@hidden> writes:
The argument, to use a function like getprotobyname
to perform a lookup in /etc/protocols, is not valid in my opinion.
The reason is, that besides I have not seen that, that the
constants above are defined in /usr/include/netinet/in.h and
are used.
I don't want to go against the advice of the GNU/Linux man page. It's
pretty explicit.
You are not going against it. You are not using them. You are only
providing constants available in /usr/include/netinet/in.h to
the guile user.
So if, a system (I do not know of any such system),
uses a different number for TCP, this number will not only be in
/etc/protocols, but also in /usr/include/netinet/in.h. A different
story are port numbers. They can (and should) be looked up in
/etc/services.
There are no constants describing the port number for an echo
server...
Well I guess both protocol and service numbers for standard stuff are
constants. I don't know why one reads a file instead of just putting
numbers in a program. Maybe it dates right back to a time when such
things were still in flux. Or maybe the theory is to avoid numbers
hard coded in programs (though strings hard coded aren't much better
:-).
You are right, both port numbers and protocol numbers are kind of
standardized. But there is two differences:
Normally a user of a program does not specify the transport protocol,
but the port (telnet 127.0.0.1 echo, for example). That is why you
need a translation service for these service names.
The second is that there are no predefined constants for port numbers
available on a system like it is for protocols.
I agree with the man page that it is bad to use
s = socket(AF_INET, SOCK_STREAM, 132);
It should be
s = socket(AF_INET, SOCK_STREAM, IPPROTO_SCTP);
because you are not using a number, you are using a constant.
So what is the difference if you use getprotocolbyname? You can move
the binaries to a different host which uses different numbers?
I have not seen that and I'm pretty sure that this is not in tune
with the socket() call.
BTW, for UDP and TCP the calls
s = socket(AF_INET, SOCK_DGRAM, 0);
s = socket(AF_INET, SOCK_STREAM, 0);
are used as acronyms for
s = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
s = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
So I think the man page and reality match no pretty good for these
things,
but the man page seems to be pretty old (1995, on
http://www.freebsd.org/cgi/man.cgi?
query=protocols&apropos=0&sektion=0&manpath=Red+Hat+Linux%2Fi386+9&forma
t=html
Best regards
Michael
PS.: The usage of the third arg of the socket() call is the one
described
in the 3rd edition of Unix Network Programming, so I guess that
some
people will try to use it that way...
- Re: Initial SCTP support for the upcoming 1.6.5 release, (continued)
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/14
- Re: Initial SCTP support for the upcoming 1.6.5 release, Kevin Ryde, 2004/08/15
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/16
- Re: Initial SCTP support for the upcoming 1.6.5 release, Kevin Ryde, 2004/08/17
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/19
- Re: Initial SCTP support for the upcoming 1.6.5 release, Kevin Ryde, 2004/08/19
- Re: Initial SCTP support for the upcoming 1.6.5 release,
Michael Tuexen <=
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/16
- Re: Initial SCTP support for the upcoming 1.6.5 release, Rob Browning, 2004/08/16
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/20
- Re: Initial SCTP support for the upcoming 1.6.5 release, Kevin Ryde, 2004/08/22
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/23
- Re: Initial SCTP support for the upcoming 1.6.5 release, Kevin Ryde, 2004/08/23
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/24
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/24
- Re: Initial SCTP support for the upcoming 1.6.5 release, Marius Vollmer, 2004/08/24
- Re: Initial SCTP support for the upcoming 1.6.5 release, Michael Tuexen, 2004/08/24