[ECOS] Porting of PPP to the eCos operating system

[Erik Aagaard Knudsen <EAK at penell dot com>]

As told in a previous mail (Fri. 23 nov. 2001) I am in the process of
porting pppd (v. 2.3.5) to eCos. I have ported the driver part (not tested
yet though) and have started porting the application part. There are a few
problems, which I would very much like to have comments on.

One is the problem of global variables and functions (there are many in
pppd). I don't want to pollute the eCos namespace with all these names (to
avoid the risk of name clashes with ports of other programs).

The other is the problem of independent incarnations of pppd. This gives a
problem with static variables, which cannot be independent across
incarnations in eCos.

I intend to solve the problem with global functions by allocating a global
structure inside which the names are defined.

And I intend to solve the problem with incarnations by utilizing the means
in eCos for making functions thread safe. I will dynamically allocate a
structure inside which global variables are defined and I will also
dynamically allocate a structure for each file inside which static variables
are defined.

For each file there will be a (global) initialization function, which
initializes pointers to global functions in the above mentioned global
structure.

For each file there will also be a constructor, which allocates and
initializes memory for static variables for this file.

And finally for each file there will be a destructor which deallocates
memory for static varibales for this file.

As far as I can see then this solves most problems. The procedure may seem
complicated and indeed the two problems that it solve are pervasive and
necessitates a great number of corrections to the pppd code. The corrections
are trivial though and easy to perform. In case data accessed in this way
are used extensively, then of course performance will suffer, but this is
not the case in pppd.

Perhaps I should note that I am well avare of the possibilities for loading
elf images into eCos. It seems though that this is too heavy ammunition for
eCos. I think perhaps you would be better off using another operating system
(like uClinux) in that case.

I do not intend to implement demand dialing.

Pppd read authentication information from two files. I intend to implement
these files as global structs.

Pppd uses the Unix concept of process id, this is not supported in eCos and
is therefore removed.

Pppd uses Unix signals (across processes). Processes are not supported in
eCos and this is therefore removed.

The following options for pppd are not ported: call, connect, disconnect,
init, lock, activefilter, demand, logfd, logfile, login, nolog, welcome,
xonxoff.

I hope to get some response on this.



Best Regards
Erik Aa. Knudsen
Project Engineer, 
Software Engineer, M.Sc.

Phone direct:			+45 9652 0356
E-mail:			eak@penell.com <mailto:eak@penell.com>   
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