Re: lib/46111: yplib will hang forever if no server can be found

[Wolfgang Stukenbrock <Wolfgang.Stukenbrock%nagler-company.com@localhost>]

The following reply was made to PR lib/46111; it has been noted by GNATS.

From: Wolfgang Stukenbrock <Wolfgang.Stukenbrock%nagler-company.com@localhost>
To: gnats-bugs%NetBSD.org@localhost
Cc: lib-bug-people%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost, 
netbsd-bugs%NetBSD.org@localhost,
        Wolfgang.Stukenbrock%nagler-company.com@localhost
Subject: Re: lib/46111: yplib will hang forever if no server can be found
Date: Wed, 29 Feb 2012 16:35:16 +0100

 Hi,
 
 I'm not shure if a function is a good idea, because there is already a 
 global variable _yplib_nerrs that is set to 5 as default.
 As far as I've figured out _yplib_nerrs is used in some files in 
 src/lib/libc/yp and is not documented in any headerfiles and/or the 
 manual. It seems to be a global libc-internal variable.
 A disadvantage of a function is the missing ability to query the current 
 state.
 So I would prefer a variable, but I can implement a function too, if you 
 prefer this.
 
 Currently after _yplib_nerrs number of retries the message "YP server 
 for ... still trying" is printed, but only if the domain is already 
 found in the _ypbindlist. No printing is done for the first contact with 
 ypbind - or I've overlooked something.
 This looks like someone has changed the original Sun behaviour in the 
 past that is printing this message as far as I remember even for the 
 first connection attemp.
 remark: an entry is added to the _ypbindlist after successfull 
 contacting ypbind or if a binding file is present and valid.
 
 If there is a binding file present for the domain, and the file locking 
 fails, YPERR_YPBIND is returned without contacting ypbind.
 When contacting ypbind, YPERR_YPBIND is returned too if clnttcp_create() 
 fails.
 Theese both should be very rare situations, but will already currently 
 not wait until a server is available.
 
 In e.g. yp_first and yp_next the variable _yplib_nerrs is used to print 
 a message too if the binding has succeeded but the clnt_call() has 
 failed the configured number of times. This will be done in an endless 
 loop too, if the binding succeded every time.
 Should this behaviour be changed too? If the binding fails, YPERR_DOMAIN 
 is returned.
 
 I aggree not to change de default behaviour of the lib, but allow to 
 change it unter program control. At least I need currently need the 
 possibility to catch the problem with ypbind to faile my request and 
 continue to work.
 
 
 My "current" patch will return YPERR_YPBIND only if there is no 
 previously setup entry in the _ypbindlist.
 Should I also terminate the processing after <n> retries, if there is an 
 entry in _ypbindlist present? I think yes.
 Should in such case the "still trying" message be written to stderr or 
 should the lib be silent. I think no printing should be done.
 
 What about the following sollution:
 I reuse _yplib_nerrs for the new functionality.
    _yplib_nerrs > 0 - current behaviour - wait endless and print a 
 message every _yplib_nerrs retries. The default value will be 5 as before.
    _yplib_nerrs == 0 - wait endless without printing to stderr
    (this is something that would already happen now when _yplib_nerrs 
 gets set to 0, because the print-check check starts with 1 and the first 
 printout will happen on the integer-wrap ...)
    _yplib_nerrs < 0 - number of retries (as negative count) with ypbind 
 after that YPERR_YPBIND is returned. And the lib will return regardless 
 if the domainname has been queried before or not.
 I will add it to the rpcsvc/ypclnt.h headerfile as extern declaration 
 and add it the to ypclnt(3) manual.
 
 This implies disabling the printing in the other routines (yp_first etc. 
 ) too on none-positive retry numbers.
 
 Is this OK?
 
 Best reguards
 
 W. Stukenbrock
 
 
 Christos Zoulas wrote:
 
 > The following reply was made to PR lib/46111; it has been noted by GNATS.
 > 
 > From: christos%zoulas.com@localhost (Christos Zoulas)
 > To: Wolfgang Stukenbrock 
 > <Wolfgang.Stukenbrock%nagler-company.com@localhost>, 
 >      gnats-bugs%NetBSD.org@localhost
 > Cc: lib-bug-people%NetBSD.org@localhost, gnats-admin%NetBSD.org@localhost, 
 >      netbsd-bugs%NetBSD.org@localhost
 > Subject: Re: lib/46111: yplib will hang forever if no server can be found
 > Date: Wed, 29 Feb 2012 08:58:53 -0500
 > 
 >  On Feb 29,  8:59am, Wolfgang.Stukenbrock%nagler-company.com@localhost 
 > (Wolfgang Stukenbrock) wrote:
 >  -- Subject: Re: lib/46111: yplib will hang forever if no server can be found
 >  
 >  | Hi,
 >  | 
 >  | I've no problem with such a sollution.
 >  | At least "my" application will have no problem with setting a global 
 >  | variable in the library to an other value.
 >  | 
 >  | Any suggestions about a name for this.
 >  | I can prepare a patch to the libs and the manual pages then.
 >  | 
 >  | best regards
 >  | 
 >  | W. Stukenbrock
 >  
 >  How about 'void yp_setbindtries(int ntries)', where 0 means infinity?
 >  
 >  christos
 >  
 >