Re: Issue with stale resolv.conf state

[Florian Weimer <fweimer@redhat.com>]

* John Levon:

> I don't understand the first part of the comment, but indeed, ->resp doesn't
> match. In particular:
>
>  62   return ctx->resp->options == ctx->conf->options                                
>
> and ctx->resp (aka _resp) has 0x47002c1 whereas ctx->conf has 0x41002c1.
>
> I'm not sure but I suspect the additional RES_SNGLKUP|RES_SNGLKUPREOP
> may be due to this code:
>
> 1000                     /* There are quite a few broken name servers out             
> 1001                        there which don't handle two outstanding                  
> 1002                        requests from the same source.  There are also            
> 1003                        broken firewall settings.  If we time out after           
> 1004                        having received one answer switch to the mode             
> 1005                        where we send the second request only once we             
> 1006                        have received the first answer.  */                       
> 1007                     if (!single_request)                                         
> 1008                       {                                                          
> 1009                         statp->options |= RES_SNGLKUP;                           
> 1010                         single_request = true;                                   
> 1011                         *gotsomewhere = save_gotsomewhere;                       
> 1012                         goto retry;                                              
> 1013                       }                                                          
> 1014                     else if (!single_request_reopen)                             
> 1015                       {                                                          
> 1016                         statp->options |= RES_SNGLKUPREOP;                       
> 1017                         single_request_reopen = true;                            
> 1018                         *gotsomewhere = save_gotsomewhere;                       
> 1019                         __res_iclose (statp, false);                             
> 1020                         goto retry_reopen;                                       
> 1021                       }


That's a very good point.  Yes, the current reloading code does not take
into account that we change _res.options dynamically based on network
behavior.

That automatic configuration change based on temporary network glitches
is problematic in other contexts as well (it may further trigger bugs in
dual query processing).

Maybe we should just remove the automatic downgrade, basically not
persist this across queries anymore.

Thanks,
Florian