[Olsr-dev] Reloading DNS server hosts file from nameserver plugin

[Andrés Ambrois]

Hello people!

  I'm a member of the Development Group of MontevideoLibre [0], a project 
dedicated to the construction of a city-wide free (as in freedom) wi-fi 
network in Montevideo, the capital city of Uruguay. 
  We have decided to use OLSR as our routing algorithm (yay!), at least for 
the early stages of the project. We have found the nameservice plugin to be a 
great solution to many of our problems (dns and service information 
flooding), and hope to contribute a bit to its development. 
  The first problem we faced was to provide DNS to nodes not running OLSR 
(temporal "clients" of the network), which is solved by running a DNS server 
on "edge" nodes who provide connectivity. However, dnsmasq (and I believe 
bind too, but I'm not sure) only read the hosts file at startup, and are 
oblivious to changes in the file. 
  We found that a SIGHUP signal would cause dnsmasq to re-read the hosts file 
(see NOTES section in its manfile), and named (the bind dns server) to reload 
(see the SIGNALS section in its manfile). In order to acomplish this from the 
nameservice plugin we wrote two patches: The first one sends a sighup 
directly to a process (specified by its pidfile in the plugin parameters) 
right after the hosts file is written. The second executes a script when the 
hosts file is written, and, optionally, another one when the services file is 
written. Of course, the first has the advantage of being much more efficient, 
and the second of having many more applications. 
  It would make us very happy to see this included in a future release of 
olsrd, so we can give back something. 
  I take the liberty of attaching the patches to this email. Please let me 
know if there's a better way to get this commited. 
  Thanks in advance!

[0] http://montevideolibre.org (in Spanish)

-- 
   -Andrés Ambrois
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