====== Olsrd internals ======

===== Olsrd plugin =====

==== olsrd's IPC Socket parser ====

A plugin register it's IPC socket with olsrd. The olsrd scheduler periodically checks all registered socket for pending actions (read/write) then calls the registered funtion.

=== Scheduler ===
main.c/main() starts scheduler.c/olsr_scheduler().

olsr_scheduler starts a loop and call scheduler.c/poll_sockets() periodically...

=== Registering plugin socket ===

==== olsrd's Package parser ====

Olsrd also registers its socket for core messages (port 689) with the scheduler. When a message arrives, the function parser.c/olsr_input() is called. There the message is processed and forwarded to parser.c/parse_packet(). This function checks the message for type and loop through the registered parser functions and forward the message to the appropriate one.

A plugin wishing to process a message should register its parser function and the respective message type with  olsrd.

===== Olsrd plugin mdns =====

==== InitMDNS() ====

<code>
...
463   //Tells OLSR to launch olsr_parser when the packets for this plugin arrive
464   olsr_parser_add_function(&olsr_parser, PARSER_TYPE);
465   //Creates captures sockets and register them to the OLSR scheduler
466   CreateBmfNetworkInterfaces(skipThisIntf);
...
</code>


'olsr_parser_add_function()' registers &olsr_parser, which will be called when a message of PARSER_TYPE is received.

'CreateBmfNetworkInterfaces(skipThisIntf)' prepares the interfaces (non olsrd??) prior to forwarding dns messages.

==== CreateBmfNetworkInterfaces(struct interface *skipThisIntf) ====

  * gets all available interfaces on system: 
    * create socket for this purpose
    * call ioctl(skfd, SIOCGIFCONF, &ifc)
  * check if each iface is in plugin's config
  * if yes pass iface_name to 'CreateInterface(ifr->ifr_name, NULL)'

==== CreateInterface(const char *ifName, struct interface *olsrIntf) ====  
  * call capturingSkfd = CreateCaptureSocket(ifName) with the parameter ifName
  * assign ioctlSkfd = (capturingSkfd >= 0) ? capturingSkfd : encapsulatingSkfd, denpending on socket type cap/encap
  * get MAC of the iface using ioctl(ioctlSkfd, SIOCGIFHWADDR, &ifr) < 0)
  * copy data to struct TBmfInterface *newIf:
    * copy captureingSkdf, encapsulatingSkfd, listeningSkfd, above MAC, ifname
    * if olsrIntf != NULL copy intAddr and broadAddr
    * else 
      * retrieve IP addr with ioctl(ioctlSkfd, SIOCGIFADDR, &ifr)
      * retrieve Broadcast IP with ioctl(ioctlSkfd, SIOCGIFBRDADDR, &ifr)
  * add newIf to BmfInterfaces

==== CreateCaptureSocket(const char *ifName) ====
  * open socket skfd = socket(PF_PACKET, SOCK_DGRAM, htons(ETH_P_IP))
  * set iface to promiscuous mode setsockopt(skfd, SOL_PACKET, PACKET_ADD_MEMBERSHIP, &mreq, sizeof(mreq))
  * get MAC ioctl(skfd, SIOCGIFHWADDR, &req) < 0)
  * bind socket
  * set socket to blocking operation
  * Register newly created socket with olsrd socket parser add_olsr_socket(skfd, &DoMDNS,NULL, NULL, SP_PR_READ)

==== DoMDNS ====
DoMDNS is registerd with olsrd socket parser and is called whenever a packet is capture on registered interfaces. DoMDNS inspects the captured packet and call BmfPacketCaptured to process it.

==== BmfPacketCaptured ====

This function check if the packet is a MDNS packet (UDP 5353). If yes it pass the packet to olsr_mdns_gen(encapsulationUdpData, nBytes); to forward it in olsrd network.

==== olsr_mdns_gen(encapsulationUdpData, nBytes) ====