next-hop announcement/withdrawal process

[Sergey Popovich]

> Hi,

Hello.

> The problem I am facing is that when I adjust a filter in order to
> withdraw the route, all routes are withdrawn and the remaining are
> announced again. According to the doc if a reload on bird brings a new
> configuration for a protocol, that protocol will be restarted. So, it is
> expected behavior.
> 

You have changed import filter of direct1 protocol, thus direct1 gets 
reconfigured (on HUP or birdc configure). However this protocol does not
perform "soft" reconfiguration on filter changes thus direct1 restarts
unconditionally to apply your filter changes (IP removal/addition).

All routes flushed out from the table (causing BGP withdrawal) and
fetched from the protocol (direct) again to the table (causing BGP update).

This seems normal behavior.


You could simply attach your loopback_ACL filter to the BGP_PEERS template
export (which any needed adjustments, or just make loopback_ACL to work as 
function returning false/true and use it in anycast_range) to solve your case.

Also I suggest you to use global prefix set definition, as local variable
(in filter/function) is created/assigned each time function is called.

For example:
------------

# It is probably good idea to have such protocol configred in most cases.
# It fetches list of the interfaces in system and provides them to the other
# protocols (except OSPF, it has it's own mechanisms).
#
protocol device {
  scan time 10;
}

# This set should be modified only when new frontend subnet is added.
# direct1 would restart on protocol filter change.
#
define ACAST_PS_DIRECT1 = 
  [
    192.168.200.0/24{32,32}
  ];

protocol direct {
  # Import directly connected routes from "lo" interface.
  interface "lo";

  # This may  be is needed to properly resolve nexthops from upstream routes.
  interface "<interface_to_your_routers>";

  # Do not import from other sources.
  interface "-*";

  # Import only allowed IPs from the "lo" and route from the upstream 
  # interface.
  import where net ~ ACAST_PS_DIRECT1 || ifname 
="<interface_to_your_routers>";

  # No export to the protocol, not necessary
  export none;
}

# This is global constant for your prefix set (PS) 192.168.200.0/24.
#
# Place this definition into external file and source it with include
# directive from the global configuration file if you wish to modify
# this PS from the outside (e.g. by some HA script).
#
define ACAST_PS_ADVERTISE = 
  [
    192.168.200.1/32,  # Frontend 1
    192.168.200.2/32   # Frontend 2
  ];

function acast_advertise()
{
  return net ~ ACAST_PS_ADVERTISE;
}

filter anycast_range
{
  if acase_advertise() then
    accept;
  reject;
}

Tested similar config with BIRD 1.3.11 and seems no unwanted
withdrawals spot.

> 
> 
> Cheers,
> Pavlos
> 
> [1]
> 23:37:52 <INFO> Reconfiguration requested by SIGHUP
> 23:37:52 <INFO> Reconfiguring
> 23:37:52 <TRACE> direct1: Reconfigured
> 23:37:52 <INFO> Reloading protocol direct1
> 23:37:52 <INFO> Restarting protocol direct1
> 23:37:52 <TRACE> direct1: Shutting down
> 23:37:52 <TRACE> direct1: State changed to flush
> 23:37:52 <TRACE> bgp_peer1: Reconfigured
> 23:37:52 <TRACE> bgp_peer2: Reconfigured
> 23:37:52 <INFO> Reconfigured
> 23:37:52 <TRACE> direct1 > removed [sole] 192.168.200.1/32 dev lo
> 23:37:52 <TRACE> direct1 > removed [sole] 192.168.200.2/32 dev lo
> 23:37:52 <TRACE> direct1: State changed to down
> 23:37:52 <TRACE> direct1: Starting
> 23:37:52 <TRACE> direct1: Connected to table master
> 23:37:52 <TRACE> direct1: State changed to feed
> 23:37:52 <TRACE> direct1 < primary address 192.168.200.1/32 on interface
> lo added
> 23:37:52 <TRACE> direct1 > filtered out 192.168.200.1/32 dev lo
> 23:37:52 <TRACE> direct1 < secondary address 127.0.0.0/8 on interface lo
> added
> 23:37:52 <TRACE> direct1 < secondary address 192.168.200.2/32 on
> interface lo added
> 23:37:52 <TRACE> direct1 > added [best] 192.168.200.2/32 dev lo
> 23:37:52 <TRACE> bgp_peer2 < filtered out 192.168.200.2/32 dev lo
> 23:37:52 <TRACE> bgp_peer1 < filtered out 192.168.200.2/32 dev lo
> 23:37:52 <TRACE> direct1 < primary address 192.168.80.0/20 on interface
> eth0 added
> 23:37:52 <TRACE> direct1: State changed to up
> 23:37:54 <TRACE> bgp_peer2: Sending KEEPALIVE
> 23:37:54 <TRACE> bgp_peer1: Sending KEEPALIVE
> 23:37:54 <TRACE> bgp_peer2: Got KEEPALIVE
> 23:37:56 <TRACE> bgp_peer1: Got KEEPALIVE
> 
> 
> bird.conf
> # Override router ID
> router id 192.168.88.194;
> 
> # Listens only on eth0's IP
> listen bgp address 192.168.88.194;
> 
> filter loopback_ACL
> prefix set anycast_prefixes;
> {
>   anycast_prefixes = [
>     192.168.200.1/32,
>     192.168.200.2/32
>   ];
>   if net ~ anycast_prefixes then accept;
>   else reject;
> }
> 
> 
> filter anycast_range {
>     if net ~ [ 192.168.200.0/24 ] then accept;
>     else reject;
> }
> 
> protocol direct {
>     interface "lo";
>         debug all;
>         import filter loopback_ACL;
>         export none;
> }
> 
> protocol kernel kernel1 {
>     disabled yes;
> }
> 
> protocol device {
>     scan time 10;
> # TODO do I need this?
> }
> 
> protocol static {
>     disabled yes;
> }
> 
> protocol bfd {
>         interface "eth0" {
>                 min rx interval 500 ms;
>                 min tx interval 500 ms;
>                 idle tx interval 1000 ms;
>                 multiplier 3;
>         };
> }
> 
> template bgp BGP_PEERS {
>     bfd on;
>     debug all;
>     import none;
>     export filter anycast_range;
>     direct;
>     hold time 30;
>     startup hold time 240;
>     connect retry time 120;
>     keepalive time 10;
>     start delay time 5;
>     error wait time 60, 300;
>     error forget time 300;
>     disable after error off;
>     next hop self;
>     path metric 1;
>     default bgp_med 0;
>     default bgp_local_pref 0;
> }
> 
> protocol bgp bgp_peer1 from BGP_PEERS {
>     disabled no;
>     description "My-BGP-Peer1";
>     local as 46111;
>     neighbor 192.168.95.252 as 46111;
>     source address 192.168.88.194;
> }
> 
> protocol bgp bgp_peer2 from BGP_PEERS {
>     disabled no;
>     description "My-BGP-Peer2";
>     local as 46111;
>     neighbor 192.168.95.253 as 46111;
>     source address 192.168.88.194;
> }

-- 
SP5474-RIPE
Sergey Popovich