[Click] XORP+Click Hotconfig

[Swati Sinha Deb]

Hi Pavlin,

Thanks for your reply. A quick check before and after applying the hotswap 
indicates that the forwarding entries have been cleared by hotswapping(as 
you guessed). Is there any way we can force XORP to re-publish the routes? 
Below is the result from read _xorp_rt4.table...

Before Hotswap
--------------
read _xorp_rt4.table
200 Read handler '_xorp_rt4.table' OK
DATA 148
# Active routes
172.20.2.1/32           0.0.0.0         2
172.20.1.1/32           0.0.0.0         2
172.20.2.0/24           0.0.0.0         0
172.20.1.0/24           0.0.0.0         1
172.20.3.0/24           172.20.2.2      0

After Hotswap
-------------
read _xorp_rt4.table
200 Read handler '_xorp_rt4.table' OK
DATA 68
# Active routes
172.20.2.1/32           0.0.0.0         2
172.20.1.1/32           0.0.0.0         2

regards,
Swati



--On 03 October 2006 10:14 -0700 Pavlin Radoslavov <pavlin at icir.org> wrote:

>> I am trying to implement hotswap in my xorp+click test bed. However, it
>> is  not functioning correctly. I would appreciate if I get some help to
>> fix  this issue. Here is what I am trying to do...
>>
>> Network configuration
>> ---------------------
>>
>>
>> PC 1---------ROUTER1------ROUTER2--------PC 2
>>             eth4  eth3   eth1  eth2
>>
>> Where Router1 and Router2 are both running Xorp+click. The xorp config
>> file  has the following entry...
>>
>> user-click {
>> 	disable: false
>> 	command-file: "/home/eessd/click/bin/click"
>> 	command-extra-arguments: "-R"
>> 	command-execute-on-startup: true
>> 	control-address: 127.0.0.1
>> 	control-socket-port: 13000
>> 	startup-config-file: "/dev/null"
>> 	user-click-config-generator-file:
>> "/usr/localxorp/fea/xorp_fea_click_config"
>> }
>
> First, a small observation: I presume that
> "/usr/localxorp/fea/xorp_fea_click_config" is either a typo
> (in your configuration the correct value is
> "/usr/local/xorp/fea/xorp_fea_click_config"), or that your XORP
> installation is indeed in the "/usr/localxorp" directory.
>
>> Given the above all is well and I can ping PC2 from PC1 with the above
>> configuration.
>>
>> Now, I try to change the click configuration in ROUTER1. For doing this,
>> I  have a separate application which connects to port 13000 on ROUTER1
>> and  invokes the relevant controlsocket server commands (writedata and
>> write on  hotconfig handler). The server returns a success i.e, 200 OK
>> indicating  that the new config has been applied correctly. However,
>> when I try to ping  PC2   from PC1 it starts failing.
>
> Note that every time any of the XORP interfaces is reconfigured
> XORP will regenerate new Click configuration using
> user-click-config-generator-file, and that configuration will
> overwrite your config. Hence, make sure that if you do hotswap by
> directly writing to port 13000, the user-click-config-generator-file
> is updated as well to contain your new changes.
> Though, if you don't change anything in the XORP configuration while
> playing with the hotswap, then this shouldn't have impact on your
> results.
>
>> I have compared the old and new click configuration and there is nothing
>> which should prevent the ping from failing (I have changed a few
>> parameters  to my custom/local click elements). Is there something
>> fundamentally  incorrect with the above approach.
>
> One thing to check is the Click forwarding table. For that purpose
> you need to talk directly to the Click forwarding element, because
> from the XORP CLI you can print only the routing entries that are
> stored inside XORP.
> Off the top of my head:
>
> telnet localhost 13000
> READ _xorp_rt4::table
>
> Do this before and after the hotswap.
>
> My guess is that the hotswap has cleared the forwarding entries
> in ROUTER1, including the entry necessary to reach PC2.
>
> If the forwarding entries are fine, then you could try to test the
> hotswap without XORP. For that purpose you need to do the following
> on ROUTER1:
>
> 1. Start XORP and make sure the forwarding is running
> 2. Read the Click configuration as installed by XORP and save it to
>    a file.
> 3. Stop XORP and start Click by hand using the above saved
>    configuration.
> 4. Perform the hotswap and see what happens.
>    If the forwarding fails as before, then you need to track the
>    problem in the Click level. If the hotswap succeeds, then the
>    problem is somewhere in XORP.
>
> Regards,
> Pavlin
>
>> I have also tried defining my own controlsocket (port 14000) via config
>> file (added a statement in /usr/localxorp/fea/xorp_fea_click_config
>> inorder  to do this). But I encounter the same issue. The server returns
>> OK after  each hotswap attempt and the ping fails.
>>
>> Would be great if I get some tips on fixing the above issue. Please let
>> me  know if I have missed out anything which would help in this
>> investigation.
>>
>> Additionally after hotswap, a tcpdump on eth3 (Router1) indicates that
>> the  ping packets are not reaching eth3, I can see it on eth4. The xorp
>> routing  table is also fine.
>>
>> Thanks
>> Swati
>>
>>
>> _______________________________________________
>> click mailing list
>> click at amsterdam.lcs.mit.edu
>> https://amsterdam.lcs.mit.edu/mailman/listinfo/click



----------------------
Swati Sinha Deb, Research Fellow
Wireless and Networks Research Laboratory,
Electrical & Electronic Engineering, University of Bristol,
Merchant Venturers Building, Woodland Road,
Bristol BS8 1UB
E-mail: Swati.Deb at bristol.ac.uk
Tel.: +44 (0)117 331 5058