upgrade 1.2.4 - 1.3.1 reverted

[Ondrej Zajicek]

On Mon, May 30, 2011 at 09:23:12AM +0200, Arjan Filius wrote:
> Hello,
>
> upgraded from bird 1.2.4 to bird 1.3.1 last weekend, but needed to revert
> due to complaints from high bgp traffic to bgpmon.net and 100% cpu load 
> on a 2x bird bgp routers setup connected with iBGP.
>
> Did some research, and noticed  a high bgp traffic situation on the iBGP
> sessions (about 10.000 bgp packets in 1.7 second)
>
> Based on graph statistics, i noticed a irregular traffic on the trans-ip's
> as well (noticed after rollback in statistical graphs)
>
>
> In the logging (mostly on the first bgp router) , i noticed quite some  
> messages (33414 in ~12h) like:
> 29-05-2011 10:57:49 <WARN> Next hop address X.X.X.242 resolvable through recursive route for X.X.X.0/24
> 29-05-2011 10:57:49 <WARN> Next hop address Y.Y.35.194 resolvable through recursive route for Y.Y.32.0/19
> 29-05-2011 10:57:52 <WARN> Next hop address X.X.X.241 resolvable through recursive route for X.X.X.0/24
> 29-05-2011 10:57:52 <WARN> Next hop address X.X.X.242 resolvable through recursive route for X.X.X.0/24
> 29-05-2011 10:57:55 <WARN> Next hop address Y.Y.35.194 resolvable through recursive route for Y.Y.32.0/19
> 29-05-2011 10:57:55 <WARN> Next hop address X.X.X.241 resolvable through recursive route for X.X.X.0/24
> 29-05-2011 10:57:55 <WARN> Next hop address X.X.X.242 resolvable through recursive route for X.X.X.0/24
>
> These are the subnets of the upstream trans-ip links of it's neigbor  
> router
>
> On the second (neighbor) bgp router, noticed only such 15 recursive  
> messages
>
> I had those upstream trans-ip interface IP's manually added once to the
> bird.conf with a "protocol static" definition with a subnet of /32.  I
> thought this might be the problem, and wel, disabled those static trans-ip
> interface routes, except i forgot one.  Noticed a lower CPU afterwards,  
> but problem persisted, and i reverted to 1.2.4.  Later i noticed i missed 
> one static route to disable, but no time left to upgrade and test again.

Generally, the IP address from the BGP NEXT_HOP attribute (i.e. the ones
mentioned in 'Next hop address X.X.X.242 resolvable ..' messages should
be resolvable through a route which is not from BGP. So, if you do not
use OSPF, adding static /32 routes for these IPs should do the trick. I
don't know why that caused problems in your setting (Perhaps the routes
have different NEXT_HOP attribute?).

Other posibilities (like using 'gateway direct' to switch to the
old behavior) were discussed here:

http://marc.info/?l=bird-users&m=130173865608861&w=2

> I created a 10.000 packet tcpdump capture (full size) of an iBGP session, 
> in case somone would like to look at it.

For such kind of problem tcpdump is not really useful, more useful would
be BIRD log with 'debug all all';

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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