ospf ptp link sending unicast packets instead of multicast; peer address config not required

[Ondrej Zajicek]

On Fri, May 07, 2021 at 11:14:27AM +0000, Joakim Tjernlund wrote:
> On Fri, 2021-05-07 at 13:09 +0200, Ondrej Zajicek wrote:
> > On Fri, May 07, 2021 at 04:53:44AM +0000, Senthil Kumar Nagappan wrote:
> > >  Hi Joakim,
> > > Thanks for your response.
> > > Will try to elaborate point2 with sample config.
> > > 1. Config at Router R1
> > > lo interfaceinterface loopback lo has ip addr 100.100.100.125 
> > > eth1for unnumbered borrowing the lo address for eth1 and 100.100.100.126 is the peer addressip addr add 100.100.100.125 peer 100.100.100.126 dev eth1
> > > eth2for unnumbered borrowing the lo address for eth2 and 100.100.100.126 is the peer addressip addr add 100.100.100.125 peer 100.100.100.126 dev eth2
> > > 2. Config at Router R2Its identical to R1 config except for the loopback ip which is 100.100.100.126 and the correspondingpeer address config for eth1 and eth2
> > > 
> > > 3. Enable ospf on eth1 and eth2 at R1 and R2
> > > 4. Only one of the ospf adj will become FULL either over eth1 or eth2 and not both
> > > 5. Since the peer address configurations adds a route to other end loopback address and since thedb packets are sent as unicast, route lookup happens and db packets wont be sent out from one of the links.
> > 
> > I do not think that should be true (at least on Linux). OSPF sockets are
> > bound to specific interface using SO_BINDTODEVICE and use SO_DONTROUTE to
> > avoid route lookups, so even unicast packets should be sent to specific
> > interface. If that really happens, that is worth investigating. What is
> > your OS and BIRD version? Did you verify that using tcpdump or similar
> > tool?
> > 
> 
> That may be so, but I still think that the issue reported in 1) is valid bug, don't you?

Yes, i agree. Just think that this issue is worth investigating
independently and not just avoiding that by fixing 1).

-- 
Elen sila lumenn' omentielvo

Ondrej 'Santiago' Zajicek (email: santiago at crfreenet.org)
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"To err is human -- to blame it on a computer is even more so."