Missing BFD session with OSPFv3 and same link-local addresses.
Hello all, Our issue is reproducible with 2 routers connected with 2 links. Those links are tagged vlans on the same physical interface (so both links share the same macaddress). bird> show ospf neighbors ospf1: Router ID Pri State DTime Interface Router IP B.B.B.B 1 full/other 00:08 vlan3509 fe80::d6ae:52ff:febf:74a6 B.B.B.B 1 full/dr 00:08 vlan106 fe80::d6ae:52ff:febf:74a6 bird> show bfd sessions bfd1: IP address Interface State Since Interval Timeout fe80::d6ae:52ff:febf:74a6 vlan3509 Up 2015-09-23 0.100 0.500 There is only one bfd session instead of two (one for each link). After digging a bit in the source code, it seems that the OSPF protocol calls `bfd_request_session()` which leads to a call to `bfd_add_request()`. `bfd_add_request()` tries to reuse an already established session with **the same destination address** before creating a new one. But B.B.B.B has the same link-local address on both interfaces (they share the same mac) so the second session is never created and the first one is returned. Perhaps a better approach would be to use the (address, iface) pair when trying to reuse a session. thank you, chris
On Fri, Sep 25, 2015 at 01:04:45PM +0300, Christos Trochalakis wrote:
Hello all,
...
There is only one bfd session instead of two (one for each link).
After digging a bit in the source code, it seems that the OSPF protocol calls `bfd_request_session()` which leads to a call to `bfd_add_request()`. `bfd_add_request()` tries to reuse an already established session with **the same destination address** before creating a new one. But B.B.B.B has the same link-local address on both interfaces (they share the same mac) so the second session is never created and the first one is returned. Perhaps a better approach would be to use the (address, iface) pair when trying to reuse a session.
Hello You are right, i just noticed the same problem several weeks ago. -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santiago@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."
participants (2)
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Christos Trochalakis -
Ondrej Zajicek