On Wed, Nov 30, 2016 at 10:35:45AM +0530, naveen chowdary Yerramneni wrote: > Hi, > > *Issue Description*: LSA ID collision issue is seen with OSPF > *stub-networks* configured and BIRD is acting as ABR
Hi, thanks for the bugreport and analysis. My comments and questions are below. > *Code Flow*: > 1. Stubnets are advertised to area-0 by generating router LSA ( > LSA_T_RT). > o ospf_disp() -> ospf_update_topology() -> ospf_originate_rt_lsa()->ospf_ > originate_lsa() > 2. Now, stubnets are added to top graph table (p->gr) with LSA type > LSA_T_RT > 3. When creating routing table, these stubnets are added to FIB ( > p->rtf). > o ospf_disp() -> ospf_rt_spf() -> ospf_rt_spfa() -> spfa_process_rt() -> > add_network() -> ri_install_net() > 4. When BIRD is acting as ABR then, walk through FIB(p->rtf) and > send summary LSA (LSA_T_SUM_NET) with LSA mode as LSA_M_RTCALC. Also, nf > pointer is set (stores fib node address) in top_hash_entry. > o ospf_disp() -> ospf_rt_abr2() -> check_sum_net_lsa() -> > ospf_originate_sum_net_lsa() ->ospf_originate_lsa() > 5. Now, stubnets are added to top graph table (p->gr) with LSA type > LSA_T_SUM_NET Until this it looks OK. > 6. Stubnets are removed from FIB(p->rtf) > o ospf_disp() -> rt_sync() -> fib_delete() This seems strange. If these networs are part of the topology, they should be in FIB(p->rtf). You mean that appropriate record in FIB is removed automatically as a conseqyence of this code seqence, or is there any external change (like stubnet removal) that causes it to be removed? > 7. Now, stubnets entries are still present in top graph table (Note: > fib_delte() doesn't free the node, it just moves the fib node to free pool, > fib_node pointer is still valid) That looks like a dangerous bug. Although fib_delete just moves the fib node back to slab pool, the pointer is considered freed and invalid (the slab pool is just optimization). > 8. With any change in network, ospf_rt_spf()is called. In > ospf_rt_reset(), LSA mode is updated fromLSA_M_RTCALC to LSA_M_STALE. > 9. Again, steps 3-6 are repeated. In step-3, fib node pointer is > changed and in step-4, fib node pointer comparison fails in > ospf_originate_lsa()which is leading to LSA id collision. > > *Issue is resolved with below code change. *Please review the change and > provide your comments. Also, please let me know if any other information is > required. Well, it seems to me that the real cause of the bug is in step 6. BTW, your stubnets are explicitly configured ones or based on prefixes of stub interfaces? -- Elen sila lumenn' omentielvo Ondrej 'Santiago' Zajicek (email: santi...@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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