[Olsr-users] problem when disconnection two network cables

[Koen Swinters]

Hi all,

We are using olsrd-0.6.8 in our system.
I have a problem with the following setup:

Node 8100 ------------- node 3
     |             X                 |
Node 8120 ------------- node 425

Each node has a wired connection to the 3 other nodes (each node has 3 Ethernet interfaces). Olsrd is running on each node.
When I disconnect the cable between node 3 and node 8120 and after this the cable between node 8120 and node 425 => node 425 cannot reach node 8120 anymore (there is still a path via node 3 and node 8100) => the routing table on node 425 is not updated.

Remark: when there is no physical Ethernet connection our systems disables the eth interface (ethx)

I`ve investigated this problem and found the following problem in olsrd:


*         disconnect the cable between node 3 and node 8120 => Link down between 3 and 8120 => disable interface
o    Line 371 in interfaces.c: "olsr_remove_interface(struct olsr_if* iface)"
*         Line 379 in "interfaces.c":  "olsr_delete_link_entry_by_ip(&ifp->ip_addr)"
?  Line 411 in "link_set.c":  "olsr_delete_link_entry(link);"
*         Line 375 in "olsr_delete_neighbor_table(&link->neighbor->neighbor_main_addr)";
*         This function will delete the neighbor from the neighbor table
*         (Line 177 in neighbor_table.c)
*         This function sets "changes_neighborhood = true;" (Line 219 in neighbor_table.c)

o    In "olsr_scheduler(void)" (line 486 in scheduler.c)
*   function "olsr_process_changes()" (line 180 in olsr.c)
*   Because "changes_neighborhood == TRUE and olsr_cnf->lq_level > 1" "olsr_calculate_lq_mpr() "is called
*   In "olsr_calculate_lq_mpr()" (line 51 in lq_mpr.c) a new mpr is calculated (8100 will now be mpr for 8120) and the function "signal_link_changes(true);" is called => link_changes  == true
*   In the next step  ANSN  is increased
o    At the tc_interval  a tc message is generated with this ANSN in => the neighbors see a change in the ANSN number(when the packet are received) an will update their tables

*         Link Down between node 8120 and 425
o    Line 371 in interfaces.c: "olsr_remove_interface(struct olsr_if* iface)"
*         Line 379 in "interfaces.c":  "olsr_delete_link_entry_by_ip(&ifp->ip_addr)"
?  Line 411 in "link_set.c":  "olsr_delete_link_entry(link);"
*         Line 375 in "olsr_delete_neighbor_table(&link->neighbor->neighbor_main_addr)";
*         This function will delete the neighbor from the neighbor table
*         (Line 177 in neighbor_table.c)
*         This function sets "changes_neighborhood = true;" (Line 219 in neighbor_table.c)

o    In "olsr_scheduler(void)" (line 486 in scheduler.c)
*   function "olsr_process_changes()" (line 180 in olsr.c)
*   Because "changes_neighborhood == TRUE and olsr_cnf->lq_level > 1" "olsr_calculate_lq_mpr() "is called
*   In "olsr_calculate_lq_mpr()" (line 51 in lq_mpr.c) no new mpr is calculated (8100 will stay mpr for 8120) and the function "signal_link_changes(true);" is not called => link_changes  == false
*   In the next step  ANSN  is not increased
o    At the tc_interval  a tc message is generated with old ANSN in => the neighbors see no change in the ANSN number(when the packet are received) an will no update their tables

Solution:
*         When a neighbor is deleted from the neighbor table (line 177 in neighbor_table: olsr_delete_neighbor_table(const union olsr_ip_addr *neighbor_addr)) also call the function signal_link_changes(true); because there is a change in the neighbor table.
I've tested this and it is working correct (routing tables are updated as expected).
Where can I post this fix, or is there a better solution?

Regards,

koen


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