Charon/vici deadlock when auto=start and acting as responder at the same time
Strongswan instances on machines A, B.
Connections are loaded using VICI, pointing towards each other (A->B, B->A). auto=start.
Seems that if an IKE negotiation of the same conn is in progress during the load-conn operation,
a deadlock situation occurs.
Stack trace on hanging machine:
#0 pthread_cond_wait@@GLIBC_2.3.2 () at ../sysdeps/unix/sysv/linux/x86_64/pthread_cond_wait.S:185 #1 0x00007ff2ea2cd993 in wait_ (this=0x8832c0, mutex=0x86cdb0) at threading/mutex.c:231 #2 0x00007ff2ea0318c4 in wait_for_entry (entry=0x884040, segment=<optimized out>, this=0x86cc60) at sa/ike_sa_manager.c:737 #3 0x00007ff2ea031d8e in checkout_by_config (this=0x86cc60, peer_cfg=0x7ff2ac008280) at sa/ike_sa_manager.c:1414 #4 0x00007ff2ea012033 in initiate_execute (job=job@entry=0x7ff2ac0087f0) at control/controller.c:409 #5 0x00007ff2ea012b2d in initiate (this=<optimized out>, peer_cfg=0x7ff2ac008280, child_cfg=child_cfg@entry=0x7ff2ac001840, callback=callback@entry=0x0, param=param@entry=0x0, timeout=timeout@entry=0, limits=false) at control/controller.c:528 #6 0x00007ff2e4bbc367 in run_start_action (peer_cfg=peer_cfg@entry=0x7ff2ac008280, child_cfg=<optimized out>, this=0x875c90) at vici_config.c:1696 #7 0x00007ff2e4bbcdd4 in handle_start_actions (this=this@entry=0x875c90, peer_cfg=peer_cfg@entry=0x7ff2ac008280, undo=undo@entry=false) at vici_config.c:1883 #8 0x00007ff2e4bbdcd5 in merge_config (peer_cfg=0x7ff2ac008280, this=0x875c90) at vici_config.c:1960 #9 _cb_config_sn (request=request@entry=0x7ff2dd174bd0, message=message@entry=0x7ff2ac005c90, ctx=ctx@entry=0x7ff2dd174b60, name=<optimized out>) at vici_config.c:2146 #10 0x00007ff2e4bb1dab in parse (this=0x7ff2ac005c90, ctx=0x7ff2dd174b60, section=0x7ff2e4bbcf50 <_cb_config_sn>, kv=0x0, li=0x0, user=0x7ff2dd174bd0) at vici_message.c:532 #11 0x00007ff2e4bba90b in _cb_load_conn (this=<optimized out>, name=<optimized out>, id=<optimized out>, message=<optimized out>) at vici_config.c:2158 #12 0x00007ff2e4bb3b96 in process_request (this=this@entry=0x87f020, name=name@entry=0x7ff2dd174c80 "load-conn", id=id@entry=11, data=...) at vici_dispatcher.c:289 #13 0x00007ff2e4bb3f31 in _cb_inbound (this=0x87f020, id=11, data=...) at vici_dispatcher.c:346 #14 0x00007ff2e4bb0aee in _cb_process_queue (sel=0x7ff2ac006090) at vici_socket.c:508 #15 0x00007ff2ea2bb0c2 in execute (this=<optimized out>) at processing/jobs/callback_job.c:77 #16 0x00007ff2ea2bb9fb in process_job (worker=0x87ab60, this=0x83ced0) at processing/processor.c:235 #17 process_jobs (worker=0x87ab60) at processing/processor.c:321 #18 0x00007ff2ea2ccdbb in thread_main (this=0x87ab90) at threading/thread.c:331 #19 0x00007ff2e9de66ba in start_thread (arg=0x7ff2dd175700) at pthread_create.c:333 #20 0x00007ff2e9b1c3dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
IKE negotiation thread:
#0 __lll_lock_wait () at ../sysdeps/unix/sysv/linux/x86_64/lowlevellock.S:135 #1 0x00007ff2e9de8dbd in _GI__pthread_mutex_lock (mutex=0x7ff2ac007f18) at ../nptl/pthread_mutex_lock.c:80 #2 0x00007ff2ea2cd5ca in lock (this=<optimized out>) at threading/mutex.c:106 #3 0x00007ff2ea00f4cc in create_child_cfg_enumerator (this=this@entry=0x7ff2ac008280) at config/peer_cfg.c:357 #4 0x00007ff2ea00f549 in select_child_cfg (this=0x7ff2ac008280, my_ts=0x7ff2a0007750, other_ts=0x7ff2a0004ed0, my_hosts=0x7ff2a0008d80, other_hosts=0x7ff2a0008e50) at config/peer_cfg.c:417 #5 0x00007ff2ea042415 in select_child_cfg (this=0x8869f0) at sa/ikev2/tasks/child_create.c:1204 #6 build_r (this=0x8869f0, message=0x7ff2a0009130) at sa/ikev2/tasks/child_create.c:1285 #7 0x00007ff2ea03c627 in build_response (request=0x7ff2a00020b0, this=0x883f00) at sa/ikev2/task_manager_v2.c:839 #8 process_request (message=<optimized out>, this=0x883f00) at sa/ikev2/task_manager_v2.c:1187 #9 process_message (this=0x883f00, msg=<optimized out>) at sa/ikev2/task_manager_v2.c:1452 #10 0x00007ff2ea02f257 in process_message (this=0x87c100, message=0x7ff2a00020b0) at sa/ike_sa.c:1559 #11 0x00007ff2ea03b63b in handle_fragment (defrag=defrag@entry=0x883fd0, msg=msg@entry=0x7ff2d0001120, this=0x883f00) at sa/ikev2/task_manager_v2.c:1234 #12 0x00007ff2ea03bed3 in process_message (this=0x883f00, msg=0x7ff2d0001120) at sa/ikev2/task_manager_v2.c:1442 #13 0x00007ff2ea02f257 in process_message (this=0x87c100, message=0x7ff2d0001120) at sa/ike_sa.c:1559 #14 0x00007ff2ea027471 in execute (this=0x7ff2d0000ac0) at processing/jobs/process_message_job.c:74 #15 0x00007ff2ea2bb9fb in process_job (worker=0x87b140, this=0x83ced0) at processing/processor.c:235 #16 process_jobs (worker=0x87b140) at processing/processor.c:321 #17 0x00007ff2ea2ccdbb in thread_main (this=0x87b170) at threading/thread.c:331 #18 0x00007ff2e9de66ba in start_thread (arg=0x7ff2dc173700) at pthread_create.c:333 #19 0x00007ff2e9b1c3dd in clone () at ../sysdeps/unix/sysv/linux/x86_64/clone.S:109
peer-cfg: Use an rwlock instead of a mutex to safely access child-cfgs
If multiple threads want to enumerate child-cfgs and potentially lock
other locks (e.g. check out IKE_SAs) while doing so a deadlock could
be caused (as was the case with VICI configs with start_action=start).
It should also improve performance for roadwarrior connections and lots
of clients connecting concurrently.
#3 Updated by Tobias Brunner over 4 years ago
- Description updated (diff)
- Status changed from New to Feedback
- Target version set to 5.6.0
- Affected version changed from 5.5.3 to 5.5.1
I see. The problem is that the peer_cfg's internal mutex is locked while enumerating the child_cfgs to perform the start action for each CHILD_SA (requiring checking IKE_SAs if charon.reuse_ikesa is enabled), while the other thread, holding an IKE_SA locked, wants to acquire the same mutex to select the child_cfg's.
For a possible solution we could probably use an rwlock instead of a mutex so both threads could enumerate the child_cfgs concurrently (might not be a bad idea anyway in case of roadwarrior connections with lots of clients). I did that in the 2374-peer-cfg-rwlock branch.
A workaround for this particular situation is to disable charon.reuse_ikesa, then
checkout_by_config won't enumerate existing IKE_SAs.