Hi, After review my code, I found that I have add a flag to the vnet_disconnect API which will call session_reset instead of session_close, the reason I do this is to make intermediate firewall just flush the state and reconstruct if I later reconnect.
It seems in session_reset logic, for half open session, it also missing to remove the session from the lookup hash which may cause the issue too. I change my code and will test with your patch along, will provide feedback later. I also noticed the bihash issue discussed in the list recently, I will merge later. Florin Coras <[email protected]> 于2023年3月21日周二 11:56写道： > Hi, > > That last thing is pretty interesting. It’s either the issue fixed by this > patch [1] or sessions are somehow cleaned up multiple times. If it’s the > latter, I’d really like to understand how that happens. > > Regards, > Florin > > [1] https://gerrit.fd.io/r/c/vpp/+/38507 > > On Mar 20, 2023, at 6:52 PM, Zhang Dongya <[email protected]> > wrote: > > Hi, > > After merge this patch and update the test environment, the issue still > persists. > > Let me clear my client app config: > 1. register a reset callback, which will call vnet_disconnect there and > also trigger reconnect by send event to the ctrl process.) > 2. register a connected callback, which will handle connect err by trigger > reconnect, on success, it will record session handle and extract tcp > sequence for our app usage. > 3. register a disconnect callback, which basically do same as reset > callback. > 4. register a cleanup callback and accept callback, which basically make > the session layer happy without actually relevant work to do. > > There is a ctrl process in mater, which will handle periodically reconnect > or triggered by event. > > BTW, I also see frequently warning 'session %u hash delete rv -3' in > session_delete in my environment, hope this helps to investigate. > > Florin Coras <[email protected]> 于2023年3月20日周一 23:29写道： > >> Hi, >> >> Understood and yes, connect will synchronously fail if port is not >> available, so you should be able to retry it later. >> >> Regards, >> Florin >> >> On Mar 20, 2023, at 1:58 AM, Zhang Dongya <[email protected]> >> wrote: >> >> Hi, >> >> It seems the issue occurs when there are disconnect called because our >> network can't guarantee a tcp can't be reset even when 3 ways handshake is >> completed (firewall issue :( ). >> >> When we find the app layer timeout, we will first disconnect (because we >> record the session handle, this session might be a half open session), does >> vnet session layer guarantee that if we reconnect from master thread when >> the half open session still not be released yet (due to asynchronous logic) >> that the reconnect fail? if then we can retry connect later. >> >> I prefer to not registered half open callback because I think it make app >> complicated from a TCP programming prospective. >> >> For your patch, I think it should be work because I can't delete the half >> open session immediately because there is worker configured, so the half >> open will be removed from bihash when syn retrans timeout. I have merged >> the patch and will provide feedback later. >> >> Florin Coras <[email protected]> 于2023年3月20日周一 13:09写道： >> >>> Hi, >>> >>> Inline. >>> >>> On Mar 19, 2023, at 6:47 PM, Zhang Dongya <[email protected]> >>> wrote: >>> >>> Hi, >>> >>> It can be aborted both in established state or half open state because I >>> will do timeout in our app layer. >>> >>> >>> [fc] Okay! Is the issue present irrespective of the state of the session >>> or does it happen only after a disconnect in hanf-open state? More lower. >>> >>> >>> Regarding your question, >>> >>> - Yes we add a builtin in app relys on C apis that mainly use >>> vnet_connect/disconnect to connect or disconnect session. >>> >>> >>> [fc] Understood >>> >>> - We call these api in a vpp ctrl process which should be running on the >>> master thread, we never do session setup/teardown on worker thread. (the >>> environment that found this issue is configured with 1 master + 1 worker >>> setup.) >>> >>> >>> [fc] With vpp latest it’s possible to connect from first workers. It’s >>> an optimization meant to avoid 1) worker barrier on syns and 2) entering >>> poll mode on main (consume less cpu) >>> >>> - We started to develop the app using 22.06 and I keep to merge upstream >>> changes to latest vpp by cherry-picking. The reason for line mismatch is >>> that I added some comment to the session layer code, it should be equal to >>> the master branch now. >>> >>> >>> [fc] Ack >>> >>> >>> When reading the code I understand that we mainly want to cleanup half >>> open from bihash in session_stream_connect_notify, however, in syn-sent >>> state if I choose to close the session, the session might be closed by my >>> app due to session setup timeout (in second scale), in that case, session >>> will be marked as half_open_done and half open session will be freed >>> shortly in the ctrl thread (the 1st worker?). >>> >>> >>> [fc] Actually, this might be the issue. We did start to provide a >>> half-open session handle to apps which if closed does clean up the session >>> but apparently it is missing the cleanup of the session lookup table. Could >>> you try this patch [1]? It might need additional work. >>> >>> Having said that, forcing a close/cleanup will not free the port >>> synchronously. So, if you’re using fixed ports, you’ll have to wait for the >>> half-open cleanup notification. >>> >>> >>> Should I also registered half open callback or there are some other >>> reason that lead to this failure? >>> >>> >>> [fc] Yes, see above. >>> >>> Regards, >>> Florin >>> >>> [1] https://gerrit.fd.io/r/c/vpp/+/38526 >>> >>> >>> Florin Coras <[email protected]> 于2023年3月20日周一 06:22写道： >>> >>>> Hi, >>>> >>>> When you abort the connection, is it fully established or half-open? >>>> Half-opens are cleaned up by the owner thread after a timeout, but the >>>> 5-tuple should be assigned to the fully established session by that point. >>>> tcp_half_open_connection_cleanup does not cleanup the bihash instead >>>> session_stream_connect_notify does once tcp connect returns either success >>>> or failure. >>>> >>>> So a few questions: >>>> - is it accurate to assume you have a builtin vpp app and rely only on >>>> C apis to interact with host stack? >>>> - on what thread (main or first worker) do you call vnet_connect? >>>> - what api do you use to close the session? >>>> - what version of vpp is this because lines don’t match vpp latest? >>>> >>>> Regards, >>>> Florin >>>> >>>> > On Mar 19, 2023, at 2:08 AM, Zhang Dongya <[email protected]> >>>> wrote: >>>> > >>>> > Hi list, >>>> > >>>> > recently in our application, we constantly triggered such abrt issue >>>> which make our connectivity interrupt for a while: >>>> > >>>> > Mar 19 16:11:26 ubuntu vnet[2565933]: received signal SIGABRT, PC >>>> 0x7fefd3b2000b >>>> > Mar 19 16:11:26 ubuntu vnet[2565933]: >>>> /home/fortitude/glx/vpp/src/vnet/tcp/tcp_input.c:3004 (tcp46_input_inline) >>>> assertion `tcp_lookup_is_valid (tc0, b[0], tcp_buffer_hdr (b[0]))' fails >>>> > >>>> > Our scenario is quite simple, we will make 4 parallel tcp connection >>>> (use 4 fixed source ports) to a remote vpp stack (fixed ip and port), and >>>> will do some keepalive in our application layer, since we only use the vpp >>>> tcp stack to make the middle box happy with the connection, we do not use >>>> the data transport of tcp statck actually. >>>> > >>>> > However, since the network condition is complex, we have to always >>>> need to abrt the connection and reconnect. >>>> > >>>> > I keep to merge upstream session and tcp fix however the issue still >>>> not fixed, what I found now it may be in some case >>>> tcp_half_open_connection_cleanup may not deleted the half open session from >>>> the lookup table (bihash) and the session index is realloced by other >>>> connection. >>>> > >>>> > Hope the list can provide some hint about how to overcome this issue, >>>> thanks a lot. >>>> > >>>> > >>>> > >>>> >>>> >>>> >>>> >>>> >>> >>> >>> >>> >>> >> >> >> >> >> > > > > >
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