Anu Thomas created PROTON-2823:
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Summary: Proton-J does not raise transport closed when TCP FIN+ACK
arrives followed by TCP RST
Key: PROTON-2823
URL: https://issues.apache.org/jira/browse/PROTON-2823
Project: Qpid Proton
Issue Type: Bug
Components: proton-j
Affects Versions: proton-j-0.34.1
Reporter: Anu Thomas
Attachments: image-2024-05-14-11-36-02-828.png
We’ve noticed that after establishing the connection to the broker, if the
broker network initiates the "TCP connection close FIN+ACK, along with RST"
then the Proton-J does not signal a terminal event (e.g., transport close),
which leaves the client application unable detect such a connection termination
and recover.
The traffic flow is –
# TCP layer on the service side sends FIN+ACK
# Client TCP layer respond with FIN+ACK
# TCP layer on the service side sends TCP RST
# The Proton-J does not propagate any terminal event (e.g., transport close)
to the registered handler for application to react to this disconnect.
Below is a Wireshark captured view of this traffic -
!image-2024-05-14-11-36-02-828.png!
While analyzing this, when this happens, we have noticed the following
internally to Proton-J -
# Proton-J SimpleSslTransportWrapper layer is in fact detecting this close
[here|https://github.com/apache/qpid-proton-j/blob/adb9ebcc1cf76e18f1ef176fd77a4ae6a73cd557/proton-j/src/main/java/org/apache/qpid/proton/engine/impl/ssl/SimpleSslTransportWrapper.java#L232]
and it marks its _head_closed flag as true indicating the outbound is closed.
# Proton-J TrasportImpl even generate TRANSPORT_HEAD_CLOSED event but it never
generates TRANSPORT_TAIL_CLOSED event, or TRANSPORT_CLOSED event which requires
tail_close also to happen.
# The Proton-J also frees all the internally registered Selectables, for
example the Selectable associated with the TCP Connection and gracefully shut
down these resources (and associated channels, timers tracking idle timeout).
# We can also see that the internal
[connectionFree|https://github.com/apache/qpid-proton-j/blob/adb9ebcc1cf76e18f1ef176fd77a4ae6a73cd557/proton-j/src/main/java/org/apache/qpid/proton/reactor/impl/IOHandler.java#L319]
handler in the IOHandler is invoked (note: none of the other terminal handlers
(connectionError, connectionExpired) are invoked)
I created below PR to address this - where it closes the transport tail when
connection is free-ed, resulting in Proton-J signaling the transport
termination to the application handlers. With this fix, the application is able
to detect the connection drop and recover.
[Close transport tail when freeing connection to avoid the client application
hanging when TCP FIN+ACK arrives along with TCP RST. by anuchandy · Pull
Request #44 · apache/qpid-proton-j
(github.com)|https://github.com/apache/qpid-proton-j/pull/44]
Can please experts from the Proton-J community take a look at this / fix?
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