Alan Conway created PROTON-1727:
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Summary: [epoll proactor] segfaults, hangs and leaked FDs around
failed connect
Key: PROTON-1727
URL: https://issues.apache.org/jira/browse/PROTON-1727
Project: Qpid Proton
Issue Type: Bug
Components: proton-c
Affects Versions: proton-c-0.18.1
Reporter: Alan Conway
Assignee: Alan Conway
There is a race condition that causes leaked FDs and segfaults in the epoll
proactor under the following conditions:
- there is more than one thread processing proactor events.
- attempting to connect to a host address that resolves to multiple socket
addresses, e.g. resolving the NULL hostname on a machine with ipv4 and ipv6
enabled.
- there is nothing listening on the target port.
The attached reproducer shows several bad behaviors:
- under rr or valgrind (--tool=memcheck and --tool=helgrind) it quickly (<
1min) shows race conditions and/or invalid memory access.
- it hangs fairly often even without valgrind/rr, more so if you increase the
thread count. Without valgrind/rr it rarely segfaults.
- it leaks FDs - the test should run forever, but runs out of FDs around 1024
iterations.
This is probably the cause of
https://issues.apache.org/jira/browse/DISPATCH-902, which does occur very
frequently under the conditions described there.
The test program should run forever without leaking or showing any faults.
Note that gcc -fsantize does not detect races or memory errors, which suggests
the bug requires a delay at the right time to manifest. Valgrind's overhead and
rr's code serialization appears to provide that delay. It seems likely that
dispatch's reconnect logic is providing the delay in DISPATCH-902.
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