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A quic_conn is instantiated and tied on the first thread which has received the first INITIAL packet. After handshake completion, listener_accept() is called. For each quic_conn, a new thread is selected among the least loaded ones Note that this occurs earlier if handling 0-RTT data. This thread connection migration is done in two steps : * inside listener_accept(), on the origin thread, quic_conn tasks/tasklet are killed. After this, no quic_conn related processing will occur on this thread. The connection is flagged with QUIC_FL_CONN_AFFINITY_CHANGED. * as soon as the first quic_conn related processing occurs on the new thread, the migration is finalized. This allows to allocate the new tasks/tasklet directly on the destination thread. This last step on the new thread must be done prior to other quic_conn access. There is two events which may trigger it : * a packet is received on the new thread. In this case, qc_finalize_affinity_rebind() is called from quic_dgram_parse(). * the recently accepted connection is popped from accept_queue_ring via accept_queue_process(). This will called session_accept_fd() as listener.bind_conf.accept callback. This instantiates a new session and start connection stack via conn_xprt_start(), which itself calls qc_xprt_start() where qc_finalize_affinity_rebind() is used. A condition was recently found which could cause a closing to be used with qc_finalize_affinity_rebind() which is forbidden with a BUG_ON(). This lat step was not compatible with layer 4 rule such as "tcp-request connection reject" which closes the connection early. In this case, most of the body of session_accept_fd() is skipped, including qc_xprt_start(), so thread migration is not finalized. At the end of the function, conn_xprt_close() is then called which flags the connection as CLOSING. If a datagram is received for this connection before it is released, this will call qc_finalize_affinity_rebind() which triggers its BUG_ON() to prevent thread migration for CLOSING quic_conn. FATAL: bug condition "qc->flags & ((1U << 29)|(1U << 30))" matched at src/quic_conn.c:2036 Thread 3 "haproxy" received signal SIGILL, Illegal instruction. [Switching to Thread 0x7ffff794f700 (LWP 2973030)] 0x00005555556221f3 in qc_finalize_affinity_rebind (qc=0x7ffff002d060) at src/quic_conn.c:2036 2036 BUG_ON(qc->flags & (QUIC_FL_CONN_CLOSING|QUIC_FL_CONN_DRAINING)); (gdb) bt #0 0x00005555556221f3 in qc_finalize_affinity_rebind (qc=0x7ffff002d060) at src/quic_conn.c:2036 #1 0x0000555555682463 in quic_dgram_parse (dgram=0x7fff5003ef10, from_qc=0x0, li=0x555555f38670) at src/quic_rx.c:2602 #2 0x0000555555651aae in quic_lstnr_dghdlr (t=0x555555fc4440, ctx=0x555555fc3f78, state=32832) at src/quic_sock.c:189 #3 0x00005555558c9393 in run_tasks_from_lists (budgets=0x7ffff7944c90) at src/task.c:596 #4 0x00005555558c9e8e in process_runnable_tasks () at src/task.c:876 #5 0x000055555586b7b2 in run_poll_loop () at src/haproxy.c:2966 #6 0x000055555586be87 in run_thread_poll_loop (data=0x555555d3d340 <ha_thread_info+64>) at src/haproxy.c:3165 #7 0x00007ffff7b59609 in start_thread () from /lib/x86_64-linux-gnu/libpthread.so.0 #8 0x00007ffff7a7e133 in clone () from /lib/x86_64-linux-gnu/libc.so.6 To fix this issue, ensure quic_conn migration is completed earlier inside session_accept_fd(), before any tcp rules processing. This is done by moving qc_finalize_affinity_rebind() invocation from qc_xprt_start() to qc_conn_init(). This must be backported up to 2.7.
The HAProxy documentation has been split into a number of different files for ease of use. Please refer to the following files depending on what you're looking for : - INSTALL for instructions on how to build and install HAProxy - BRANCHES to understand the project's life cycle and what version to use - LICENSE for the project's license - CONTRIBUTING for the process to follow to submit contributions The more detailed documentation is located into the doc/ directory : - doc/intro.txt for a quick introduction on HAProxy - doc/configuration.txt for the configuration's reference manual - doc/lua.txt for the Lua's reference manual - doc/SPOE.txt for how to use the SPOE engine - doc/network-namespaces.txt for how to use network namespaces under Linux - doc/management.txt for the management guide - doc/regression-testing.txt for how to use the regression testing suite - doc/peers.txt for the peers protocol reference - doc/coding-style.txt for how to adopt HAProxy's coding style - doc/internals for developer-specific documentation (not all up to date)