• Menglong Dong's avatar
    mptcp: fix unreleased socket in accept queue · 30e51b92
    Menglong Dong authored
    The mptcp socket and its subflow sockets in accept queue can't be
    released after the process exit.
    
    While the release of a mptcp socket in listening state, the
    corresponding tcp socket will be released too. Meanwhile, the tcp
    socket in the unaccept queue will be released too. However, only init
    subflow is in the unaccept queue, and the joined subflow is not in the
    unaccept queue, which makes the joined subflow won't be released, and
    therefore the corresponding unaccepted mptcp socket will not be released
    to.
    
    This can be reproduced easily with following steps:
    
    1. create 2 namespace and veth:
       $ ip netns add mptcp-client
       $ ip netns add mptcp-server
       $ sysctl -w net.ipv4.conf.all.rp_filter=0
       $ ip netns exec mptcp-client sysctl -w net.mptcp.enabled=1
       $ ip netns exec mptcp-server sysctl -w net.mptcp.enabled=1
       $ ip link add red-client netns mptcp-client type veth peer red-server \
         netns mptcp-server
       $ ip -n mptcp-server address add 10.0.0.1/24 dev red-server
       $ ip -n mptcp-server address add 192.168.0.1/24 dev red-server
       $ ip -n mptcp-client address add 10.0.0.2/24 dev red-client
       $ ip -n mptcp-client address add 192.168.0.2/24 dev red-client
       $ ip -n mptcp-server link set red-server up
       $ ip -n mptcp-client link set red-client up
    
    2. configure the endpoint and limit for client and server:
       $ ip -n mptcp-server mptcp endpoint flush
       $ ip -n mptcp-server mptcp limits set subflow 2 add_addr_accepted 2
       $ ip -n mptcp-client mptcp endpoint flush
       $ ip -n mptcp-client mptcp limits set subflow 2 add_addr_accepted 2
       $ ip -n mptcp-client mptcp endpoint add 192.168.0.2 dev red-client id \
         1 subflow
    
    3. listen and accept on a port, such as 9999. The nc command we used
       here is modified, which makes it use mptcp protocol by default.
       $ ip netns exec mptcp-server nc -l -k -p 9999
    
    4. open another *two* terminal and use each of them to connect to the
       server with the following command:
       $ ip netns exec mptcp-client nc 10.0.0.1 9999
       Input something after connect to trigger the connection of the second
       subflow. So that there are two established mptcp connections, with the
       second one still unaccepted.
    
    5. exit all the nc command, and check the tcp socket in server namespace.
       And you will find that there is one tcp socket in CLOSE_WAIT state
       and can't release forever.
    
    Fix this by closing all of the unaccepted mptcp socket in
    mptcp_subflow_queue_clean() with __mptcp_close().
    
    Now, we can ensure that all unaccepted mptcp sockets will be cleaned by
    __mptcp_close() before they are released, so mptcp_sock_destruct(), which
    is used to clean the unaccepted mptcp socket, is not needed anymore.
    
    The selftests for mptcp is ran for this commit, and no new failures.
    
    Fixes: f296234c ("mptcp: Add handling of incoming MP_JOIN requests")
    Fixes: 6aeed904 ("mptcp: fix race on unaccepted mptcp sockets")
    Cc: stable@vger.kernel.org
    Reviewed-by: default avatarJiang Biao <benbjiang@tencent.com>
    Reviewed-by: default avatarMengen Sun <mengensun@tencent.com>
    Acked-by: default avatarPaolo Abeni <pabeni@redhat.com>
    Signed-off-by: default avatarMenglong Dong <imagedong@tencent.com>
    Signed-off-by: default avatarMat Martineau <mathew.j.martineau@linux.intel.com>
    Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
    30e51b92
protocol.c 96.2 KB