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    Subject[PATCH 3.13 026/162] sctp: handle association restarts when the socket is closed.
    Date
    3.13.11.11 -stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Vlad Yasevich <vyasevich@gmail.com>

    [ Upstream commit bdf6fa52f01b941d4a80372d56de465bdbbd1d23 ]

    Currently association restarts do not take into consideration the
    state of the socket. When a restart happens, the current assocation
    simply transitions into established state. This creates a condition
    where a remote system, through a the restart procedure, may create a
    local association that is no way reachable by user. The conditions
    to trigger this are as follows:
    1) Remote does not acknoledge some data causing data to remain
    outstanding.
    2) Local application calls close() on the socket. Since data
    is still outstanding, the association is placed in SHUTDOWN_PENDING
    state. However, the socket is closed.
    3) The remote tries to create a new association, triggering a restart
    on the local system. The association moves from SHUTDOWN_PENDING
    to ESTABLISHED. At this point, it is no longer reachable by
    any socket on the local system.

    This patch addresses the above situation by moving the newly ESTABLISHED
    association into SHUTDOWN-SENT state and bundling a SHUTDOWN after
    the COOKIE-ACK chunk. This way, the restarted associate immidiately
    enters the shutdown procedure and forces the termination of the
    unreachable association.

    Reported-by: David Laight <David.Laight@aculab.com>
    Signed-off-by: Vlad Yasevich <vyasevich@gmail.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Kamal Mostafa <kamal@canonical.com>
    ---
    include/net/sctp/command.h | 2 +-
    net/sctp/sm_statefuns.c | 19 ++++++++++++++++---
    2 files changed, 17 insertions(+), 4 deletions(-)

    diff --git a/include/net/sctp/command.h b/include/net/sctp/command.h
    index 832f219..c3f0cd9 100644
    --- a/include/net/sctp/command.h
    +++ b/include/net/sctp/command.h
    @@ -116,7 +116,7 @@ typedef enum {
    * analysis of the state functions, but in reality just taken from
    * thin air in the hopes othat we don't trigger a kernel panic.
    */
    -#define SCTP_MAX_NUM_COMMANDS 14
    +#define SCTP_MAX_NUM_COMMANDS 20

    typedef union {
    __s32 i32;
    diff --git a/net/sctp/sm_statefuns.c b/net/sctp/sm_statefuns.c
    index cd0d5a2..4b549a3 100644
    --- a/net/sctp/sm_statefuns.c
    +++ b/net/sctp/sm_statefuns.c
    @@ -1776,9 +1776,22 @@ static sctp_disposition_t sctp_sf_do_dupcook_a(struct net *net,
    /* Update the content of current association. */
    sctp_add_cmd_sf(commands, SCTP_CMD_UPDATE_ASSOC, SCTP_ASOC(new_asoc));
    sctp_add_cmd_sf(commands, SCTP_CMD_EVENT_ULP, SCTP_ULPEVENT(ev));
    - sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
    - SCTP_STATE(SCTP_STATE_ESTABLISHED));
    - sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
    + if (sctp_state(asoc, SHUTDOWN_PENDING) &&
    + (sctp_sstate(asoc->base.sk, CLOSING) ||
    + sock_flag(asoc->base.sk, SOCK_DEAD))) {
    + /* if were currently in SHUTDOWN_PENDING, but the socket
    + * has been closed by user, don't transition to ESTABLISHED.
    + * Instead trigger SHUTDOWN bundled with COOKIE_ACK.
    + */
    + sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
    + return sctp_sf_do_9_2_start_shutdown(net, ep, asoc,
    + SCTP_ST_CHUNK(0), NULL,
    + commands);
    + } else {
    + sctp_add_cmd_sf(commands, SCTP_CMD_NEW_STATE,
    + SCTP_STATE(SCTP_STATE_ESTABLISHED));
    + sctp_add_cmd_sf(commands, SCTP_CMD_REPLY, SCTP_CHUNK(repl));
    + }
    return SCTP_DISPOSITION_CONSUME;

    nomem_ev:
    --
    1.9.1


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