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    Subject[PATCH 216/241] tcp: fix retransmission in repair mode
    Date
    3.5.7.2 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Andrew Vagin <avagin@openvz.org>

    commit ec34232575083fd0f43d3a101e8ebb041b203761 upstream.

    Currently if a socket was repaired with a few packet in a write queue,
    a kernel bug may be triggered:

    kernel BUG at net/ipv4/tcp_output.c:2330!
    RIP: 0010:[<ffffffff8155784f>] tcp_retransmit_skb+0x5ff/0x610

    According to the initial realization v3.4-rc2-963-gc0e88ff,
    all skb-s should look like already posted. This patch fixes code
    according with this sentence.

    Here are three points, which were not done in the initial patch:
    1. A tcp send head should not be changed
    2. Initialize TSO state of a skb
    3. Reset the retransmission time

    This patch moves logic from tcp_sendmsg to tcp_write_xmit. A packet
    passes the ussual way, but isn't sent to network. This patch solves
    all described problems and handles tcp_sendpages.

    Cc: Pavel Emelyanov <xemul@parallels.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
    Cc: James Morris <jmorris@namei.org>
    Cc: Hideaki YOSHIFUJI <yoshfuji@linux-ipv6.org>
    Cc: Patrick McHardy <kaber@trash.net>
    Signed-off-by: Andrey Vagin <avagin@openvz.org>
    Acked-by: Pavel Emelyanov <xemul@parallels.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    [ herton: adjust context ]
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    net/ipv4/tcp.c | 4 ++--
    net/ipv4/tcp_output.c | 4 ++++
    2 files changed, 6 insertions(+), 2 deletions(-)

    diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
    index d758741..34b23da 100644
    --- a/net/ipv4/tcp.c
    +++ b/net/ipv4/tcp.c
    @@ -1180,7 +1180,7 @@ new_segment:
    wait_for_sndbuf:
    set_bit(SOCK_NOSPACE, &sk->sk_socket->flags);
    wait_for_memory:
    - if (copied && likely(!tp->repair))
    + if (copied)
    tcp_push(sk, flags & ~MSG_MORE, mss_now, TCP_NAGLE_PUSH);

    if ((err = sk_stream_wait_memory(sk, &timeo)) != 0)
    @@ -1191,7 +1191,7 @@ wait_for_memory:
    }

    out:
    - if (copied && likely(!tp->repair))
    + if (copied)
    tcp_push(sk, flags, mss_now, tp->nonagle);
    release_sock(sk);
    return copied;
    diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
    index 90b10d0..305aafe 100644
    --- a/net/ipv4/tcp_output.c
    +++ b/net/ipv4/tcp_output.c
    @@ -1784,6 +1784,9 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
    tso_segs = tcp_init_tso_segs(sk, skb, mss_now);
    BUG_ON(!tso_segs);

    + if (unlikely(tp->repair) && tp->repair_queue == TCP_SEND_QUEUE)
    + goto repair; /* Skip network transmission */
    +
    cwnd_quota = tcp_cwnd_test(tp, skb);
    if (!cwnd_quota)
    break;
    @@ -1817,6 +1820,7 @@ static bool tcp_write_xmit(struct sock *sk, unsigned int mss_now, int nonagle,
    if (unlikely(tcp_transmit_skb(sk, skb, 1, gfp)))
    break;

    +repair:
    /* Advance the send_head. This one is sent out.
    * This call will increment packets_out.
    */
    --
    1.7.9.5


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