lkml.org 
[lkml]   [2013]   [Jan]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    Patch in this message
    /
    From
    Subject[PATCH 188/222] tcp: refine SYN handling in tcp_validate_incoming
    Date
    3.5.7.3 -stable review patch.  If anyone has any objections, please let me know.

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

    From: Eric Dumazet <edumazet@google.com>

    commit e371589917011efe6ff8c7dfb4e9e81934ac5855 upstream.

    Followup of commit 0c24604b68fc (tcp: implement RFC 5961 4.2)

    As reported by Vijay Subramanian, we should send a challenge ACK
    instead of a dup ack if a SYN flag is set on a packet received out of
    window.

    This permits the ratelimiting to work as intended, and to increase
    correct SNMP counters.

    Suggested-by: Vijay Subramanian <subramanian.vijay@gmail.com>
    Signed-off-by: Eric Dumazet <edumazet@google.com>
    Acked-by: Vijay Subramanian <subramanian.vijay@gmail.com>
    Cc: Kiran Kumar Kella <kkiran@broadcom.com>
    Signed-off-by: David S. Miller <davem@davemloft.net>
    Signed-off-by: Herton Ronaldo Krzesinski <herton.krzesinski@canonical.com>
    ---
    net/ipv4/tcp_input.c | 6 +++++-
    1 file changed, 5 insertions(+), 1 deletion(-)

    diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
    index e859775..afb436d 100644
    --- a/net/ipv4/tcp_input.c
    +++ b/net/ipv4/tcp_input.c
    @@ -5477,8 +5477,11 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
    * an acknowledgment should be sent in reply (unless the RST
    * bit is set, if so drop the segment and return)".
    */
    - if (!th->rst)
    + if (!th->rst) {
    + if (th->syn)
    + goto syn_challenge;
    tcp_send_dupack(sk, skb);
    + }
    goto discard;
    }

    @@ -5508,6 +5511,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
    * RFC 5691 4.2 : Send a challenge ack
    */
    if (th->syn) {
    +syn_challenge:
    if (syn_inerr)
    TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
    NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
    --
    1.7.9.5


    \
     
     \ /
      Last update: 2013-01-16 20:24    [W:4.077 / U:0.632 seconds]
    ©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site