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  1. Oct 09, 2013
  2. Oct 08, 2013
  3. Oct 05, 2013
    • Eric Dumazet's avatar
      tcp: do not forget FIN in tcp_shifted_skb() · 5e8a402f
      Eric Dumazet authored
      Yuchung found following problem :
      
       There are bugs in the SACK processing code, merging part in
       tcp_shift_skb_data(), that incorrectly resets or ignores the sacked
       skbs FIN flag. When a receiver first SACK the FIN sequence, and later
       throw away ofo queue (e.g., sack-reneging), the sender will stop
       retransmitting the FIN flag, and hangs forever.
      
      Following packetdrill test can be used to reproduce the bug.
      
      $ cat sack-merge-bug.pkt
      `sysctl -q net.ipv4.tcp_fack=0`
      
      // Establish a connection and send 10 MSS.
      0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
      +.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
      +.000 bind(3, ..., ...) = 0
      +.000 listen(3, 1) = 0
      
      +.050 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
      +.000 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 6>
      +.001 < . 1:1(0) ack 1 win 1024
      +.000 accept(3, ..., ...) = 4
      
      +.100 write(4, ..., 12000) = 12000
      +.000 shutdown(4, SHUT_WR) = 0
      +.000 > . 1:10001(10000) ack 1
      +.050 < . 1:1(0) ack 2001 win 257
      +.000 > FP. 10001:12001(2000) ack 1
      +.050 < . 1:1(0) ack 2001 win 257 <sack 10001:11001,nop,nop>
      +.050 < . 1:1(0) ack 2001 win 257 <sack 10001:12002,nop,nop>
      // SACK reneg
      +.050 < . 1:1(0) ack 12001 win 257
      +0 %{ print "unacked: ",tcpi_unacked }%
      +5 %{ print "" }%
      
      First, a typo inverted left/right of one OR operation, then
      code forgot to advance end_seq if the merged skb carried FIN.
      
      Bug was added in 2.6.29 by commit 832d11c5
      
      
      ("tcp: Try to restore large SKBs while SACK processing")
      
      Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
      Signed-off-by: default avatarYuchung Cheng <ycheng@google.com>
      Acked-by: default avatarNeal Cardwell <ncardwell@google.com>
      Cc: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
      Acked-by: default avatarIlpo Järvinen <ilpo.jarvinen@helsinki.fi>
      Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
      5e8a402f
  4. Oct 04, 2013
  5. Oct 03, 2013