[PATCH 4.9 23/51] tcp: initialize max window for a new fastopen socket

From	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Newsgroups	linux.kernel
Subject	[PATCH 4.9 23/51] tcp: initialize max window for a new fastopen socket
Date	2017-02-02 19:50 +0100
Message-ID	<t6uCd-7FA-13@gated-at.bofh.it> (permalink)
References	<t6usx-7Bs-3@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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4.9-stable review patch.  If anyone has any objections, please let me know.

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

From: Alexey Kodanev <alexey.kodanev@oracle.com>


[ Upstream commit 0dbd7ff3ac5017a46033a9d0a87a8267d69119d9 ]

Found that if we run LTP netstress test with large MSS (65K),
the first attempt from server to send data comparable to this
MSS on fastopen connection will be delayed by the probe timer.

Here is an example:

     < S  seq 0:0 win 43690 options [mss 65495 wscale 7 tfo cookie] length 32
     > S. seq 0:0 ack 1 win 43690 options [mss 65495 wscale 7] length 0
     < .  ack 1 win 342 length 0

Inside tcp_sendmsg(), tcp_send_mss() returns max MSS in 'mss_now',
as well as in 'size_goal'. This results the segment not queued for
transmition until all the data copied from user buffer. Then, inside
__tcp_push_pending_frames(), it breaks on send window test and
continues with the check probe timer.

Fragmentation occurs in tcp_write_wakeup()...

+0.2 > P. seq 1:43777 ack 1 win 342 length 43776
     < .  ack 43777, win 1365 length 0
     > P. seq 43777:65001 ack 1 win 342 options [...] length 21224
     ...

This also contradicts with the fact that we should bound to the half
of the window if it is large.

Fix this flaw by correctly initializing max_window. Before that, it
could have large values that affect further calculations of 'size_goal'.

Fixes: 168a8f58059a ("tcp: TCP Fast Open Server - main code path")
Signed-off-by: Alexey Kodanev <alexey.kodanev@oracle.com>
Acked-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
 net/ipv4/tcp_fastopen.c |    1 +
 1 file changed, 1 insertion(+)

--- a/net/ipv4/tcp_fastopen.c
+++ b/net/ipv4/tcp_fastopen.c
@@ -205,6 +205,7 @@ static struct sock *tcp_fastopen_create_
 	 * scaled. So correct it appropriately.
 	 */
 	tp->snd_wnd = ntohs(tcp_hdr(skb)->window);
+	tp->max_window = tp->snd_wnd;
 
 	/* Activate the retrans timer so that SYNACK can be retransmitted.
 	 * The request socket is not added to the ehash

Thread

[PATCH 4.9 00/51] 4.9.8-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 35/51] xfs: adjust allocation length in xfs_alloc_space_available Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 36/51] xfs: dont rely on ->total in xfs_alloc_space_available Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 09/51] tcp: fix tcp_fastopen unaligned access complaints on sparc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 05/51] mlxsw: pci: Fix EQE structure definition Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 04/51] mlxsw: switchx2: Fix memory leak at skb reallocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 03/51] mlxsw: spectrum: Fix memory leak at skb reallocation Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 26/51] net: mpls: Fix multipath selection for LSR use case Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:40 +0100
  [PATCH 4.9 11/51] mlx4: do not call napi_schedule() without care Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 14/51] ax25: Fix segfault after sock connection timeout Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 47/51] xfs: verify dirblocklog correctly Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 43/51] xfs: sanity check inode di_mode Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 39/51] xfs: sanity check directory inode di_size Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 15/51] net sched actions: fix refcnt when GETing of action after bind Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 50/51] xfs: clear _XBF_PAGES from buffers when readahead page Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 22/51] ipv6: addrconf: Avoid addrconf_disable_change() using RCU read-side lock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 31/51] lwtunnel: Fix oops on state free after encap module unload Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 23/51] tcp: initialize max window for a new fastopen socket Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 49/51] xfs: extsize hints are not unlikely in xfs_bmap_btalloc Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 24/51] net/mlx5e: Do not recycle pages from emergency reserve Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 08/51] net: systemport: Decouple flow control from __bcm_sysport_tx_reclaim Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 30/51] net: Specify the owning module for lwtunnel ops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 20/51] net: phy: bcm63xx: Utilize correct config_intr function Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 27/51] r8152: dont execute runtime suspend if the tx is not empty Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 46/51] xfs: fix COW writeback race Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 44/51] xfs: dont wrap ID in xfs_dq_get_next_id Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 06/51] net: lwtunnel: Handle lwtunnel_fill_encap failure Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 42/51] xfs: sanity check inode mode when creating new dentry Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 32/51] net: dsa: Bring back device detaching in dsa_slave_suspend() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 41/51] xfs: replace xfs_mode_to_ftype table with switch statement Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 10/51] openvswitch: maintain correct checksum state in conntrack actions Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 13/51] ip6_tunnel: Account for tunnel header in tunnel MTU Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 45/51] xfs: fix xfs_mode_to_ftype() prototype Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 28/51] af_unix: move unix_mknod() out of bindlock Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 25/51] bridge: netlink: call br_changelink() during br_dev_newlink() Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 34/51] xfs: fix bogus minleft manipulations Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 37/51] xfs: dont print warnings when xfs_log_force fails Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 48/51] xfs: remove racy hasattr check from attr ops Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 12/51] ravb: do not use zero-length alignment DMA descriptor Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 51/51] xfs: fix bmv_count confusion w/ shared extents Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 33/51] xfs: bump up reserved blocks in xfs_alloc_set_aside Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 19:50 +0100
  [PATCH 4.9 02/51] netvsc: add rcu_read locking to netvsc callback Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 20:00 +0100
  [PATCH 4.9 17/51] virtio-net: restore VIRTIO_HDR_F_DATA_VALID on receiving Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 20:00 +0100
  [PATCH 4.9 07/51] net: ipv4: fix table id in getroute response Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 20:00 +0100
  [PATCH 4.9 01/51] r8152: fix the sw rx checksum is unavailable Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 20:00 +0100
  Re: [PATCH 4.9 00/51] 4.9.8-stable review Shuah Khan <shuahkh@osg.samsung.com> - 2017-02-02 21:40 +0100
    Re: [PATCH 4.9 00/51] 4.9.8-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-02 22:00 +0100
  Re: [PATCH 4.9 00/51] 4.9.8-stable review Guenter Roeck <linux@roeck-us.net> - 2017-02-03 06:20 +0100
    Re: [PATCH 4.9 00/51] 4.9.8-stable review Greg Kroah-Hartman <gregkh@linuxfoundation.org> - 2017-02-03 08:20 +0100

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