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Neal Cardwell 0c9ab09223 tcp: fix ssthresh and undo for consecutive short FRTO episodes 
Fix TCP FRTO logic so that it always notices when snd_una advances,
indicating that any RTO after that point will be a new and distinct
loss episode.

Previously there was a very specific sequence that could cause FRTO to
fail to notice a new loss episode had started:

(1) RTO timer fires, enter FRTO and retransmit packet 1 in write queue
(2) receiver ACKs packet 1
(3) FRTO sends 2 more packets
(4) RTO timer fires again (should start a new loss episode)

The problem was in step (3) above, where tcp_process_loss() returned
early (in the spot marked "Step 2.b"), so that it never got to the
logic to clear icsk_retransmits. Thus icsk_retransmits stayed
non-zero. Thus in step (4) tcp_enter_loss() would see the non-zero
icsk_retransmits, decide that this RTO is not a new episode, and
decide not to cut ssthresh and remember the current cwnd and ssthresh
for undo.

There were two main consequences to the bug that we have
observed. First, ssthresh was not decreased in step (4). Second, when
there was a series of such FRTO (1-4) sequences that happened to be
followed by an FRTO undo, we would restore the cwnd and ssthresh from
before the entire series started (instead of the cwnd and ssthresh
from before the most recent RTO). This could result in cwnd and
ssthresh being restored to values much bigger than the proper values.

Signed-off-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Yuchung Cheng <ycheng@google.com>
Fixes: e33099f96d ("tcp: implement RFC5682 F-RTO")
Signed-off-by: David S. Miller <davem@davemloft.net>
 		2014-08-14 14:38:55 -07:00
..
netfilter netfilter: kill remnants of ulog targets 2014-07-25 14:55:44 +02:00
Kconfig udp: Add udp_sock_create for UDP tunnels to open listener socket 2014-07-14 16:12:15 -07:00
Makefile udp: Add udp_sock_create for UDP tunnels to open listener socket 2014-07-14 16:12:15 -07:00
af_inet.c net-gre-gro: Fix a bug that breaks the forwarding path 2014-07-16 14:45:26 -07:00
ah4.c ah4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
arp.c ipv4: arp: update neighbour address when a gratuitous arp is received and arp_accept is set 2014-01-02 00:08:38 -05:00
cipso_ipv4.c netlabel: shorter names for the NetLabel catmap funcs/structs 2014-08-01 11:17:37 -04:00
datagram.c net: Save TX flow hash in sock and set in skbuf on xmit 2014-07-07 21:14:21 -07:00
devinet.c ipv4: fail early when creating netdev named all or default 2014-07-29 11:43:50 -07:00
esp4.c esp4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
fib_frontend.c ipv4, fib: pass LOOPBACK_IFINDEX instead of 0 to flowi4_iif 2014-04-16 15:05:11 -04:00
fib_lookup.h ipv4: make fib_detect_death static 2013-12-28 17:01:46 -05:00
fib_rules.c inet: fix NULL pointer Oops in fib(6)_rule_suppress 2013-12-10 17:54:23 -05:00
fib_semantics.c ipv4: fib_semantics: increment fib_info_cnt after fib_info allocation 2014-05-07 17:14:32 -04:00
fib_trie.c list: fix order of arguments for hlist_add_after(_rcu) 2014-08-06 18:01:24 -07:00
gre_demux.c GRE: enable offloads for GRE 2014-07-11 13:53:39 -07:00
gre_offload.c net/ipv4: Use IS_ERR_OR_NULL 2014-07-29 15:31:56 -07:00
icmp.c ipv4: remove nested rcu_read_lock/unlock 2014-08-02 15:27:35 -07:00
igmp.c igmp: remove exceptional & on function name 2014-07-24 23:23:31 -07:00
inet_connection_sock.c ipv4: make ip_local_reserved_ports per netns 2014-05-14 15:31:45 -04:00
inet_diag.c inet_diag: fix inet_diag_dump_icsk() to use correct state for timewait sockets 2014-01-13 22:35:46 -08:00
inet_fragment.c inet: frags: use kmem_cache for inet_frag_queue 2014-08-02 15:31:31 -07:00
inet_hashtables.c net: Use a more standard macro for INET_ADDR_COOKIE 2014-05-14 16:07:23 -04:00
inet_lro.c lro: remove dead code 2013-12-29 16:34:25 -05:00
inet_timewait_sock.c
…
inetpeer.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2014-06-12 14:27:40 -07:00
ip_forward.c net: rename local_df to ignore_df 2014-05-12 14:03:41 -04:00
ip_fragment.c inet: frags: use kmem_cache for inet_frag_queue 2014-08-02 15:31:31 -07:00
ip_gre.c gre: allow changing mac address when device is up 2014-06-10 22:46:42 -07:00
ip_input.c net: Fix memory leak if TPROXY used with TCP early demux 2014-01-27 16:22:11 -08:00
ip_options.c ipv4: fix buffer overflow in ip_options_compile() 2014-07-21 20:16:26 -07:00
ip_output.c net-timestamp: add key to disambiguate concurrent datagrams 2014-08-05 16:35:54 -07:00
ip_sockglue.c ipv4: clean up cast warning in do_ip_getsockopt 2014-07-29 16:31:16 -07:00
ip_tunnel.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-08-05 18:46:26 -07:00
ip_tunnel_core.c net: Support for multiple checksums with gso 2014-06-04 22:46:38 -07:00
ip_vti.c vti: Simplify error handling in module init and exit 2014-06-26 08:21:57 +02:00
ipcomp.c ipcomp4: Use the IPsec protocol multiplexer API 2014-02-25 07:04:17 +01:00
ipconfig.c ipconfig: Only bootp paths should reference ic_dev_xid. 2014-07-09 22:25:18 -07:00
ipip.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-06-11 16:02:55 -07:00
ipmr.c net: set name_assign_type in alloc_netdev() 2014-07-15 16:12:48 -07:00
netfilter.c netfilter: remove double colon 2014-02-19 11:41:25 +01:00
ping.c net: use inet6_iif instead of IP6CB()->iif 2014-07-31 22:37:06 -07:00
proc.c inet: frag: don't account number of fragment queues 2014-07-27 22:34:36 -07:00
protocol.c net: remove outdated comment for ipv4 and ipv6 protocol handler 2013-11-28 18:47:51 -05:00
raw.c ipv4: Make IP_MULTICAST_ALL and IP_MSFILTER work on raw sockets 2014-07-23 15:13:26 -07:00
route.c ipv4: removed redundant conditional 2014-08-08 10:22:22 -07:00
syncookies.c tcp: cookie_v4_init_sequence: skb should be const 2014-06-27 15:53:35 -07:00
sysctl_net_ipv4.c ipv4: make ip_local_reserved_ports per netns 2014-05-14 15:31:45 -04:00
tcp.c tcp: don't use timestamp from repaired skb-s to calculate RTT (v2) 2014-08-14 14:38:54 -07:00
tcp_bic.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_cong.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_cubic.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-05-12 13:19:14 -04:00
tcp_diag.c
…
tcp_fastopen.c tcp: remove unnecessary tcp_sk assignment. 2014-06-16 21:35:00 -07:00
tcp_highspeed.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_htcp.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_hybla.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_illinois.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_input.c tcp: fix ssthresh and undo for consecutive short FRTO episodes 2014-08-14 14:38:55 -07:00
tcp_ipv4.c tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced() 2014-08-14 14:38:54 -07:00
tcp_lp.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_memcontrol.c cgroup: replace cgroup_add_cftypes() with cgroup_add_legacy_cftypes() 2014-07-15 11:05:09 -04:00
tcp_metrics.c tcp: don't allow syn packets without timestamps to pass tcp_tw_recycle logic 2014-08-14 14:38:54 -07:00
tcp_minisocks.c inet: move ipv6only in sock_common 2014-07-01 23:46:21 -07:00
tcp_offload.c net-timestamp: cumulative tcp timestamping fixes 2014-08-06 14:09:01 -07:00
tcp_output.c tcp: fix tcp_release_cb() to dispatch via address family for mtu_reduced() 2014-08-14 14:38:54 -07:00
tcp_probe.c tcp: switch rtt estimations to usec resolution 2014-02-26 17:08:40 -05:00
tcp_scalable.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tcp_timer.c tcp: reduce spurious retransmits due to transient SACK reneging 2014-08-05 16:29:33 -07:00
tcp_vegas.c tcp: Fix integer-overflow in TCP vegas 2014-07-30 17:31:06 -07:00
tcp_vegas.h net: ipv4/ipv6: Remove extern from function prototypes 2013-10-19 19:12:11 -04:00
tcp_veno.c tcp: Fix integer-overflows in TCP veno 2014-07-30 17:31:06 -07:00
tcp_westwood.c tcp: remove unused min_cwnd member of tcp_congestion_ops 2014-02-13 18:22:34 -05:00
tcp_yeah.c tcp: remove in_flight parameter from cong_avoid() methods 2014-05-03 19:23:07 -04:00
tunnel4.c
…
udp.c sock: remove skb argument from sk_rcvqueues_full 2014-07-23 13:23:06 -07:00
udp_diag.c
…
udp_impl.h net: ipv4/ipv6: Remove extern from function prototypes 2013-10-19 19:12:11 -04:00
udp_offload.c net/udp_offload: Use IS_ERR_OR_NULL 2014-07-29 15:31:56 -07:00
udp_tunnel.c udp: Add udp_sock_create for UDP tunnels to open listener socket 2014-07-14 16:12:15 -07:00
udplite.c net: Eliminate no_check from protosw 2014-05-23 16:28:53 -04:00
xfrm4_input.c xfrm4: Add IPsec protocol multiplexer 2014-02-25 07:04:16 +01:00
xfrm4_mode_beet.c ipv4: ERROR: code indent should use tabs where possible 2013-12-26 13:43:21 -05:00
xfrm4_mode_transport.c
…
xfrm4_mode_tunnel.c inetpeer: get rid of ip_id_count 2014-06-02 11:00:41 -07:00
xfrm4_output.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2014-05-24 00:32:30 -04:00
xfrm4_policy.c xfrm: Introduce xfrm_input_afinfo to access the the callbacks properly 2014-03-14 07:28:07 +01:00
xfrm4_protocol.c xfrm4: Remove duplicate semicolon 2014-06-30 07:49:47 +02:00
xfrm4_state.c inet: make no_pmtu_disc per namespace and kill ipv4_config 2013-12-18 16:58:20 -05:00
xfrm4_tunnel.c
…