linux/net/ipv4
Yuchung Cheng a0496ef2c2 tcp: do not delay ACK in DCTCP upon CE status change
Per DCTCP RFC8257 (Section 3.2) the ACK reflecting the CE status change
has to be sent immediately so the sender can respond quickly:

""" When receiving packets, the CE codepoint MUST be processed as follows:

   1.  If the CE codepoint is set and DCTCP.CE is false, set DCTCP.CE to
       true and send an immediate ACK.

   2.  If the CE codepoint is not set and DCTCP.CE is true, set DCTCP.CE
       to false and send an immediate ACK.
"""

Previously DCTCP implementation may continue to delay the ACK. This
patch fixes that to implement the RFC by forcing an immediate ACK.

Tested with this packetdrill script provided by Larry Brakmo

0.000 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
0.000 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
0.000 setsockopt(3, SOL_TCP, TCP_CONGESTION, "dctcp", 5) = 0
0.000 bind(3, ..., ...) = 0
0.000 listen(3, 1) = 0

0.100 < [ect0] SEW 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
0.100 > SE. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 8>
0.110 < [ect0] . 1:1(0) ack 1 win 257
0.200 accept(3, ..., ...) = 4
   +0 setsockopt(4, SOL_SOCKET, SO_DEBUG, [1], 4) = 0

0.200 < [ect0] . 1:1001(1000) ack 1 win 257
0.200 > [ect01] . 1:1(0) ack 1001

0.200 write(4, ..., 1) = 1
0.200 > [ect01] P. 1:2(1) ack 1001

0.200 < [ect0] . 1001:2001(1000) ack 2 win 257
+0.005 < [ce] . 2001:3001(1000) ack 2 win 257

+0.000 > [ect01] . 2:2(0) ack 2001
// Previously the ACK below would be delayed by 40ms
+0.000 > [ect01] E. 2:2(0) ack 3001

+0.500 < F. 9501:9501(0) ack 4 win 257

Signed-off-by: Yuchung Cheng <ycheng@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
2018-07-20 14:32:23 -07:00
..
bpfilter net: bpfilter: make function bpfilter_mbox_request() static 2018-05-29 09:51:44 -04:00
netfilter netfilter: nf_tproxy: fix possible non-linear access to transport header 2018-07-06 14:32:44 +02:00
af_inet.c Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
ah4.c net: use -ENOSPC for transient busy indication 2017-11-03 22:11:17 +08:00
arp.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
cipso_ipv4.c tcp/dccp: fix ireq->opt races 2017-10-21 01:33:19 +01:00
datagram.c
devinet.c net/ipv4: Add support for specifying metric of connected routes 2018-05-29 10:12:45 -04:00
esp4_offload.c esp: check the NETIF_F_HW_ESP_TX_CSUM bit before segmenting 2018-02-27 10:46:01 +01:00
esp4.c esp4: remove redundant initialization of pointer esph 2018-02-13 13:59:03 +01:00
fib_frontend.c net/ipv4: Set oif in fib_compute_spec_dst 2018-07-08 10:54:58 +09:00
fib_lookup.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fib_notifier.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
fib_rules.c net: fib_rules: add extack support 2018-04-23 10:21:24 -04:00
fib_semantics.c net: metrics: add proper netlink validation 2018-06-05 12:29:43 -04:00
fib_trie.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
fou.c net: fix use-after-free in GRO with ESP 2018-07-02 20:34:04 +09:00
gre_demux.c
gre_offload.c net: fix use-after-free in GRO with ESP 2018-07-02 20:34:04 +09:00
icmp.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
igmp.c ipv4/igmp: init group mode as INCLUDE when join source group 2018-07-16 11:20:06 -07:00
inet_connection_sock.c net: ipv4: remove define INET_CSK_DEBUG and unnecessary EXPORT_SYMBOL 2018-05-10 17:43:55 -04:00
inet_diag.c sock_diag: request _diag module only when the family or proto has been registered 2018-03-12 11:03:42 -04:00
inet_fragment.c ipfrag: really prevent allocation on netns exit 2018-07-08 13:05:33 +09:00
inet_hashtables.c net/tcp: Fix socket lookups with SO_BINDTODEVICE 2018-06-20 08:03:06 +09:00
inet_timewait_sock.c soreuseport: initialise timewait reuseport field 2018-04-07 22:32:32 -04:00
inetpeer.c inetpeer: fix uninit-value in inet_getpeer 2018-04-09 10:57:35 -04:00
ip_forward.c net: rename skb_gso_validate_mtu -> skb_gso_validate_network_len 2018-03-04 17:49:17 -05:00
ip_fragment.c inet: frags: fix ip6frag_low_thresh boundary 2018-04-04 12:04:59 -04:00
ip_gre.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-05-21 16:01:54 -04:00
ip_input.c net: Make ip_ra_chain per struct net 2018-03-22 15:12:56 -04:00
ip_options.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
ip_output.c ip: limit use of gso_size to udp 2018-06-20 14:41:04 +09:00
ip_sockglue.c ipv4/igmp: init group mode as INCLUDE when join source group 2018-07-16 11:20:06 -07:00
ip_tunnel_core.c net/ipv4: Update ip_tunnel_metadata_cnt static key to modern api 2018-05-10 15:13:33 -04:00
ip_tunnel.c ip_tunnel: Fix name string concatenate in __ip_tunnel_create() 2018-06-07 16:27:16 -04:00
ip_vti.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
ipcomp.c
ipconfig.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
ipip.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
ipmr_base.c ipmr: fix error path when ipmr_new_table fails 2018-06-05 12:26:41 -04:00
ipmr.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
Kconfig ipmr,ipmr6: Define a uniform vif_device 2018-03-01 13:13:23 -05:00
Makefile ipv4: support sport, dport and ip_proto in RTM_GETROUTE 2018-05-23 15:14:12 -04:00
metrics.c net: metrics: add proper netlink validation 2018-06-05 12:29:43 -04:00
netfilter.c netfilter: remove struct nf_afinfo and its helper functions 2018-01-08 18:11:02 +01:00
netlink.c ipv4: support sport, dport and ip_proto in RTM_GETROUTE 2018-05-23 15:14:12 -04:00
ping.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
proc.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
protocol.c
raw_diag.c net: ipv6: add second dif to raw socket lookups 2017-08-07 11:39:22 -07:00
raw.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
route.c treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
syncookies.c net/ipv4: disable SMC TCP option with SYN Cookies 2018-03-25 20:53:54 -04:00
sysctl_net_ipv4.c ipv4: Return EINVAL when ping_group_range sysctl doesn't map to user ns 2018-07-06 11:51:18 +09:00
tcp_bbr.c tcp_bbr: fix to zero idle_restart only upon S/ACKed data 2018-05-02 11:12:32 -04:00
tcp_bic.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp_cdg.c tcp: cdg: make struct tcp_cdg static 2017-10-16 21:24:25 +01:00
tcp_cong.c tcp: Namespace-ify sysctl_tcp_default_congestion_control 2017-11-15 14:09:52 +09:00
tcp_cubic.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp_dctcp.c tcp: do not delay ACK in DCTCP upon CE status change 2018-07-20 14:32:23 -07:00
tcp_diag.c net: sock: replace sk_state_load with inet_sk_state_load and remove sk_state_store 2017-12-20 14:00:25 -05:00
tcp_fastopen.c tcp: pause Fast Open globally after third consecutive timeout 2017-12-13 15:51:12 -05:00
tcp_highspeed.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp_htcp.c
tcp_hybla.c
tcp_illinois.c net/tcp/illinois: replace broken algorithm reference link 2018-02-28 12:03:47 -05:00
tcp_input.c tcp: do not delay ACK in DCTCP upon CE status change 2018-07-20 14:32:23 -07:00
tcp_ipv4.c tcp: fix sequence numbers for repaired sockets re-using TIME-WAIT sockets 2018-07-12 14:33:45 -07:00
tcp_lp.c
tcp_metrics.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
tcp_minisocks.c net-tcp: remove useless tw_timeout field 2018-06-05 10:45:24 -04:00
tcp_nv.c tcp_nv: fix potential integer overflow in tcpnv_acked 2018-01-31 10:26:30 -05:00
tcp_offload.c tcp: Do not reload skb pointer after skb_gro_receive(). 2018-06-11 20:00:56 -07:00
tcp_output.c tcp: do not cancel delay-AcK on DCTCP special ACK 2018-07-20 14:32:23 -07:00
tcp_rate.c tcp: invalidate rate samples during SACK reneging 2017-12-08 10:07:02 -05:00
tcp_recovery.c tcp: tcp_rack_reo_wnd() can be static 2018-05-18 13:28:40 -04:00
tcp_scalable.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp_timer.c tcp: add SACK compression 2018-05-18 11:40:27 -04:00
tcp_ulp.c net: add a UID to use for ULP socket assignment 2018-02-06 11:39:31 +01:00
tcp_vegas.c tcp: fix under-evaluated ssthresh in TCP Vegas 2017-09-29 06:07:00 +01:00
tcp_vegas.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
tcp_veno.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp_westwood.c tcp: Revert "tcp: remove CA_ACK_SLOWPATH" 2017-08-30 11:20:08 -07:00
tcp_yeah.c tcp: consolidate congestion control undo functions 2017-08-06 21:25:10 -07:00
tcp.c tcp: identify cryptic messages as TCP seq # bugs 2018-07-18 15:26:33 -07:00
tunnel4.c inet: whitespace cleanup 2018-02-28 11:43:28 -05:00
udp_diag.c udp: fix rx queue len reported by diag and proc interface 2018-06-08 19:55:15 -04:00
udp_impl.h License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
udp_offload.c net: fix use-after-free in GRO with ESP 2018-07-02 20:34:04 +09:00
udp_tunnel.c
udp.c Revert changes to convert to ->poll_mask() and aio IOCB_CMD_POLL 2018-06-28 10:40:47 -07:00
udplite.c proc: introduce proc_create_net{,_data} 2018-05-16 07:24:30 +02:00
xfrm4_input.c xfrm: Reinject transport-mode packets through tasklet 2017-12-19 08:23:21 +01:00
xfrm4_mode_beet.c
xfrm4_mode_transport.c
xfrm4_mode_tunnel.c xfrm: Verify MAC header exists before overwriting eth_hdr(skb)->h_proto 2018-03-07 10:54:29 +01:00
xfrm4_output.c net: xfrm: use skb_gso_validate_network_len() to check gso sizes 2018-03-04 17:49:17 -05:00
xfrm4_policy.c net: Drop pernet_operations::async 2018-03-27 13:18:09 -04:00
xfrm4_protocol.c
xfrm4_state.c License cleanup: add SPDX GPL-2.0 license identifier to files with no license 2017-11-02 11:10:55 +01:00
xfrm4_tunnel.c