forked from Minki/linux
08abdffa1c
With TLP, the peer may reply to a probe with an
ACK+D-SACK, with ack value set to tlp_high_seq. In the current code,
such ACK+DSACK will be missed and only at next, higher ack will the TLP
episode be considered done. Since the DSACK is not present anymore,
this will cost a cwnd reduction.
This patch ensures that this scenario does not cause a cwnd reduction, since
receiving an ACK+DSACK indicates that both the initial segment and the probe
have been received by the peer.
The following packetdrill test, from Neal Cardwell, validates this patch:
// Establish a connection.
0 socket(..., SOCK_STREAM, IPPROTO_TCP) = 3
+0 setsockopt(3, SOL_SOCKET, SO_REUSEADDR, [1], 4) = 0
+0 bind(3, ..., ...) = 0
+0 listen(3, 1) = 0
+0 < S 0:0(0) win 32792 <mss 1000,sackOK,nop,nop,nop,wscale 7>
+0 > S. 0:0(0) ack 1 <mss 1460,nop,nop,sackOK,nop,wscale 6>
+.020 < . 1:1(0) ack 1 win 257
+0 accept(3, ..., ...) = 4
// Send 1 packet.
+0 write(4, ..., 1000) = 1000
+0 > P. 1:1001(1000) ack 1
// Loss probe retransmission.
// packets_out == 1 => schedule PTO in max(2*RTT, 1.5*RTT + 200ms)
// In this case, this means: 1.5*RTT + 200ms = 230ms
+.230 > P. 1:1001(1000) ack 1
+0 %{ assert tcpi_snd_cwnd == 10 }%
// Receiver ACKs at tlp_high_seq with a DSACK,
// indicating they received the original packet and probe.
+.020 < . 1:1(0) ack 1001 win 257 <sack 1:1001,nop,nop>
+0 %{ assert tcpi_snd_cwnd == 10 }%
// Send another packet.
+0 write(4, ..., 1000) = 1000
+0 > P. 1001:2001(1000) ack 1
// Receiver ACKs above tlp_high_seq, which should end the TLP episode
// if we haven't already. We should not reduce cwnd.
+.020 < . 1:1(0) ack 2001 win 257
+0 %{ assert tcpi_snd_cwnd == 10, tcpi_snd_cwnd }%
Credits:
-Gregory helped in finding that tcp_process_tlp_ack was where the cwnd
got reduced in our MPTCP tests.
-Neal wrote the packetdrill test above
-Yuchung reworked the patch to make it more readable.
Cc: Gregory Detal <gregory.detal@uclouvain.be>
Cc: Nandita Dukkipati <nanditad@google.com>
Tested-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Yuchung Cheng <ycheng@google.com>
Reviewed-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: Sébastien Barré <sebastien.barre@uclouvain.be>
Acked-by: Eric Dumazet <edumazet@google.com>
Acked-by: Neal Cardwell <ncardwell@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
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|---|---|---|
| .. | ||
| netfilter | ||
| af_inet.c | ||
| ah4.c | ||
| arp.c | ||
| cipso_ipv4.c | ||
| datagram.c | ||
| devinet.c | ||
| esp4.c | ||
| fib_frontend.c | ||
| fib_lookup.h | ||
| fib_rules.c | ||
| fib_semantics.c | ||
| fib_trie.c | ||
| fou.c | ||
| geneve.c | ||
| gre_demux.c | ||
| gre_offload.c | ||
| icmp.c | ||
| igmp.c | ||
| inet_connection_sock.c | ||
| inet_diag.c | ||
| inet_fragment.c | ||
| inet_hashtables.c | ||
| inet_lro.c | ||
| inet_timewait_sock.c | ||
| inetpeer.c | ||
| ip_forward.c | ||
| ip_fragment.c | ||
| ip_gre.c | ||
| ip_input.c | ||
| ip_options.c | ||
| ip_output.c | ||
| ip_sockglue.c | ||
| ip_tunnel_core.c | ||
| ip_tunnel.c | ||
| ip_vti.c | ||
| ipcomp.c | ||
| ipconfig.c | ||
| ipip.c | ||
| ipmr.c | ||
| Kconfig | ||
| Makefile | ||
| netfilter.c | ||
| ping.c | ||
| proc.c | ||
| protocol.c | ||
| raw.c | ||
| route.c | ||
| syncookies.c | ||
| sysctl_net_ipv4.c | ||
| tcp_bic.c | ||
| tcp_cong.c | ||
| tcp_cubic.c | ||
| tcp_dctcp.c | ||
| tcp_diag.c | ||
| tcp_fastopen.c | ||
| tcp_highspeed.c | ||
| tcp_htcp.c | ||
| tcp_hybla.c | ||
| tcp_illinois.c | ||
| tcp_input.c | ||
| tcp_ipv4.c | ||
| tcp_lp.c | ||
| tcp_memcontrol.c | ||
| tcp_metrics.c | ||
| tcp_minisocks.c | ||
| tcp_offload.c | ||
| tcp_output.c | ||
| tcp_probe.c | ||
| tcp_scalable.c | ||
| tcp_timer.c | ||
| tcp_vegas.c | ||
| tcp_vegas.h | ||
| tcp_veno.c | ||
| tcp_westwood.c | ||
| tcp_yeah.c | ||
| tcp.c | ||
| tunnel4.c | ||
| udp_diag.c | ||
| udp_impl.h | ||
| udp_offload.c | ||
| udp_tunnel.c | ||
| udp.c | ||
| udplite.c | ||
| xfrm4_input.c | ||
| xfrm4_mode_beet.c | ||
| xfrm4_mode_transport.c | ||
| xfrm4_mode_tunnel.c | ||
| xfrm4_output.c | ||
| xfrm4_policy.c | ||
| xfrm4_protocol.c | ||
| xfrm4_state.c | ||
| xfrm4_tunnel.c | ||