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3d2af9cce3
linux/net/ipv4
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Neal Cardwell 3d2af9cce3 tcp: fix indefinite deferral of RTO with SACK reneging 
This commit fixes a bug that can cause a TCP data sender to repeatedly
defer RTOs when encountering SACK reneging.

The bug is that when we're in fast recovery in a scenario with SACK
reneging, every time we get an ACK we call tcp_check_sack_reneging()
and it can note the apparent SACK reneging and rearm the RTO timer for
srtt/2 into the future. In some SACK reneging scenarios that can
happen repeatedly until the receive window fills up, at which point
the sender can't send any more, the ACKs stop arriving, and the RTO
fires at srtt/2 after the last ACK. But that can take far too long
(O(10 secs)), since the connection is stuck in fast recovery with a
low cwnd that cannot grow beyond ssthresh, even if more bandwidth is
available.

This fix changes the logic in tcp_check_sack_reneging() to only rearm
the RTO timer if data is cumulatively ACKed, indicating forward
progress. This avoids this kind of nearly infinite loop of RTO timer
re-arming. In addition, this meets the goals of
tcp_check_sack_reneging() in handling Windows TCP behavior that looks
temporarily like SACK reneging but is not really.

Many thanks to Jakub Kicinski and Neil Spring, who reported this issue
and provided critical packet traces that enabled root-causing this
issue. Also, many thanks to Jakub Kicinski for testing this fix.

Fixes: 5ae344c949 ("tcp: reduce spurious retransmits due to transient SACK reneging")
Reported-by: Jakub Kicinski <kuba@kernel.org>
Reported-by: Neil Spring <ntspring@fb.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Tested-by: Jakub Kicinski <kuba@kernel.org>
Link: https://lore.kernel.org/r/20221021170821.1093930-1-ncardwell.kernel@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
2022-10-24 10:34:48 -07:00
..
bpfilter net: Revert "net: optimize the sockptr_t for unified kernel/user address spaces" 2020-08-10 12:06:44 -07:00
netfilter netfilter: rpfilter/fib: Set ->flowic_uid correctly for user namespaces. 2022-10-19 08:46:48 +02:00
af_inet.c ipv6: Fix data races around sk->sk_prot. 2022-10-12 17:50:37 -07:00
ah4.c xfrm: ah: add extack to ah_init_state, ah6_init_state 2022-09-29 07:17:59 +02:00
arp.c ipv4: move from strlcpy with unused retval to strscpy 2022-08-22 17:59:37 -07:00
bpf_tcp_ca.c bpf: Use 0 instead of NOT_INIT for btf_struct_access() writes 2022-09-10 17:27:32 -07:00
cipso_ipv4.c cipso: Fix data-races around sysctl. 2022-07-08 12:10:33 +01:00
datagram.c Networking fixes for 6.1-rc2, including fixes from netfilter 2022-10-20 17:24:59 -07:00
devinet.c net: Fix data-races around sysctl_devconf_inherit_init_net. 2022-08-24 13:46:58 +01:00
esp4_offload.c esp: choose the correct inner protocol for GSO on inter address family tunnels 2022-08-29 10:20:58 +02:00
esp4.c Merge branch 'master' of git://git.kernel.org/pub/scm/linux/kernel/git/klassert/ipsec-next 2022-10-03 07:52:13 +01:00
fib_frontend.c ip: fix triggering of 'icmp redirect' 2022-08-31 19:50:36 -07:00
fib_lookup.h Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-02-17 11:44:20 -08:00
fib_notifier.c net: ipv4: remove superfluous header files from fib_notifier.c 2021-09-28 17:32:56 -07:00
fib_rules.c ipv4: remove unnecessary type castings 2022-04-30 15:12:58 +01:00
fib_semantics.c ipv4: Handle attempt to delete multipath route when fib_info contains an nh reference 2022-10-07 08:47:08 +01:00
fib_trie.c ipv4: Fix data-races around sysctl_fib_notify_on_flag_change. 2022-07-25 12:42:10 +01:00
fou.c genetlink: start to validate reserved header bytes 2022-08-29 12:47:15 +01:00
gre_demux.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
gre_offload.c net: gro: skb_gro_header helper function 2022-08-25 10:33:21 +02:00
icmp.c ip: Fix data-races around sysctl_ip_no_pmtu_disc. 2022-07-15 11:49:55 +01:00
igmp.c treewide: use prandom_u32_max() when possible, part 1 2022-10-11 17:42:55 -06:00
inet_connection_sock.c treewide: use prandom_u32_max() when possible, part 1 2022-10-11 17:42:55 -06:00
inet_diag.c net: inet: Retire port only listening_hash 2022-05-12 16:52:18 -07:00
inet_fragment.c ipv4: remove unnecessary type castings 2022-04-30 15:12:58 +01:00
inet_hashtables.c treewide: use prandom_u32_max() when possible, part 1 2022-10-11 17:42:55 -06:00
inet_timewait_sock.c tcp: Clean up kernel listener's reqsk in inet_twsk_purge() 2022-10-13 09:33:16 -07:00
inetpeer.c inetpeer: Fix data-races around sysctl. 2022-07-08 12:10:33 +01:00
ip_forward.c ip: Fix data-races around sysctl_ip_fwd_update_priority. 2022-07-15 11:49:55 +01:00
ip_fragment.c net: ip: Handle delivery_time in ip defrag 2022-03-03 14:38:48 +00:00
ip_gre.c ip_tunnel: Respect tunnel key's "flow_flags" in IP tunnels 2022-08-18 21:18:28 +02:00
ip_input.c tcp/udp: Make early_demux back namespacified. 2022-07-15 18:50:35 -07:00
ip_options.c ipv4: drop fragmentation code from ip_options_build() 2022-01-29 17:53:07 +00:00
ip_output.c treewide: use get_random_{u8,u16}() when possible, part 1 2022-10-11 17:42:58 -06:00
ip_sockglue.c Merge https://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf-next 2022-09-06 23:21:18 +02:00
ip_tunnel_core.c net: Add helper function to parse netlink msg of ip_tunnel_parm 2022-10-03 07:59:06 +01:00
ip_tunnel.c ip_tunnel: Respect tunnel key's "flow_flags" in IP tunnels 2022-08-18 21:18:28 +02:00
ip_vti.c ip: use dev_addr_set() in tunnels 2021-10-13 09:41:37 -07:00
ipcomp.c xfrm: ipcomp: add extack to ipcomp{4,6}_init_state 2022-09-29 07:18:00 +02:00
ipconfig.c Driver core / kernfs changes for 6.0-rc1 2022-08-04 11:31:20 -07:00
ipip.c net: Add helper function to parse netlink msg of ip_tunnel_parm 2022-10-03 07:59:06 +01:00
ipmr_base.c ipmr: adopt rcu_read_lock() in mr_dump() 2022-06-24 11:34:38 +01:00
ipmr.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-09-22 13:02:10 -07:00
Kconfig fou: Remove XRFM from NET_FOU Kconfig 2022-04-12 14:56:33 -07:00
Makefile bpf: Clean up sockmap related Kconfigs 2021-02-26 12:28:03 -08:00
metrics.c treewide: rename nla_strlcpy to nla_strscpy. 2020-11-16 08:08:54 -08:00
netfilter.c netfilter: Use l3mdev flow key when re-routing mangled packets 2022-05-16 13:03:29 +02:00
netlink.c
nexthop.c nexthop: Fix data-races around nexthop_compat_mode. 2022-07-13 12:56:50 +01:00
ping.c inet: ping: fix recent breakage 2022-10-12 09:10:02 +01:00
proc.c tcp: Don't allocate tcp_death_row outside of struct netns_ipv4. 2022-09-20 10:21:49 -07:00
protocol.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
raw_diag.c raw: complete rcu conversion 2022-06-21 11:38:29 +02:00
raw.c raw: fix a typo in raw_icmp_error() 2022-06-24 22:48:33 -07:00
route.c treewide: use get_random_bytes() when possible 2022-10-11 17:42:58 -06:00
syncookies.c tcp: Fix data-races around sysctl knobs related to SYN option. 2022-07-20 10:14:49 +01:00
sysctl_net_ipv4.c tcp: Introduce optional per-netns ehash. 2022-09-20 10:21:50 -07:00
tcp_bbr.c bpf: Switch to new kfunc flags infrastructure 2022-07-21 20:59:42 -07:00
tcp_bic.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_bpf.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-06-23 12:33:24 -07:00
tcp_cdg.c Random number generator fixes for Linux 6.1-rc1. 2022-10-16 15:27:07 -07:00
tcp_cong.c tcp: Add tracepoint for tcp_set_ca_state 2022-04-07 20:33:15 -07:00
tcp_cubic.c bpf: Switch to new kfunc flags infrastructure 2022-07-21 20:59:42 -07:00
tcp_dctcp.c bpf: Switch to new kfunc flags infrastructure 2022-07-21 20:59:42 -07:00
tcp_dctcp.h
tcp_diag.c tcp: Access &tcp_hashinfo via net. 2022-09-20 10:21:49 -07:00
tcp_fastopen.c tcp: Make SYN ACK RTO tunable by BPF programs with TFO 2022-08-17 10:19:22 +01:00
tcp_highspeed.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_htcp.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_hybla.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_illinois.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_input.c tcp: fix indefinite deferral of RTO with SACK reneging 2022-10-24 10:34:48 -07:00
tcp_ipv4.c tcp: fix a signed-integer-overflow bug in tcp_add_backlog() 2022-10-24 13:04:25 +01:00
tcp_lp.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_metrics.c genetlink: start to validate reserved header bytes 2022-08-29 12:47:15 +01:00
tcp_minisocks.c tcp: Clean up kernel listener's reqsk in inet_twsk_purge() 2022-10-13 09:33:16 -07:00
tcp_nv.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_offload.c gro: add support of (hw)gro packets to gro stack 2022-10-03 12:38:34 +01:00
tcp_output.c tcp: fix tcp_cwnd_validate() to not forget is_cwnd_limited 2022-09-30 12:37:45 +01:00
tcp_rate.c Merge git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net 2022-04-28 13:02:01 -07:00
tcp_recovery.c tcp: Fix data-races around sysctl_tcp_recovery. 2022-07-20 10:14:50 +01:00
tcp_scalable.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_timer.c tcp: Make SYN ACK RTO tunable by BPF programs with TFO 2022-08-17 10:19:22 +01:00
tcp_ulp.c
tcp_vegas.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_vegas.h
tcp_veno.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_westwood.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp_yeah.c tcp: add accessors to read/set tp->snd_cwnd 2022-04-06 12:05:41 -07:00
tcp.c tcp: Fix data races around icsk->icsk_af_ops. 2022-10-12 17:50:37 -07:00
tunnel4.c net: Remove the member netns_ok 2021-05-17 15:29:35 -07:00
udp_bpf.c net: remove noblock parameter from recvmsg() entities 2022-04-12 15:00:25 +02:00
udp_diag.c net: Use nlmsg_unicast() instead of netlink_unicast() 2021-07-13 09:28:29 -07:00
udp_impl.h net: remove noblock parameter from recvmsg() entities 2022-04-12 15:00:25 +02:00
udp_offload.c gro: remove rcu_read_lock/rcu_read_unlock from gro_complete handlers 2021-11-24 17:21:42 -08:00
udp_tunnel_core.c rxrpc: Fix ICMP/ICMP6 error handling 2022-09-01 11:42:12 +01:00
udp_tunnel_nic.c udp_tunnel: Fix end of loop test in udp_tunnel_nic_unregister() 2022-02-23 12:35:00 +00:00
udp_tunnel_stub.c
udp.c Networking fixes for 6.1-rc2, including fixes from netfilter 2022-10-20 17:24:59 -07:00
udplite.c tcp/udp: Call inet6_destroy_sock() in IPv6 sk->sk_destruct(). 2022-10-12 17:50:37 -07:00
xfrm4_input.c
xfrm4_output.c
xfrm4_policy.c net: rename reference+tracking helpers 2022-06-09 21:52:55 -07:00
xfrm4_protocol.c net: xfrm: unexport __init-annotated xfrm4_protocol_init() 2022-06-08 10:10:13 -07:00
xfrm4_state.c
xfrm4_tunnel.c xfrm: tunnel: add extack to ipip_init_state, xfrm6_tunnel_init_state 2022-09-29 07:18:00 +02:00