From 43e59a05c78564807876ae8529c71b261e8cceff Mon Sep 17 00:00:00 2001 From: Jianfeng Wang Date: Tue, 16 Jun 2020 17:41:19 +0000 Subject: [PATCH 13/19] net-tcp_bbr: v2: inform CC module of losses repaired by TLP probe Before this commit, when there is a packet loss that creates a sequence hole that is filled by a TLP loss probe, then tcp_process_tlp_ack() only informs the congestion control (CC) module via a back-to-back entry and exit of CWR. But some congestion control modules (e.g. BBR) do not respond to CWR events. This commit adds a new CA event with which the core TCP stack notifies the CC module when a loss is repaired by a TLP. This will allow CC modules that do not use the CWR mechanism to have a custom handler for such TLP recoveries. Effort: net-tcp_bbr Change-Id: Ieba72332b401b329bff5a641d2b2043a3fb8f632 Signed-off-by: Alexandre Frade --- include/net/tcp.h | 1 + net/ipv4/tcp_input.c | 1 + 2 files changed, 2 insertions(+) --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -1115,6 +1115,7 @@ enum tcp_ca_event { CA_EVENT_LOSS, /* loss timeout */ CA_EVENT_ECN_NO_CE, /* ECT set, but not CE marked */ CA_EVENT_ECN_IS_CE, /* received CE marked IP packet */ + CA_EVENT_TLP_RECOVERY, /* a lost segment was repaired by TLP probe */ }; /* Information about inbound ACK, passed to cong_ops->in_ack_event() */ --- a/net/ipv4/tcp_input.c +++ b/net/ipv4/tcp_input.c @@ -3879,6 +3879,7 @@ static void tcp_process_tlp_ack(struct s /* ACK advances: there was a loss, so reduce cwnd. Reset * tlp_high_seq in tcp_init_cwnd_reduction() */ + tcp_ca_event(sk, CA_EVENT_TLP_RECOVERY); tcp_init_cwnd_reduction(sk); tcp_set_ca_state(sk, TCP_CA_CWR); tcp_end_cwnd_reduction(sk);