From 9ea1c2d1c8582e4271d1c93492ca00342a8436d1 Mon Sep 17 00:00:00 2001 From: Adithya Abraham Philip Date: Fri, 11 Jun 2021 21:56:10 +0000 Subject: [PATCH] net-tcp_bbr: v3: ensure ECN-enabled BBR flows set ECT on retransmits Adds a new flag TCP_ECN_ECT_PERMANENT that is used by CCAs to indicate that retransmitted packets and pure ACKs must have the ECT bit set. This is necessary for BBR, which when using ECN expects ECT to be set even on retransmitted packets and ACKs. Previous to this addition of TCP_ECN_ECT_PERMANENT, CCAs which can use ECN but don't "need" it did not have a way to indicate that ECT should be set on retransmissions/ACKs. Signed-off-by: Adithya Abraham Philip Signed-off-by: Neal Cardwell Change-Id: I8b048eaab35e136fe6501ef6cd89fd9faa15e6d2 Signed-off-by: Alexandre Frade --- include/net/tcp.h | 1 + net/ipv4/tcp_bbr.c | 3 +++ net/ipv4/tcp_output.c | 3 ++- 3 files changed, 6 insertions(+), 1 deletion(-) diff --git a/include/net/tcp.h b/include/net/tcp.h index 0c717d4687fc9..09f52c1358976 100644 --- a/include/net/tcp.h +++ b/include/net/tcp.h @@ -376,6 +376,7 @@ static inline void tcp_dec_quickack_mode(struct sock *sk, #define TCP_ECN_DEMAND_CWR 4 #define TCP_ECN_SEEN 8 #define TCP_ECN_LOW 16 +#define TCP_ECN_ECT_PERMANENT 32 enum tcp_tw_status { TCP_TW_SUCCESS = 0, diff --git a/net/ipv4/tcp_bbr.c b/net/ipv4/tcp_bbr.c index 1ce01643709c5..ff3bfff15099d 100644 --- a/net/ipv4/tcp_bbr.c +++ b/net/ipv4/tcp_bbr.c @@ -2151,6 +2151,9 @@ static void bbr_init(struct sock *sk) bbr->plb.pause_until = 0; tp->fast_ack_mode = bbr_fast_ack_mode ? 1 : 0; + + if (bbr_can_use_ecn(sk)) + tp->ecn_flags |= TCP_ECN_ECT_PERMANENT; } /* BBR marks the current round trip as a loss round. */ diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c index 0b404e881549d..ae253a0187689 100644 --- a/net/ipv4/tcp_output.c +++ b/net/ipv4/tcp_output.c @@ -381,7 +381,8 @@ static void tcp_ecn_send(struct sock *sk, struct sk_buff *skb, th->cwr = 1; skb_shinfo(skb)->gso_type |= SKB_GSO_TCP_ECN; } - } else if (!tcp_ca_needs_ecn(sk)) { + } else if (!(tp->ecn_flags & TCP_ECN_ECT_PERMANENT) && + !tcp_ca_needs_ecn(sk)) { /* ACK or retransmitted segment: clear ECT|CE */ INET_ECN_dontxmit(sk); }