linux-egoist-arch/0042-net-tcp_bbr-v3-ensure-ECN-enabled-BBR-flows-set-ECT-.patch at main · love4taylor/linux-egoist-arch · GitHub

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From d884ab11ebb699e41bc201cba6b469d3b682a3b7 Mon Sep 17 00:00:00 2001
From: Adithya Abraham Philip <abrahamphilip@google.com>
Date: Fri, 11 Jun 2021 21:56:10 +0000
Subject: [PATCH 17/18] 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 <abrahamphilip@google.com>
Signed-off-by: Neal Cardwell <ncardwell@google.com>
Change-Id: I8b048eaab35e136fe6501ef6cd89fd9faa15e6d2
Signed-off-by: Alexandre Frade <kernel@xanmod.org>
---
 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 7db5d4df2a52..4d4d323e9d7b 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -373,6 +373,7 @@ 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 4fec37e8f900..f4f477a69917 100644
--- a/net/ipv4/tcp_bbr.c
+++ b/net/ipv4/tcp_bbr.c
@@ -2151,6 +2151,9 @@ __bpf_kfunc 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 1e8e9dc5fd20..5f8e18e9a3ee 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -386,7 +386,8 @@ 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);
 		}
--
2.39.2