diff mbox series

[net-next,40/44] tcp: accecn: stop sending AccECN option when loss ACK with AccECN option

Message ID 20241015102940.26157-41-chia-yu.chang@nokia-bell-labs.com (mailing list archive)
State Changes Requested
Delegated to: Netdev Maintainers
Headers show
Series DualPI2, Accurate ECN, TCP Prague patch series | expand

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Context Check Description
netdev/series_format fail Series longer than 15 patches
netdev/tree_selection success Clearly marked for net-next, async
netdev/ynl success Generated files up to date; no warnings/errors; no diff in generated;
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16 this patch: 16
netdev/build_tools success Errors and warnings before: 0 (+1) this patch: 0 (+1)
netdev/cc_maintainers fail 4 maintainers not CCed: edumazet@google.com pabeni@redhat.com dsahern@kernel.org kuba@kernel.org
netdev/build_clang success Errors and warnings before: 36 this patch: 36
netdev/verify_signedoff success Signed-off-by tag matches author and committer
netdev/deprecated_api success None detected
netdev/check_selftest success No net selftest shell script
netdev/verify_fixes success No Fixes tag
netdev/build_allmodconfig_warn success Errors and warnings before: 2068 this patch: 2068
netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 49 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
netdev/kdoc success Errors and warnings before: 6 this patch: 6
netdev/source_inline success Was 0 now: 0

Commit Message

Chia-Yu Chang (Nokia) Oct. 15, 2024, 10:29 a.m. UTC 
From: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>

Detect spurious retransmission of a previously sent ACK carrying the
AccECN option after the second retransmission. Since this might be caused
by the middlebox dropping ACK with options it does not recognize, disable
the sending of the AccECN option in all subsequent ACKs.

Based on specification:
  https://tools.ietf.org/id/draft-ietf-tcpm-accurate-ecn-28.txt

3.2.3.2.2. Testing for Loss of Packets Carrying the AccECN Option -
If a middlebox is dropping packets with options it does not recognize,
a host that is sending little or no data but mostly pure ACKs will not
inherently detect such losses. Such a host MAY detect loss of ACKs
carrying the AccECN Option by detecting whether the acknowledged data
always reappears as a retransmission. In such cases, the host SHOULD
disable the sending of the AccECN Option for this half-connection.

Signed-off-by: Chia-Yu Chang <chia-yu.chang@nokia-bell-labs.com>
---
 include/linux/tcp.h   | 3 ++-
 include/net/tcp.h     | 1 +
 net/ipv4/tcp_input.c  | 9 +++++++++
 net/ipv4/tcp_output.c | 3 +++
 4 files changed, 15 insertions(+), 1 deletion(-)
diff mbox series

Patch

diff --git a/include/linux/tcp.h b/include/linux/tcp.h
index 9dbfaa76d721..ecc9cfa7210f 100644
--- a/include/linux/tcp.h
+++ b/include/linux/tcp.h
@@ -304,7 +304,8 @@  struct tcp_sock {
 	u32	received_ce;	/* Like the above but for received CE marked packets */
 	u32	received_ecn_bytes[3];
 	u8	received_ce_pending:4, /* Not yet transmitted cnt of received_ce */
-		unused2:4;
+		accecn_opt_sent:1,/* Sent AccECN option in previous ACK */
+		unused2:3;
 	u8	accecn_minlen:2,/* Minimum length of AccECN option sent */
 		prev_ecnfield:2,/* ECN bits from the previous segment */
 		accecn_opt_demand:2,/* Demand AccECN option for n next ACKs */
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 4d055a54c645..ffb3971105b1 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1050,6 +1050,7 @@  static inline void tcp_accecn_init_counters(struct tcp_sock *tp)
 	tp->received_ce_pending = 0;
 	__tcp_accecn_init_bytes_counters(tp->received_ecn_bytes);
 	__tcp_accecn_init_bytes_counters(tp->delivered_ecn_bytes);
+	tp->accecn_opt_sent = 0;
 	tp->accecn_minlen = 0;
 	tp->accecn_opt_demand = 0;
 	tp->estimate_ecnfield = 0;
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 0786e7127064..74d66c075d6e 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -5098,6 +5098,7 @@  static void tcp_dsack_extend(struct sock *sk, u32 seq, u32 end_seq)
 
 static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
 {
+	struct tcp_sock *tp = tcp_sk(sk);
 	/* When the ACK path fails or drops most ACKs, the sender would
 	 * timeout and spuriously retransmit the same segment repeatedly.
 	 * If it seems our ACKs are not reaching the other side,
@@ -5117,6 +5118,14 @@  static void tcp_rcv_spurious_retrans(struct sock *sk, const struct sk_buff *skb)
 	/* Save last flowlabel after a spurious retrans. */
 	tcp_save_lrcv_flowlabel(sk, skb);
 #endif
+	/* Check DSACK info to detect that the previous ACK carrying the
+	 * AccECN option was lost after the second retransmision, and then
+	 * stop sending AccECN option in all subsequent ACKs.
+	 */
+	if (tcp_ecn_mode_accecn(tp) &&
+	    TCP_SKB_CB(skb)->seq == tp->duplicate_sack[0].start_seq &&
+	    tp->accecn_opt_sent)
+		tcp_accecn_fail_mode_set(tp, TCP_ACCECN_OPT_FAIL_SEND);
 }
 
 static void tcp_send_dupack(struct sock *sk, const struct sk_buff *skb)
diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
index 74ba08a33434..4e00ebf6bd42 100644
--- a/net/ipv4/tcp_output.c
+++ b/net/ipv4/tcp_output.c
@@ -804,9 +804,12 @@  static void tcp_options_write(struct tcphdr *th, struct tcp_sock *tp,
 		if (tp) {
 			tp->accecn_minlen = 0;
 			tp->accecn_opt_tstamp = tp->tcp_mstamp;
+			tp->accecn_opt_sent = 1;
 			if (tp->accecn_opt_demand)
 				tp->accecn_opt_demand--;
 		}
+	} else if (tp) {
+		tp->accecn_opt_sent = 0;
 	}
 
 	if (unlikely(OPTION_SACK_ADVERTISE & options)) {