tcp: accecn: add tcpi_ecn_mode and tcpi_option2 in tcp_info

Add 2-bit tcpi_ecn_mode feild within tcp_info to indicate which ECN
mode is negotiated: ECN_MODE_DISABLED, ECN_MODE_RFC3168, ECN_MODE_ACCECN,
or ECN_MODE_PENDING. This is done by utilizing available bits from
tcpi_accecn_opt_seen (reduced from 16 bits to 2 bits) and
tcpi_accecn_fail_mode (reduced from 16 bits to 4 bits).

Also, an extra 24-bit tcpi_options2 field is identified to represent
newer options and connection features, as all 8 bits of tcpi_options
field have been used.

Signed-off-by: Chia-Yu Chang <[e-mail]>
Co-developed-by: Neal Cardwell <[e-mail]>
Signed-off-by: Neal Cardwell <[e-mail]>
Reviewed-by: Eric Dumazet <[e-mail]>
Link: https://patch.msgid.link/[e-mail]
Signed-off-by: Paolo Abeni <[e-mail]>

include/net/tcp_ecn.h

···
 	tp->ecn_flags &= ~TCP_ECN_QUEUE_CWR;
 }
 
-/* tp->accecn_fail_mode */
-#define TCP_ACCECN_ACE_FAIL_SEND	BIT(0)
-#define TCP_ACCECN_ACE_FAIL_RECV	BIT(1)
-#define TCP_ACCECN_OPT_FAIL_SEND	BIT(2)
-#define TCP_ACCECN_OPT_FAIL_RECV	BIT(3)
-
 static inline bool tcp_accecn_ace_fail_send(const struct tcp_sock *tp)
 {
 	return tp->accecn_fail_mode & TCP_ACCECN_ACE_FAIL_SEND;
···
 {
 	tp->accecn_fail_mode |= mode;
 }
-
-#define TCP_ACCECN_OPT_NOT_SEEN		0x0
-#define TCP_ACCECN_OPT_EMPTY_SEEN	0x1
-#define TCP_ACCECN_OPT_COUNTER_SEEN	0x2
-#define TCP_ACCECN_OPT_FAIL_SEEN	0x3
 
 static inline u8 tcp_accecn_ace(const struct tcphdr *th)
 {

include/uapi/linux/tcp.h

···
 #define TCPF_CA_Loss	(1<<TCP_CA_Loss)
 };
 
+/* Values for tcpi_ecn_mode after negotiation */
+#define TCPI_ECN_MODE_DISABLED		0x0
+#define TCPI_ECN_MODE_RFC3168		0x1
+#define TCPI_ECN_MODE_ACCECN		0x2
+#define TCPI_ECN_MODE_PENDING		0x3
+
+/* Values for accecn_opt_seen */
+#define TCP_ACCECN_OPT_NOT_SEEN		0x0
+#define TCP_ACCECN_OPT_EMPTY_SEEN	0x1
+#define TCP_ACCECN_OPT_COUNTER_SEEN	0x2
+#define TCP_ACCECN_OPT_FAIL_SEEN	0x3
+
+/* Values for accecn_fail_mode */
+#define TCP_ACCECN_ACE_FAIL_SEND	BIT(0)
+#define TCP_ACCECN_ACE_FAIL_RECV	BIT(1)
+#define TCP_ACCECN_OPT_FAIL_SEND	BIT(2)
+#define TCP_ACCECN_OPT_FAIL_RECV	BIT(3)
+
 struct tcp_info {
 	__u8	tcpi_state;
 	__u8	tcpi_ca_state;
···
 					 * in milliseconds, including any
 					 * unfinished recovery.
 					 */
-	__u32	tcpi_received_ce;    /* # of CE marks received */
+	__u32	tcpi_received_ce;    /* # of CE marked segments received */
 	__u32	tcpi_delivered_e1_bytes;  /* Accurate ECN byte counters */
 	__u32	tcpi_delivered_e0_bytes;
 	__u32	tcpi_delivered_ce_bytes;
 	__u32	tcpi_received_e1_bytes;
 	__u32	tcpi_received_e0_bytes;
 	__u32	tcpi_received_ce_bytes;
-	__u16	tcpi_accecn_fail_mode;
-	__u16	tcpi_accecn_opt_seen;
+	__u32	tcpi_ecn_mode:2,
+		tcpi_accecn_opt_seen:2,
+		tcpi_accecn_fail_mode:4,
+		tcpi_options2:24;
 };
 
 /* netlink attributes types for SCM_TIMESTAMPING_OPT_STATS */

net/ipv4/tcp.c

···
 	if (tp->rto_stamp)
 		info->tcpi_total_rto_time += tcp_clock_ms() - tp->rto_stamp;
 
+	if (tcp_ecn_disabled(tp))
+		info->tcpi_ecn_mode = TCPI_ECN_MODE_DISABLED;
+	else if (tcp_ecn_mode_rfc3168(tp))
+		info->tcpi_ecn_mode = TCPI_ECN_MODE_RFC3168;
+	else if (tcp_ecn_mode_accecn(tp))
+		info->tcpi_ecn_mode = TCPI_ECN_MODE_ACCECN;
+	else if (tcp_ecn_mode_pending(tp))
+		info->tcpi_ecn_mode = TCPI_ECN_MODE_PENDING;
 	info->tcpi_accecn_fail_mode = tp->accecn_fail_mode;
 	info->tcpi_accecn_opt_seen = tp->saw_accecn_opt;
 	info->tcpi_received_ce = tp->received_ce;