Merge branch 'tcp-support-rstreasons-in-the-passive-logic'

Jason Xing says:

====================
tcp: support rstreasons in the passive logic

In this series, I split all kinds of reasons into five part which,
I think, can be easily reviewed. I respectively implement corresponding
rstreasons in those functions. After this, we can trace the whole tcp
passive reset with clear reasons.
====================

Link: https://lore.kernel.org/r/20240510122502.27850-1-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>

Author: kuba-moo

include/net/rstreason.h

@@ -8,6 +8,15 @@
 #define DEFINE_RST_REASON(FN, FNe)	\
 	FN(NOT_SPECIFIED)		\
 	FN(NO_SOCKET)			\
+	FN(TCP_INVALID_ACK_SEQUENCE)	\
+	FN(TCP_RFC7323_PAWS)		\
+	FN(TCP_TOO_OLD_ACK)		\
+	FN(TCP_ACK_UNSENT_DATA)		\
+	FN(TCP_FLAGS)			\
+	FN(TCP_OLD_ACK)			\
+	FN(TCP_ABORT_ON_DATA)		\
+	FN(TCP_TIMEWAIT_SOCKET)		\
+	FN(INVALID_SYN)			\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -37,6 +46,44 @@ enum sk_rst_reason {
 	SK_RST_REASON_NOT_SPECIFIED,
 	/** @SK_RST_REASON_NO_SOCKET: no valid socket that can be used */
 	SK_RST_REASON_NO_SOCKET,
+	/**
+	 * @SK_RST_REASON_TCP_INVALID_ACK_SEQUENCE: Not acceptable ACK SEQ
+	 * field because ack sequence is not in the window between snd_una
+	 * and snd_nxt
+	 */
+	SK_RST_REASON_TCP_INVALID_ACK_SEQUENCE,
+	/**
+	 * @SK_RST_REASON_TCP_RFC7323_PAWS: PAWS check, corresponding to
+	 * LINUX_MIB_PAWSESTABREJECTED, LINUX_MIB_PAWSACTIVEREJECTED
+	 */
+	SK_RST_REASON_TCP_RFC7323_PAWS,
+	/** @SK_RST_REASON_TCP_TOO_OLD_ACK: TCP ACK is too old */
+	SK_RST_REASON_TCP_TOO_OLD_ACK,
+	/**
+	 * @SK_RST_REASON_TCP_ACK_UNSENT_DATA: TCP ACK for data we haven't
+	 * sent yet
+	 */
+	SK_RST_REASON_TCP_ACK_UNSENT_DATA,
+	/** @SK_RST_REASON_TCP_FLAGS: TCP flags invalid */
+	SK_RST_REASON_TCP_FLAGS,
+	/** @SK_RST_REASON_TCP_OLD_ACK: TCP ACK is old, but in window */
+	SK_RST_REASON_TCP_OLD_ACK,
+	/**
+	 * @SK_RST_REASON_TCP_ABORT_ON_DATA: abort on data
+	 * corresponding to LINUX_MIB_TCPABORTONDATA
+	 */
+	SK_RST_REASON_TCP_ABORT_ON_DATA,
+
+	/* Here start with the independent reasons */
+	/** @SK_RST_REASON_TCP_TIMEWAIT_SOCKET: happen on the timewait socket */
+	SK_RST_REASON_TCP_TIMEWAIT_SOCKET,
+	/**
+	 * @SK_RST_REASON_INVALID_SYN: receive bad syn packet
+	 * RFC 793 says if the state is not CLOSED/LISTEN/SYN-SENT then
+	 * "fourth, check the SYN bit,...If the SYN is in the window it is
+	 * an error, send a reset"
+	 */
+	SK_RST_REASON_INVALID_SYN,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
@@ -113,6 +160,20 @@ sk_rst_convert_drop_reason(enum skb_drop_reason reason)
 		return SK_RST_REASON_NOT_SPECIFIED;
 	case SKB_DROP_REASON_NO_SOCKET:
 		return SK_RST_REASON_NO_SOCKET;
+	case SKB_DROP_REASON_TCP_INVALID_ACK_SEQUENCE:
+		return SK_RST_REASON_TCP_INVALID_ACK_SEQUENCE;
+	case SKB_DROP_REASON_TCP_RFC7323_PAWS:
+		return SK_RST_REASON_TCP_RFC7323_PAWS;
+	case SKB_DROP_REASON_TCP_TOO_OLD_ACK:
+		return SK_RST_REASON_TCP_TOO_OLD_ACK;
+	case SKB_DROP_REASON_TCP_ACK_UNSENT_DATA:
+		return SK_RST_REASON_TCP_ACK_UNSENT_DATA;
+	case SKB_DROP_REASON_TCP_FLAGS:
+		return SK_RST_REASON_TCP_FLAGS;
+	case SKB_DROP_REASON_TCP_OLD_ACK:
+		return SK_RST_REASON_TCP_OLD_ACK;
+	case SKB_DROP_REASON_TCP_ABORT_ON_DATA:
+		return SK_RST_REASON_TCP_ABORT_ON_DATA;
 	default:
 		/* If we don't have our own corresponding reason */
 		return SK_RST_REASON_NOT_SPECIFIED;

net/ipv4/tcp_ipv4.c

@@ -2427,7 +2427,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
 		tcp_v4_timewait_ack(sk, skb);
 		break;
 	case TCP_TW_RST:
-		tcp_v4_send_reset(sk, skb, sk_rst_convert_drop_reason(drop_reason));
+		tcp_v4_send_reset(sk, skb, SK_RST_REASON_TCP_TIMEWAIT_SOCKET);
 		inet_twsk_deschedule_put(inet_twsk(sk));
 		goto discard_it;
 	case TCP_TW_SUCCESS:;

net/ipv4/tcp_minisocks.c

@@ -879,7 +879,7 @@ struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
 		 * avoid becoming vulnerable to outside attack aiming at
 		 * resetting legit local connections.
 		 */
-		req->rsk_ops->send_reset(sk, skb, SK_RST_REASON_NOT_SPECIFIED);
+		req->rsk_ops->send_reset(sk, skb, SK_RST_REASON_INVALID_SYN);
 	} else if (fastopen) { /* received a valid RST pkt */
 		reqsk_fastopen_remove(sk, req, true);
 		tcp_reset(sk, skb);

net/ipv6/tcp_ipv6.c

@@ -1999,7 +1999,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 		tcp_v6_timewait_ack(sk, skb);
 		break;
 	case TCP_TW_RST:
-		tcp_v6_send_reset(sk, skb, sk_rst_convert_drop_reason(drop_reason));
+		tcp_v6_send_reset(sk, skb, SK_RST_REASON_TCP_TIMEWAIT_SOCKET);
 		inet_twsk_deschedule_put(inet_twsk(sk));
 		goto discard_it;
 	case TCP_TW_SUCCESS: