[PATCH net-next 0/5] tcp: support rstreasons in the passive logic

[PATCH net-next 0/5] tcp: support rstreasons in the passive logic

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

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.

Jason Xing (5):
  tcp: fully support sk reset reasons in tcp_rcv_synsent_state_process()
  tcp: fully support sk reset reason in tcp_ack()
  tcp: fully support sk reset reason in tcp_rcv_state_process()
  tcp: handle timewait cases in rstreason logic
  tcp: handle rstreason in tcp_check_req()

 include/net/rstreason.h  | 58 ++++++++++++++++++++++++++++++++++++++++
 net/ipv4/tcp_ipv4.c      |  2 +-
 net/ipv4/tcp_minisocks.c |  2 +-
 net/ipv6/tcp_ipv6.c      |  2 +-
 4 files changed, 61 insertions(+), 3 deletions(-)

-- 
2.37.3

[PATCH net-next 1/5] tcp: fully support sk reset reasons in tcp_rcv_synsent_state_process()

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

In this function, only updating the map can finish the job for socket
reset reason because the corresponding drop reasons are ready.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 include/net/rstreason.h | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index df3b6ac0c9b3..f87814a60205 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -8,6 +8,8 @@
 #define DEFINE_RST_REASON(FN, FNe)	\
 	FN(NOT_SPECIFIED)		\
 	FN(NO_SOCKET)			\
+	FN(TCP_INVALID_ACK_SEQUENCE)	\
+	FN(TCP_RFC7323_PAWS)		\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -37,6 +39,17 @@ 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,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
@@ -113,6 +126,10 @@ 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;
 	default:
 		/* If we don't have our own corresponding reason */
 		return SK_RST_REASON_NOT_SPECIFIED;
-- 
2.37.3

[PATCH net-next 2/5] tcp: fully support sk reset reason in tcp_ack()

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

Based on the existing skb drop reason, updating the rstreason map can
help us finish the rstreason job in this function.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 include/net/rstreason.h | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index f87814a60205..a32b0fa17de2 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -10,6 +10,8 @@
 	FN(NO_SOCKET)			\
 	FN(TCP_INVALID_ACK_SEQUENCE)	\
 	FN(TCP_RFC7323_PAWS)		\
+	FN(TCP_TOO_OLD_ACK)		\
+	FN(TCP_ACK_UNSENT_DATA)		\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -50,6 +52,10 @@ enum sk_rst_reason {
 	 * 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 */
+	SK_RST_REASON_TCP_ACK_UNSENT_DATA,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
@@ -130,6 +136,10 @@ sk_rst_convert_drop_reason(enum skb_drop_reason reason)
 		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;
 	default:
 		/* If we don't have our own corresponding reason */
 		return SK_RST_REASON_NOT_SPECIFIED;
-- 
2.37.3

Re: [PATCH net-next 2/5] tcp: fully support sk reset reason in tcp_ack()

[Jason Xing]

On Thu, May 9, 2024 at 9:13 PM Jason Xing <kerneljasonxing@gmail.com> wrote:
>
> From: Jason Xing <kernelxing@tencent.com>
>
> Based on the existing skb drop reason, updating the rstreason map can
> help us finish the rstreason job in this function.
>
> Signed-off-by: Jason Xing <kernelxing@tencent.com>
> ---
>  include/net/rstreason.h | 10 ++++++++++
>  1 file changed, 10 insertions(+)
>
> diff --git a/include/net/rstreason.h b/include/net/rstreason.h
> index f87814a60205..a32b0fa17de2 100644
> --- a/include/net/rstreason.h
> +++ b/include/net/rstreason.h
> @@ -10,6 +10,8 @@
>         FN(NO_SOCKET)                   \
>         FN(TCP_INVALID_ACK_SEQUENCE)    \
>         FN(TCP_RFC7323_PAWS)            \
> +       FN(TCP_TOO_OLD_ACK)             \
> +       FN(TCP_ACK_UNSENT_DATA)         \
>         FN(MPTCP_RST_EUNSPEC)           \
>         FN(MPTCP_RST_EMPTCP)            \
>         FN(MPTCP_RST_ERESOURCE)         \
> @@ -50,6 +52,10 @@ enum sk_rst_reason {
>          * 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 */

I'll add the detailed comment into this kdoc which was found by
patchwork in V2 series to make sure every item has its own
explanation.

Thanks,
Jason

> +       SK_RST_REASON_TCP_ACK_UNSENT_DATA,
>
>         /* Copy from include/uapi/linux/mptcp.h.
>          * These reset fields will not be changed since they adhere to
> @@ -130,6 +136,10 @@ sk_rst_convert_drop_reason(enum skb_drop_reason reason)
>                 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;
>         default:
>                 /* If we don't have our own corresponding reason */
>                 return SK_RST_REASON_NOT_SPECIFIED;
> --
> 2.37.3
>

[PATCH net-next 3/5] tcp: fully support sk reset reason in tcp_rcv_state_process()

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

Like the previous patch does in this series, finish the conversion map is
enough to let rstreason mechanism work in this function.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 include/net/rstreason.h | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index a32b0fa17de2..61855d4b27e2 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -12,6 +12,9 @@
 	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(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -56,6 +59,15 @@ enum sk_rst_reason {
 	SK_RST_REASON_TCP_TOO_OLD_ACK,
 	/** @SK_RST_REASON_TCP_ACK_UNSENT_DATA */
 	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,
 
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
@@ -140,6 +152,12 @@ sk_rst_convert_drop_reason(enum skb_drop_reason reason)
 		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;
-- 
2.37.3

[PATCH net-next 4/5] tcp: handle timewait cases in rstreason logic

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

There are two possible cases where TCP layer can send an RST. Since they
happen in the same place, I think using one independent reason is enough
to identify this special situation.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 include/net/rstreason.h | 5 +++++
 net/ipv4/tcp_ipv4.c     | 2 +-
 net/ipv6/tcp_ipv6.c     | 2 +-
 3 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index 61855d4b27e2..62e869089da4 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -15,6 +15,7 @@
 	FN(TCP_FLAGS)			\
 	FN(TCP_OLD_ACK)			\
 	FN(TCP_ABORT_ON_DATA)		\
+	FN(TCP_TIMEWAIT_SOCKET)		\
 	FN(MPTCP_RST_EUNSPEC)		\
 	FN(MPTCP_RST_EMPTCP)		\
 	FN(MPTCP_RST_ERESOURCE)		\
@@ -69,6 +70,10 @@ enum sk_rst_reason {
 	 */
 	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,
+
 	/* Copy from include/uapi/linux/mptcp.h.
 	 * These reset fields will not be changed since they adhere to
 	 * RFC 8684. So do not touch them. I'm going to list each definition
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 0427deca3e0e..d35cdb77d7b5 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -2421,7 +2421,7 @@ 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:;
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 37201c4fb393..bee26b961835 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/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:
-- 
2.37.3

[PATCH net-next 5/5] tcp: handle rstreason in tcp_check_req()

[Jason Xing]

From: Jason Xing <kernelxing@tencent.com>

We're going to send an RST due to invalid syn packet which is already
checked whether 1) it is in sequence, 2) it is a retransmitted skb.

As RFC 793 says, if the state of socket is not CLOSED/LISTEN/SYN-SENT,
then we should send an RST when receiving bad syn packet:
"fourth, check the SYN bit,...If the SYN is in the window it is an
error, send a reset"

Signed-off-by: Jason Xing <kernelxing@tencent.com>
---
 include/net/rstreason.h  | 8 ++++++++
 net/ipv4/tcp_minisocks.c | 2 +-
 2 files changed, 9 insertions(+), 1 deletion(-)

diff --git a/include/net/rstreason.h b/include/net/rstreason.h
index 62e869089da4..bfea05ff8d88 100644
--- a/include/net/rstreason.h
+++ b/include/net/rstreason.h
@@ -16,6 +16,7 @@
 	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)		\
@@ -73,6 +74,13 @@ enum sk_rst_reason {
 	/* 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
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index 7d543569a180..b93619b2384b 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/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);
-- 
2.37.3