Commit 11f46ea9 authored by Jason Xing's avatar Jason Xing Committed by Jakub Kicinski
Browse files

tcp: rstreason: fully support in tcp_check_req() 



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: default avatarJason Xing <kernelxing@tencent.com>
Link: https://lore.kernel.org/r/20240510122502.27850-6-kerneljasonxing@gmail.com


Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 22a32557

include/net/rstreason.h

+8 −0
Original line number Diff line number Diff line
@@ -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)		\
@@ -76,6 +77,13 @@ 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

net/ipv4/tcp_minisocks.c

+1 −1
Original line number Diff line number Diff line
@@ -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);