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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: Jason Xing <kernelxing@tencent.com>
Link: https://lore.kernel.org/r/20240510122502.27850-6-kerneljasonxing@gmail.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
This commit is contained in:
Jason Xing 2024-05-10 20:25:02 +08:00 committed by Jakub Kicinski
parent 22a3255775
commit 11f46ea981
2 changed files with 9 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

8
include/net/rstreason.h
View File

@ -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

2
net/ipv4/tcp_minisocks.c
View File

@ -879,7 +879,7 @@ embryonic_reset:
* 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);