[PATCH net-next v8 01/10] tcp: add a dropreason definitions and prepare for cookie check

[Jason Xing <kerneljasonxing@gmail.com>]

From: Jason Xing <kernelxing@tencent.com>

Adding one drop reason to detect the condition of skb dropped
because of hook points in cookie check and extending NO_SOCKET
to consider another two cases can be used later.

Signed-off-by: Jason Xing <kernelxing@tencent.com>
Reviewed-by: Eric Dumazet <edumazet@google.com>
--
v8
Link: https://lore.kernel.org/netdev/CANn89iJ3gLMn5psbzfVCOo2=v4nMn4m41wpr6svxyAmO4R1m6g@mail.gmail.com/
1. add reviewed-by tag (Eric)

v7
Link: https://lore.kernel.org/all/20240219040630.94637-1-kuniyu@amazon.com/
1. nit: change "invalid" to "valid" (Kuniyuki)
2. add more description.

v6
Link: https://lore.kernel.org/netdev/20240215210922.19969-1-kuniyu@amazon.com/
1. Modify the description NO_SOCKET to extend other two kinds of invalid
socket cases.
What I think about it is we can use it as a general indicator for three kinds of
sockets which are invalid/NULL, like what we did to TCP_FLAGS.
Any better ideas/suggestions are welcome :)

v5
Link: https://lore.kernel.org/netdev/CANn89i+iELpsoea6+C-08m6+=JkneEEM=nAj-28eNtcOCkwQjw@mail.gmail.com/
Link: https://lore.kernel.org/netdev/632c6fd4-e060-4b8e-a80e-5d545a6c6b6c@kernel.org/
1. Use SKB_DROP_REASON_IP_OUTNOROUTES instead of introducing a new one (Eric, David)
2. Reuse SKB_DROP_REASON_NOMEM to handle failure of request socket allocation (Eric)
3. Reuse NO_SOCKET instead of introducing COOKIE_NOCHILD
4. Reuse IP_OUTNOROUTES instead of INVALID_DST (Eric)
5. adjust the title and description.

v4
Link: https://lore.kernel.org/netdev/20240212172302.3f95e454@kernel.org/
1. fix misspelled name in kdoc as Jakub said
---
 include/net/dropreason-core.h | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/net/dropreason-core.h b/include/net/dropreason-core.h
index 6d3a20163260..a871f061558d 100644
--- a/include/net/dropreason-core.h
+++ b/include/net/dropreason-core.h
@@ -54,6 +54,7 @@
 	FN(NEIGH_QUEUEFULL)		\
 	FN(NEIGH_DEAD)			\
 	FN(TC_EGRESS)			\
+	FN(SECURITY_HOOK)		\
 	FN(QDISC_DROP)			\
 	FN(CPU_BACKLOG)			\
 	FN(XDP)				\
@@ -105,7 +106,13 @@ enum skb_drop_reason {
 	SKB_CONSUMED,
 	/** @SKB_DROP_REASON_NOT_SPECIFIED: drop reason is not specified */
 	SKB_DROP_REASON_NOT_SPECIFIED,
-	/** @SKB_DROP_REASON_NO_SOCKET: socket not found */
+	/**
+	 * @SKB_DROP_REASON_NO_SOCKET: no valid socket that can be used.
+	 * Reason could be one of three cases:
+	 * 1) no established/listening socket found during lookup process
+	 * 2) no valid request socket during 3WHS process
+	 * 3) no valid child socket during 3WHS process
+	 */
 	SKB_DROP_REASON_NO_SOCKET,
 	/** @SKB_DROP_REASON_PKT_TOO_SMALL: packet size is too small */
 	SKB_DROP_REASON_PKT_TOO_SMALL,
@@ -271,6 +278,8 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_NEIGH_DEAD,
 	/** @SKB_DROP_REASON_TC_EGRESS: dropped in TC egress HOOK */
 	SKB_DROP_REASON_TC_EGRESS,
+	/** @SKB_DROP_REASON_SECURITY_HOOK: dropped due to security HOOK */
+	SKB_DROP_REASON_SECURITY_HOOK,
 	/**
 	 * @SKB_DROP_REASON_QDISC_DROP: dropped by qdisc when packet outputting (
 	 * failed to enqueue to current qdisc)
-- 
2.37.3