[PATCH net-next 5/9] net: tcp: store drop reasons in tcp_timewait_state_process()

[menglong8.dong@gmail.com]

From: Menglong Dong <imagedong@tencent.com>

Store the drop reason to the tcp_skb_cb in tcp_timewait_state_process()
when the skb is going to be dropped. The new drop reason 'TIMEWAIT' is
added.

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
 include/net/dropreason.h |  7 +++++++
 net/ipv4/tcp_minisocks.c | 15 +++++++++++++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/include/net/dropreason.h b/include/net/dropreason.h
index 0f0edcd5f95f..cbfd88493ef2 100644
--- a/include/net/dropreason.h
+++ b/include/net/dropreason.h
@@ -69,6 +69,7 @@
 	FN(IP_INNOROUTES)		\
 	FN(PKT_TOO_BIG)			\
 	FN(TCP_PAWSACTIVEREJECTED)	\
+	FN(TIMEWAIT)			\
 	FNe(MAX)
 
 /**
@@ -305,6 +306,12 @@ enum skb_drop_reason {
 	 * LINUX_MIB_PAWSACTIVEREJECTED
 	 */
 	SKB_DROP_REASON_TCP_PAWSACTIVEREJECTED,
+	/**
+	 * @SKB_DROP_REASON_TIMEWAIT: socket is in time-wait state and all
+	 * packet that received will be treated as 'drop', except a good
+	 * 'SYN' packet
+	 */
+	SKB_DROP_REASON_TIMEWAIT,
 	/**
 	 * @SKB_DROP_REASON_MAX: the maximum of drop reason, which shouldn't be
 	 * used as a real 'reason'
diff --git a/net/ipv4/tcp_minisocks.c b/net/ipv4/tcp_minisocks.c
index c375f603a16c..e1963394dc4a 100644
--- a/net/ipv4/tcp_minisocks.c
+++ b/net/ipv4/tcp_minisocks.c
@@ -113,11 +113,16 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
 			return tcp_timewait_check_oow_rate_limit(
 				tw, skb, LINUX_MIB_TCPACKSKIPPEDFINWAIT2);
 
-		if (th->rst)
+		if (th->rst) {
+			TCP_SKB_DR(skb, TCP_RESET);
 			goto kill;
+		}
 
-		if (th->syn && !before(TCP_SKB_CB(skb)->seq, tcptw->tw_rcv_nxt))
+		if (th->syn && !before(TCP_SKB_CB(skb)->seq,
+				       tcptw->tw_rcv_nxt)) {
+			TCP_SKB_DR(skb, TCP_FLAGS);
 			return TCP_TW_RST;
+		}
 
 		/* Dup ACK? */
 		if (!th->ack ||
@@ -143,6 +148,9 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
 		}
 
 		inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
+
+		/* skb should be free normally on this case. */
+		TCP_SKB_CB(skb)->drop_reason = SKB_NOT_DROPPED_YET;
 		return TCP_TW_ACK;
 	}
 
@@ -174,6 +182,7 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
 			 * protocol bug yet.
 			 */
 			if (!READ_ONCE(twsk_net(tw)->ipv4.sysctl_tcp_rfc1337)) {
+				TCP_SKB_DR(skb, TCP_RESET);
 kill:
 				inet_twsk_deschedule_put(tw);
 				return TCP_TW_SUCCESS;
@@ -232,9 +241,11 @@ tcp_timewait_state_process(struct inet_timewait_sock *tw, struct sk_buff *skb,
 		if (paws_reject || th->ack)
 			inet_twsk_reschedule(tw, TCP_TIMEWAIT_LEN);
 
+		TCP_SKB_DR(skb, TIMEWAIT);
 		return tcp_timewait_check_oow_rate_limit(
 			tw, skb, LINUX_MIB_TCPACKSKIPPEDTIMEWAIT);
 	}
+	TCP_SKB_DR(skb, TCP_RESET);
 	inet_twsk_put(tw);
 	return TCP_TW_SUCCESS;
 }
-- 
2.37.2