[Devel] [PATCH 16/47] net: tcp: use tcp_drop_reason() for tcp_data_queue()

[Nikolay Borisov]

From: Menglong Dong <imagedong at tencent.com>

Replace tcp_drop() used in tcp_data_queue() with tcp_drop_reason().
Following drop reasons are introduced:

SKB_DROP_REASON_TCP_ZEROWINDOW
SKB_DROP_REASON_TCP_OLD_DATA
SKB_DROP_REASON_TCP_OVERWINDOW

SKB_DROP_REASON_TCP_OLD_DATA is used for the case that end_seq of skb
less than the left edges of receive window. (Maybe there is a better
name?)

Reviewed-by: Mengen Sun <mengensun at tencent.com>
Reviewed-by: Hao Peng <flyingpeng at tencent.com>
Signed-off-by: Menglong Dong <imagedong at tencent.com>
Reviewed-by: Eric Dumazet <edumazet at google.com>
Reviewed-by: David Ahern <dsahern at kernel.org>
Signed-off-by: David S. Miller <davem at davemloft.net>
Acked-by: Nikolay Borisov <nborisov at suse.com>
Signed-off-by: Nikolay Borisov <nikolay.borisov at virtuozzo.com>
---
 include/linux/skbuff.h     | 14 ++++++++++++++
 include/trace/events/skb.h |  4 ++++
 net/ipv4/tcp_input.c       | 13 +++++++++++--
 3 files changed, 29 insertions(+), 2 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 8febe5c6cb47..680a6185219d 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -361,6 +361,20 @@ enum skb_drop_reason {
 					 * LINUX_MIB_TCPBACKLOGDROP)
 					 */
 	SKB_DROP_REASON_TCP_FLAGS,      /* TCP flags invalid */
+	SKB_DROP_REASON_TCP_ZEROWINDOW, /* TCP receive window size is zero,
+					 * see LINUX_MIB_TCPZEROWINDOWDROP
+					 */
+	SKB_DROP_REASON_TCP_OLD_DATA,   /* the TCP data reveived is already
+					 * received before (spurious retrans
+					 * may happened), see
+					 * LINUX_MIB_DELAYEDACKLOST
+					 */
+	SKB_DROP_REASON_TCP_OVERWINDOW, /* the TCP data is out of window,
+					 * the seq of the first byte exceed
+					 * the right edges of receive
+					 * window
+					 */
+
 
 	SKB_DROP_REASON_MAX,
 };
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 792e2ff696f7..0d9e1ad02228 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -33,6 +33,10 @@
 	EM(SKB_DROP_REASON_TCP_MD5FAILURE, TCP_MD5FAILURE)      \
 	EM(SKB_DROP_REASON_SOCKET_BACKLOG, SOCKET_BACKLOG)      \
 	EM(SKB_DROP_REASON_TCP_FLAGS, TCP_FLAGS)		\
+	EM(SKB_DROP_REASON_TCP_ZEROWINDOW, TCP_ZEROWINDOW)      \
+	EM(SKB_DROP_REASON_TCP_OLD_DATA, TCP_OLD_DATA)          \
+	EM(SKB_DROP_REASON_TCP_OVERWINDOW, TCP_OVERWINDOW)      \
+
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 7e65ba089bf0..37df05cf5e35 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4950,6 +4950,7 @@ void tcp_data_ready(struct sock *sk)
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
+	enum skb_drop_reason reason;
 	bool fragstolen;
 	int eaten;
 
@@ -4968,6 +4969,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 	skb_dst_drop(skb);
 	__skb_pull(skb, tcp_hdr(skb)->doff * 4);
 
+	reason = SKB_DROP_REASON_NOT_SPECIFIED;
 	tp->rx_opt.dsack = 0;
 
 	/*  Queue data for delivery to the user.
@@ -4976,6 +4978,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 	 */
 	if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
 		if (tcp_receive_window(tp) == 0) {
+			reason = SKB_DROP_REASON_TCP_ZEROWINDOW;
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
 			goto out_of_window;
 		}
@@ -4985,6 +4988,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 		if (skb_queue_len(&sk->sk_receive_queue) == 0)
 			sk_forced_mem_schedule(sk, skb->truesize);
 		else if (tcp_try_rmem_schedule(sk, skb, skb->truesize)) {
+			reason = SKB_DROP_REASON_PROTO_MEM;
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPRCVQDROP);
 			sk->sk_data_ready(sk);
 			goto drop;
@@ -5021,6 +5025,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 	if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
 		tcp_rcv_spurious_retrans(sk, skb);
 		/* A retransmit, 2nd most common case.  Force an immediate ack. */
+		reason = SKB_DROP_REASON_TCP_OLD_DATA;
 		NET_INC_STATS(sock_net(sk), LINUX_MIB_DELAYEDACKLOST);
 		tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq);
 
@@ -5028,13 +5033,16 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 		tcp_enter_quickack_mode(sk, TCP_MAX_QUICKACKS);
 		inet_csk_schedule_ack(sk);
 drop:
-		tcp_drop(sk, skb);
+		tcp_drop_reason(sk, skb, reason);
 		return;
 	}
 
 	/* Out of window. F.e. zero window probe. */
-	if (!before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt + tcp_receive_window(tp)))
+	if (!before(TCP_SKB_CB(skb)->seq,
+		    tp->rcv_nxt + tcp_receive_window(tp))) {
+		reason = SKB_DROP_REASON_TCP_OVERWINDOW;
 		goto out_of_window;
+	}
 
 	if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
 		/* Partial packet, seq < rcv_next < end_seq */
@@ -5044,6 +5052,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 		 * remembering D-SACK for its head made in previous line.
 		 */
 		if (!tcp_receive_window(tp)) {
+			reason = SKB_DROP_REASON_TCP_ZEROWINDOW;
 			NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
 			goto out_of_window;
 		}
-- 
2.34.1