[Devel] [PATCH 42/47] tcp: add two drop reasons for tcp_ack()

[Nikolay Borisov]

From: Eric Dumazet <edumazet at google.com>

Add TCP_TOO_OLD_ACK and TCP_ACK_UNSENT_DATA drop
reasons so that tcp_rcv_established() can report
them.

Signed-off-by: Eric Dumazet <edumazet at google.com>
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     | 2 ++
 include/trace/events/skb.h | 3 +++
 net/ipv4/tcp_input.c       | 7 ++++---
 3 files changed, 9 insertions(+), 3 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 217dce9f6f0f..4033019e93d1 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -388,6 +388,8 @@ enum skb_drop_reason {
 	SKB_DROP_REASON_TCP_CLOSE,      /* TCP socket in CLOSE state */
 	SKB_DROP_REASON_TCP_FASTOPEN,   /* dropped by FASTOPEN request socket */
 	SKB_DROP_REASON_TCP_OLD_ACK,    /* TCP ACK is old, but in window */
+	SKB_DROP_REASON_TCP_TOO_OLD_ACK, /* TCP ACK is too old */
+	SKB_DROP_REASON_TCP_ACK_UNSENT_DATA, /* TCP ACK for data we haven't sent yet */
 	SKB_DROP_REASON_IP_OUTNOROUTES, /* route lookup failed */
 	SKB_DROP_REASON_BPF_CGROUP_EGRESS,      /* dropped by
 						 * BPF_PROG_TYPE_CGROUP_SKB
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index a726a70f7596..4f3776c7dfcf 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -45,6 +45,9 @@
 	EM(SKB_DROP_REASON_TCP_CLOSE, TCP_CLOSE)                \
 	EM(SKB_DROP_REASON_TCP_FASTOPEN, TCP_FASTOPEN)          \
 	EM(SKB_DROP_REASON_TCP_OLD_ACK, TCP_OLD_ACK)            \
+	EM(SKB_DROP_REASON_TCP_TOO_OLD_ACK, TCP_TOO_OLD_ACK)    \
+	EM(SKB_DROP_REASON_TCP_ACK_UNSENT_DATA,                 \
+	   TCP_ACK_UNSENT_DATA)                                 \
 	EM(SKB_DROP_REASON_IP_OUTNOROUTES, IP_OUTNOROUTES)      \
 	EM(SKB_DROP_REASON_BPF_CGROUP_EGRESS,                   \
 	   BPF_CGROUP_EGRESS)                                   \
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index fad3792f71f4..7c46a90bd7af 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3728,7 +3728,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		if (before(ack, prior_snd_una - tp->max_window)) {
 			if (!(flag & FLAG_NO_CHALLENGE_ACK))
 				tcp_send_challenge_ack(sk, skb);
-			return -1;
+			return -SKB_DROP_REASON_TCP_TOO_OLD_ACK;
 		}
 		goto old_ack;
 	}
@@ -3737,7 +3737,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	 * this segment (RFC793 Section 3.9).
 	 */
 	if (after(ack, tp->snd_nxt))
-		return -1;
+		return -SKB_DROP_REASON_TCP_ACK_UNSENT_DATA;
 
 	if (after(ack, prior_snd_una)) {
 		flag |= FLAG_SND_UNA_ADVANCED;
@@ -5923,7 +5923,8 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb)
 		return;
 
 step5:
-	if (tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT) < 0)
+	reason = tcp_ack(sk, skb, FLAG_SLOWPATH | FLAG_UPDATE_TS_RECENT);
+	if (reason < 0)
 		goto discard;
 
 	tcp_rcv_rtt_measure_ts(sk, skb);
-- 
2.34.1