tcp: increment sk_drops for dropped rx packets

BugLink: https://bugs.launchpad.net/bugs/1801893

[ Upstream commit 532182cd ]

Now ss can report sk_drops, we can instruct TCP to increment
this per socket counter when it drops an incoming frame, to refine
monitoring and debugging.

Following patch takes care of listeners drops.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Mao Wenan <maowenan@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Khalid Elmously <khalid.elmously@canonical.com>

include/net/sock.h

@@ -2164,6 +2164,13 @@ sock_skb_set_dropcount(const struct sock *sk, struct sk_buff *skb)
 	SOCK_SKB_CB(skb)->dropcount = atomic_read(&sk->sk_drops);
 }
 
+static inline void sk_drops_add(struct sock *sk, const struct sk_buff *skb)
+{
+	int segs = max_t(u16, 1, skb_shinfo(skb)->gso_segs);
+
+	atomic_add(segs, &sk->sk_drops);
+}
+
 void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 			   struct sk_buff *skb);
 void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,

net/ipv4/tcp_input.c

@@ -4293,6 +4293,12 @@ static bool tcp_try_coalesce(struct sock *sk,
 	return true;
 }
 
+static void tcp_drop(struct sock *sk, struct sk_buff *skb)
+{
+	sk_drops_add(sk, skb);
+	__kfree_skb(skb);
+}
+
 /* This one checks to see if we can put data from the
  * out_of_order queue into the receive_queue.
  */
@@ -4317,7 +4323,7 @@ static void tcp_ofo_queue(struct sock *sk)
 		__skb_unlink(skb, &tp->out_of_order_queue);
 		if (!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt)) {
 			SOCK_DEBUG(sk, "ofo packet was already received\n");
-			__kfree_skb(skb);
+			tcp_drop(sk, skb);
 			continue;
 		}
 		SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
@@ -4369,7 +4375,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 
 	if (unlikely(tcp_try_rmem_schedule(sk, skb, skb->truesize))) {
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFODROP);
-		__kfree_skb(skb);
+		tcp_drop(sk, skb);
 		return;
 	}
 
@@ -4433,7 +4439,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 		if (!after(end_seq, TCP_SKB_CB(skb1)->end_seq)) {
 			/* All the bits are present. Drop. */
 			NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
-			__kfree_skb(skb);
+			tcp_drop(sk, skb);
 			skb = NULL;
 			tcp_dsack_set(sk, seq, end_seq);
 			goto add_sack;
@@ -4472,7 +4478,7 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 		tcp_dsack_extend(sk, TCP_SKB_CB(skb1)->seq,
 				 TCP_SKB_CB(skb1)->end_seq);
 		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_TCPOFOMERGE);
-		__kfree_skb(skb1);
+		tcp_drop(sk, skb1);
 	}
 
 add_sack:
@@ -4555,12 +4561,13 @@ int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size)
 static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
-	int eaten = -1;
 	bool fragstolen = false;
+	int eaten = -1;
 
-	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq)
-		goto drop;
-
+	if (TCP_SKB_CB(skb)->seq == TCP_SKB_CB(skb)->end_seq) {
+		__kfree_skb(skb);
+		return;
+	}
 	skb_dst_drop(skb);
 	__skb_pull(skb, tcp_hdr(skb)->doff * 4);
 
@@ -4642,7 +4649,7 @@ 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:
-		__kfree_skb(skb);
+		tcp_drop(sk, skb);
 		return;
 	}
 
@@ -5233,7 +5240,7 @@ static bool tcp_validate_incoming(struct sock *sk, struct sk_buff *skb,
 	return true;
 
 discard:
-	__kfree_skb(skb);
+	tcp_drop(sk, skb);
 	return false;
 }
 
@@ -5451,7 +5458,7 @@ void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
 	TCP_INC_STATS_BH(sock_net(sk), TCP_MIB_INERRS);
 
 discard:
-	__kfree_skb(skb);
+	tcp_drop(sk, skb);
 }
 EXPORT_SYMBOL(tcp_rcv_established);
 
@@ -5681,7 +5688,7 @@ static int tcp_rcv_synsent_state_process(struct sock *sk, struct sk_buff *skb,
 						  TCP_DELACK_MAX, TCP_RTO_MAX);
 
 discard:
-			__kfree_skb(skb);
+			tcp_drop(sk, skb);
 			return 0;
 		} else {
 			tcp_send_ack(sk);
@@ -6035,7 +6042,7 @@ int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb)
 
 	if (!queued) {
 discard:
-		__kfree_skb(skb);
+		tcp_drop(sk, skb);
 	}
 	return 0;
 }

net/ipv4/tcp_ipv4.c

@@ -1716,6 +1716,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
 	return 0;
 
 discard_and_relse:
+	sk_drops_add(sk, skb);
 	sock_put(sk);
 	goto discard_it;
 

net/ipv6/tcp_ipv6.c

@@ -1505,6 +1505,7 @@ static int tcp_v6_rcv(struct sk_buff *skb)
 	return 0;
 
 discard_and_relse:
+	sk_drops_add(sk, skb);
 	sock_put(sk);
 	goto discard_it;