tcp: add drop reason support to tcp_ofo_queue()

packets in OFO queue might be redundant, and dropped.

tcp_drop() is no longer needed.
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/skbuff.h

@@ -393,6 +393,7 @@ enum skb_drop_reason {
 	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_TCP_OFO_QUEUE_PRUNE, /* pruned from TCP OFO queue */
+	SKB_DROP_REASON_TCP_OFO_DROP,	/* data already in receive queue */
 	SKB_DROP_REASON_IP_OUTNOROUTES,	/* route lookup failed */
 	SKB_DROP_REASON_BPF_CGROUP_EGRESS,	/* dropped by
 						 * BPF_PROG_TYPE_CGROUP_SKB

include/trace/events/skb.h

@@ -37,6 +37,7 @@
 	EM(SKB_DROP_REASON_TCP_OLD_DATA, TCP_OLD_DATA)		\
 	EM(SKB_DROP_REASON_TCP_OVERWINDOW, TCP_OVERWINDOW)	\
 	EM(SKB_DROP_REASON_TCP_OFOMERGE, TCP_OFOMERGE)		\
+	EM(SKB_DROP_REASON_TCP_OFO_DROP, TCP_OFO_DROP)		\
 	EM(SKB_DROP_REASON_TCP_RFC7323_PAWS, TCP_RFC7323_PAWS)	\
 	EM(SKB_DROP_REASON_TCP_INVALID_SEQUENCE,		\
 	   TCP_INVALID_SEQUENCE)				\

net/ipv4/tcp_input.c

@@ -4674,7 +4674,7 @@ static bool tcp_ooo_try_coalesce(struct sock *sk,
 {
 	bool res = tcp_try_coalesce(sk, to, from, fragstolen);
 
-	/* In case tcp_drop() is called later, update to->gso_segs */
+	/* In case tcp_drop_reason() is called later, update to->gso_segs */
 	if (res) {
 		u32 gso_segs = max_t(u16, 1, skb_shinfo(to)->gso_segs) +
 			       max_t(u16, 1, skb_shinfo(from)->gso_segs);
@@ -4691,11 +4691,6 @@ static void tcp_drop_reason(struct sock *sk, struct sk_buff *skb,
 	kfree_skb_reason(skb, reason);
 }
 
-static void tcp_drop(struct sock *sk, struct sk_buff *skb)
-{
-	tcp_drop_reason(sk, skb, SKB_DROP_REASON_NOT_SPECIFIED);
-}
-
 /* This one checks to see if we can put data from the
  * out_of_order queue into the receive_queue.
  */
@@ -4723,7 +4718,7 @@ static void tcp_ofo_queue(struct sock *sk)
 		rb_erase(&skb->rbnode, &tp->out_of_order_queue);
 
 		if (unlikely(!after(TCP_SKB_CB(skb)->end_seq, tp->rcv_nxt))) {
-			tcp_drop(sk, skb);
+			tcp_drop_reason(sk, skb, SKB_DROP_REASON_TCP_OFO_DROP);
 			continue;
 		}