[bpf-next 1/2] tcp: replace SOCK_DEBUG() with tcp_stats()

[Yafang Shao <laoar.shao@gmail.com>]

SOCK_DEBUG is a very ancient debugging interface, and it's not very useful
for debugging.
So this patch removes the SOCK_DEBUG() and introduce a new function
tcp_stats() to trace this kind of events.
Some MIBs are added for these events.

Regarding the SO_DEBUG in sock_{s,g}etsockopt, I think it is better to
keep as-is, because if we return an errno to tell the application that
this optname isn't supported for TCP, it may break the application.
The application still can use this option but don't take any effect for
TCP.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
 include/uapi/linux/snmp.h |  3 +++
 net/ipv4/proc.c           |  3 +++
 net/ipv4/tcp_input.c      | 26 +++++++++++---------------
 net/ipv6/tcp_ipv6.c       |  2 --
 4 files changed, 17 insertions(+), 17 deletions(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 86dc24a..fd5c09c 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -283,6 +283,9 @@ enum
 	LINUX_MIB_TCPACKCOMPRESSED,		/* TCPAckCompressed */
 	LINUX_MIB_TCPZEROWINDOWDROP,		/* TCPZeroWindowDrop */
 	LINUX_MIB_TCPRCVQDROP,			/* TCPRcvQDrop */
+	LINUX_MIB_TCPINVALIDACK,		/* TCPInvalidAck */
+	LINUX_MIB_TCPOLDACK,			/* TCPOldAck */
+	LINUX_MIB_TCPPARTIALPACKET,		/* TCPPartialPacket */
 	__LINUX_MIB_MAX
 };
 
diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index c3610b3..1b0320a 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -291,6 +291,9 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
 	SNMP_MIB_ITEM("TCPAckCompressed", LINUX_MIB_TCPACKCOMPRESSED),
 	SNMP_MIB_ITEM("TCPZeroWindowDrop", LINUX_MIB_TCPZEROWINDOWDROP),
 	SNMP_MIB_ITEM("TCPRcvQDrop", LINUX_MIB_TCPRCVQDROP),
+	SNMP_MIB_ITEM("TCPInvalidAck", LINUX_MIB_TCPINVALIDACK),
+	SNMP_MIB_ITEM("TCPOldAck", LINUX_MIB_TCPOLDACK),
+	SNMP_MIB_ITEM("TCPPartialPacket", LINUX_MIB_TCPPARTIALPACKET),
 	SNMP_MIB_SENTINEL
 };
 
diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 7a027dec..88deb1f 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -3554,6 +3554,11 @@ static u32 tcp_newly_delivered(struct sock *sk, u32 prior_delivered, int flag)
 	return delivered;
 }
 
+static void tcp_stats(struct sock *sk, int mib_idx)
+{
+	NET_INC_STATS(sock_net(sk), mib_idx);
+}
+
 /* This routine deals with incoming acks, but not outgoing ones. */
 static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 {
@@ -3715,7 +3720,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 	return 1;
 
 invalid_ack:
-	SOCK_DEBUG(sk, "Ack %u after %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
+	tcp_stats(sk, LINUX_MIB_TCPINVALIDACK);
 	return -1;
 
 old_ack:
@@ -3731,7 +3736,7 @@ static int tcp_ack(struct sock *sk, const struct sk_buff *skb, int flag)
 		tcp_xmit_recovery(sk, rexmit);
 	}
 
-	SOCK_DEBUG(sk, "Ack %u before %u:%u\n", ack, tp->snd_una, tp->snd_nxt);
+	tcp_stats(sk, LINUX_MIB_TCPOLDACK);
 	return 0;
 }
 
@@ -4432,13 +4437,10 @@ 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))) {
-			SOCK_DEBUG(sk, "ofo packet was already received\n");
+			tcp_stats(sk, LINUX_MIB_TCPOFODROP);
 			tcp_drop(sk, skb);
 			continue;
 		}
-		SOCK_DEBUG(sk, "ofo requeuing : rcv_next %X seq %X - %X\n",
-			   tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
-			   TCP_SKB_CB(skb)->end_seq);
 
 		tail = skb_peek_tail(&sk->sk_receive_queue);
 		eaten = tail && tcp_try_coalesce(sk, tail, skb, &fragstolen);
@@ -4499,11 +4501,9 @@ static void tcp_data_queue_ofo(struct sock *sk, struct sk_buff *skb)
 	tp->pred_flags = 0;
 	inet_csk_schedule_ack(sk);
 
-	NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPOFOQUEUE);
 	seq = TCP_SKB_CB(skb)->seq;
 	end_seq = TCP_SKB_CB(skb)->end_seq;
-	SOCK_DEBUG(sk, "out of order segment: rcv_next %X seq %X - %X\n",
-		   tp->rcv_nxt, seq, end_seq);
+	tcp_stats(sk, LINUX_MIB_TCPOFOQUEUE);
 
 	p = &tp->out_of_order_queue.rb_node;
 	if (RB_EMPTY_ROOT(&tp->out_of_order_queue)) {
@@ -4779,9 +4779,7 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
 
 	if (before(TCP_SKB_CB(skb)->seq, tp->rcv_nxt)) {
 		/* Partial packet, seq < rcv_next < end_seq */
-		SOCK_DEBUG(sk, "partial packet: rcv_next %X seq %X - %X\n",
-			   tp->rcv_nxt, TCP_SKB_CB(skb)->seq,
-			   TCP_SKB_CB(skb)->end_seq);
+		tcp_stats(sk, LINUX_MIB_TCPPARTIALPACKET);
 
 		tcp_dsack_set(sk, TCP_SKB_CB(skb)->seq, tp->rcv_nxt);
 
@@ -5061,9 +5059,7 @@ static int tcp_prune_queue(struct sock *sk)
 {
 	struct tcp_sock *tp = tcp_sk(sk);
 
-	SOCK_DEBUG(sk, "prune_queue: c=%x\n", tp->copied_seq);
-
-	NET_INC_STATS(sock_net(sk), LINUX_MIB_PRUNECALLED);
+	tcp_stats(sk, LINUX_MIB_PRUNECALLED);
 
 	if (atomic_read(&sk->sk_rmem_alloc) >= sk->sk_rcvbuf)
 		tcp_clamp_window(sk);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index e51cda7..57ef69a1 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -220,8 +220,6 @@ static int tcp_v6_connect(struct sock *sk, struct sockaddr *uaddr,
 		u32 exthdrlen = icsk->icsk_ext_hdr_len;
 		struct sockaddr_in sin;
 
-		SOCK_DEBUG(sk, "connect: ipv4 mapped\n");
-
 		if (__ipv6_only_sock(sk))
 			return -ENETUNREACH;
 
-- 
1.8.3.1