[Devel] [PATCH 13/47] net: tcp: add skb drop reasons to tcp_add_backlog()

[Nikolay Borisov]

From: Menglong Dong <imagedong at tencent.com>

Pass the address of drop_reason to tcp_add_backlog() to store the
reasons for skb drops when fails. Following drop reasons are
introduced:

SKB_DROP_REASON_SOCKET_BACKLOG

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     | 5 +++++
 include/net/tcp.h          | 3 ++-
 include/trace/events/skb.h | 1 +
 net/ipv4/tcp_ipv4.c        | 7 +++++--
 net/ipv6/tcp_ipv6.c        | 2 +-
 5 files changed, 14 insertions(+), 4 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 307dbbea8e45..700996e9987a 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -356,6 +356,11 @@ enum skb_drop_reason {
 					 * corresponding to
 					 * LINUX_MIB_TCPMD5FAILURE
 					 */
+	SKB_DROP_REASON_SOCKET_BACKLOG, /* failed to add skb to socket
+					 * backlog (see
+					 * LINUX_MIB_TCPBACKLOGDROP)
+					 */
+
 
 
 
diff --git a/include/net/tcp.h b/include/net/tcp.h
index 47dec7010e6a..36d85dfb6762 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1381,7 +1381,8 @@ static inline bool tcp_checksum_complete(struct sk_buff *skb)
 		__skb_checksum_complete(skb);
 }
 
-bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb);
+bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
+		     enum skb_drop_reason *reason);
 int tcp_filter(struct sock *sk, struct sk_buff *skb);
 void tcp_set_state(struct sock *sk, int state);
 void tcp_done(struct sock *sk);
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 2742080fa181..841d0bfebf73 100644
--- a/include/trace/events/skb.h
+++ b/include/trace/events/skb.h
@@ -31,6 +31,7 @@
 	EM(SKB_DROP_REASON_TCP_MD5UNEXPECTED,                   \
 	   TCP_MD5UNEXPECTED)                                   \
 	EM(SKB_DROP_REASON_TCP_MD5FAILURE, TCP_MD5FAILURE)      \
+	EM(SKB_DROP_REASON_SOCKET_BACKLOG, SOCKET_BACKLOG)      \
 	EMe(SKB_DROP_REASON_MAX, MAX)
 
 #undef EM
diff --git a/net/ipv4/tcp_ipv4.c b/net/ipv4/tcp_ipv4.c
index 7931903edbd8..cdc51d377d49 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1796,7 +1796,8 @@ int tcp_v4_early_demux(struct sk_buff *skb)
 	return 0;
 }
 
-bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
+bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb,
+		     enum skb_drop_reason *reason)
 {
 	u32 limit = READ_ONCE(sk->sk_rcvbuf) + READ_ONCE(sk->sk_sndbuf);
 	u32 tail_gso_size, tail_gso_segs;
@@ -1823,6 +1824,7 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
 	if (unlikely(tcp_checksum_complete(skb))) {
 		bh_unlock_sock(sk);
 		trace_tcp_bad_csum(skb);
+		*reason = SKB_DROP_REASON_TCP_CSUM;
 		__TCP_INC_STATS(sock_net(sk), TCP_MIB_CSUMERRORS);
 		__TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
 		return true;
@@ -1911,6 +1913,7 @@ bool tcp_add_backlog(struct sock *sk, struct sk_buff *skb)
 
 	if (unlikely(sk_add_backlog(sk, skb, limit))) {
 		bh_unlock_sock(sk);
+		*reason = SKB_DROP_REASON_SOCKET_BACKLOG;
 		__NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPBACKLOGDROP);
 		return true;
 	}
@@ -2114,7 +2117,7 @@ int tcp_v4_rcv(struct sk_buff *skb)
 	if (!sock_owned_by_user(sk)) {
 		ret = tcp_v4_do_rcv(sk, skb);
 	} else {
-		if (tcp_add_backlog(sk, skb))
+		if (tcp_add_backlog(sk, skb, &drop_reason))
 			goto discard_and_relse;
 	}
 	bh_unlock_sock(sk);
diff --git a/net/ipv6/tcp_ipv6.c b/net/ipv6/tcp_ipv6.c
index 6c8dcfcbcf89..42854bdb6e1f 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1771,7 +1771,7 @@ INDIRECT_CALLABLE_SCOPE int tcp_v6_rcv(struct sk_buff *skb)
 	if (!sock_owned_by_user(sk)) {
 		ret = tcp_v6_do_rcv(sk, skb);
 	} else {
-		if (tcp_add_backlog(sk, skb))
+		if (tcp_add_backlog(sk, skb, &drop_reason))
 			goto discard_and_relse;
 	}
 	bh_unlock_sock(sk);
-- 
2.34.1