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Subject[PATCH net-next v2 5/9] net: tcp: add skb drop reasons to tcp_add_backlog()
Date
From: Menglong Dong <imagedong@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

Signed-off-by: Menglong Dong <imagedong@tencent.com>
---
include/linux/skbuff.h | 4 ++++
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, 13 insertions(+), 4 deletions(-)

diff --git a/include/linux/skbuff.h b/include/linux/skbuff.h
index 46678eb587ff..f7f33c79945b 100644
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -358,6 +358,10 @@ 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)
+ */
SKB_DROP_REASON_MAX,
};

diff --git a/include/net/tcp.h b/include/net/tcp.h
index eff2487d972d..04f4650e0ff0 100644
--- a/include/net/tcp.h
+++ b/include/net/tcp.h
@@ -1367,7 +1367,8 @@ 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);

#ifdef CONFIG_INET
void __sk_defer_free_flush(struct sock *sk);
diff --git a/include/trace/events/skb.h b/include/trace/events/skb.h
index 46c06b0be850..bfccd77e9071 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 d3c417119057..cbca8637ba2f 100644
--- a/net/ipv4/tcp_ipv4.c
+++ b/net/ipv4/tcp_ipv4.c
@@ -1811,7 +1811,8 @@ 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, tail_gso_size, tail_gso_segs;
struct skb_shared_info *shinfo;
@@ -1837,6 +1838,7 @@ 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;
@@ -1925,6 +1927,7 @@ 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;
}
@@ -2133,7 +2136,7 @@ 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 1262b790b146..abf0ad547858 100644
--- a/net/ipv6/tcp_ipv6.c
+++ b/net/ipv6/tcp_ipv6.c
@@ -1784,7 +1784,7 @@ 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
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