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Subject[PATCH net-next] tcp: add SNMP counter for zero-window drops
Date
It will be helpful if we could display the drops due to zero window or no
enough window space.
So a new SNMP MIB entry is added to track this behavior.
This entry is named LINUX_MIB_TCPZEROWINDOWDROP and published in
/proc/net/netstat in TcpExt line as TCPZeroWindowDrop.

Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
---
include/uapi/linux/snmp.h | 1 +
net/ipv4/proc.c | 1 +
net/ipv4/tcp_input.c | 8 ++++++--
3 files changed, 8 insertions(+), 2 deletions(-)

diff --git a/include/uapi/linux/snmp.h b/include/uapi/linux/snmp.h
index 750d891..97517f3 100644
--- a/include/uapi/linux/snmp.h
+++ b/include/uapi/linux/snmp.h
@@ -279,6 +279,7 @@ enum
LINUX_MIB_TCPDELIVERED, /* TCPDelivered */
LINUX_MIB_TCPDELIVEREDCE, /* TCPDeliveredCE */
LINUX_MIB_TCPACKCOMPRESSED, /* TCPAckCompressed */
+ LINUX_MIB_TCPZEROWINDOWDROP, /* TCPZeroWindowDrop */
__LINUX_MIB_MAX
};

diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
index 77350c1..225ef34 100644
--- a/net/ipv4/proc.c
+++ b/net/ipv4/proc.c
@@ -287,6 +287,7 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
SNMP_MIB_ITEM("TCPDelivered", LINUX_MIB_TCPDELIVERED),
SNMP_MIB_ITEM("TCPDeliveredCE", LINUX_MIB_TCPDELIVEREDCE),
SNMP_MIB_ITEM("TCPAckCompressed", LINUX_MIB_TCPACKCOMPRESSED),
+ SNMP_MIB_ITEM("TCPZeroWindowDrop", LINUX_MIB_TCPZEROWINDOWDROP),
SNMP_MIB_SENTINEL
};

diff --git a/net/ipv4/tcp_input.c b/net/ipv4/tcp_input.c
index 355d3df..b0482b1 100644
--- a/net/ipv4/tcp_input.c
+++ b/net/ipv4/tcp_input.c
@@ -4665,8 +4665,10 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
* Out of sequence packets to the out_of_order_queue.
*/
if (TCP_SKB_CB(skb)->seq == tp->rcv_nxt) {
- if (tcp_receive_window(tp) == 0)
+ if (tcp_receive_window(tp) == 0) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
goto out_of_window;
+ }

/* Ok. In sequence. In window. */
queue_and_out:
@@ -4732,8 +4734,10 @@ static void tcp_data_queue(struct sock *sk, struct sk_buff *skb)
/* If window is closed, drop tail of packet. But after
* remembering D-SACK for its head made in previous line.
*/
- if (!tcp_receive_window(tp))
+ if (!tcp_receive_window(tp)) {
+ NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPZEROWINDOWDROP);
goto out_of_window;
+ }
goto queue_and_out;
}

--
1.8.3.1
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