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tcp: add SNMP counter for zero-window drops

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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>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Yafang Shao 2018-06-24 10:02:54 -04:00 committed by David S. Miller
parent 7e55052783
commit fb223502ec
3 changed files with 8 additions and 2 deletions
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1
include/uapi/linux/snmp.h
View File

@ -279,6 +279,7 @@ enum
LINUX_MIB_TCPDELIVERED, /* TCPDelivered */
LINUX_MIB_TCPDELIVEREDCE, /* TCPDeliveredCE */
LINUX_MIB_TCPACKCOMPRESSED, /* TCPAckCompressed */
LINUX_MIB_TCPZEROWINDOWDROP, /* TCPZeroWindowDrop */
__LINUX_MIB_MAX
};

1
net/ipv4/proc.c
View File

@ -287,6 +287,7 @@ static const struct snmp_mib snmp4_net_list[] = {
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
};

8
net/ipv4/tcp_input.c
View File

@ -4668,8 +4668,10 @@ 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:
@ -4735,8 +4737,10 @@ drop:
/* 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;
}