Commit fb223502 authored by Yafang Shao's avatar Yafang Shao Committed by David S. Miller
Browse files

tcp: add SNMP counter for zero-window drops 



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: default avatarYafang Shao <laoar.shao@gmail.com>
Signed-off-by: default avatarEric Dumazet <edumazet@google.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 7e550527

include/uapi/linux/snmp.h

+1 −0
Original line number Diff line number Diff line
@@ -279,6 +279,7 @@ enum 
	LINUX_MIB_TCPDELIVERED,			/* TCPDelivered */

	LINUX_MIB_TCPDELIVEREDCE,		/* TCPDeliveredCE */

	LINUX_MIB_TCPACKCOMPRESSED,		/* TCPAckCompressed */

	LINUX_MIB_TCPZEROWINDOWDROP,		/* TCPZeroWindowDrop */

	__LINUX_MIB_MAX

};

net/ipv4/proc.c

+1 −0
Original line number Diff line number Diff line
@@ -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

};

net/ipv4/tcp_input.c

+6 −2
Original line number Diff line number Diff line
@@ -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;

	}

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