tcp: add some mibs to track collapsing

Signed-off-by: Ilpo Järvinen <ilpo.jarvinen@helsinki.fi>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/linux/snmp.h

@@ -216,6 +216,9 @@ enum
 	LINUX_MIB_TCPSPURIOUSRTOS,		/* TCPSpuriousRTOs */
 	LINUX_MIB_TCPMD5NOTFOUND,		/* TCPMD5NotFound */
 	LINUX_MIB_TCPMD5UNEXPECTED,		/* TCPMD5Unexpected */
+	LINUX_MIB_SACKSHIFTED,
+	LINUX_MIB_SACKMERGED,
+	LINUX_MIB_SACKSHIFTFALLBACK,
 	__LINUX_MIB_MAX
 };
 

net/ipv4/proc.c

@@ -234,6 +234,9 @@ static const struct snmp_mib snmp4_net_list[] = {
 	SNMP_MIB_ITEM("TCPSpuriousRTOs", LINUX_MIB_TCPSPURIOUSRTOS),
 	SNMP_MIB_ITEM("TCPMD5NotFound", LINUX_MIB_TCPMD5NOTFOUND),
 	SNMP_MIB_ITEM("TCPMD5Unexpected", LINUX_MIB_TCPMD5UNEXPECTED),
+	SNMP_MIB_ITEM("TCPSackShifted", LINUX_MIB_SACKSHIFTED),
+	SNMP_MIB_ITEM("TCPSackMerged", LINUX_MIB_SACKMERGED),
+	SNMP_MIB_ITEM("TCPSackShiftFallback", LINUX_MIB_SACKSHIFTFALLBACK),
 	SNMP_MIB_SENTINEL
 };
 

net/ipv4/tcp_input.c

@@ -1415,6 +1415,7 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
 
 	if (skb->len > 0) {
 		BUG_ON(!tcp_skb_pcount(skb));
+		NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTED);
 		return 0;
 	}
 
@@ -1436,6 +1437,8 @@ static int tcp_shifted_skb(struct sock *sk, struct sk_buff *prev,
 	tcp_unlink_write_queue(skb, sk);
 	sk_wmem_free_skb(sk, skb);
 
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKMERGED);
+
 	return 1;
 }
 
@@ -1594,6 +1597,7 @@ noop:
 	return skb;
 
 fallback:
+	NET_INC_STATS_BH(sock_net(sk), LINUX_MIB_SACKSHIFTFALLBACK);
 	return NULL;
 }