netstat: Add TCP In/Out Segs (#1185)

* netstat: Add TCP In/Out Segs

In order to get a better idea of TCP packet loss, we need to know how
many `node_netstat_Tcp_OutSegs` there are so we can compare this to
`node_netstat_Tcp_RetransSegs`.

Signed-off-by: Ben Kochie <superq@gmail.com>

* Update fixtures

Signed-off-by: Ben Kochie <superq@gmail.com>

collector/fixtures/e2e-64k-page-output.txt

@@ -1760,6 +1760,12 @@ node_netstat_Tcp_CurrEstab 0
 # HELP node_netstat_Tcp_InErrs Statistic TcpInErrs.
 # TYPE node_netstat_Tcp_InErrs untyped
 node_netstat_Tcp_InErrs 5
+# HELP node_netstat_Tcp_InSegs Statistic TcpInSegs.
+# TYPE node_netstat_Tcp_InSegs untyped
+node_netstat_Tcp_InSegs 5.7252008e+07
+# HELP node_netstat_Tcp_OutSegs Statistic TcpOutSegs.
+# TYPE node_netstat_Tcp_OutSegs untyped
+node_netstat_Tcp_OutSegs 5.4915039e+07
 # HELP node_netstat_Tcp_PassiveOpens Statistic TcpPassiveOpens.
 # TYPE node_netstat_Tcp_PassiveOpens untyped
 node_netstat_Tcp_PassiveOpens 230

collector/fixtures/e2e-output.txt

@@ -1760,6 +1760,12 @@ node_netstat_Tcp_CurrEstab 0
 # HELP node_netstat_Tcp_InErrs Statistic TcpInErrs.
 # TYPE node_netstat_Tcp_InErrs untyped
 node_netstat_Tcp_InErrs 5
+# HELP node_netstat_Tcp_InSegs Statistic TcpInSegs.
+# TYPE node_netstat_Tcp_InSegs untyped
+node_netstat_Tcp_InSegs 5.7252008e+07
+# HELP node_netstat_Tcp_OutSegs Statistic TcpOutSegs.
+# TYPE node_netstat_Tcp_OutSegs untyped
+node_netstat_Tcp_OutSegs 5.4915039e+07
 # HELP node_netstat_Tcp_PassiveOpens Statistic TcpPassiveOpens.
 # TYPE node_netstat_Tcp_PassiveOpens untyped
 node_netstat_Tcp_PassiveOpens 230

collector/netstat_linux.go

@@ -33,7 +33,7 @@ const (
 )
 
 var (
-	netStatFields = kingpin.Flag("collector.netstat.fields", "Regexp of fields to return for netstat collector.").Default("^(.*_(InErrors|InErrs)|Ip_Forwarding|Ip(6|Ext)_(InOctets|OutOctets)|Icmp6?_(InMsgs|OutMsgs)|TcpExt_(Listen.*|Syncookies.*|TCPSynRetrans)|Tcp_(ActiveOpens|PassiveOpens|RetransSegs|CurrEstab)|Udp6?_(InDatagrams|OutDatagrams|NoPorts))$").String()
+	netStatFields = kingpin.Flag("collector.netstat.fields", "Regexp of fields to return for netstat collector.").Default("^(.*_(InErrors|InErrs)|Ip_Forwarding|Ip(6|Ext)_(InOctets|OutOctets)|Icmp6?_(InMsgs|OutMsgs)|TcpExt_(Listen.*|Syncookies.*|TCPSynRetrans)|Tcp_(ActiveOpens|InSegs|OutSegs|PassiveOpens|RetransSegs|CurrEstab)|Udp6?_(InDatagrams|OutDatagrams|NoPorts))$").String()
 )
 
 type netStatCollector struct {