Add TCPSynRetrans to netstat default filter (#1143)

Tcp SYN packet retransmits are a very useful signal as they affect
network performance disproportionately to regular TCP retransmits.

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

CHANGELOG.md

@@ -5,7 +5,7 @@
 ### Changes
 
 * [BUGFIX]
-* [CHANGE]
+* [CHANGE] Add TCPSynRetrans to netstat default filter #1143
 * [ENHANCEMENT] Add Infiniband counters #1120
 * [FEATURE]
 

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