Add --collector.netdev.device-whitelist flag (#1279)

* Add --collector.netdev.device-whitelist flag

Sometimes it is desired to monitor only one netdev. The golang regexp
does not support a negated regex, so the ignored-devices flag is too
cumbersome for this task.
This change introduces a new flag: accept-devices, which is mutually
exclusive to ignored-devices. This flag allows specifying ONLY the
netdev you'd like.

Signed-off-by: Noam Meltzer <noam@cynerio.co>

1 files changed, 22 insertions, 2 deletions

diff --git a/collector/netdev_linux_test.go b/collector/netdev_linux_test.go
index 7228ae2..163c87f 100644
--- a/collector/netdev_linux_test.go
+++ b/collector/netdev_linux_test.go
@@ -19,14 +19,14 @@ import (
         "testing"
 )
 
-func TestNetDevStats(t *testing.T) {
+func TestNetDevStatsIgnore(t *testing.T) {
         file, err := os.Open("fixtures/proc/net/dev")
         if err != nil {
                 t.Fatal(err)
         }
         defer file.Close()
 
-        netStats, err := parseNetDevStats(file, regexp.MustCompile("^veth"))
+        netStats, err := parseNetDevStats(file, regexp.MustCompile("^veth"), nil)
         if err != nil {
                 t.Fatal(err)
         }
@@ -59,3 +59,23 @@ func TestNetDevStats(t *testing.T) {
                 t.Error("want fixture interface 💩0 to exist, but it does not")
         }
 }
+
+func TestNetDevStatsAccept(t *testing.T) {
+        file, err := os.Open("fixtures/proc/net/dev")
+        if err != nil {
+                t.Fatal(err)
+        }
+        defer file.Close()
+
+        netStats, err := parseNetDevStats(file, nil, regexp.MustCompile("^💩0$"))
+        if err != nil {
+                t.Fatal(err)
+        }
+
+        if want, got := 1, len(netStats); want != got {
+                t.Errorf("want count of devices to be %d, got %d", want, got)
+        }
+        if want, got := "72", netStats["💩0"]["receive_multicast"]; want != got {
+                t.Error("want fixture interface 💩0 to exist, but it does not")
+        }
+}