From f2f29d92d603e30bd9133aecf1400150916a42c0 Mon Sep 17 00:00:00 2001
From: Ole Markus With <o.with@sportradar.com>
Date: Thu, 20 Feb 2020 20:21:45 +0100
Subject: [PATCH] Properly detect that bpffs has been mounted

---
 go.mod                       |  1 +
 nodeup/pkg/model/BUILD.bazel |  1 +
 nodeup/pkg/model/network.go  | 16 ++++++++--------
 3 files changed, 10 insertions(+), 8 deletions(-)

diff --git a/go.mod b/go.mod
index 0293a552b2..75491f11fc 100644
--- a/go.mod
+++ b/go.mod
@@ -124,6 +124,7 @@ require (
 	golang.org/x/crypto v0.0.0-20191202143827-86a70503ff7e
 	golang.org/x/net v0.0.0-20191126235420-ef20fe5d7933
 	golang.org/x/oauth2 v0.0.0-20190604053449-0f29369cfe45
+	golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a
 	golang.org/x/tools v0.0.0-20191203134012-c197fd4bf371
 	google.golang.org/api v0.17.0
 	gopkg.in/gcfg.v1 v1.2.0
diff --git a/nodeup/pkg/model/BUILD.bazel b/nodeup/pkg/model/BUILD.bazel
index e8e852c8e3..0af942bff1 100644
--- a/nodeup/pkg/model/BUILD.bazel
+++ b/nodeup/pkg/model/BUILD.bazel
@@ -72,6 +72,7 @@ go_library(
         "//vendor/github.com/aws/aws-sdk-go/aws/session:go_default_library",
         "//vendor/github.com/aws/aws-sdk-go/service/ec2:go_default_library",
         "//vendor/github.com/blang/semver:go_default_library",
+        "//vendor/golang.org/x/sys/unix:go_default_library",
         "//vendor/k8s.io/api/core/v1:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/api/resource:go_default_library",
         "//vendor/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",
diff --git a/nodeup/pkg/model/network.go b/nodeup/pkg/model/network.go
index 2f2775a057..e02d9f5cfa 100644
--- a/nodeup/pkg/model/network.go
+++ b/nodeup/pkg/model/network.go
@@ -18,9 +18,9 @@ package model
 
 import (
 	"fmt"
-	"os"
 	"path/filepath"
 
+	"golang.org/x/sys/unix"
 	"k8s.io/kops/upup/pkg/fi"
 	"k8s.io/kops/upup/pkg/fi/nodeup/nodetasks"
 )
@@ -70,15 +70,15 @@ func (b *NetworkBuilder) Build(c *fi.ModelBuilderContext) error {
 	if networking.Cilium != nil {
 		// systemd v238 includes the bpffs mount by default; and gives an error "has a bad unit file setting" if we try to mount it again (see mount_point_is_api)
 		var alreadyMounted bool
-		_, err := os.Stat("/sys/fs/bpf")
+		// bpffs magic number
+		magic := uint32(0xCAFE4A11)
+		var fsdata unix.Statfs_t
+		err := unix.Statfs("/sys/fs/bpf", &fsdata)
+
 		if err != nil {
-			if os.IsNotExist(err) {
-				alreadyMounted = false
-			} else {
-				return fmt.Errorf("error checking for /sys/fs/bpf: %v", err)
-			}
+			alreadyMounted = false
 		} else {
-			alreadyMounted = true
+			alreadyMounted = int32(magic) == int32(fsdata.Type)
 		}
 
 		if !alreadyMounted {