From 0fc6511989cd7e69f08ef3f5aef13ffa5836be4f Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Iago=20L=C3=B3pez=20Galeiras?= <iago@kinvolk.io>
Date: Thu, 2 Mar 2017 17:36:52 +0100
Subject: [PATCH] ebpf: print a user-friendly error if kernel <4.4

---
 probe/endpoint/ebpf.go | 41 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 41 insertions(+)

diff --git a/probe/endpoint/ebpf.go b/probe/endpoint/ebpf.go
index cbe210a80b..32bc189fae 100644
--- a/probe/endpoint/ebpf.go
+++ b/probe/endpoint/ebpf.go
@@ -2,11 +2,14 @@ package endpoint
 
 import (
 	"errors"
+	"fmt"
+	"regexp"
 	"strconv"
 	"sync"
 
 	log "github.com/Sirupsen/logrus"
 	"github.com/weaveworks/scope/probe/endpoint/procspy"
+	"github.com/weaveworks/scope/probe/host"
 	"github.com/weaveworks/tcptracer-bpf/pkg/tracer"
 )
 
@@ -40,11 +43,49 @@ type EbpfTracker struct {
 	closedConnections []ebpfConnection
 }
 
+var releaseRegex = regexp.MustCompile(`^(\d+)\.(\d+).*$`)
+
+func isKernelSupported() error {
+	release, _, err := host.GetKernelReleaseAndVersion()
+	if err != nil {
+		return err
+	}
+
+	releaseParts := releaseRegex.FindStringSubmatch(release)
+	if len(releaseParts) != 3 {
+		return fmt.Errorf("got invalid release version %q (expected format '4.4[.2-1]')", release)
+	}
+
+	major, err := strconv.Atoi(releaseParts[1])
+	if err != nil {
+		return err
+	}
+
+	minor, err := strconv.Atoi(releaseParts[2])
+	if err != nil {
+		return err
+	}
+
+	if major > 4 {
+		return nil
+	}
+
+	if major < 4 || minor < 4 {
+		return fmt.Errorf("got kernel %s but need kernel >=4.4", release)
+	}
+
+	return nil
+}
+
 func newEbpfTracker(useEbpfConn bool) (eventTracker, error) {
 	if !useEbpfConn {
 		return nil, errors.New("ebpf tracker not enabled")
 	}
 
+	if err := isKernelSupported(); err != nil {
+		return nil, fmt.Errorf("kernel not supported: %v", err)
+	}
+
 	t, err := tracer.NewTracer(tcpEventCbV4, tcpEventCbV6)
 	if err != nil {
 		return nil, err