loader: remove ctx from uncancellable functions

Loading bpf objects used to be done by iproute2, where propagating ctx to the
exec.Cmd invocations made sense, since realistically any shellout can hang for
arbitrary reasons.

Now the loader is fully hosted in the agent process, this no longer makes sense.
Once we're blocked in a bpf() syscall, e.g. for loading a program, the verifier
can be interrupted by sending a signal to the calling thread. Since the Go runtime
routinely sends these signals under normal operation, ebpf-go will retry a few
times when bpf() returns EINTR. The API currently doesn't expose a way to cancel
program loading/verification, and there's no clear benefit to doing so in the first
place.

Verification is relatively lightweight compared to datapath compilation, so
interrupting it during teardown is of questionable benefit. The agent doesn't expect
it to be interruptible, it's bound to leave endpoints in an undefined state.

This commit introduces the assumption that, once endpoint loading/attachment is
kicked off (after compilation), it cannot be cancelled. This is reflected in the
interface exposed to the rest of the system, by removing the ctx parameter on many
methods. Only compilation can be interrupted, since it can take a long time on some
systems, especially lower-spec.

Signed-off-by: Timo Beckers <timo@isovalent.com>

pkg/datapath/fake/types/datapath.go

@@ -130,7 +130,7 @@ func (f *FakeLoader) CompileOrLoad(ctx context.Context, ep datapath.Endpoint, st
 	panic("implement me")
 }
 
-func (f *FakeLoader) ReloadDatapath(ctx context.Context, ep datapath.Endpoint, stats *metrics.SpanStat) error {
+func (f *FakeLoader) ReloadDatapath(ep datapath.Endpoint, stats *metrics.SpanStat) error {
 	panic("implement me")
 }
 

pkg/datapath/loader/base.go

@@ -164,7 +164,7 @@ func cleanIngressQdisc(devices []string) error {
 }
 
 // reinitializeIPSec is used to recompile and load encryption network programs.
-func (l *loader) reinitializeIPSec(ctx context.Context) error {
+func (l *loader) reinitializeIPSec() error {
 	// We need to take care not to load bpf_network and bpf_host onto the same
 	// device. If devices are required, we load bpf_host and hence don't need
 	// the code below, specific to EncryptInterface. Specifically, we will load
@@ -200,7 +200,7 @@ func (l *loader) reinitializeIPSec(ctx context.Context) error {
 		return nil
 	}
 
-	coll, finalize, err := loadDatapath(ctx, networkObj)
+	coll, finalize, err := loadDatapath(networkObj)
 	if err != nil {
 		return fmt.Errorf("loading %s: %w", networkObj, err)
 	}
@@ -449,7 +449,7 @@ func (l *loader) Reinitialize(ctx context.Context, tunnelConfig tunnel.Config, d
 			log.WithError(err).Fatal("failed to compile encryption programs")
 		}
 
-		if err := l.reinitializeIPSec(ctx); err != nil {
+		if err := l.reinitializeIPSec(); err != nil {
 			return err
 		}
 	}

pkg/datapath/loader/loader.go

@@ -399,20 +399,14 @@ func removeObsoleteNetdevPrograms(devices []string) error {
 // - cilium_host: ingress and egress
 // - cilium_net: ingress
 // - native devices: ingress and (optionally) egress if certain features require it
-func (l *loader) reloadHostDatapath(ctx context.Context, ep datapath.Endpoint, objPath string, devices []string) error {
-	// Warning: here be dragons. There used to be a single loop over
-	// interfaces+objs+progs here from the iproute2 days, but this was never
-	// correct to begin with. Tail call maps were always reused when possible,
-	// causing control flow to transition through invalid states as new tail calls
-	// were sequentially upserted into the array.
-
+func (l *loader) reloadHostDatapath(ep datapath.Endpoint, objPath string, devices []string) error {
 	// Replace programs on cilium_host.
 	host, err := netlink.LinkByName(ep.InterfaceName())
 	if err != nil {
 		return fmt.Errorf("retrieving device %s: %w", ep.InterfaceName(), err)
 	}
 
-	coll, finalize, err := loadDatapath(ctx, objPath)
+	coll, finalize, err := loadDatapath(objPath)
 	if err != nil {
 		return err
 	}
@@ -442,7 +436,7 @@ func (l *loader) reloadHostDatapath(ctx context.Context, ep datapath.Endpoint, o
 		return err
 	}
 
-	coll, finalize, err = loadDatapath(ctx, secondDevObjPath)
+	coll, finalize, err = loadDatapath(secondDevObjPath)
 	if err != nil {
 		return err
 	}
@@ -472,7 +466,7 @@ func (l *loader) reloadHostDatapath(ctx context.Context, ep datapath.Endpoint, o
 		}
 
 		// Load bpf_netdev_<dev>.o.
-		coll, finalize, err := loadDatapath(ctx, netdevObjPath)
+		coll, finalize, err := loadDatapath(netdevObjPath)
 		if err != nil {
 			return err
 		}
@@ -520,7 +514,7 @@ func (l *loader) reloadHostDatapath(ctx context.Context, ep datapath.Endpoint, o
 	return nil
 }
 
-func (l *loader) reloadDatapath(ctx context.Context, ep datapath.Endpoint, dirs *directoryInfo) error {
+func (l *loader) reloadDatapath(ep datapath.Endpoint, dirs *directoryInfo) error {
 	// Replace the current program
 	objPath := path.Join(dirs.Output, endpointObj)
 	device := ep.InterfaceName()
@@ -535,11 +529,11 @@ func (l *loader) reloadDatapath(ctx context.Context, ep datapath.Endpoint, dirs
 		}
 
 		objPath = path.Join(dirs.Output, hostEndpointObj)
-		if err := l.reloadHostDatapath(ctx, ep, objPath, devices); err != nil {
+		if err := l.reloadHostDatapath(ep, objPath, devices); err != nil {
 			return err
 		}
 	} else {
-		coll, finalize, err := loadDatapath(ctx, objPath)
+		coll, finalize, err := loadDatapath(objPath)
 		if err != nil {
 			return err
 		}
@@ -594,12 +588,16 @@ func (l *loader) replaceOverlayDatapath(ctx context.Context, cArgs []string, ifa
 		return fmt.Errorf("compiling overlay program: %w", err)
 	}
 
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	device, err := netlink.LinkByName(iface)
 	if err != nil {
 		return fmt.Errorf("retrieving device %s: %w", iface, err)
 	}
 
-	coll, finalize, err := loadDatapath(ctx, overlayObj)
+	coll, finalize, err := loadDatapath(overlayObj)
 	if err != nil {
 		return err
 	}
@@ -693,19 +691,19 @@ func (l *loader) compileOrLoad(ctx context.Context, ep datapath.Endpoint, dirs *
 	}
 	stats.BpfWriteELF.End(err == nil)
 
-	return l.ReloadDatapath(ctx, ep, stats)
+	return l.ReloadDatapath(ep, stats)
 }
 
 // ReloadDatapath reloads the BPF datapath programs for the specified endpoint.
-func (l *loader) ReloadDatapath(ctx context.Context, ep datapath.Endpoint, stats *metrics.SpanStat) (err error) {
+func (l *loader) ReloadDatapath(ep datapath.Endpoint, stats *metrics.SpanStat) (err error) {
 	dirs := directoryInfo{
 		Library: option.Config.BpfDir,
 		Runtime: option.Config.StateDir,
 		State:   ep.StateDir(),
 		Output:  ep.StateDir(),
 	}
 	stats.BpfLoadProg.Start()
-	err = l.reloadDatapath(ctx, ep, &dirs)
+	err = l.reloadDatapath(ep, &dirs)
 	stats.BpfLoadProg.End(err == nil)
 	return err
 }

pkg/datapath/loader/loader_test.go

@@ -137,7 +137,7 @@ func TestReload(t *testing.T) {
 	linkDir := testutils.TempBPFFS(t)
 
 	for range 2 {
-		coll, finalize, err := loadDatapath(ctx, objPath)
+		coll, finalize, err := loadDatapath(objPath)
 		require.NoError(t, err)
 
 		require.NoError(t, attachSKBProgram(l, coll.Programs[symbolFromEndpoint],
@@ -279,7 +279,7 @@ func BenchmarkReplaceDatapath(b *testing.B) {
 	objPath := fmt.Sprintf("%s/%s", dirInfo.Output, endpointObj)
 	b.ResetTimer()
 	for i := 0; i < b.N; i++ {
-		coll, finalize, err := loadDatapath(ctx, objPath)
+		coll, finalize, err := loadDatapath(objPath)
 		if err != nil {
 			b.Fatal(err)
 		}

pkg/datapath/loader/netlink.go

@@ -4,7 +4,6 @@
 package loader
 
 import (
-	"context"
 	"errors"
 	"fmt"
 	"net"
@@ -50,12 +49,7 @@ func directionToParent(dir string) uint32 {
 // For example, this is the case with from-netdev and to-netdev. If eth0:to-netdev
 // gets its program and maps replaced and unpinned, its eth0:from-netdev counterpart
 // will miss tail calls (and drop packets) until it has been replaced as well.
-func loadDatapath(ctx context.Context, obj string) (*ebpf.Collection, func(), error) {
-	// Avoid unnecessarily loading a prog.
-	if err := ctx.Err(); err != nil {
-		return nil, nil, err
-	}
-
+func loadDatapath(obj string) (*ebpf.Collection, func(), error) {
 	l := log.WithField("objPath", obj)
 
 	// Load the ELF from disk.

pkg/datapath/loader/types/types.go

@@ -23,7 +23,7 @@ type Loader interface {
 	HostDatapathInitialized() <-chan struct{}
 	Reinitialize(ctx context.Context, tunnelConfig tunnel.Config, deviceMTU int, iptMgr types.IptablesManager, p types.Proxy) error
 	ReinitializeXDP(ctx context.Context, extraCArgs []string) error
-	ReloadDatapath(ctx context.Context, ep types.Endpoint, stats *metrics.SpanStat) (err error)
+	ReloadDatapath(ep types.Endpoint, stats *metrics.SpanStat) (err error)
 	RestoreTemplates(stateDir string) error
 	Unload(ep types.Endpoint)
 }

pkg/datapath/loader/xdp.go

@@ -157,7 +157,7 @@ func compileAndLoadXDPProg(ctx context.Context, xdpDev, xdpMode string, extraCAr
 		return fmt.Errorf("retrieving device %s: %w", xdpDev, err)
 	}
 
-	coll, finalize, err := loadDatapath(ctx, objPath)
+	coll, finalize, err := loadDatapath(objPath)
 	if err != nil {
 		return err
 	}

pkg/datapath/types/loader.go

@@ -18,7 +18,7 @@ type Loader interface {
 	CallsMapPath(id uint16) string
 	CustomCallsMapPath(id uint16) string
 	CompileOrLoad(ctx context.Context, ep Endpoint, stats *metrics.SpanStat) error
-	ReloadDatapath(ctx context.Context, ep Endpoint, stats *metrics.SpanStat) error
+	ReloadDatapath(ep Endpoint, stats *metrics.SpanStat) error
 	ReinitializeXDP(ctx context.Context, extraCArgs []string) error
 	EndpointHash(cfg EndpointConfiguration) (string, error)
 	Unload(ep Endpoint)

pkg/endpoint/bpf.go

@@ -671,7 +671,7 @@ func (e *Endpoint) realizeBPFState(regenContext *regenerationContext) (compilati
 			}
 			compilationExecuted = true
 		} else { // RegenerateWithDatapathLoad
-			err = e.owner.Datapath().Loader().ReloadDatapath(datapathRegenCtxt.completionCtx, datapathRegenCtxt.epInfoCache, &stats.datapathRealization)
+			err = e.owner.Datapath().Loader().ReloadDatapath(datapathRegenCtxt.epInfoCache, &stats.datapathRealization)
 			if err == nil {
 				e.getLogger().Info("Reloaded endpoint BPF program")
 			} else {