Add support to disable BPF programs.

If the page size for an enhanced event is 0, then don't attempt to load
that BPF program. This is helpful for BPF programs that generate massive
amounts of events (like disk events).

lib/bpf/bpf.go

@@ -124,23 +124,23 @@ func New(config *Config) (BPF, error) {
 	start := time.Now()
 	log.Debugf("Starting enhanced session recording.")
 
-	// Compile and start BPF programs.
-	s.exec, err = startExec(closeContext, config.CommandBufferSize)
+	// Compile and start BPF programs if they are enabled (buffer size given).
+	s.exec, err = startExec(closeContext, *config.CommandBufferSize)
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}
-	s.open, err = startOpen(closeContext, config.DiskBufferSize)
+	s.open, err = startOpen(closeContext, *config.DiskBufferSize)
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}
-	s.conn, err = startConn(closeContext, config.NetworkBufferSize)
+	s.conn, err = startConn(closeContext, *config.NetworkBufferSize)
 	if err != nil {
 		return nil, trace.Wrap(err)
 	}
 
 	log.Debugf("Started enhanced session recording with buffer sizes (command=%v, "+
 		"disk=%v, network=%v) and cgroup mount path: %v. Took %v.",
-		s.CommandBufferSize, s.DiskBufferSize, s.NetworkBufferSize, s.CgroupPath,
+		*s.CommandBufferSize, *s.DiskBufferSize, *s.NetworkBufferSize, s.CgroupPath,
 		time.Since(start))
 
 	// Start pulling events off the perf buffers and emitting them to the

lib/bpf/command.go

@@ -89,6 +89,11 @@ func startExec(closeContext context.Context, pageCount int) (*exec, error) {
 		closeContext: closeContext,
 	}
 
+	// If the page count is zero, don't start any BPF module.
+	if pageCount == 0 {
+		return e, nil
+	}
+
 	// Compile the BPF program.
 	e.module = bcc.NewModule(execveSource, []string{})
 	if e.module == nil {

lib/bpf/common.go

@@ -85,28 +85,31 @@ type Config struct {
 	Enabled bool
 
 	// CommandBufferSize is the size of the perf buffer for command events.
-	CommandBufferSize int
+	CommandBufferSize *int
 
 	// DiskBufferSize is the size of the perf buffer for disk events.
-	DiskBufferSize int
+	DiskBufferSize *int
 
 	// NetworkBufferSize is the size of the perf buffer for network events.
-	NetworkBufferSize int
+	NetworkBufferSize *int
 
 	// CgroupPath is where the cgroupv2 hierarchy is mounted.
 	CgroupPath string
 }
 
 // CheckAndSetDefaults checks BPF configuration.
 func (c *Config) CheckAndSetDefaults() error {
-	if c.CommandBufferSize == 0 {
-		c.CommandBufferSize = defaults.PerfBufferPageCount
+	var perfBufferPageCount = defaults.PerfBufferPageCount
+	var openPerfBufferPageCount = defaults.OpenPerfBufferPageCount
+
+	if c.CommandBufferSize == nil {
+		c.CommandBufferSize = &perfBufferPageCount
 	}
-	if c.DiskBufferSize == 0 {
-		c.DiskBufferSize = defaults.OpenPerfBufferPageCount
+	if c.DiskBufferSize == nil {
+		c.DiskBufferSize = &openPerfBufferPageCount
 	}
-	if c.NetworkBufferSize == 0 {
-		c.NetworkBufferSize = defaults.PerfBufferPageCount
+	if c.NetworkBufferSize == nil {
+		c.NetworkBufferSize = &perfBufferPageCount
 	}
 	if c.CgroupPath == "" {
 		c.CgroupPath = defaults.CgroupPath

lib/bpf/common_test.go

@@ -0,0 +1,87 @@
+/*
+Copyright 2019 Gravitational, Inc.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package bpf
+
+import (
+	"fmt"
+
+	"github.com/gravitational/teleport/lib/defaults"
+	"github.com/gravitational/teleport/lib/utils"
+
+	"gopkg.in/check.v1"
+)
+
+type CommonSuite struct{}
+
+var _ = fmt.Printf
+var _ = check.Suite(&CommonSuite{})
+
+func (s *CommonSuite) SetUpSuite(c *check.C) {
+	utils.InitLoggerForTests()
+}
+func (s *CommonSuite) TearDownSuite(c *check.C) {}
+func (s *CommonSuite) SetUpTest(c *check.C)     {}
+func (s *CommonSuite) TearDownTest(c *check.C)  {}
+
+// TestCheckAndSetDefaults makes sure defaults are set when the user does not
+// provide values for the page sizes and hard coded values (like zero or a
+// specific page size) are respected when given.
+func (s *CommonSuite) TestCheckAndSetDefaults(c *check.C) {
+	var perfBufferPageCount = defaults.PerfBufferPageCount
+	var openPerfBufferPageCount = defaults.OpenPerfBufferPageCount
+	var zeroPageCount = 0
+
+	var tests = []struct {
+		inConfig  *Config
+		outConfig *Config
+	}{
+		// Empty values get defaults.
+		{
+			inConfig: &Config{
+				CommandBufferSize: nil,
+				DiskBufferSize:    nil,
+				NetworkBufferSize: nil,
+			},
+			outConfig: &Config{
+				CommandBufferSize: &perfBufferPageCount,
+				DiskBufferSize:    &openPerfBufferPageCount,
+				NetworkBufferSize: &perfBufferPageCount,
+			},
+		},
+		// Values are not wiped out with defaults.
+		{
+			inConfig: &Config{
+				CommandBufferSize: &zeroPageCount,
+				DiskBufferSize:    &zeroPageCount,
+				NetworkBufferSize: &perfBufferPageCount,
+			},
+			outConfig: &Config{
+				CommandBufferSize: &zeroPageCount,
+				DiskBufferSize:    &zeroPageCount,
+				NetworkBufferSize: &perfBufferPageCount,
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		err := tt.inConfig.CheckAndSetDefaults()
+		c.Assert(err, check.IsNil)
+		c.Assert(*tt.inConfig.CommandBufferSize, check.Equals, *tt.outConfig.CommandBufferSize)
+		c.Assert(*tt.inConfig.DiskBufferSize, check.Equals, *tt.outConfig.DiskBufferSize)
+		c.Assert(*tt.inConfig.NetworkBufferSize, check.Equals, *tt.outConfig.NetworkBufferSize)
+	}
+}

lib/bpf/disk.go

@@ -86,6 +86,11 @@ func startOpen(closeContext context.Context, pageCount int) (*open, error) {
 		closeContext: closeContext,
 	}
 
+	// If the page count is zero, don't start any BPF module.
+	if pageCount == 0 {
+		return e, nil
+	}
+
 	// Compile the BPF program.
 	e.module = bcc.NewModule(openSource, []string{})
 	if e.module == nil {

lib/bpf/network.go

@@ -118,6 +118,11 @@ func startConn(closeContext context.Context, pageCount int) (*conn, error) {
 		closeContext: closeContext,
 	}
 
+	// If the page count is zero, don't start any BPF module.
+	if pageCount == 0 {
+		return e, nil
+	}
+
 	e.module = bcc.NewModule(connSource, []string{})
 	if e.module == nil {
 		return nil, trace.BadParameter("failed to load libbcc")

lib/config/fileconf.go

@@ -725,13 +725,13 @@ type BPF struct {
 	Enabled string `yaml:"enabled"`
 
 	// CommandBufferSize is the size of the perf buffer for command events.
-	CommandBufferSize int `yaml:"command_buffer_size"`
+	CommandBufferSize *int `yaml:"command_buffer_size,omitempty"`
 
 	// DiskBufferSize is the size of the perf buffer for disk events.
-	DiskBufferSize int `yaml:"disk_buffer_size"`
+	DiskBufferSize *int `yaml:"disk_buffer_size,omitempty"`
 
 	// NetworkBufferSize is the size of the perf buffer for network events.
-	NetworkBufferSize int `yaml:"network_buffer_size"`
+	NetworkBufferSize *int `yaml:"network_buffer_size,omitempty"`
 
 	// CgroupPath controls where cgroupv2 hierarchy is mounted.
 	CgroupPath string `yaml:"cgroup_path"`