github.com/inspektor-gadget/inspektor-gadget@v0.28.1/pkg/gadgets/trace/tcp/tracer/tracer.go

// Copyright 2019-2023 The Inspektor Gadget authors
//
// 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.

//go:build !withoutebpf

package tracer

import (
	"errors"
	"fmt"
	"os"
	"unsafe"

	"github.com/cilium/ebpf"
	"github.com/cilium/ebpf/link"
	"github.com/cilium/ebpf/perf"

	gadgetcontext "github.com/inspektor-gadget/inspektor-gadget/pkg/gadget-context"
	"github.com/inspektor-gadget/inspektor-gadget/pkg/gadgets"
	"github.com/inspektor-gadget/inspektor-gadget/pkg/gadgets/trace/tcp/types"
	eventtypes "github.com/inspektor-gadget/inspektor-gadget/pkg/types"
)

//go:generate go run github.com/cilium/ebpf/cmd/bpf2go -target $TARGET -cc clang -cflags ${CFLAGS} -no-global-types -type event -type event_type tcptracer ./bpf/tcptracer.bpf.c -- -I./bpf/

type Config struct {
	MountnsMap *ebpf.Map
}

type Tracer struct {
	config        *Config
	enricher      gadgets.DataEnricherByMntNs
	eventCallback func(*types.Event)

	objs tcptracerObjects

	tcpv4connectEnterLink link.Link
	tcpv4connectExitLink  link.Link
	tcpv6connectEnterLink link.Link
	tcpv6connectExitLink  link.Link
	tcpCloseEnterLink     link.Link
	tcpSetStateEnterLink  link.Link
	inetCskAcceptExitLink link.Link

	reader *perf.Reader
}

func NewTracer(config *Config, enricher gadgets.DataEnricherByMntNs,
	eventCallback func(*types.Event),
) (*Tracer, error) {
	t := &Tracer{
		config:        config,
		enricher:      enricher,
		eventCallback: eventCallback,
	}

	if err := t.install(); err != nil {
		t.close()
		return nil, err
	}

	go t.run()

	return t, nil
}

// Stop stops the tracer
// TODO: Remove after refactoring
func (t *Tracer) Stop() {
	t.close()
}

func (t *Tracer) close() {
	t.tcpv4connectEnterLink = gadgets.CloseLink(t.tcpv4connectEnterLink)
	t.tcpv4connectExitLink = gadgets.CloseLink(t.tcpv4connectExitLink)
	t.tcpv6connectEnterLink = gadgets.CloseLink(t.tcpv6connectEnterLink)
	t.tcpv6connectExitLink = gadgets.CloseLink(t.tcpv6connectExitLink)
	t.tcpCloseEnterLink = gadgets.CloseLink(t.tcpCloseEnterLink)
	t.tcpSetStateEnterLink = gadgets.CloseLink(t.tcpSetStateEnterLink)
	t.inetCskAcceptExitLink = gadgets.CloseLink(t.inetCskAcceptExitLink)

	if t.reader != nil {
		t.reader.Close()
	}

	t.objs.Close()
}

func (t *Tracer) install() error {
	spec, err := loadTcptracer()
	if err != nil {
		return fmt.Errorf("loading ebpf program: %w", err)
	}

	if err := gadgets.LoadeBPFSpec(t.config.MountnsMap, spec, nil, &t.objs); err != nil {
		return fmt.Errorf("loading ebpf spec: %w", err)
	}

	t.tcpv4connectEnterLink, err = link.Kprobe("tcp_v4_connect", t.objs.IgTcpV4CoE, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	t.tcpv4connectExitLink, err = link.Kretprobe("tcp_v4_connect", t.objs.IgTcpV4CoX, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	t.tcpv6connectEnterLink, err = link.Kprobe("tcp_v6_connect", t.objs.IgTcpV6CoE, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	t.tcpv6connectExitLink, err = link.Kretprobe("tcp_v6_connect", t.objs.IgTcpV6CoX, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	// TODO: rename function in ebpf program
	t.tcpCloseEnterLink, err = link.Kprobe("tcp_close", t.objs.IgTcpClose, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	t.tcpSetStateEnterLink, err = link.Kprobe("tcp_set_state", t.objs.IgTcpState, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	t.inetCskAcceptExitLink, err = link.Kretprobe("inet_csk_accept", t.objs.IgTcpAccept, nil)
	if err != nil {
		return fmt.Errorf("attaching kprobe: %w", err)
	}

	reader, err := perf.NewReader(t.objs.tcptracerMaps.Events, gadgets.PerfBufferPages*os.Getpagesize())
	if err != nil {
		return fmt.Errorf("creating perf ring buffer: %w", err)
	}
	t.reader = reader

	return nil
}

func (t *Tracer) run() {
	for {
		record, err := t.reader.Read()
		if err != nil {
			if errors.Is(err, perf.ErrClosed) {
				// nothing to do, we're done
				return
			}

			msg := fmt.Sprintf("Error reading perf ring buffer: %s", err)
			t.eventCallback(types.Base(eventtypes.Err(msg)))
			return
		}

		if record.LostSamples > 0 {
			msg := fmt.Sprintf("lost %d samples", record.LostSamples)
			t.eventCallback(types.Base(eventtypes.Warn(msg)))
			continue
		}

		bpfEvent := (*tcptracerEvent)(unsafe.Pointer(&record.RawSample[0]))

		ipversion := gadgets.IPVerFromAF(bpfEvent.Af)

		event := types.Event{
			Event: eventtypes.Event{
				Type:      eventtypes.NORMAL,
				Timestamp: gadgets.WallTimeFromBootTime(bpfEvent.Timestamp),
			},
			WithMountNsID: eventtypes.WithMountNsID{MountNsID: bpfEvent.MntnsId},
			Pid:           bpfEvent.Pid,
			Uid:           bpfEvent.Uid,
			Gid:           bpfEvent.Gid,
			Comm:          gadgets.FromCString(bpfEvent.Task[:]),
			SrcEndpoint: eventtypes.L4Endpoint{
				L3Endpoint: eventtypes.L3Endpoint{
					Addr:    gadgets.IPStringFromBytes(bpfEvent.Saddr, ipversion),
					Version: uint8(ipversion),
				},
				Port: gadgets.Htons(bpfEvent.Sport),
			},
			DstEndpoint: eventtypes.L4Endpoint{
				L3Endpoint: eventtypes.L3Endpoint{
					Addr:    gadgets.IPStringFromBytes(bpfEvent.Daddr, ipversion),
					Version: uint8(ipversion),
				},
				Port: gadgets.Htons(bpfEvent.Dport),
			},
			IPVersion: ipversion,
		}

		switch bpfEvent.Type {
		case tcptracerEventTypeTCP_EVENT_TYPE_CONNECT:
			event.Operation = "connect"
		case tcptracerEventTypeTCP_EVENT_TYPE_ACCEPT:
			event.Operation = "accept"
		case tcptracerEventTypeTCP_EVENT_TYPE_CLOSE:
			event.Operation = "close"
		}

		if t.enricher != nil {
			t.enricher.EnrichByMntNs(&event.CommonData, event.MountNsID)
		}

		t.eventCallback(&event)
	}
}

// --- Registry changes

func (t *Tracer) Run(gadgetCtx gadgets.GadgetContext) error {
	defer t.close()
	if err := t.install(); err != nil {
		return fmt.Errorf("installing tracer: %w", err)
	}

	go t.run()
	gadgetcontext.WaitForTimeoutOrDone(gadgetCtx)

	return nil
}

func (t *Tracer) SetMountNsMap(mountnsMap *ebpf.Map) {
	t.config.MountnsMap = mountnsMap
}

func (t *Tracer) SetEventHandler(handler any) {
	nh, ok := handler.(func(ev *types.Event))
	if !ok {
		panic("event handler invalid")
	}
	t.eventCallback = nh
}

func (g *GadgetDesc) NewInstance() (gadgets.Gadget, error) {
	tracer := &Tracer{
		config: &Config{},
	}
	return tracer, nil
}