v2sessionless.go

package bmc

import (
	"context"
	"errors"
	"fmt"
	"time"

	"github.com/gebn/bmc/internal/pkg/transport"
	"github.com/gebn/bmc/pkg/ipmi"
	"github.com/gebn/bmc/pkg/layerexts"

	"github.com/cenkalti/backoff/v4"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/prometheus/client_golang/prometheus"
)

var (
	errRetryableCode = errors.New("completion code indicated temporary failure")

	// these not only save a map lookup each open, but also register the labels
	v2ConnectionOpenAttempts = connectionOpenAttempts.WithLabelValues("2.0")
	v2ConnectionOpenFailures = connectionOpenFailures.WithLabelValues("2.0")
	v2ConnectionsOpen        = connectionsOpen.WithLabelValues("2.0")
)

// v2ConnectionLayers contains layers common to all v2.0 connections. Although
// these layers are common, both V2Sessionless and V2Session embed this as a
// value, so each gets a fresh set of layers. This uses a little more memory,
// but it means when a session is closed, its session layer doesn't have a
// dangling confidentiality layer etc. This is why this is not embedded in
// v2ConnectionShared.
type v2ConnectionLayers struct {
	rmcpLayer            layers.RMCP
	sessionSelectorLayer ipmi.SessionSelector
	v2SessionLayer       ipmi.V2Session
	messageLayer         ipmi.Message
}

// v2ConnectionShared contains fields that a session-less connection passes to
// sessions created from it. V2Sessionless embeds a value of this type, and
// V2Session embeds a pointer which is set to the V2Sessionless's value.
//
// Note that a given BMC only supports a single command at a time, which is what
// makes this possible - if a session is sending a command, the session-less
// connection it was initiated from cannot send concurrently.
type v2ConnectionShared struct {

	// transport is the underlying UDP socket for the connection.
	transport transport.Transport

	// buffer is used to build all packets to send during this connection.
	// Reusing this between sends drastically reduces the number of allocations
	// we have to do when building packets, and reusing it between session-less
	// and session-based connections reduces it a little further.
	buffer gopacket.SerializeBuffer

	// layers contains layer types decoded by the connection's
	// gopacket.DecodingLayerParser. Although this slice is shared, each
	// connection has its own DLP, as each session may have a different
	// confidentiality layer.
	layers []gopacket.LayerType

	// backoff saves allocating a backoff each request. We must call .Reset() to
	// reset this between requests.
	backoff backoff.BackOff
}

// V2Sessionless represents a session-less connection to a BMC using a "null"
// IPMI v2.0 session wrapper.
type V2Sessionless struct {
	v2ConnectionLayers
	v2ConnectionShared

	// timeout is the time we allow the BMC to respond to each UDP request. This
	// contrasts with the context, which includes retries.
	timeout time.Duration

	// decode parses the layers in v2ConnectionShared.
	decode gopacket.DecodingLayerFunc
}

func newV2Sessionless(t transport.Transport, timeout time.Duration) *V2Sessionless {
	s := &V2Sessionless{
		v2ConnectionShared: v2ConnectionShared{
			transport: t,
			buffer:    gopacket.NewSerializeBuffer(),
			backoff:   backoff.NewExponentialBackOff(),
		},
		timeout: timeout,
	}
	dlc := gopacket.DecodingLayerContainer(gopacket.DecodingLayerArray(nil))
	dlc = dlc.Put(&s.rmcpLayer)
	dlc = dlc.Put(&s.sessionSelectorLayer)
	dlc = dlc.Put(&s.v2SessionLayer)
	dlc = dlc.Put(&s.messageLayer)
	s.decode = dlc.LayersDecoder(s.rmcpLayer.LayerType(), gopacket.NilDecodeFeedback)
	return s
}

func (s *V2Sessionless) Version() string {
	return "2.0"
}

// SetTimeout configures the per-request timeout for a given RMCP+ or IPMI
// command. Methods will retry temporary errors until the context expires; this
// configures how long we will wait for a response.
func (s *V2Sessionless) SetTimeout(t time.Duration) {
	s.timeout = t
}

func (s *V2Sessionless) buildAndSendPayload(ctx context.Context, p ipmi.Payload) error {
	s.rmcpLayer = layers.RMCP{
		Version:  layers.RMCPVersion1,
		Sequence: 0xFF, // do not send us an ACK
		Class:    layers.RMCPClassIPMI,
	}
	s.v2SessionLayer = ipmi.V2Session{
		PayloadDescriptor: *p.Descriptor(),
	}

	// we don't need to increment a sequence number between retries, so can
	// serialise this just once
	// N.B. no message layer as this is only used for RMCP+ session setup (see
	// ipmi.Payload interface for more details)
	if err := gopacket.SerializeLayers(s.buffer, serializeOptions,
		&s.rmcpLayer,
		// session selector only used when decoding
		&s.v2SessionLayer,
		p.Request()); err != nil {
		return err
	}

	s.backoff.Reset()
	retryable := func() error {
		requestCtx, cancel := context.WithTimeout(ctx, s.timeout)
		response, err := s.transport.Send(requestCtx, s.buffer.Bytes())
		cancel()
		if err != nil {
			return err
		}
		if _, err := s.decode(response, &s.layers); err != nil {
			return err
		}
		types := layerexts.DecodedTypes(s.layers)
		if err := types.InnermostEquals(ipmi.LayerTypeV2Session); err != nil {
			return err
		}
		return nil
	}
	if err := backoff.Retry(retryable, backoff.WithContext(s.backoff, ctx)); err != nil {
		return err
	}

	return p.Response().DecodeFromBytes(
		s.v2SessionLayer.LayerPayload(), gopacket.NilDecodeFeedback)
}

// saves having to write two SerializeLayers calls in SendCommand
func serializableLayerOrEmpty(s gopacket.SerializableLayer) gopacket.SerializableLayer {
	if s == nil {
		return gopacket.Payload(nil)
	}
	return s
}

func (s *V2Sessionless) SendCommand(ctx context.Context, c ipmi.Command) (ipmi.CompletionCode, error) {
	timer := prometheus.NewTimer(commandDuration)
	defer timer.ObserveDuration()
	commandAttempts.WithLabelValues(c.Name()).Inc()

	if err := s.buildAndSendCommand(ctx, c); err != nil {
		commandFailures.WithLabelValues(c.Name()).Inc()
		return 0, err
	}

	// we got a message, so we have a completion code. Note that if this is
	// non-normal, BMCs are allowed to truncate the response after that field,
	// however we attempt to parse a response regardless for the sake of those
	// BMCs that don't. If we get an error, it is passed back along with the
	// correct completion code. Users of this function should not rely on the
	// response if the code is non-normal.
	code := s.messageLayer.CompletionCode

	if c.Response() != nil {
		// the command is expecting a response body in the success case - do our
		// best; this may validly fail if the code is non-normal
		if err := c.Response().DecodeFromBytes(s.messageLayer.LayerPayload(),
			gopacket.NilDecodeFeedback); err != nil {
			commandFailures.WithLabelValues(c.Name()).Inc()
			return code, err
		}
	}

	// even if code is non-normal, if we didn't have any issues, we don't report
	// it as a command failure, as execution itself completed successfully; it
	// just didn't have the intended result
	return code, nil
}

func (s *V2Sessionless) buildAndSendCommand(ctx context.Context, c ipmi.Command) error {
	s.rmcpLayer = layers.RMCP{
		Version:  layers.RMCPVersion1,
		Sequence: 0xFF, // do not send us an ACK
		Class:    layers.RMCPClassIPMI,
	}
	s.v2SessionLayer = ipmi.V2Session{
		PayloadDescriptor: ipmi.PayloadDescriptorIPMI,
	}
	s.messageLayer = ipmi.Message{
		Operation:     *c.Operation(),
		RemoteAddress: ipmi.SlaveAddressBMC.Address(),
		RemoteLUN:     c.RemoteLUN(),
		LocalAddress:  ipmi.SoftwareIDRemoteConsole1.Address(),
		Sequence:      1,
	}

	// we don't need to increment a sequence number between retries, so can
	// serialise this just once
	if err := gopacket.SerializeLayers(s.buffer, serializeOptions,
		&s.rmcpLayer,
		// session selector only used when decoding
		&s.v2SessionLayer,
		&s.messageLayer,
		serializableLayerOrEmpty(c.Request())); err != nil {
		return err
	}

	s.backoff.Reset()
	firstAttempt := true
	return backoff.Retry(func() error {
		if firstAttempt {
			firstAttempt = false
		} else {
			commandRetries.Inc()
		}

		requestCtx, cancel := context.WithTimeout(ctx, s.timeout)
		response, err := s.transport.Send(requestCtx, s.buffer.Bytes())
		cancel()
		if err != nil {
			return err
		}

		// parse bytes
		if _, err := s.decode(response, &s.layers); err != nil {
			return err
		}

		// ensure we got a message (we don't attempt to parse below message
		// here)
		types := layerexts.DecodedTypes(s.layers)
		if err := types.InnermostEquals(ipmi.LayerTypeMessage); err != nil {
			return err
		}

		code := s.messageLayer.CompletionCode
		// must increment here, otherwise we'll miss temporary codes at the
		// higher levels
		commandResponses.WithLabelValues(code.String()).Inc()
		// check completion code is permanent
		if code.IsTemporary() {
			return errRetryableCode
		}
		return nil
	}, backoff.WithContext(s.backoff, ctx))
}

func (s *V2Sessionless) GetSystemGUID(ctx context.Context) ([16]byte, error) {
	return getSystemGUID(ctx, s)
}

func getSystemGUID(ctx context.Context, c Connection) ([16]byte, error) {
	cmd := &ipmi.GetSystemGUIDCmd{}
	if err := ValidateResponse(c.SendCommand(ctx, cmd)); err != nil {
		return [16]byte{}, err
	}

	// we could return a google/uuid type, however that requires the BMC return
	// a valid GUID in network byte order, and the spec says it should be
	// treated as an opaque value. The user can interpret these bytes how they
	// wish.
	return cmd.Rsp.GUID, nil
}

func (s *V2Sessionless) GetChannelAuthenticationCapabilities(
	ctx context.Context,
	r *ipmi.GetChannelAuthenticationCapabilitiesReq,
) (*ipmi.GetChannelAuthenticationCapabilitiesRsp, error) {
	return getChannelAuthenticationCapabilities(ctx, s, r)
}

func getChannelAuthenticationCapabilities(
	ctx context.Context,
	c Connection,
	req *ipmi.GetChannelAuthenticationCapabilitiesReq,
) (*ipmi.GetChannelAuthenticationCapabilitiesRsp, error) {
	// we could set req.ExtendedData here as we're guaranteed to be IPMI v2.0,
	// however let the user decide
	cmd := &ipmi.GetChannelAuthenticationCapabilitiesCmd{
		Req: *req,
	}
	if err := ValidateResponse(c.SendCommand(ctx, cmd)); err != nil {
		return nil, err
	}
	return &cmd.Rsp, nil
}

func (s *V2Sessionless) openSession(ctx context.Context, r *ipmi.OpenSessionReq) (*ipmi.OpenSessionRsp, error) {
	// if we were being *really* aggressive, we could store these payloads in
	// the sessionless struct for reuse during any future session establishments
	payload := &ipmi.OpenSessionPayload{
		Req: *r,
	}
	if err := s.buildAndSendPayload(ctx, payload); err != nil {
		return nil, err
	}
	rsp := &payload.Rsp
	if rsp.Tag != r.Tag {
		return nil, fmt.Errorf("tag mismatch; expected %v, got %v", r.Tag,
			rsp.Tag)
	}
	if rsp.Status != ipmi.StatusCodeOK {
		return nil, fmt.Errorf("managed system returned non-OK status: %v",
			rsp.Status)
	}
	return rsp, nil
}

func (s *V2Sessionless) rakpMessage1(ctx context.Context, r *ipmi.RAKPMessage1) (*ipmi.RAKPMessage2, error) {
	payload := &ipmi.RAKPMessage1Payload{
		Req: *r,
	}
	if err := s.buildAndSendPayload(ctx, payload); err != nil {
		return nil, err
	}
	rsp := &payload.Rsp
	if rsp.Tag != r.Tag {
		return nil, fmt.Errorf("tag mismatch; expected %v, got %v", r.Tag,
			rsp.Tag)
	}
	if rsp.Status != ipmi.StatusCodeOK {
		return nil, fmt.Errorf("managed system returned non-OK status: %v",
			rsp.Status)
	}
	return rsp, nil
}

func (s *V2Sessionless) rakpMessage3(ctx context.Context, r *ipmi.RAKPMessage3) (*ipmi.RAKPMessage4, error) {
	payload := &ipmi.RAKPMessage3Payload{
		Req: *r,
	}
	if err := s.buildAndSendPayload(ctx, payload); err != nil {
		return nil, err
	}
	rsp := &payload.Rsp
	if rsp.Tag != r.Tag {
		return nil, fmt.Errorf("tag mismatch; expected %v, got %v", r.Tag,
			rsp.Tag)
	}
	if rsp.Status != ipmi.StatusCodeOK {
		return nil, fmt.Errorf("managed system returned non-OK status: %v",
			rsp.Status)
	}
	return rsp, nil
}