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package sidechannel
import (
"context"
"encoding/binary"
"fmt"
"net"
"strconv"
"time"
"gitlab.com/gitlab-org/gitaly/v14/internal/backchannel"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/metadata"
)
var magicBytes = []byte("sidechannel")
// sidechannelTimeout is the timeout for establishing a sidechannel
// connection. The sidechannel is supposed to be opened on the same wire with
// incoming grpc request. There won't be real handshaking involved, so it
// should be fast.
const (
sidechannelTimeout = 5 * time.Second
sidechannelMetadataKey = "gitaly-sidechannel-id"
)
// OpenSidechannel opens a sidechannel connection from the stream opener
// extracted from the current peer connection.
func OpenSidechannel(ctx context.Context) (_ net.Conn, err error) {
md, ok := metadata.FromIncomingContext(ctx)
if !ok {
return nil, fmt.Errorf("sidechannel: failed to extract incoming metadata")
}
ids := md.Get(sidechannelMetadataKey)
if len(ids) == 0 {
return nil, fmt.Errorf("sidechannel: sidechannel-id not found in incoming metadata")
}
sidechannelID, _ := strconv.ParseInt(ids[len(ids)-1], 10, 64)
muxSession, err := backchannel.GetYamuxSession(ctx)
if err != nil {
return nil, fmt.Errorf("sidechannel: fail to extract yamux session: %w", err)
}
stream, err := muxSession.Open()
if err != nil {
return nil, fmt.Errorf("sidechannel: open stream: %w", err)
}
defer func() {
if err != nil {
stream.Close()
}
}()
if err := stream.SetDeadline(time.Now().Add(sidechannelTimeout)); err != nil {
return nil, err
}
if _, err := stream.Write(magicBytes); err != nil {
return nil, fmt.Errorf("sidechannel: write magic bytes: %w", err)
}
if err := binary.Write(stream, binary.BigEndian, sidechannelID); err != nil {
return nil, fmt.Errorf("sidechannel: write stream id: %w", err)
}
if err := stream.SetDeadline(time.Time{}); err != nil {
return nil, err
}
return stream, nil
}
// RegisterSidechannel registers the caller into the waiting list of the
// sidechannel registry and injects the sidechannel ID into outgoing metadata.
// The caller is expected to establish the request with the returned context. The
// callback is executed automatically when the sidechannel connection arrives.
// The result is pushed to the error channel of the returned waiter.
func RegisterSidechannel(ctx context.Context, registry *Registry, callback func(net.Conn) error) (context.Context, *Waiter) {
waiter := registry.Register(callback)
ctxOut := metadata.AppendToOutgoingContext(ctx, sidechannelMetadataKey, fmt.Sprintf("%d", waiter.id))
return ctxOut, waiter
}
// ServerHandshaker implements the server-side sidechannel handshake.
type ServerHandshaker struct {
registry *Registry
}
// Magic returns the magic bytes for sidechannel
func (s *ServerHandshaker) Magic() string {
return string(magicBytes)
}
// Handshake implements the handshaking logic for sidechannel so that
// this handshaker reads the sidechannel ID from the wire, and then delegates
// the connection to the sidechannel registry
func (s *ServerHandshaker) Handshake(conn net.Conn, authInfo credentials.AuthInfo) (net.Conn, credentials.AuthInfo, error) {
var sidechannelID sidechannelID
if err := binary.Read(conn, binary.BigEndian, &sidechannelID); err != nil {
return nil, nil, fmt.Errorf("sidechannel: fail to extract sidechannel ID: %w", err)
}
if err := s.registry.receive(sidechannelID, conn); err != nil {
return nil, nil, err
}
// credentials.ErrConnDispatched, indicating that the connection is already
// dispatched out of gRPC. gRPC should leave it alone and exit in peace.
return nil, nil, credentials.ErrConnDispatched
}
// NewServerHandshaker creates a new handshaker for sidechannel to
// embed into listenmux.
func NewServerHandshaker(registry *Registry) *ServerHandshaker {
return &ServerHandshaker{registry: registry}
}
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