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package backchannel
import (
"context"
"errors"
"fmt"
"io"
"net"
"github.com/hashicorp/yamux"
"github.com/sirupsen/logrus"
"google.golang.org/grpc"
"google.golang.org/grpc/credentials"
"google.golang.org/grpc/credentials/insecure"
"google.golang.org/grpc/peer"
)
// ErrNonMultiplexedConnection is returned when attempting to get the peer id of a non-multiplexed
// connection.
var ErrNonMultiplexedConnection = errors.New("non-multiplexed connection")
// authInfoWrapper is used to pass the peer id through the context to the RPC handlers.
type authInfoWrapper struct {
id ID
session *yamux.Session
credentials.AuthInfo
}
func (w authInfoWrapper) peerID() ID { return w.id }
func (w authInfoWrapper) yamuxSession() *yamux.Session { return w.session }
// GetPeerID gets the ID of the current peer connection.
func GetPeerID(ctx context.Context) (ID, error) {
peerInfo, ok := peer.FromContext(ctx)
if !ok {
return 0, errors.New("no peer info in context")
}
wrapper, ok := peerInfo.AuthInfo.(interface{ peerID() ID })
if !ok {
return 0, ErrNonMultiplexedConnection
}
return wrapper.peerID(), nil
}
// WithID stores the ID in the provided AuthInfo so it can be later accessed by the RPC handler.
// GetYamuxSession gets the yamux session of the current peer connection.
// This is exported to facilitate testing.
func WithID(authInfo credentials.AuthInfo, id ID) credentials.AuthInfo {
return authInfoWrapper{id: id, AuthInfo: authInfo}
}
// GetYamuxSession gets the yamux session of the current peer connection.
func GetYamuxSession(ctx context.Context) (*yamux.Session, error) {
peerInfo, ok := peer.FromContext(ctx)
if !ok {
return nil, errors.New("no peer info in context")
}
wrapper, ok := peerInfo.AuthInfo.(interface{ yamuxSession() *yamux.Session })
if !ok {
return nil, ErrNonMultiplexedConnection
}
return wrapper.yamuxSession(), nil
}
func withSessionInfo(authInfo credentials.AuthInfo, id ID, muxSession *yamux.Session) credentials.AuthInfo {
return authInfoWrapper{id: id, AuthInfo: authInfo, session: muxSession}
}
// ServerHandshaker implements the server side handshake of the multiplexed connection.
type ServerHandshaker struct {
registry *Registry
logger logrus.FieldLogger
dialOpts []grpc.DialOption
}
// Magic is used by listenmux to retrieve the magic string for
// backchannel connections.
func (s *ServerHandshaker) Magic() string { return string(magicBytes) }
// NewServerHandshaker returns a new server side implementation of the backchannel. The provided TransportCredentials
// are handshaked prior to initializing the multiplexing session. The Registry is used to store the backchannel connections.
// DialOptions can be used to set custom dial options for the backchannel connections. They must not contain a dialer or
// transport credentials as those set by the handshaker.
func NewServerHandshaker(logger logrus.FieldLogger, reg *Registry, dialOpts []grpc.DialOption) *ServerHandshaker {
return &ServerHandshaker{registry: reg, logger: logger, dialOpts: dialOpts}
}
// Handshake establishes a gRPC ClientConn back to the backchannel client
// on the other side and stores its ID in the AuthInfo where it can be
// later accessed by the RPC handlers. gRPC sets an IO timeout on the
// connection before calling ServerHandshake, so we don't have to handle
// timeouts separately.
func (s *ServerHandshaker) Handshake(conn net.Conn, authInfo credentials.AuthInfo) (net.Conn, credentials.AuthInfo, error) {
// It is not necessary to clean up any of the multiplexing-related sessions on errors as the
// gRPC server closes the conn if there is an error, which closes the multiplexing
// session as well.
logger := s.logger.WithField("component", "backchannel.YamuxServer").WriterLevel(logrus.ErrorLevel)
// Open the server side of the multiplexing session.
//
// Gitaly is using custom settings with a lower accept backlog and higher receive
// buffer size than Praefect and the clients. We should eventually strive to match
// the settings here to avoid Gitaly from buffering too much.
cfg := DefaultConfiguration()
cfg.AcceptBacklog = 1
cfg.MaximumStreamWindowSizeBytes = 16 * 1024 * 1024
muxSession, err := yamux.Server(conn, muxConfig(logger, cfg))
if err != nil {
logger.Close()
return nil, nil, fmt.Errorf("create multiplexing session: %w", err)
}
// Accept the client's stream. This is the client's gRPC session to the server.
clientToServerStream, err := muxSession.Accept()
if err != nil {
logger.Close()
return nil, nil, fmt.Errorf("accept client's stream: %w", err)
}
// The address does not actually matter but we set it so clientConn.Target returns a meaningful value.
// Insecure credentials are used as the multiplexer operates within a TLS session already if one is configured.
backchannelConn, err := grpc.Dial(
"multiplexed/"+conn.RemoteAddr().String(),
append(
s.dialOpts,
grpc.WithTransportCredentials(insecure.NewCredentials()),
grpc.WithContextDialer(func(context.Context, string) (net.Conn, error) { return muxSession.Open() }),
)...,
)
if err != nil {
logger.Close()
return nil, nil, fmt.Errorf("dial backchannel: %w", err)
}
id := s.registry.RegisterBackchannel(backchannelConn)
// The returned connection must close the underlying network connection, we redirect the close
// to the muxSession which also closes the underlying connection.
return &connCloser{
Conn: clientToServerStream,
close: func() error {
s.registry.RemoveBackchannel(id)
var firstErr error
for _, closer := range []io.Closer{
backchannelConn, muxSession, logger,
} {
if err := closer.Close(); err != nil && firstErr == nil {
firstErr = err
}
}
return firstErr
},
},
withSessionInfo(authInfo, id, muxSession),
nil
}
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