1package yamux
2
3import (
4	"fmt"
5	"io"
6	"log"
7	"os"
8	"time"
9)
10
11// Config is used to tune the Yamux session
12type Config struct {
13	// AcceptBacklog is used to limit how many streams may be
14	// waiting an accept.
15	AcceptBacklog int
16
17	// EnableKeepalive is used to do a period keep alive
18	// messages using a ping.
19	EnableKeepAlive bool
20
21	// KeepAliveInterval is how often to perform the keep alive
22	KeepAliveInterval time.Duration
23
24	// ConnectionWriteTimeout is meant to be a "safety valve" timeout after
25	// we which will suspect a problem with the underlying connection and
26	// close it. This is only applied to writes, where's there's generally
27	// an expectation that things will move along quickly.
28	ConnectionWriteTimeout time.Duration
29
30	// MaxStreamWindowSize is used to control the maximum
31	// window size that we allow for a stream.
32	MaxStreamWindowSize uint32
33
34	// LogOutput is used to control the log destination. Either Logger or
35	// LogOutput can be set, not both.
36	LogOutput io.Writer
37
38	// Logger is used to pass in the logger to be used. Either Logger or
39	// LogOutput can be set, not both.
40	Logger *log.Logger
41}
42
43// DefaultConfig is used to return a default configuration
44func DefaultConfig() *Config {
45	return &Config{
46		AcceptBacklog:          256,
47		EnableKeepAlive:        true,
48		KeepAliveInterval:      30 * time.Second,
49		ConnectionWriteTimeout: 10 * time.Second,
50		MaxStreamWindowSize:    initialStreamWindow,
51		LogOutput:              os.Stderr,
52	}
53}
54
55// VerifyConfig is used to verify the sanity of configuration
56func VerifyConfig(config *Config) error {
57	if config.AcceptBacklog <= 0 {
58		return fmt.Errorf("backlog must be positive")
59	}
60	if config.KeepAliveInterval == 0 {
61		return fmt.Errorf("keep-alive interval must be positive")
62	}
63	if config.MaxStreamWindowSize < initialStreamWindow {
64		return fmt.Errorf("MaxStreamWindowSize must be larger than %d", initialStreamWindow)
65	}
66	if config.LogOutput != nil && config.Logger != nil {
67		return fmt.Errorf("both Logger and LogOutput may not be set, select one")
68	} else if config.LogOutput == nil && config.Logger == nil {
69		return fmt.Errorf("one of Logger or LogOutput must be set, select one")
70	}
71	return nil
72}
73
74// Server is used to initialize a new server-side connection.
75// There must be at most one server-side connection. If a nil config is
76// provided, the DefaultConfiguration will be used.
77func Server(conn io.ReadWriteCloser, config *Config) (*Session, error) {
78	if config == nil {
79		config = DefaultConfig()
80	}
81	if err := VerifyConfig(config); err != nil {
82		return nil, err
83	}
84	return newSession(config, conn, false), nil
85}
86
87// Client is used to initialize a new client-side connection.
88// There must be at most one client-side connection.
89func Client(conn io.ReadWriteCloser, config *Config) (*Session, error) {
90	if config == nil {
91		config = DefaultConfig()
92	}
93
94	if err := VerifyConfig(config); err != nil {
95		return nil, err
96	}
97	return newSession(config, conn, true), nil
98}
99