telegabber/xmpp/jingle/convert.go

// XEP-0166 Jingle stanzas <-> SDP strings
package jingle

import (
	"errors"
	"fmt"
	"strings"
)

const (
	hardcodedMediaProtocol = "UDP/TLS/RTP/SAVPF"
	hardcodedMediaPort     = "9"
	hardcodedConnection    = "IN IP4 0.0.0.0"
	hardcodedOrigin        = "- 8770656990916039506 2 IN IP4 127.0.0.1"
)

var (
	defaultICEOptions   = []string{"trickle"}
	wellKnownICEOptions = map[string]bool{"trickle": true, "renomination": true}
)

// direction-flag resolution and metadata for SDPToJingle
type ConvertOpts struct {
	// governs how senders=initiator/responder maps to sendonly/recvonly
	Initiator bool
	// <content creator='...'/> value; defaults to "initiator"
	LocalCreator string
	// <jingle sid='...'/> value
	SessionID string
}

func JingleToSDP(j *JingleIQ, opts ConvertOpts) (string, error) {
	if j == nil {
		return "", errors.New("nil JingleIQ")
	}
	b := &sdpBuilder{}
	b.line("v=0")
	b.line("o=" + hardcodedOrigin)
	b.line("s=-")
	b.line("t=0 0")

	sessAttrs, err := buildSessionAttrs(j)
	if err != nil {
		return "", err
	}
	b.appendAttrs(sessAttrs)

	bundled := j.Group != nil && j.Group.Semantics != ""

	for _, c := range j.Contents {
		if c.Description == nil || c.Transport == nil {
			continue
		}
		mediaAttrs, err := buildMediaAttrs(&c, bundled, opts)
		if err != nil {
			return "", err
		}
		formats := make([]string, 0, len(c.Description.PayloadTypes))
		for _, pt := range c.Description.PayloadTypes {
			formats = append(formats, pt.ID)
		}
		mline := "m=" + c.Description.Media + " " + hardcodedMediaPort + " " + hardcodedMediaProtocol
		if len(formats) > 0 {
			mline += " " + strings.Join(formats, " ")
		}
		b.line(mline)
		b.line("c=" + hardcodedConnection)
		b.appendAttrs(mediaAttrs)
	}
	return b.String(), nil
}

func SDPToJingle(sdp string, opts ConvertOpts) (*JingleIQ, error) {
	doc, err := parseSDP(sdp)
	if err != nil {
		return nil, err
	}
	creator := opts.LocalCreator
	if creator == "" {
		creator = "initiator"
	}
	j := &JingleIQ{SID: opts.SessionID}

	if groupVal := mmFirst(doc.sessionAttrs, "group", ""); groupVal != "" {
		parts := strings.Fields(groupVal)
		if len(parts) >= 1 {
			sem := parts[0]
			if strings.ContainsAny(sem, " \t\r\n") {
				return nil, fmt.Errorf("group semantics contains whitespace: %q", sem)
			}
			g := &Group{Semantics: sem}
			for _, name := range parts[1:] {
				if strings.ContainsAny(name, " \t\r\n") {
					return nil, fmt.Errorf("group content name contains whitespace: %q", name)
				}
				g.Contents = append(g.Contents, GroupContent{Name: name})
			}
			j.Group = g
		}
	}

	for _, m := range doc.media {
		content, err := buildJingleContent(&m, doc.sessionAttrs, creator, opts.Initiator)
		if err != nil {
			return nil, err
		}
		j.Contents = append(j.Contents, *content)
	}
	return j, nil
}

func buildSessionAttrs(j *JingleIQ) ([]kv, error) {
	var attrs []kv
	if j.Group != nil && j.Group.Semantics != "" {
		sem := j.Group.Semantics
		if strings.ContainsAny(sem, " \t\r\n") {
			return nil, fmt.Errorf("group semantics contains whitespace: %q", sem)
		}
		tags := make([]string, 0, len(j.Group.Contents))
		for _, gc := range j.Group.Contents {
			if strings.ContainsAny(gc.Name, " \t\r\n") {
				return nil, fmt.Errorf("group content name contains whitespace: %q", gc.Name)
			}
			tags = append(tags, gc.Name)
		}
		val := sem
		if len(tags) > 0 {
			val += " " + strings.Join(tags, " ")
		}
		attrs = append(attrs, kv{"group", val})
	}
	attrs = append(attrs, kv{"msid-semantic", " WMS my-media-stream"})
	return attrs, nil
}

// attr order matches jinglesdp.tcl: transport, payload/feedback/ssrc,
// mid/direction/rtcp/candidates
func buildMediaAttrs(c *Content, bundled bool, opts ConvertOpts) ([]kv, error) {
	var attrs []kv
	if err := appendTransportAttrs(c.Transport, &attrs); err != nil {
		return nil, err
	}
	if err := appendDescriptionAttrs(c.Description, &attrs); err != nil {
		return nil, err
	}
	attrs = append(attrs, kv{"mid", c.Name})
	attrs = append(attrs, kv{sendersToSDP(c.Senders, opts.Initiator), ""})
	if c.Description.RtcpMux != nil || bundled {
		attrs = append(attrs, kv{"rtcp-mux", ""})
	}
	attrs = append(attrs, kv{"rtcp", "9 IN IP4 0.0.0.0"})
	for _, cand := range c.Transport.Candidates {
		s, err := candidateToSDP(&cand)
		if err != nil {
			return nil, err
		}
		attrs = append(attrs, kv{"candidate", s})
	}
	return attrs, nil
}

func buildJingleContent(m *mediaSection, sessAttrs []kv, creator string, initiator bool) (*Content, error) {
	name := mmFirst(m.attrs, "mid", m.media)
	c := &Content{
		Creator: creator,
		Name:    name,
	}
	if s := sendersFromMM(m.attrs, initiator); s != "both" {
		c.Senders = s
	}
	desc, err := buildJingleDescription(m)
	if err != nil {
		return nil, err
	}
	c.Description = desc
	transport, err := buildJingleTransport(m, sessAttrs)
	if err != nil {
		return nil, err
	}
	c.Transport = transport
	return c, nil
}

// SDP direction attr name; value is empty because a=sendrecv is bare
func sendersToSDP(senders string, initiator bool) string {
	switch senders {
	case "", "both":
		return "sendrecv"
	case "none":
		return "inactive"
	case "initiator":
		if initiator {
			return "sendonly"
		}
		return "recvonly"
	case "responder":
		if initiator {
			return "recvonly"
		}
		return "sendonly"
	}
	return "sendrecv"
}

func sendersFromMM(mm []kv, initiator bool) string {
	if mmHas(mm, "sendrecv") {
		return "both"
	}
	if mmHas(mm, "inactive") {
		return "none"
	}
	if mmHas(mm, "sendonly") {
		if initiator {
			return "initiator"
		}
		return "responder"
	}
	if mmHas(mm, "recvonly") {
		if initiator {
			return "responder"
		}
		return "initiator"
	}
	return "both"
}