From 3001499cae03a79d1edc8f92f22f4d64a61af5b4 Mon Sep 17 00:00:00 2001
From: Josh Deprez <josh.deprez@gmail.com>
Date: Sun, 7 Apr 2024 14:05:07 +1000
Subject: [PATCH] Add RTMP packet formats

---
 atalk/rtmp/data.go     | 89 ++++++++++++++++++++++++++++++++++++++++++
 atalk/rtmp/request.go  | 15 +++++++
 atalk/rtmp/response.go | 43 ++++++++++++++++++++
 3 files changed, 147 insertions(+)
 create mode 100644 atalk/rtmp/data.go
 create mode 100644 atalk/rtmp/request.go
 create mode 100644 atalk/rtmp/response.go

diff --git a/atalk/rtmp/data.go b/atalk/rtmp/data.go
new file mode 100644
index 0000000..77be855
--- /dev/null
+++ b/atalk/rtmp/data.go
@@ -0,0 +1,89 @@
+package rtmp
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/sfiera/multitalk/pkg/ddp"
+)
+
+// DataPacket represents an RTMP Data packet.
+type DataPacket struct {
+	RouterAddr    ddp.Addr
+	NetworkTuples []NetworkTuple
+}
+
+// NetworkTuple represents routing information.
+type NetworkTuple struct {
+	Extended   bool
+	RangeStart ddp.Network
+	RangeEnd   ddp.Network
+	Distance   uint8
+}
+
+// UnmarshalDataPacket unmarshals a DataPacket.
+func UnmarshalDataPacket(data []byte) (*DataPacket, error) {
+	if len(data) < 7 || (len(data)-4)%3 != 0 {
+		return nil, fmt.Errorf("invalid input length %d for RTMP Data packet", len(data))
+	}
+	if data[2] != 8 {
+		return nil, fmt.Errorf("unsupported node ID length %d for RTMP Data packet", data[2])
+	}
+	dp := &DataPacket{
+		RouterAddr: ddp.Addr{
+			Network: ddp.Network(binary.BigEndian.Uint16(data[:2])),
+			Node:    ddp.Node(data[3]),
+		},
+	}
+	data = data[4:]
+
+	first := true
+	for len(data) > 0 {
+		if len(data) < 3 {
+			return nil, fmt.Errorf("insufficient remaining input length %d for RTMP Data network tuple", len(data))
+		}
+		nt := NetworkTuple{
+			RangeStart: ddp.Network(binary.BigEndian.Uint16(data[:2])),
+			Distance:   data[2],
+		}
+		data = data[3:]
+		if nt.RangeStart == 0 {
+			// if non-extended, first tuple should contain version
+			if !first {
+				return nil, fmt.Errorf("invalid RTMP network tuple range start 0")
+			}
+			// initial non-extended tuple with Distance field containing version
+			if nt.Distance != 0x82 {
+				return nil, fmt.Errorf("unsupported RTMP version %x", nt.Distance)
+			}
+			first = false
+			continue
+		}
+		nt.Extended = nt.Distance&0x80 != 0
+		if !nt.Extended {
+			// ordinary non-extended tuple
+			if first && nt.RangeStart != 0 {
+				return nil, fmt.Errorf("first RTMP network tuple is not version tuple")
+			}
+			dp.NetworkTuples = append(dp.NetworkTuples, nt)
+			continue
+		}
+
+		// extended tuple
+		if len(data) < 3 {
+			return nil, fmt.Errorf("insufficient remaining input length %d for RTMP Data extended network tuple", len(data))
+		}
+		nt.Distance &^= 0x80
+		nt.RangeEnd = ddp.Network(binary.BigEndian.Uint16(data[:2]))
+		if first {
+			if data[2] != 0x82 {
+				return nil, fmt.Errorf("unsupported RTMP version %x", data[2])
+			}
+		}
+		first = false
+		dp.NetworkTuples = append(dp.NetworkTuples, nt)
+		data = data[3:]
+	}
+
+	return dp, nil
+}
diff --git a/atalk/rtmp/request.go b/atalk/rtmp/request.go
new file mode 100644
index 0000000..ce9a2ae
--- /dev/null
+++ b/atalk/rtmp/request.go
@@ -0,0 +1,15 @@
+package rtmp
+
+import "fmt"
+
+// RequestPacket represents an RTMP Request or RTMP Route Data Request packet.
+type RequestPacket struct {
+	Function uint8
+}
+
+func UnmarshalRequestPacket(data []byte) (*RequestPacket, error) {
+	if len(data) != 1 {
+		return nil, fmt.Errorf("invalid data length %d for RTMP Request or RTMP RDR packet", len(data))
+	}
+	return &RequestPacket{Function: data[0]}, nil
+}
diff --git a/atalk/rtmp/response.go b/atalk/rtmp/response.go
new file mode 100644
index 0000000..2cbaec6
--- /dev/null
+++ b/atalk/rtmp/response.go
@@ -0,0 +1,43 @@
+package rtmp
+
+import (
+	"encoding/binary"
+	"fmt"
+
+	"github.com/sfiera/multitalk/pkg/ddp"
+)
+
+type ResponsePacket struct {
+	SenderAddr ddp.Addr
+	Extended   bool
+	RangeStart ddp.Network
+	RangeEnd   ddp.Network
+}
+
+func UnmarshalResponsePacket(data []byte) (*ResponsePacket, error) {
+	if len(data) != 4 && len(data) != 10 {
+		return nil, fmt.Errorf("invalid input length %d for RTMP Response packet", len(data))
+	}
+	if data[2] != 8 {
+		return nil, fmt.Errorf("unsupported node ID length %d for RTMP Response packet", data[2])
+	}
+	rp := &ResponsePacket{
+		SenderAddr: ddp.Addr{
+			Network: ddp.Network(binary.BigEndian.Uint16(data[:2])),
+			Node:    ddp.Node(data[3]),
+		},
+	}
+	if len(data) == 4 {
+		return rp, nil
+	}
+
+	rp.RangeStart = ddp.Network(binary.BigEndian.Uint16(data[4:6]))
+	if data[6] != 0x80 {
+		return nil, fmt.Errorf("invalid intermediate byte %x for RTMP Response packet", data[6])
+	}
+	rp.RangeEnd = ddp.Network(binary.BigEndian.Uint16(data[7:9]))
+	if data[9] != 0x82 {
+		return nil, fmt.Errorf("unsupported version %x for RTMP Response packet", data[9])
+	}
+	return rp, nil
+}