emulator::get-controller - returning SSMP GET value

Rev.0/emulator/ssmp/bisync.go

@@ -3,6 +3,7 @@ package ssmp
 import (
 	"bytes"
 	"encoding/binary"
+	"fmt"
 )
 
 const SOH byte = 1
@@ -93,3 +94,69 @@ func encode(msgid uint32, packet []byte) ([]byte, error) {
 
 	return b.Bytes(), nil
 }
+
+func decode(msg []uint8) (uint32, []byte, error) {
+	packet := bytes.Buffer{}
+	msgid := uint32(0)
+	ix := 0
+
+	// .. get message header
+	for ix < len(msg) {
+		if b := msg[ix]; b == SOH {
+			break
+		} else {
+			ix++
+		}
+	}
+
+	if msg[ix] != SOH {
+		return 0, nil, fmt.Errorf("missing SOH")
+	} else {
+		ix++
+	}
+
+	for i := 0; i < 4; i++ {
+		if ix < len(msg) {
+			b := msg[ix]
+			ix++
+
+			msgid <<= 8
+			msgid += uint32(b)
+		} else {
+			return 0, nil, fmt.Errorf("missing message ID")
+		}
+	}
+
+	// ... get message content
+	for ix < len(msg) {
+		if b := msg[ix]; b == STX {
+			break
+		} else {
+			ix++
+		}
+	}
+
+	if msg[ix] != STX {
+		return 0, nil, fmt.Errorf("missing STX")
+	} else {
+		ix++
+	}
+
+	for ix < len(msg) {
+		if b := msg[ix]; b == ETX {
+			break
+		} else if err := packet.WriteByte(b); err != nil {
+			return 0, nil, err
+		} else {
+			ix++
+		}
+	}
+
+	if msg[ix] != ETX {
+		return 0, nil, fmt.Errorf("missing ETX")
+	} else {
+		ix++
+	}
+
+	return msgid, packet.Bytes(), nil
+}

Rev.0/emulator/ssmp/ssmp.go

@@ -19,8 +19,8 @@ type SSMP struct {
 }
 
 type request struct {
-	id     uint32
 	packet []byte
+	pipe   chan []byte
 }
 
 var write = make(chan request)
@@ -30,9 +30,9 @@ func Get(oid []uint32) (any, error) {
 	logger := gosnmp.NewLogger(syslog.New(os.Stdout, "", 0))
 
 	pdu := gosnmp.SnmpPDU{
-		Value: nil,
+		Value: uint32(405419896),
 		Name:  ".1.3.6.655136.1.1",
-		Type:  gosnmp.Null,
+		Type:  gosnmp.Uinteger32,
 	}
 
 	packet := gosnmp.SnmpPacket{
@@ -55,18 +55,32 @@ func Get(oid []uint32) (any, error) {
 	if bytes, err := packet.MarshalMsg(); err != nil {
 		return nil, err
 	} else {
-		id := uint32(1) // rqid.Add(1)
-		if encoded, err := encode(id, bytes); err != nil {
-			return nil, err
-		} else {
-			write <- request{
-				id:     id,
-				packet: encoded,
+		rq := request{
+			packet: bytes,
+			pipe:   make(chan []byte),
+		}
+
+		timeout := time.After(500 * time.Millisecond)
+
+		write <- rq
+		select {
+		case reply := <-rq.pipe:
+			debugf("reply to SSMP GET request (%v)", reply)
+
+			if value, err := get(reply, ".1.3.6.655136.1.1"); err != nil {
+				return 0, fmt.Errorf("invalid reply to SSMP GET %v request", ".1.3.6.655136.1.1")
+			} else if v, ok := value.(uint32); !ok {
+				return 0, fmt.Errorf("invalid valid in reply to SSMP GET %v request", ".1.3.6.655136.1.1")
+			} else {
+				return v, nil
 			}
+
+		case <-timeout:
+			return 0, fmt.Errorf("no reply to SSMP GET %v request", ".1.3.6.655136.1.1")
 		}
 	}
 
-	return uint32(405419896), nil
+	return 0, fmt.Errorf("SSMP GET %v failed", ".1.3.6.655136.1.1")
 }
 
 func (ssmp SSMP) Run() {
@@ -80,6 +94,8 @@ func (ssmp SSMP) Run() {
 }
 
 func (ssmp SSMP) read() error {
+	handlers := map[uint32]request{}
+
 	if t, err := term.Open(ssmp.USB, term.Speed(9600), term.RawMode); err != nil {
 		return err
 	} else {
@@ -149,15 +165,35 @@ func (ssmp SSMP) read() error {
 
 		for {
 			select {
-			case reply := <-pipe:
-				debugf("read %v %v", len(reply), reply)
+			case msg := <-pipe:
+				debugf("read %v %v", len(msg), msg)
+				if id, reply, err := decode(msg); err != nil {
+					warnf("read error (%v)", err)
+				} else {
+					debugf("read %v %v", id, reply)
+
+					if h, ok := handlers[id]; ok {
+						h.pipe <- reply
+					} else {
+						warnf("read error (%v)", fmt.Errorf("missing handler for message %v", id))
+					}
+
+					delete(handlers, id)
+				}
 
 			case request := <-write:
 				debugf("write %v", request)
-				if N, err := t.Write(request.packet); err != nil {
+				id := uint32(1) // rqid.Add(1)
+				if encoded, err := encode(id, request.packet); err != nil {
 					warnf("write error (%v)", err)
+				} else if N, err := t.Write(encoded); err != nil {
+					warnf("write error (%v)", err)
+				} else if N != len(encoded) {
+					warnf("write error (%v)", fmt.Errorf("sent %v bytes of %v)", N, len(encoded)))
 				} else {
 					debugf("write (%v bytes)", N)
+
+					handlers[id] = request
 				}
 
 			case <-idle:
@@ -172,6 +208,22 @@ func (ssmp SSMP) read() error {
 	}
 }
 
+func get(msg []uint8, OID string) (any, error) {
+	snmp := gosnmp.GoSNMP{}
+
+	if packet, err := snmp.SnmpDecodePacket(msg); err != nil {
+		return nil, err
+	} else {
+		for _, pdu := range packet.Variables {
+			if pdu.Name == OID {
+				return pdu.Value, nil
+			}
+		}
+	}
+
+	return nil, fmt.Errorf("OID %v not found", OID)
+}
+
 func debugf(format string, args ...any) {
 	log.Debugf("SSMP", format, args...)
 }

TODO.md

@@ -5,19 +5,29 @@
       - https://www.raspberrypi.com/documentation/pico-sdk/hardware.html#rpip2aed586200427c10f67f
       - compile time constant
 
+### emulator
+    - [ ] get-controller
+          - [x] from MIB
+          - [ ] populate MIB from SSMP
+          - [ ] errors pipe in request
+          - [ ] prune handlers
+          - [ ] move encoding to encoding/BER
+          - [ ] move encoding to encoding/bisync
+          - [ ] use SNMP request/message ID
+    - [ ] walk MIB to initialise/refresh cache
+    - [ ] // TODO: exponential backoff
+    - [ ] tinygo
+
+
 ### SSMP
    - [x] disable print/println in SSMP mode
    - [x] SYN-SYN-ENQ/SYN-SYN-ACK
    - [ ] MIB
    - [ ] GET
          - [x] // FIXME doesn't work with binary protocol
-         - [x] DLE
-```
-write [22 22 1 0 0 0 1 2 48 37 2 1 0 4 6 112 117 98 108 105 99 160 24 2 1 1 2 1 0 2 1 0 48 13 48 11 6 7 43 6 167 254 32 1 1 5 0 3]
-read  [22 22 1 0 0 0 1 2 48 37 2 1 0 4 6 112 117 98 108 105 99 160 24 2 1 1 2 1 0 2 1 0 48 13 48 11 6 7 43 6 167 254 32 1 1 5 0 3]
-```
-         - (?) hexadecimal text
-   - [ ] usb_init
+         - [x] decode::DLE 
+         - [ ] return SnmpGetResponse
+         - [ ] encode::DLE 
    - [ ] Enable FIFO
    - [ ] pico: txrx/uart conflict
    - https://www.baeldung.com/cs/bisync
@@ -36,13 +46,6 @@ read  [22 22 1 0 0 0 1 2 48 37 2 1 0 4 6 112 117 98 108 105 99 160 24 2 1 1 2 1
     - [ ] dropping last typed character if echo uses sys::print
           - printf works but sys::print doesn't
 
-### emulator
-    - [ ] get-controller
-          - [x] from MIB
-          - [ ] populate MIB from SSMP
-    - [ ] // TODO: exponential backoff
-    - [ ] tinygo
-
 ## PiZeroW
    - [ ] Reduce power consumption
    - [ ] NB: 24/7 operation - Cam said to ask him