New error messages

internal/radio/errors.go

@@ -10,5 +10,7 @@ import (
 )
 
 var (
-	ErrNilCtx = errors.New("nil context")
+	ErrNilCtx     = errors.New("nil context")
+	ErrNilUdpConn = errors.New("nil UDP Connection")
+	ErrUnknownUE  = errors.New("Unknown UE")
 )

internal/radio/radio.go

@@ -9,7 +9,6 @@ import (
 	"bytes"
 	"context"
 	"encoding/json"
-	"fmt"
 	"net"
 	"net/http"
 	"net/netip"
@@ -61,7 +60,7 @@ func (r *Radio) Write(pkt []byte, srv *net.UDPConn, ue jsonapi.ControlURI) error
 	ueRan, ok := r.peerMap.Load(ue)
 	if !ok {
 		logrus.Trace("Unknown UE")
-		return fmt.Errorf("Unknown UE")
+		return ErrUnknownUE
 	}
 
 	_, err := srv.WriteToUDPAddrPort(pkt, ueRan.(netip.AddrPort))

internal/radio/radio_daemon.go

@@ -7,7 +7,6 @@ package radio
 
 import (
 	"context"
-	"fmt"
 	"net"
 	"net/netip"
 
@@ -44,7 +43,7 @@ func NewRadioDaemon(radio *Radio, psMan *session.PduSessionsManager, gnbRanAddr
 func (r *RadioDaemon) runUplinkDaemon(ctx context.Context, srv *net.UDPConn) error {
 	if srv == nil {
 		logrus.Error("nil server")
-		return fmt.Errorf("nil srv")
+		return ErrNilUdpConn
 	}
 	for {
 		select {
@@ -71,7 +70,7 @@ type DLPkt struct {
 
 func (r *RadioDaemon) WriteDownlink(payload []byte, ue jsonapi.ControlURI) error {
 	if r.srv == nil {
-		return fmt.Errorf("nil srv")
+		return ErrNilUdpConn
 	}
 	return r.radio.Write(payload, r.srv, ue)
 }
@@ -93,7 +92,7 @@ func (r *RadioDaemon) Start(ctx context.Context) error {
 	}).Info("Starting Radio Simulatior")
 	go func(ctx context.Context, srv *net.UDPConn) error {
 		if srv == nil {
-			return fmt.Errorf("nil srv")
+			return ErrNilUdpConn
 		}
 		select {
 		case <-ctx.Done():

internal/session/errors.go

@@ -11,4 +11,7 @@ import (
 
 var (
 	ErrNilCtx = errors.New("nil context")
+
+	ErrUnsupportedPDUType = errors.New("Unsupported PDU type")
+	ErrPduSessionNotFound = errors.New("PDU Session not found")
 )

internal/session/pdu_sessions_manager.go

@@ -7,7 +7,6 @@ package session
 
 import (
 	"context"
-	"fmt"
 	"math/rand"
 	"net"
 	"net/netip"
@@ -44,19 +43,19 @@ func NewPduSessionsManager(gtpAddr netip.Addr) *PduSessionsManager {
 func (p *PduSessionsManager) WriteUplink(ctx context.Context, pkt []byte) error {
 	if len(pkt) < 20 {
 		logrus.Trace("too small to be an ipv4 packet")
-		return fmt.Errorf("Too small to be an ipv4 packet")
+		return ErrUnsupportedPDUType
 	}
 	if (pkt[0] >> 4) != 4 {
 		logrus.Trace("not an ipv4 packet")
-		return fmt.Errorf("Not an ipv4 packet")
+		return ErrUnsupportedPDUType
 	}
 	src := netip.AddrFrom4([4]byte{pkt[12], pkt[13], pkt[14], pkt[15]})
 	fteid, ok := p.Uplink[src]
 	if !ok {
 		logrus.WithFields(logrus.Fields{
 			"ue": src,
 		}).Trace("unknown UE")
-		return fmt.Errorf("Unknown UE")
+		return ErrPduSessionNotFound
 	}
 	gpdu := message.NewHeaderWithExtensionHeaders(0x30, message.MsgTypeTPDU, fteid.Teid, 0, pkt, []*message.ExtensionHeader{}...)
 	b, err := gpdu.Marshal()
@@ -94,7 +93,7 @@ func (p *PduSessionsManager) WriteUplink(ctx context.Context, pkt []byte) error
 func (p *PduSessionsManager) GetUECtrl(teid uint32) (jsonapi.ControlURI, error) {
 	ueCtrl, ok := p.Downlink[teid]
 	if !ok {
-		return ueCtrl, fmt.Errorf("Unknown UE")
+		return ueCtrl, ErrPduSessionNotFound
 	}
 	return ueCtrl, nil
 }