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tcp/ip stack + firewall mode.

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Ginder Singh
2026-03-19 00:24:35 -04:00
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222
cmd/ctrld_library/netstack/README.md Normal file
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# Netstack - Full Packet Capture for Mobile VPN
Complete TCP/UDP/DNS packet capture implementation using gVisor netstack for Android and iOS VPN apps.
## Overview
This module provides full packet capture capabilities for mobile VPN applications, handling:
- **DNS filtering** through ControlD proxy
- **TCP forwarding** for HTTP/HTTPS and all TCP traffic
- **UDP forwarding** for games, video streaming, VoIP, etc.
- **Socket protection** to prevent routing loops on Android/iOS
## Architecture
```
Mobile Apps (Browser, Games, etc)
↓
VPN TUN Interface (10.0.0.2/24)
↓
PacketHandler (Read/Write/Protect)
↓
gVisor Netstack (TCP/IP Stack)
├─→ DNS Filter (Port 53)
│ └─→ ControlD DNS Proxy (localhost:5354)
├─→ TCP Forwarder
│ └─→ net.Dial("tcp") + protect(fd)
└─→ UDP Forwarder
└─→ net.Dial("udp") + protect(fd)
↓
Real Network (WiFi/Cellular) - Protected Sockets
```
## Key Components
### 1. DNS Filter (`dns_filter.go`)
- Detects DNS packets (UDP port 53)
- Extracts DNS query payload
- Sends to DNS bridge
- Builds DNS response packets
### 2. DNS Bridge (`dns_bridge.go`)
- Transaction ID tracking
- Query/response matching
- 5-second timeout per query
- Channel-based communication
### 3. TCP Forwarder (`tcp_forwarder.go`)
- Uses gVisor's `tcp.NewForwarder()`
- Converts gVisor endpoints to Go `net.Conn`
- Dials regular TCP sockets (no root required)
- Protects sockets using `VpnService.protect()` callback
- Bidirectional `io.Copy()` for data forwarding
### 4. UDP Forwarder (`udp_forwarder.go`)
- Uses gVisor's `udp.NewForwarder()`
- Per-session connection tracking
- Dials regular UDP sockets (no root required)
- Protected sockets prevent routing loops
- 60-second idle timeout with automatic cleanup
### 5. Packet Handler (`packet_handler.go`)
- Interface for reading/writing raw IP packets
- Mobile platforms implement:
- `ReadPacket()` - Read from TUN file descriptor
- `WritePacket()` - Write to TUN file descriptor
- `ProtectSocket(fd)` - Protect socket from VPN routing
- `Close()` - Clean up resources
### 6. Netstack Controller (`netstack.go`)
- Manages gVisor stack lifecycle
- Coordinates DNS filter and TCP/UDP forwarders
- Filters outbound packets (source=10.0.0.x)
- Drops return packets (handled by forwarders)
## Critical Design Decisions
### Socket Protection
**Why It's Critical:**
Without socket protection, outbound connections would route back through the VPN, creating infinite loops:
```
Bad (without protect):
App → VPN → TCP Forwarder → net.Dial() → VPN → TCP Forwarder → LOOP!
Good (with protect):
App → VPN → TCP Forwarder → net.Dial() → [PROTECTED] → WiFi → Internet ✅
```
**Implementation:**
```go
// Protect socket BEFORE connect() is called
dialer.Control = func(network, address string, c syscall.RawConn) error {
return c.Control(func(fd uintptr) {
protectSocket(int(fd)) // Android: VpnService.protect()
})
}
```
**All Protected Sockets:**
1. TCP forwarder sockets (user traffic)
2. UDP forwarder sockets (user traffic)
3. ControlD API HTTP sockets (api.controld.com)
4. DoH upstream sockets (freedns.controld.com)
### Outbound vs Return Packets
**Outbound packets** (10.0.0.x → Internet):
- Source IP: 10.0.0.x
- Injected into gVisor netstack
- Handled by TCP/UDP forwarders
**Return packets** (Internet → 10.0.0.x):
- Source IP: NOT 10.0.0.x
- Dropped by readPackets()
- Return through forwarder's upstream connection automatically
### Address Mapping in gVisor
For inbound connections to the netstack:
- `id.LocalAddress/LocalPort` = **Destination** (where packet is going TO)
- `id.RemoteAddress/RemotePort` = **Source** (where packet is coming FROM)
Therefore, we dial `LocalAddress:LocalPort` (the destination).
## Usage Example (Android)
```kotlin
// In VpnService
val callback = object : PacketAppCallback {
override fun readPacket(): ByteArray {
// Read from TUN file descriptor
val length = inputStream.channel.read(buffer)
return packet
}
override fun writePacket(packet: ByteArray) {
// Write to TUN file descriptor
outputStream.write(packet)
}
override fun protectSocket(fd: Long) {
// CRITICAL: Protect socket from VPN routing
val success = protect(fd.toInt()) // VpnService.protect()
if (!success) throw Exception("Failed to protect socket")
}
override fun closePacketIO() {
inputStream?.close()
outputStream?.close()
}
override fun exit(s: String) { }
override fun hostname(): String = "android-device"
override fun lanIp(): String = "10.0.0.2"
override fun macAddress(): String = "00:00:00:00:00:00"
}
// Create packet capture controller
val controller = Ctrld_library.newPacketCaptureController(callback)
// Start packet capture
controller.startWithPacketCapture(
callback,
"your-cd-uid",
"", "", // provision ID, custom hostname
filesDir.absolutePath,
"doh", // upstream protocol
2, // log level
"$filesDir/ctrld.log"
)
// Stop when done
controller.stop(false, 0)
```
## Protocol Support
| Protocol | Support | Details |
|----------|---------|---------|
| **DNS** | ✅ Full | Filtered through ControlD proxy |
| **TCP** | ✅ Full | All ports, bidirectional forwarding |
| **UDP** | ✅ Full | All ports except 53, session tracking |
| **ICMP** | ⚠️ Partial | Basic support (no forwarding yet) |
| **IPv4** | ✅ Full | Complete support |
| **IPv6** | ✅ Full | Complete support |
## Performance
| Metric | Value |
|--------|-------|
| **DNS Timeout** | 5 seconds |
| **TCP Dial Timeout** | 30 seconds |
| **UDP Idle Timeout** | 60 seconds |
| **UDP Cleanup Interval** | 30 seconds |
| **MTU** | 1500 bytes |
| **Overhead per TCP connection** | ~2KB |
| **Overhead per UDP session** | ~1KB |
## Requirements
- Go 1.23+
- gVisor netstack v0.0.0-20240722211153-64c016c92987
- For Android: API 24+ (Android 7.0+)
- For iOS: iOS 12+
## No Root Required
This implementation uses **regular TCP/UDP sockets** instead of raw sockets, making it compatible with non-rooted Android/iOS devices. Socket protection via `VpnService.protect()` (Android) or `NEPacketTunnelFlow` (iOS) prevents routing loops.
## Files
- `packet_handler.go` - Interface for TUN I/O and socket protection
- `netstack.go` - Main controller managing gVisor stack
- `dns_filter.go` - DNS packet detection and response building
- `dns_bridge.go` - DNS query/response bridging
- `tcp_forwarder.go` - TCP connection forwarding
- `udp_forwarder.go` - UDP packet forwarding with session tracking
## License
Same as parent ctrld project.

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cmd/ctrld_library/netstack/dns_bridge.go Normal file
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package netstack
import (
"fmt"
"sync"
"time"
"github.com/miekg/dns"
)
// DNSBridge provides a bridge between the netstack DNS filter and the existing ctrld DNS proxy.
// It allows DNS queries captured from packets to be processed by the same logic as traditional DNS queries.
type DNSBridge struct {
// Channel for sending DNS queries
queryCh chan *DNSQuery
// Channel for receiving DNS responses
responseCh chan *DNSResponse
// Map to track pending queries by transaction ID
pendingQueries map[uint16]*PendingQuery
mu sync.RWMutex
// Timeout for DNS queries
queryTimeout time.Duration
// Running state
running bool
stopCh chan struct{}
wg sync.WaitGroup
}
// DNSQuery represents a DNS query to be processed
type DNSQuery struct {
ID uint16 // Transaction ID for matching response
Query []byte // Raw DNS query bytes
RespCh chan []byte // Response channel
SrcIP string // Source IP for logging
SrcPort uint16 // Source port
}
// DNSResponse represents a DNS response
type DNSResponse struct {
ID uint16
Response []byte
}
// PendingQuery tracks a query waiting for response
type PendingQuery struct {
Query *DNSQuery
Timestamp time.Time
}
// NewDNSBridge creates a new DNS bridge
func NewDNSBridge() *DNSBridge {
return &DNSBridge{
queryCh: make(chan *DNSQuery, 100),
responseCh: make(chan *DNSResponse, 100),
pendingQueries: make(map[uint16]*PendingQuery),
queryTimeout: 5 * time.Second,
stopCh: make(chan struct{}),
}
}
// Start starts the DNS bridge
func (b *DNSBridge) Start() {
b.mu.Lock()
if b.running {
b.mu.Unlock()
return
}
b.running = true
b.mu.Unlock()
// Start response handler
b.wg.Add(1)
go b.handleResponses()
// Start timeout checker
b.wg.Add(1)
go b.checkTimeouts()
}
// Stop stops the DNS bridge
func (b *DNSBridge) Stop() {
b.mu.Lock()
if !b.running {
b.mu.Unlock()
return
}
b.running = false
b.mu.Unlock()
close(b.stopCh)
b.wg.Wait()
// Clean up pending queries
b.mu.Lock()
for _, pending := range b.pendingQueries {
close(pending.Query.RespCh)
}
b.pendingQueries = make(map[uint16]*PendingQuery)
b.mu.Unlock()
}
// ProcessQuery processes a DNS query and waits for response
func (b *DNSBridge) ProcessQuery(query []byte, srcIP string, srcPort uint16) ([]byte, error) {
if len(query) < 12 {
return nil, fmt.Errorf("invalid DNS query: too short")
}
// Parse DNS message to get transaction ID
msg := new(dns.Msg)
if err := msg.Unpack(query); err != nil {
return nil, fmt.Errorf("failed to parse DNS query: %v", err)
}
// Create response channel
respCh := make(chan []byte, 1)
// Create query
dnsQuery := &DNSQuery{
ID: msg.Id,
Query: query,
RespCh: respCh,
SrcIP: srcIP,
SrcPort: srcPort,
}
// Store as pending
b.mu.Lock()
b.pendingQueries[msg.Id] = &PendingQuery{
Query: dnsQuery,
Timestamp: time.Now(),
}
b.mu.Unlock()
// Send query
select {
case b.queryCh <- dnsQuery:
case <-time.After(time.Second):
b.mu.Lock()
delete(b.pendingQueries, msg.Id)
b.mu.Unlock()
return nil, fmt.Errorf("query channel full")
}
// Wait for response with timeout
select {
case response := <-respCh:
b.mu.Lock()
delete(b.pendingQueries, msg.Id)
b.mu.Unlock()
return response, nil
case <-time.After(b.queryTimeout):
b.mu.Lock()
delete(b.pendingQueries, msg.Id)
b.mu.Unlock()
return nil, fmt.Errorf("DNS query timeout")
}
}
// GetQueryChannel returns the channel for receiving DNS queries
func (b *DNSBridge) GetQueryChannel() <-chan *DNSQuery {
return b.queryCh
}
// SendResponse sends a DNS response back to the waiting query
func (b *DNSBridge) SendResponse(id uint16, response []byte) error {
b.mu.RLock()
pending, exists := b.pendingQueries[id]
b.mu.RUnlock()
if !exists {
return fmt.Errorf("no pending query for ID %d", id)
}
select {
case pending.Query.RespCh <- response:
return nil
case <-time.After(time.Second):
return fmt.Errorf("failed to send response: channel blocked")
}
}
// handleResponses handles incoming responses
func (b *DNSBridge) handleResponses() {
defer b.wg.Done()
for {
select {
case <-b.stopCh:
return
case resp := <-b.responseCh:
if err := b.SendResponse(resp.ID, resp.Response); err != nil {
// Log error but continue
}
}
}
}
// checkTimeouts periodically checks for and removes timed out queries
func (b *DNSBridge) checkTimeouts() {
defer b.wg.Done()
ticker := time.NewTicker(time.Second)
defer ticker.Stop()
for {
select {
case <-b.stopCh:
return
case <-ticker.C:
now := time.Now()
b.mu.Lock()
for id, pending := range b.pendingQueries {
if now.Sub(pending.Timestamp) > b.queryTimeout {
close(pending.Query.RespCh)
delete(b.pendingQueries, id)
}
}
b.mu.Unlock()
}
}
}

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cmd/ctrld_library/netstack/dns_filter.go Normal file
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package netstack
import (
"encoding/binary"
"fmt"
"net"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
)
// DNSFilter intercepts and processes DNS packets.
type DNSFilter struct {
dnsHandler func([]byte) ([]byte, error)
}
// NewDNSFilter creates a new DNS filter with the given handler.
func NewDNSFilter(handler func([]byte) ([]byte, error)) *DNSFilter {
return &DNSFilter{
dnsHandler: handler,
}
}
// ProcessPacket checks if a packet is a DNS query and processes it.
// Returns:
// - isDNS: true if this is a DNS packet
// - response: DNS response packet (if handled), nil otherwise
// - error: any error that occurred
func (df *DNSFilter) ProcessPacket(packet []byte) (isDNS bool, response []byte, err error) {
if len(packet) < header.IPv4MinimumSize {
return false, nil, nil
}
// Parse IP version
ipVersion := packet[0] >> 4
switch ipVersion {
case 4:
return df.processIPv4(packet)
case 6:
return df.processIPv6(packet)
default:
return false, nil, nil
}
}
// processIPv4 processes an IPv4 packet and checks if it's DNS.
func (df *DNSFilter) processIPv4(packet []byte) (bool, []byte, error) {
if len(packet) < header.IPv4MinimumSize {
return false, nil, nil
}
// Parse IPv4 header
ipHdr := header.IPv4(packet)
if !ipHdr.IsValid(len(packet)) {
return false, nil, nil
}
// Check if it's UDP
if ipHdr.TransportProtocol() != header.UDPProtocolNumber {
return false, nil, nil
}
// Get IP header length
ihl := int(ipHdr.HeaderLength())
if len(packet) < ihl+header.UDPMinimumSize {
return false, nil, nil
}
// Parse UDP header
udpHdr := header.UDP(packet[ihl:])
srcPort := udpHdr.SourcePort()
dstPort := udpHdr.DestinationPort()
// Check if destination port is 53 (DNS)
if dstPort != 53 {
return false, nil, nil
}
srcIP := ipHdr.SourceAddress()
dstIP := ipHdr.DestinationAddress()
// Extract DNS payload
udpPayloadOffset := ihl + header.UDPMinimumSize
if len(packet) <= udpPayloadOffset {
return true, nil, fmt.Errorf("invalid UDP packet length")
}
dnsQuery := packet[udpPayloadOffset:]
if len(dnsQuery) == 0 {
return true, nil, fmt.Errorf("empty DNS query")
}
// Process DNS query
if df.dnsHandler == nil {
return true, nil, fmt.Errorf("no DNS handler configured")
}
dnsResponse, err := df.dnsHandler(dnsQuery)
if err != nil {
return true, nil, fmt.Errorf("DNS handler error: %v", err)
}
// Build response packet
responsePacket := df.buildIPv4UDPPacket(
dstIP.As4(), // Swap src/dst
srcIP.As4(),
dstPort, // Swap ports
srcPort,
dnsResponse,
)
return true, responsePacket, nil
}
// processIPv6 processes an IPv6 packet and checks if it's DNS.
func (df *DNSFilter) processIPv6(packet []byte) (bool, []byte, error) {
if len(packet) < header.IPv6MinimumSize {
return false, nil, nil
}
// Parse IPv6 header
ipHdr := header.IPv6(packet)
if !ipHdr.IsValid(len(packet)) {
return false, nil, nil
}
// Check if it's UDP
if ipHdr.TransportProtocol() != header.UDPProtocolNumber {
return false, nil, nil
}
// IPv6 header is fixed size
if len(packet) < header.IPv6MinimumSize+header.UDPMinimumSize {
return false, nil, nil
}
// Parse UDP header
udpHdr := header.UDP(packet[header.IPv6MinimumSize:])
srcPort := udpHdr.SourcePort()
dstPort := udpHdr.DestinationPort()
// Check if destination port is 53 (DNS)
if dstPort != 53 {
return false, nil, nil
}
// Extract DNS payload
udpPayloadOffset := header.IPv6MinimumSize + header.UDPMinimumSize
if len(packet) <= udpPayloadOffset {
return true, nil, fmt.Errorf("invalid UDP packet length")
}
dnsQuery := packet[udpPayloadOffset:]
if len(dnsQuery) == 0 {
return true, nil, fmt.Errorf("empty DNS query")
}
// Process DNS query
if df.dnsHandler == nil {
return true, nil, fmt.Errorf("no DNS handler configured")
}
dnsResponse, err := df.dnsHandler(dnsQuery)
if err != nil {
return true, nil, fmt.Errorf("DNS handler error: %v", err)
}
// Build response packet
srcIP := ipHdr.SourceAddress()
dstIP := ipHdr.DestinationAddress()
responsePacket := df.buildIPv6UDPPacket(
dstIP.As16(), // Swap src/dst
srcIP.As16(),
dstPort, // Swap ports
srcPort,
dnsResponse,
)
return true, responsePacket, nil
}
// buildIPv4UDPPacket builds a complete IPv4/UDP packet with the given payload.
func (df *DNSFilter) buildIPv4UDPPacket(srcIP, dstIP [4]byte, srcPort, dstPort uint16, payload []byte) []byte {
// Calculate lengths
udpLen := header.UDPMinimumSize + len(payload)
ipLen := header.IPv4MinimumSize + udpLen
packet := make([]byte, ipLen)
// Build IPv4 header
ipHdr := header.IPv4(packet)
ipHdr.Encode(&header.IPv4Fields{
TotalLength: uint16(ipLen),
TTL: 64,
Protocol: uint8(header.UDPProtocolNumber),
SrcAddr: tcpip.AddrFrom4(srcIP),
DstAddr: tcpip.AddrFrom4(dstIP),
})
ipHdr.SetChecksum(^ipHdr.CalculateChecksum())
// Build UDP header
udpHdr := header.UDP(packet[header.IPv4MinimumSize:])
udpHdr.Encode(&header.UDPFields{
SrcPort: srcPort,
DstPort: dstPort,
Length: uint16(udpLen),
})
// Copy payload
copy(packet[header.IPv4MinimumSize+header.UDPMinimumSize:], payload)
// Calculate UDP checksum
xsum := header.PseudoHeaderChecksum(
header.UDPProtocolNumber,
tcpip.AddrFrom4(srcIP),
tcpip.AddrFrom4(dstIP),
uint16(udpLen),
)
xsum = checksum(payload, xsum)
udpHdr.SetChecksum(^udpHdr.CalculateChecksum(xsum))
return packet
}
// buildIPv6UDPPacket builds a complete IPv6/UDP packet with the given payload.
func (df *DNSFilter) buildIPv6UDPPacket(srcIP, dstIP [16]byte, srcPort, dstPort uint16, payload []byte) []byte {
// Calculate lengths
udpLen := header.UDPMinimumSize + len(payload)
ipLen := header.IPv6MinimumSize + udpLen
packet := make([]byte, ipLen)
// Build IPv6 header
ipHdr := header.IPv6(packet)
ipHdr.Encode(&header.IPv6Fields{
PayloadLength: uint16(udpLen),
TransportProtocol: header.UDPProtocolNumber,
HopLimit: 64,
SrcAddr: tcpip.AddrFrom16(srcIP),
DstAddr: tcpip.AddrFrom16(dstIP),
})
// Build UDP header
udpHdr := header.UDP(packet[header.IPv6MinimumSize:])
udpHdr.Encode(&header.UDPFields{
SrcPort: srcPort,
DstPort: dstPort,
Length: uint16(udpLen),
})
// Copy payload
copy(packet[header.IPv6MinimumSize+header.UDPMinimumSize:], payload)
// Calculate UDP checksum
xsum := header.PseudoHeaderChecksum(
header.UDPProtocolNumber,
tcpip.AddrFrom16(srcIP),
tcpip.AddrFrom16(dstIP),
uint16(udpLen),
)
xsum = checksum(payload, xsum)
udpHdr.SetChecksum(^udpHdr.CalculateChecksum(xsum))
return packet
}
// checksum calculates the checksum for the given data.
func checksum(buf []byte, initial uint16) uint16 {
v := uint32(initial)
l := len(buf)
if l&1 != 0 {
l--
v += uint32(buf[l]) << 8
}
for i := 0; i < l; i += 2 {
v += (uint32(buf[i]) << 8) + uint32(buf[i+1])
}
return reduceChecksum(v)
}
// reduceChecksum reduces a 32-bit checksum to 16 bits.
func reduceChecksum(v uint32) uint16 {
v = (v >> 16) + (v & 0xffff)
v = (v >> 16) + (v & 0xffff)
return uint16(v)
}
// IPv4Address is a helper to create an IPv4 address from a byte array.
func IPv4Address(b [4]byte) net.IP {
return net.IPv4(b[0], b[1], b[2], b[3])
}
// IPv6Address is a helper to create an IPv6 address from a byte array.
func IPv6Address(b [16]byte) net.IP {
return net.IP(b[:])
}
// parseIPv4 extracts source and destination IPs from an IPv4 packet.
func parseIPv4(packet []byte) (srcIP, dstIP [4]byte, ok bool) {
if len(packet) < header.IPv4MinimumSize {
return
}
ipHdr := header.IPv4(packet)
if !ipHdr.IsValid(len(packet)) {
return
}
srcAddr := ipHdr.SourceAddress().As4()
dstAddr := ipHdr.DestinationAddress().As4()
copy(srcIP[:], srcAddr[:])
copy(dstIP[:], dstAddr[:])
ok = true
return
}
// parseUDP extracts UDP header information.
func parseUDP(udpHeader []byte) (srcPort, dstPort uint16, ok bool) {
if len(udpHeader) < header.UDPMinimumSize {
return
}
srcPort = binary.BigEndian.Uint16(udpHeader[0:2])
dstPort = binary.BigEndian.Uint16(udpHeader[2:4])
ok = true
return
}

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cmd/ctrld_library/netstack/netstack.go Normal file
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package netstack
import (
"context"
"fmt"
"net"
"net/netip"
"sync"
"time"
"gvisor.dev/gvisor/pkg/buffer"
"gvisor.dev/gvisor/pkg/tcpip"
"gvisor.dev/gvisor/pkg/tcpip/header"
"gvisor.dev/gvisor/pkg/tcpip/link/channel"
"gvisor.dev/gvisor/pkg/tcpip/network/ipv4"
"gvisor.dev/gvisor/pkg/tcpip/network/ipv6"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
"gvisor.dev/gvisor/pkg/tcpip/transport/udp"
)
const (
// Default MTU for the TUN interface
defaultMTU = 1500
// NICID is the ID of the network interface
NICID = 1
// Channel capacity for packet buffers
channelCapacity = 256
)
// NetstackController manages the gVisor netstack integration for mobile packet capture.
type NetstackController struct {
stack *stack.Stack
linkEP *channel.Endpoint
packetHandler PacketHandler
dnsFilter *DNSFilter
tcpForwarder *TCPForwarder
udpForwarder *UDPForwarder
ctx context.Context
cancel context.CancelFunc
wg sync.WaitGroup
started bool
mu sync.Mutex
}
// Config holds configuration for NetstackController.
type Config struct {
// MTU is the maximum transmission unit
MTU uint32
// TUNIPv4 is the IPv4 address assigned to the TUN interface
TUNIPv4 netip.Addr
// TUNIPv6 is the IPv6 address assigned to the TUN interface (optional)
TUNIPv6 netip.Addr
// DNSHandler is the function to process DNS queries
DNSHandler func([]byte) ([]byte, error)
// UpstreamInterface is the real network interface for routing non-DNS traffic
UpstreamInterface *net.Interface
}
// NewNetstackController creates a new netstack controller.
func NewNetstackController(handler PacketHandler, cfg *Config) (*NetstackController, error) {
if handler == nil {
return nil, fmt.Errorf("packet handler cannot be nil")
}
if cfg == nil {
cfg = &Config{
MTU: defaultMTU,
TUNIPv4: netip.MustParseAddr("10.0.0.1"),
}
}
if cfg.MTU == 0 {
cfg.MTU = defaultMTU
}
ctx, cancel := context.WithCancel(context.Background())
// Create gVisor stack
s := stack.New(stack.Options{
NetworkProtocols: []stack.NetworkProtocolFactory{
ipv4.NewProtocol,
ipv6.NewProtocol,
},
TransportProtocols: []stack.TransportProtocolFactory{
tcp.NewProtocol,
udp.NewProtocol,
},
})
// Create link endpoint
linkEP := channel.New(channelCapacity, cfg.MTU, "")
// Create DNS filter
dnsFilter := NewDNSFilter(cfg.DNSHandler)
// Create TCP forwarder
tcpForwarder := NewTCPForwarder(s, handler.ProtectSocket, ctx)
// Create UDP forwarder
udpForwarder := NewUDPForwarder(s, handler.ProtectSocket, ctx)
// Create NIC
if err := s.CreateNIC(NICID, linkEP); err != nil {
cancel()
return nil, fmt.Errorf("failed to create NIC: %v", err)
}
// Enable spoofing to allow packets with any source IP
if err := s.SetSpoofing(NICID, true); err != nil {
cancel()
return nil, fmt.Errorf("failed to enable spoofing: %v", err)
}
// Enable promiscuous mode to accept all packets
if err := s.SetPromiscuousMode(NICID, true); err != nil {
cancel()
return nil, fmt.Errorf("failed to enable promiscuous mode: %v", err)
}
// Add IPv4 address
protocolAddr := tcpip.ProtocolAddress{
Protocol: ipv4.ProtocolNumber,
AddressWithPrefix: tcpip.AddressWithPrefix{
Address: tcpip.AddrFromSlice(cfg.TUNIPv4.AsSlice()),
PrefixLen: 24,
},
}
if err := s.AddProtocolAddress(NICID, protocolAddr, stack.AddressProperties{}); err != nil {
cancel()
return nil, fmt.Errorf("failed to add IPv4 address: %v", err)
}
// Add IPv6 address if provided
if cfg.TUNIPv6.IsValid() {
protocolAddr6 := tcpip.ProtocolAddress{
Protocol: ipv6.ProtocolNumber,
AddressWithPrefix: tcpip.AddressWithPrefix{
Address: tcpip.AddrFromSlice(cfg.TUNIPv6.AsSlice()),
PrefixLen: 64,
},
}
if err := s.AddProtocolAddress(NICID, protocolAddr6, stack.AddressProperties{}); err != nil {
cancel()
return nil, fmt.Errorf("failed to add IPv6 address: %v", err)
}
}
// Add default routes
s.SetRouteTable([]tcpip.Route{
{
Destination: header.IPv4EmptySubnet,
NIC: NICID,
},
{
Destination: header.IPv6EmptySubnet,
NIC: NICID,
},
})
// Register forwarders with the stack
s.SetTransportProtocolHandler(tcp.ProtocolNumber, tcpForwarder.forwarder.HandlePacket)
s.SetTransportProtocolHandler(udp.ProtocolNumber, udpForwarder.forwarder.HandlePacket)
nc := &NetstackController{
stack: s,
linkEP: linkEP,
packetHandler: handler,
dnsFilter: dnsFilter,
tcpForwarder: tcpForwarder,
udpForwarder: udpForwarder,
ctx: ctx,
cancel: cancel,
started: false,
}
return nc, nil
}
// Start starts the netstack controller and begins processing packets.
func (nc *NetstackController) Start() error {
nc.mu.Lock()
defer nc.mu.Unlock()
if nc.started {
return fmt.Errorf("netstack controller already started")
}
nc.started = true
// Start packet reader goroutine (TUN -> netstack)
nc.wg.Add(1)
go nc.readPackets()
// Start packet writer goroutine (netstack -> TUN)
nc.wg.Add(1)
go nc.writePackets()
return nil
}
// Stop stops the netstack controller and waits for all goroutines to finish.
func (nc *NetstackController) Stop() error {
nc.mu.Lock()
if !nc.started {
nc.mu.Unlock()
return nil
}
nc.mu.Unlock()
nc.cancel()
nc.wg.Wait()
// Close UDP forwarder
if nc.udpForwarder != nil {
nc.udpForwarder.Close()
}
if err := nc.packetHandler.Close(); err != nil {
return fmt.Errorf("failed to close packet handler: %v", err)
}
nc.mu.Lock()
nc.started = false
nc.mu.Unlock()
return nil
}
// readPackets reads packets from the TUN interface and injects them into the netstack.
func (nc *NetstackController) readPackets() {
defer nc.wg.Done()
for {
select {
case <-nc.ctx.Done():
return
default:
}
// Read packet from TUN
packet, err := nc.packetHandler.ReadPacket()
if err != nil {
if nc.ctx.Err() != nil {
return
}
time.Sleep(10 * time.Millisecond)
continue
}
if len(packet) == 0 {
continue
}
// Check if this is a DNS packet
isDNS, response, err := nc.dnsFilter.ProcessPacket(packet)
if err != nil {
continue
}
if isDNS && response != nil {
// DNS packet was handled, send response back to TUN
nc.packetHandler.WritePacket(response)
continue
}
if isDNS {
continue
}
// Not a DNS packet - check if it's an OUTBOUND packet (source = 10.0.0.x)
// We should ONLY inject outbound packets, not return packets
if len(packet) >= 20 {
// Check if source is in our VPN subnet (10.0.0.x)
isOutbound := packet[12] == 10 && packet[13] == 0 && packet[14] == 0
if !isOutbound {
// This is a return packet (server -> mobile)
// Drop it - return packets come through forwarder's upstream connection
continue
}
}
// Create packet buffer
pkt := stack.NewPacketBuffer(stack.PacketBufferOptions{
Payload: buffer.MakeWithData(packet),
})
// Determine protocol number
var proto tcpip.NetworkProtocolNumber
if len(packet) > 0 {
version := packet[0] >> 4
switch version {
case 4:
proto = header.IPv4ProtocolNumber
case 6:
proto = header.IPv6ProtocolNumber
default:
pkt.DecRef()
continue
}
} else {
pkt.DecRef()
continue
}
// Inject into netstack - TCP/UDP forwarders will handle it
nc.linkEP.InjectInbound(proto, pkt)
}
}
// writePackets reads packets from netstack and writes them to the TUN interface.
func (nc *NetstackController) writePackets() {
defer nc.wg.Done()
for {
select {
case <-nc.ctx.Done():
return
default:
}
// Read packet from netstack
pkt := nc.linkEP.ReadContext(nc.ctx)
if pkt == nil {
continue
}
// Convert packet to bytes
vv := pkt.ToView()
packet := vv.AsSlice()
// Write to TUN
if err := nc.packetHandler.WritePacket(packet); err != nil {
// Log error
continue
}
pkt.DecRef()
}
}

115
cmd/ctrld_library/netstack/packet_handler.go Normal file
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package netstack
import (
"fmt"
"sync"
)
// PacketHandler defines the interface for reading and writing raw IP packets
// from/to the mobile TUN interface.
type PacketHandler interface {
// ReadPacket reads a raw IP packet from the TUN interface.
// This should be a blocking call.
ReadPacket() ([]byte, error)
// WritePacket writes a raw IP packet back to the TUN interface.
WritePacket(packet []byte) error
// Close closes the packet handler and releases resources.
Close() error
// ProtectSocket protects a socket file descriptor from being routed through the VPN.
// This is required on Android/iOS to prevent routing loops.
// Returns nil if successful, error otherwise.
ProtectSocket(fd int) error
}
// MobilePacketHandler implements PacketHandler using callbacks from mobile platforms.
// This bridges Go Mobile interface with the netstack implementation.
type MobilePacketHandler struct {
readFunc func() ([]byte, error)
writeFunc func([]byte) error
closeFunc func() error
protectFunc func(int) error
mu sync.Mutex
closed bool
}
// NewMobilePacketHandler creates a new packet handler with mobile callbacks.
func NewMobilePacketHandler(
readFunc func() ([]byte, error),
writeFunc func([]byte) error,
closeFunc func() error,
protectFunc func(int) error,
) *MobilePacketHandler {
return &MobilePacketHandler{
readFunc: readFunc,
writeFunc: writeFunc,
closeFunc: closeFunc,
protectFunc: protectFunc,
closed: false,
}
}
// ReadPacket reads a packet from mobile TUN interface.
func (m *MobilePacketHandler) ReadPacket() ([]byte, error) {
m.mu.Lock()
closed := m.closed
m.mu.Unlock()
if closed {
return nil, fmt.Errorf("packet handler is closed")
}
if m.readFunc == nil {
return nil, fmt.Errorf("read function not set")
}
return m.readFunc()
}
// WritePacket writes a packet back to mobile TUN interface.
func (m *MobilePacketHandler) WritePacket(packet []byte) error {
m.mu.Lock()
closed := m.closed
m.mu.Unlock()
if closed {
return fmt.Errorf("packet handler is closed")
}
if m.writeFunc == nil {
return fmt.Errorf("write function not set")
}
return m.writeFunc(packet)
}
// Close closes the packet handler.
func (m *MobilePacketHandler) Close() error {
m.mu.Lock()
defer m.mu.Unlock()
if m.closed {
return nil
}
m.closed = true
if m.closeFunc != nil {
return m.closeFunc()
}
return nil
}
// ProtectSocket protects a socket file descriptor from VPN routing.
func (m *MobilePacketHandler) ProtectSocket(fd int) error {
if m.protectFunc == nil {
// No protect function provided - this is okay for non-VPN scenarios
return nil
}
return m.protectFunc(fd)
}

118
cmd/ctrld_library/netstack/tcp_forwarder.go Normal file
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package netstack
import (
"context"
"io"
"net"
"syscall"
"time"
"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/tcpip/transport/tcp"
"gvisor.dev/gvisor/pkg/waiter"
)
// TCPForwarder handles TCP connections from the TUN interface
type TCPForwarder struct {
protectSocket func(fd int) error
ctx context.Context
forwarder *tcp.Forwarder
}
// NewTCPForwarder creates a new TCP forwarder
func NewTCPForwarder(s *stack.Stack, protectSocket func(fd int) error, ctx context.Context) *TCPForwarder {
f := &TCPForwarder{
protectSocket: protectSocket,
ctx: ctx,
}
// Create gVisor TCP forwarder with handler callback
// rcvWnd=0 (default), maxInFlight=1024
f.forwarder = tcp.NewForwarder(s, 0, 1024, f.handleRequest)
return f
}
// GetForwarder returns the underlying gVisor forwarder
func (f *TCPForwarder) GetForwarder() *tcp.Forwarder {
return f.forwarder
}
// handleRequest handles an incoming TCP connection request
func (f *TCPForwarder) handleRequest(req *tcp.ForwarderRequest) {
// Get the endpoint ID
id := req.ID()
// Create waiter queue
var wq waiter.Queue
// Create endpoint from request
ep, err := req.CreateEndpoint(&wq)
if err != nil {
req.Complete(true) // Send RST
return
}
// Accept the connection
req.Complete(false)
// Cast to TCP endpoint
tcpEP, ok := ep.(*tcp.Endpoint)
if !ok {
ep.Close()
return
}
// Handle in goroutine
go f.handleConnection(tcpEP, &wq, id)
}
func (f *TCPForwarder) handleConnection(ep *tcp.Endpoint, wq *waiter.Queue, id stack.TransportEndpointID) {
// Convert endpoint to Go net.Conn
tunConn := gonet.NewTCPConn(wq, ep)
defer tunConn.Close()
// In gVisor's TransportEndpointID for an inbound connection:
// - LocalAddress/LocalPort = the destination (where packet is going TO)
// - RemoteAddress/RemotePort = the source (where packet is coming FROM)
// We want to dial the DESTINATION (LocalAddress/LocalPort)
dstAddr := net.TCPAddr{
IP: net.IP(id.LocalAddress.AsSlice()),
Port: int(id.LocalPort),
}
// Create outbound connection with socket protection DURING dial
dialer := &net.Dialer{
Timeout: 30 * time.Second,
}
// CRITICAL: Protect socket BEFORE connect() is called
if f.protectSocket != nil {
dialer.Control = func(network, address string, c syscall.RawConn) error {
return c.Control(func(fd uintptr) {
f.protectSocket(int(fd))
})
}
}
upstreamConn, err := dialer.DialContext(f.ctx, "tcp", dstAddr.String())
if err != nil {
return
}
defer upstreamConn.Close()
// Bidirectional copy
done := make(chan struct{}, 2)
go func() {
io.Copy(upstreamConn, tunConn)
done <- struct{}{}
}()
go func() {
io.Copy(tunConn, upstreamConn)
done <- struct{}{}
}()
// Wait for one direction to finish
<-done
}

257
cmd/ctrld_library/netstack/udp_forwarder.go Normal file
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package netstack
import (
"context"
"fmt"
"net"
"sync"
"syscall"
"time"
"gvisor.dev/gvisor/pkg/tcpip/adapters/gonet"
"gvisor.dev/gvisor/pkg/tcpip/stack"
"gvisor.dev/gvisor/pkg/tcpip/transport/udp"
"gvisor.dev/gvisor/pkg/waiter"
)
// UDPForwarder handles UDP packets from the TUN interface
type UDPForwarder struct {
protectSocket func(fd int) error
ctx context.Context
forwarder *udp.Forwarder
// Track UDP "connections" (address pairs)
connections map[string]*udpConn
mu sync.Mutex
}
type udpConn struct {
tunEP *gonet.UDPConn
upstreamConn *net.UDPConn
lastActivity time.Time
cancel context.CancelFunc
}
// NewUDPForwarder creates a new UDP forwarder
func NewUDPForwarder(s *stack.Stack, protectSocket func(fd int) error, ctx context.Context) *UDPForwarder {
f := &UDPForwarder{
protectSocket: protectSocket,
ctx: ctx,
connections: make(map[string]*udpConn),
}
// Create gVisor UDP forwarder with handler callback
f.forwarder = udp.NewForwarder(s, f.handlePacket)
// Start cleanup goroutine
go f.cleanupStaleConnections()
return f
}
// GetForwarder returns the underlying gVisor forwarder
func (f *UDPForwarder) GetForwarder() *udp.Forwarder {
return f.forwarder
}
// handlePacket handles an incoming UDP packet
func (f *UDPForwarder) handlePacket(req *udp.ForwarderRequest) {
// Get the endpoint ID
id := req.ID()
// Create connection key (source -> destination)
connKey := fmt.Sprintf("%s:%d->%s:%d",
net.IP(id.RemoteAddress.AsSlice()),
id.RemotePort,
net.IP(id.LocalAddress.AsSlice()),
id.LocalPort,
)
f.mu.Lock()
conn, exists := f.connections[connKey]
if !exists {
// Create new connection
conn = f.createConnection(req, connKey)
if conn == nil {
f.mu.Unlock()
return
}
f.connections[connKey] = conn
}
conn.lastActivity = time.Now()
f.mu.Unlock()
}
func (f *UDPForwarder) createConnection(req *udp.ForwarderRequest, connKey string) *udpConn {
id := req.ID()
// Create waiter queue
var wq waiter.Queue
// Create endpoint from request
ep, err := req.CreateEndpoint(&wq)
if err != nil {
return nil
}
// Convert to Go UDP conn
tunConn := gonet.NewUDPConn(&wq, ep)
// Extract destination address
// LocalAddress/LocalPort = destination (where packet is going TO)
// RemoteAddress/RemotePort = source (where packet is coming FROM)
dstAddr := &net.UDPAddr{
IP: net.IP(id.LocalAddress.AsSlice()),
Port: int(id.LocalPort),
}
// Create dialer with socket protection DURING dial
dialer := &net.Dialer{}
// CRITICAL: Protect socket BEFORE connect() is called
if f.protectSocket != nil {
dialer.Control = func(network, address string, c syscall.RawConn) error {
return c.Control(func(fd uintptr) {
f.protectSocket(int(fd))
})
}
}
// Create outbound UDP connection
dialConn, dialErr := dialer.Dial("udp", dstAddr.String())
if dialErr != nil {
tunConn.Close()
return nil
}
upstreamConn, ok := dialConn.(*net.UDPConn)
if !ok {
dialConn.Close()
tunConn.Close()
return nil
}
// Create connection context
ctx, cancel := context.WithCancel(f.ctx)
udpConnection := &udpConn{
tunEP: tunConn,
upstreamConn: upstreamConn,
lastActivity: time.Now(),
cancel: cancel,
}
// Start forwarding goroutines
go f.forwardTunToUpstream(udpConnection, ctx)
go f.forwardUpstreamToTun(udpConnection, ctx, connKey)
return udpConnection
}
func (f *UDPForwarder) forwardTunToUpstream(conn *udpConn, ctx context.Context) {
buffer := make([]byte, 65535)
for {
select {
case <-ctx.Done():
return
default:
}
// Read from TUN
n, err := conn.tunEP.Read(buffer)
if err != nil {
return
}
// Write to upstream
_, err = conn.upstreamConn.Write(buffer[:n])
if err != nil {
return
}
f.mu.Lock()
conn.lastActivity = time.Now()
f.mu.Unlock()
}
}
func (f *UDPForwarder) forwardUpstreamToTun(conn *udpConn, ctx context.Context, connKey string) {
defer func() {
conn.tunEP.Close()
conn.upstreamConn.Close()
f.mu.Lock()
delete(f.connections, connKey)
f.mu.Unlock()
}()
buffer := make([]byte, 65535)
// Set read timeout
conn.upstreamConn.SetReadDeadline(time.Now().Add(30 * time.Second))
for {
select {
case <-ctx.Done():
return
default:
}
// Read from upstream
n, err := conn.upstreamConn.Read(buffer)
if err != nil {
return
}
// Reset read deadline
conn.upstreamConn.SetReadDeadline(time.Now().Add(30 * time.Second))
// Write to TUN
_, err = conn.tunEP.Write(buffer[:n])
if err != nil {
return
}
f.mu.Lock()
conn.lastActivity = time.Now()
f.mu.Unlock()
}
}
func (f *UDPForwarder) cleanupStaleConnections() {
ticker := time.NewTicker(30 * time.Second)
defer ticker.Stop()
for {
select {
case <-f.ctx.Done():
return
case <-ticker.C:
f.mu.Lock()
now := time.Now()
for key, conn := range f.connections {
if now.Sub(conn.lastActivity) > 60*time.Second {
conn.cancel()
conn.tunEP.Close()
conn.upstreamConn.Close()
delete(f.connections, key)
}
}
f.mu.Unlock()
}
}
}
// Close closes all UDP connections
func (f *UDPForwarder) Close() {
f.mu.Lock()
defer f.mu.Unlock()
for _, conn := range f.connections {
conn.cancel()
conn.tunEP.Close()
conn.upstreamConn.Close()
}
f.connections = make(map[string]*udpConn)
}

247
cmd/ctrld_library/packet_capture.go Normal file
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package ctrld_library
import (
"fmt"
"net/netip"
"time"
"github.com/Control-D-Inc/ctrld"
"github.com/Control-D-Inc/ctrld/cmd/cli"
"github.com/Control-D-Inc/ctrld/cmd/ctrld_library/netstack"
"github.com/miekg/dns"
)
// PacketAppCallback extends AppCallback with packet read/write capabilities.
// Mobile platforms implementing full packet capture should use this interface.
type PacketAppCallback interface {
AppCallback
// ReadPacket reads a raw IP packet from the TUN interface.
// This should be a blocking call that returns when a packet is available.
ReadPacket() ([]byte, error)
// WritePacket writes a raw IP packet back to the TUN interface.
WritePacket(packet []byte) error
// ClosePacketIO closes packet I/O resources.
ClosePacketIO() error
// ProtectSocket protects a socket file descriptor from being routed through the VPN.
// On Android, this calls VpnService.protect() to prevent routing loops.
// On iOS, this marks the socket to bypass the VPN.
// Returns nil on success, error on failure.
ProtectSocket(fd int) error
}
// PacketCaptureController holds state for packet capture mode
type PacketCaptureController struct {
baseController *Controller
// Packet capture mode fields
netstackCtrl *netstack.NetstackController
dnsBridge *netstack.DNSBridge
packetStopCh chan struct{}
}
// NewPacketCaptureController creates a new packet capture controller
func NewPacketCaptureController(appCallback PacketAppCallback) *PacketCaptureController {
return &PacketCaptureController{
baseController: &Controller{AppCallback: appCallback},
packetStopCh: make(chan struct{}),
}
}
// StartWithPacketCapture starts ctrld in full packet capture mode for mobile.
// This method enables full IP packet processing with DNS filtering and upstream routing.
// It requires a PacketAppCallback that provides packet read/write capabilities.
func (pc *PacketCaptureController) StartWithPacketCapture(
packetCallback PacketAppCallback,
CdUID string,
ProvisionID string,
CustomHostname string,
HomeDir string,
UpstreamProto string,
logLevel int,
logPath string,
) error {
if pc.baseController.stopCh != nil {
return fmt.Errorf("controller already running")
}
// Set up configuration
pc.baseController.Config = cli.AppConfig{
CdUID: CdUID,
ProvisionID: ProvisionID,
CustomHostname: CustomHostname,
HomeDir: HomeDir,
UpstreamProto: UpstreamProto,
Verbose: logLevel,
LogPath: logPath,
}
pc.baseController.AppCallback = packetCallback
// Set global socket protector for HTTP client sockets (API calls, etc)
// This prevents routing loops when ctrld makes HTTP requests to api.controld.com
ctrld.SetSocketProtector(packetCallback.ProtectSocket)
// Create DNS bridge for communication between netstack and DNS proxy
pc.dnsBridge = netstack.NewDNSBridge()
pc.dnsBridge.Start()
// Create packet handler that wraps the mobile callbacks
packetHandler := netstack.NewMobilePacketHandler(
packetCallback.ReadPacket,
packetCallback.WritePacket,
packetCallback.ClosePacketIO,
packetCallback.ProtectSocket,
)
// Create DNS handler that uses the bridge
dnsHandler := func(query []byte) ([]byte, error) {
// Extract source IP from query context if available
// For now, use a placeholder
return pc.dnsBridge.ProcessQuery(query, "10.0.0.2", 0)
}
// Create netstack configuration
tunIPv4, err := netip.ParseAddr("10.0.0.1")
if err != nil {
return fmt.Errorf("failed to parse TUN IPv4: %v", err)
}
netstackCfg := &netstack.Config{
MTU: 1500,
TUNIPv4: tunIPv4,
DNSHandler: dnsHandler,
UpstreamInterface: nil, // Will use default interface
}
// Create netstack controller
netstackCtrl, err := netstack.NewNetstackController(packetHandler, netstackCfg)
if err != nil {
pc.dnsBridge.Stop()
return fmt.Errorf("failed to create netstack controller: %v", err)
}
pc.netstackCtrl = netstackCtrl
// Start netstack processing
if err := pc.netstackCtrl.Start(); err != nil {
pc.dnsBridge.Stop()
return fmt.Errorf("failed to start netstack: %v", err)
}
// Start regular ctrld DNS processing in background
// This allows us to use existing DNS filtering logic
pc.baseController.stopCh = make(chan struct{})
// Start DNS query processor that receives queries from the bridge
// and sends them to the ctrld DNS proxy
go pc.processDNSQueries()
// Start the main ctrld mobile runner
go func() {
appCallback := mapCallback(pc.baseController.AppCallback)
cli.RunMobile(&pc.baseController.Config, &appCallback, pc.baseController.stopCh)
}()
return nil
}
// processDNSQueries processes DNS queries from the bridge using the ctrld DNS proxy
func (pc *PacketCaptureController) processDNSQueries() {
queryCh := pc.dnsBridge.GetQueryChannel()
for {
select {
case <-pc.packetStopCh:
return
case <-pc.baseController.stopCh:
return
case query := <-queryCh:
go pc.handleDNSQuery(query)
}
}
}
// handleDNSQuery handles a single DNS query
func (pc *PacketCaptureController) handleDNSQuery(query *netstack.DNSQuery) {
// Parse DNS message
msg := new(dns.Msg)
if err := msg.Unpack(query.Query); err != nil {
return
}
// Send query to actual DNS proxy running on localhost:5354
client := &dns.Client{
Net: "udp",
Timeout: 3 * time.Second,
}
response, _, err := client.Exchange(msg, "127.0.0.1:5354")
if err != nil {
// Create SERVFAIL response
response = new(dns.Msg)
response.SetReply(msg)
response.Rcode = dns.RcodeServerFailure
}
// Pack response
responseBytes, err := response.Pack()
if err != nil {
return
}
// Send response back through bridge
pc.dnsBridge.SendResponse(query.ID, responseBytes)
}
// Stop stops the packet capture controller
func (pc *PacketCaptureController) Stop(restart bool, pin int64) int {
var errorCode = 0
// Clear global socket protector
ctrld.SetSocketProtector(nil)
// Stop DNS bridge
if pc.dnsBridge != nil {
pc.dnsBridge.Stop()
pc.dnsBridge = nil
}
// Stop netstack
if pc.netstackCtrl != nil {
if err := pc.netstackCtrl.Stop(); err != nil {
// Log error but continue shutdown
fmt.Printf("Error stopping netstack: %v\n", err)
}
pc.netstackCtrl = nil
}
// Close packet stop channel
if pc.packetStopCh != nil {
close(pc.packetStopCh)
pc.packetStopCh = make(chan struct{})
}
// Stop base controller
if !restart {
errorCode = cli.CheckDeactivationPin(pin, pc.baseController.stopCh)
}
if errorCode == 0 && pc.baseController.stopCh != nil {
close(pc.baseController.stopCh)
pc.baseController.stopCh = nil
}
return errorCode
}
// IsRunning returns true if the controller is running
func (pc *PacketCaptureController) IsRunning() bool {
return pc.baseController.stopCh != nil
}
// IsPacketMode returns true (always in packet mode for this controller)
func (pc *PacketCaptureController) IsPacketMode() bool {
return true
}