> ## Documentation Index
> Fetch the complete documentation index at: https://mintlify.com/serenityOS/serenity/llms.txt
> Use this file to discover all available pages before exploring further.

# Network Stack

> TCP/IP network stack implementation with IPv4 and IPv6 support

SerenityOS includes a fully functional network stack built from scratch, supporting modern networking protocols and standards.

## Overview

The SerenityOS network stack provides comprehensive networking capabilities with support for multiple protocols, network interfaces, and socket types.

<CardGroup cols={2}>
  <Card title="TCP/IP Stack" icon="network-wired">
    Full IPv4 and IPv6 protocol implementation
  </Card>

  <Card title="Socket API" icon="plug">
    POSIX-compliant socket interface
  </Card>

  <Card title="Network Drivers" icon="ethernet">
    Hardware and virtual network adapters
  </Card>

  <Card title="Protocol Support" icon="layer-group">
    TCP, UDP, ICMP, ARP, and more
  </Card>
</CardGroup>

## Network Protocols

### Internet Protocol (IP)

#### IPv4 Support

Complete IPv4 implementation with:

* IP packet forwarding
* Fragmentation and reassembly
* Time-to-live (TTL) handling
* IP options processing
* Checksum validation
* Source routing
* ICMP integration

#### IPv6 Support

Growing IPv6 capabilities including:

* IPv6 addressing and routing
* Neighbor Discovery Protocol
* ICMPv6 support
* IPv6 extension headers
* Dual-stack operation (IPv4/IPv6)
* Stateless address autoconfiguration (SLAAC)

<Info>
  Both IPv4 and IPv6 can be used simultaneously, with proper dual-stack support for modern network environments.
</Info>

### Transport Layer Protocols

<Accordion title="TCP (Transmission Control Protocol)">
  Full-featured TCP implementation:

  **Features:**

  * Three-way handshake
  * Reliable, ordered delivery
  * Flow control (sliding window)
  * Congestion control
  * Retransmission on packet loss
  * Connection state management
  * Graceful connection termination
  * TCP options support (MSS, window scaling, timestamps)
  * Keep-alive mechanism

  **TCP States:**

  * LISTEN, SYN\_SENT, SYN\_RECEIVED
  * ESTABLISHED
  * FIN\_WAIT\_1, FIN\_WAIT\_2
  * CLOSE\_WAIT, CLOSING
  * LAST\_ACK, TIME\_WAIT, CLOSED
</Accordion>

<Accordion title="UDP (User Datagram Protocol)">
  Lightweight datagram protocol:

  **Features:**

  * Connectionless communication
  * Low overhead
  * Broadcast and multicast support
  * Port multiplexing
  * Checksum validation (optional)
  * No delivery guarantees

  **Use Cases:**

  * DNS queries
  * DHCP
  * NTP time synchronization
  * Streaming media
  * Real-time applications
</Accordion>

### Network Layer Protocols

#### ICMP (Internet Control Message Protocol)

ICMP implementation for network diagnostics:

**Message Types:**

* Echo Request/Reply (ping)
* Destination Unreachable
* Time Exceeded
* Redirect
* Source Quench
* Parameter Problem

**ICMPv6:**

* Echo Request/Reply
* Neighbor Solicitation/Advertisement
* Router Solicitation/Advertisement
* Packet Too Big
* Time Exceeded

#### ARP (Address Resolution Protocol)

MAC address resolution for IPv4:

* ARP request/reply handling
* ARP cache management
* Gratuitous ARP
* ARP cache timeout
* Proxy ARP support

### Link Layer

#### Ethernet

Ethernet frame handling:

* Frame parsing and validation
* MAC address filtering
* EtherType identification
* VLAN tagging support (802.1Q)
* Jumbo frames

**Supported EtherTypes:**

* IPv4 (0x0800)
* IPv6 (0x86DD)
* ARP (0x0806)
* VLAN (0x8100)

## Application Layer Protocols

SerenityOS includes implementations of common application protocols:

<CardGroup cols={2}>
  <Card title="HTTP/HTTPS" icon="globe">
    Web protocol with TLS encryption
  </Card>

  <Card title="DNS" icon="server">
    Domain name resolution
  </Card>

  <Card title="DHCP" icon="network-wired">
    Dynamic IP configuration
  </Card>

  <Card title="NTP" icon="clock">
    Network time synchronization
  </Card>

  <Card title="IMAP" icon="envelope">
    Email retrieval protocol
  </Card>

  <Card title="Gemini" icon="gem">
    Alternative internet protocol
  </Card>

  <Card title="Telnet" icon="terminal">
    Remote terminal access
  </Card>

  <Card title="WebSocket" icon="plug">
    Bidirectional web communication
  </Card>
</CardGroup>

### HTTP/HTTPS

**HTTP Features:**

* HTTP/1.0 and HTTP/1.1
* Keep-alive connections
* Chunked transfer encoding
* Content negotiation
* Cookie management
* Redirect handling
* Compression (gzip, deflate)

**HTTPS/TLS:**

* TLS 1.2 and 1.3
* Modern cipher suites
* Certificate validation
* Perfect Forward Secrecy
* SNI (Server Name Indication)
* ALPN (Application-Layer Protocol Negotiation)

### DNS

Domain Name System implementation via LookupServer:

**Features:**

* A and AAAA record queries
* CNAME resolution
* MX records for mail
* PTR records (reverse DNS)
* NS records
* SOA records
* Query caching
* Multiple nameserver support
* /etc/hosts file integration
* Recursive resolution

### DHCP

Dynamic Host Configuration Protocol client:

* Automatic IP address assignment
* Network parameter configuration (gateway, DNS)
* Lease management and renewal
* DHCP discovery and negotiation
* DHCP release on shutdown

## Socket API

SerenityOS provides a POSIX-compliant socket API for network programming:

### Socket Types

```cpp theme={null}
// Stream socket (TCP)
int sock = socket(AF_INET, SOCK_STREAM, 0);

// Datagram socket (UDP)
int sock = socket(AF_INET, SOCK_DGRAM, 0);

// Raw socket (requires privileges)
int sock = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
```

### Address Families

* **AF\_INET** - IPv4 addressing
* **AF\_INET6** - IPv6 addressing
* **AF\_LOCAL** (AF\_UNIX) - Local/Unix domain sockets

### Socket Operations

Full socket API support:

* `socket()` - Create socket
* `bind()` - Bind to address/port
* `listen()` - Listen for connections
* `accept()` - Accept incoming connection
* `connect()` - Establish connection
* `send()` / `recv()` - Send/receive data
* `sendto()` / `recvfrom()` - Datagram operations
* `close()` - Close socket
* `shutdown()` - Shut down part of connection
* `getsockopt()` / `setsockopt()` - Socket options

### Non-blocking and Async I/O

* Non-blocking socket mode
* `select()` for multiplexing
* `poll()` for event notification
* `epoll()` for scalable event handling

## Network Adapters

Support for various network interface types:

### Hardware Adapters

<Accordion title="Intel E1000 Family">
  E1000 and E1000E network adapter drivers:

  * PCI and PCIe variants
  * Interrupt and polling modes
  * Transmit and receive queues
  * Hardware checksums
  * Link state detection
</Accordion>

<Accordion title="Intel i225 Series">
  Modern Intel Ethernet controllers with:

  * Multi-gigabit support
  * Advanced features
  * Energy efficient operation
</Accordion>

### Virtual Adapters

<Accordion title="Loopback Interface">
  Standard loopback (127.0.0.1/::1):

  * Local communication
  * No hardware required
  * Testing and development
  * Perfect reliability
</Accordion>

<Accordion title="VirtIO Network">
  Paravirtualized network for virtual machines:

  * KVM/QEMU support
  * High performance in VMs
  * Low overhead
  * Modern virtqueue interface
</Accordion>

## Network Configuration

### Static Configuration

Manual network setup:

```bash theme={null}
# Configure IP address
ifconfig eth0 192.168.1.100 netmask 255.255.255.0

# Set default gateway
route add default gw 192.168.1.1

# Configure DNS
echo "nameserver 8.8.8.8" > /etc/resolv.conf
```

### Dynamic Configuration (DHCP)

Automatic configuration via DHCPClient service:

* Automatic IP assignment
* Default gateway configuration
* DNS server configuration
* Network interface activation

### Network Settings Application

GUI application for network configuration:

* Interface management
* IP address configuration
* Gateway and DNS setup
* Connection status monitoring

## Network Tools

SerenityOS includes standard network utilities:

### Diagnostic Tools

* **ping** - Test connectivity with ICMP echo
* **ifconfig** - Configure network interfaces
* **route** - View and modify routing table
* **netstat** - Network statistics and connections
* **arp** - View and modify ARP cache
* **traceroute** - Trace packet route to destination
* **nslookup** - DNS query tool
* **host** - DNS lookup utility

### Network Applications

* **fetch** - Download files via HTTP/HTTPS
* **telnet** - Telnet client
* **nc (netcat)** - Network Swiss Army knife
* **wget** - Non-interactive file downloader

## Network Security

### Firewall & Filtering

Packet filtering capabilities:

* Connection state tracking
* Port-based filtering
* Protocol filtering
* Network address translation (NAT) in development

### TLS/SSL

Secure communication with LibTLS:

**Cipher Suites:**

* RSA and ECDHE key exchange
* AES-GCM, ChaCha20-Poly1305 encryption
* SHA-256, SHA-384 hashing
* Modern, secure algorithms only

**Certificate Validation:**

* X.509 certificate parsing
* Certificate chain validation
* Hostname verification
* Certificate expiration checking
* Revocation checking (in development)

### Security Features

* TCP SYN cookies for DoS protection
* Rate limiting for ICMP
* Randomized port allocation
* Sequence number randomization
* Path MTU discovery

<Info>
  Network services are sandboxed using `pledge()` and `unveil()` to limit potential security exposure.
</Info>

## Performance Features

### Optimizations

* Zero-copy networking where possible
* Scatter-gather I/O
* TCP window scaling
* Selective acknowledgment (SACK)
* Fast retransmit and recovery
* Nagle's algorithm
* Delayed ACK

### Buffer Management

* Efficient mbuf (memory buffer) system
* Buffer pooling
* Dynamic buffer allocation
* Memory pressure handling

## Routing

Routing table management:

* Static routes
* Default gateway
* Network-specific routes
* Host-specific routes
* Route metrics and preferences
* Multiple routing tables (in development)

## Network Monitoring

Tools for monitoring network activity:

* Real-time connection monitoring
* Packet statistics
* Interface statistics (bytes, packets, errors)
* Protocol-specific counters
* SystemMonitor integration

<Info>
  The network stack is continuously being improved with new features, better performance, and enhanced protocol support.
</Info>