NetFilter SDK for macOS

NetFilter SDK for macOS is a framework for transparent filtering of data packets transmitted over the network. It is suitable for developing content filters, basic application-level firewalls, traffic analyzers/shapers, other software that requires viewing and modifying TCP traffic and controlling UDP access.

Key features

• The solution allows filtering outgoing TCP connections and allowing/blocking UDP datagrams from a user-mode application. It is possible to filter a specified subset of connections/datagrams, limited by filtering rules. The outgoing TCP connections can be redirected to a different address.

• The filtering operates at the transport level, on top of the TCP/IP stack. As a result, it automatically supports all kinds of TCP/IP-capable network adapters: Ethernet, Dial-up/DSL/Cable modems, wireless adapters including Wi-Fi and Bluetooth, virtual adapters like loopback or VPN.

• Both IPv6 and IPv4 are supported.

• Process and user context information is available for all network activity.

• The filtering works on Intel and ARM64 architectures.

• Installation
• Building the network extension
• Using API
  • Usage scenarios
• I found a bug
• Signing the network extension
• API reference
  • Functions
    • Initialization
      • nf_init()
      • nf_free()
      • nf_setOptions()
    • Filtering rules
      • nf_addRule()
      • nf_addRuleEx()
      • nf_setRules()
      • nf_setRulesEx()
      • nf_deleteRules()
    • TCP protocol
      • nf_tcpClose()
      • nf_tcpPostReceive()
      • nf_tcpPostSend()
      • nf_tcpSetConnectionState()
      • nf_tcpDisableFiltering()
      • nf_getTCPConnInfo()
    • UDP protocol
    • Common functions
      • nf_getProcessName()
      • nf_getUid()
      • nf_getUserName()
      • nf_requireFileLimit()
      • nf_isDisconnected()
  • Structures
    • NF_EventHandler
      • threadStart()
      • threadEnd()
      • tcpConnectRequest()
      • tcpConnected()
      • tcpClosed()
      • tcpReceive()
      • tcpSend()
      • tcpCanReceive()
      • tcpCanSend()
      • udpCreated()
      • udpConnectRequest()
      • udpClosed()
      • udpReceive()
      • udpSend()
      • udpCanReceive()
      • udpCanSend()
    • NF_RULE
    • NF_RULE_EX
    • NF_TCP_CONN_INFO
    • NF_UDP_CONN_INFO
    • NF_UDP_OPTIONS