Networking

Refer to Networking subsystem (netdev) for a guide on netdev development process specifics.

Contents:

• AF_XDP
  • Overview
  • Concepts
  • Libbpf
  • XSKMAP / BPF_MAP_TYPE_XSKMAP
  • Configuration Flags and Socket Options
  • Multi-Buffer Support
  • Sample application
  • FAQ
  • Credits
• Bare UDP Tunnelling Module Documentation
  • Special Handling
  • Usage
• batman-adv
  • Configuration
  • Usage
  • Logging/Debugging
  • batctl
  • Contact
• SocketCAN - Controller Area Network
  • Overview / What is SocketCAN
  • Motivation / Why Using the Socket API
  • SocketCAN Concept
  • How to use SocketCAN
  • SocketCAN Core Module
  • CAN Network Drivers
  • SocketCAN Resources
  • Credits
• The UCAN Protocol
  • USB Endpoints
  • CONTROL Messages
  • IN Message Format
  • OUT Message Format
  • CAN Error Handling
  • Example Conversation
• Hardware Device Drivers
  • Asynchronous Transfer Mode (ATM) Device Drivers
  • Cable Modem Device Drivers
  • Controller Area Network (CAN) Device Drivers
  • Cellular Modem Device Drivers
  • Ethernet Device Drivers
  • Fiber Distributed Data Interface (FDDI) Device Drivers
  • Amateur Radio Device Drivers
  • Wi-Fi Device Drivers
  • WWAN Device Drivers
• Networking Diagnostics
  • Diagnostic Concept for Investigating Twisted Pair Ethernet Variants at OSI Layer 1
• Distributed Switch Architecture
  • Architecture
  • Broadcom RoboSwitch Ethernet switch driver
  • Broadcom Starfighter 2 Ethernet switch driver
  • LAN9303 Ethernet switch driver
  • NXP SJA1105 switch driver
  • DSA switch configuration from userspace
• Linux Devlink Documentation
  • Locking
  • Nested instances
  • Interface documentation
  • Driver-specific documentation
• CAIF
  • Linux CAIF
  • Using Linux CAIF
• Netlink interface for ethtool
  • Basic information
  • Conventions
  • Request header
  • Bit sets
  • List of message types
  • STRSET_GET
  • LINKINFO_GET
  • LINKINFO_SET
  • LINKMODES_GET
  • LINKMODES_SET
  • LINKSTATE_GET
  • DEBUG_GET
  • DEBUG_SET
  • WOL_GET
  • WOL_SET
  • FEATURES_GET
  • FEATURES_SET
  • PRIVFLAGS_GET
  • PRIVFLAGS_SET
  • RINGS_GET
  • RINGS_SET
  • CHANNELS_GET
  • CHANNELS_SET
  • COALESCE_GET
  • COALESCE_SET
  • PAUSE_GET
  • PAUSE_SET
  • EEE_GET
  • EEE_SET
  • TSINFO_GET
  • CABLE_TEST
  • CABLE_TEST TDR
  • TUNNEL_INFO
  • FEC_GET
  • FEC_SET
  • MODULE_EEPROM_GET
  • STATS_GET
  • PHC_VCLOCKS_GET
  • MODULE_GET
  • MODULE_SET
  • PSE_GET
  • PSE_SET
  • RSS_GET
  • PLCA_GET_CFG
  • PLCA_SET_CFG
  • PLCA_GET_STATUS
  • MM_GET
  • MM_SET
  • MODULE_FW_FLASH_ACT
  • PHY_GET
  • Request translation
• IEEE 802.15.4 Developer’s Guide
  • Introduction
  • Socket API
  • 6LoWPAN Linux implementation
  • Drivers
  • Device drivers API
• ISO 15765-2 (ISO-TP)
  • Overview
  • How to Use ISO-TP
  • Examples
• J1939 Documentation
  • Overview / What Is J1939
  • Motivation
  • J1939 concepts
  • How to Use J1939
• Linux Networking and Network Devices APIs
  • Linux Networking
  • Network device support
• MSG_ZEROCOPY
  • Intro
  • Interface
  • Implementation
  • Testing
• FAILOVER
  • Overview
• Net DIM - Generic Network Dynamic Interrupt Moderation
  • Assumptions
  • Introduction
  • Net DIM Algorithm
  • Registering a Network Device to DIM
  • Example
  • Tuning DIM
  • Dynamic Interrupt Moderation (DIM) library API
• NET_FAILOVER
  • Overview
  • virtio-net accelerated datapath: STANDBY mode
  • Live Migration of a VM with SR-IOV VF & virtio-net in STANDBY mode
• Page Pool API
  • Architecture overview
  • Monitoring
  • API interface
  • Coding examples
• PHY Abstraction Layer
  • Purpose
  • The MDIO bus
  • (RG)MII/electrical interface considerations
  • Connecting to a PHY
  • Letting the PHY Abstraction Layer do Everything
  • PHY interface modes
  • Pause frames / flow control
  • Keeping Close Tabs on the PAL
  • Doing it all yourself
  • PHY Device Drivers
  • Board Fixups
  • Standards
• phylink
  • Overview
  • Modes of operation
  • Rough guide to converting a network driver to sfp/phylink
• IP-Aliasing
  • Alias creation
  • Alias deletion
  • Alias (re-)configuring
  • Relationship with main device
• Ethernet Bridging
  • Introduction
  • Bridge kAPI
  • Bridge uAPI
  • STP
  • VLAN
  • Multicast
  • Switchdev
  • Netfilter
  • Other Features
  • FAQ
  • Contact Info
  • External Links
• SNMP counter
  • General IPv4 counters
  • ICMP counters
  • General TCP counters
  • TCP Fast Open
  • TCP Fast Path
  • TCP abort
  • TCP Hybrid Slow Start
  • TCP retransmission and congestion control
  • DSACK
  • invalid SACK and DSACK
  • SACK shift
  • TCP out of order
  • TCP PAWS
  • TCP ACK skip
  • TCP receive window
  • Delayed ACK
  • Tail Loss Probe (TLP)
  • TCP Fast Open description
  • SYN cookies
  • Challenge ACK
  • prune
  • examples
• Checksum Offloads
  • Introduction
  • TX Checksum Offload
  • LCO: Local Checksum Offload
  • RCO: Remote Checksum Offload
• Segmentation Offloads
  • Introduction
  • TCP Segmentation Offload
  • UDP Fragmentation Offload
  • IPIP, SIT, GRE, UDP Tunnel, and Remote Checksum Offloads
  • Generic Segmentation Offload
  • Generic Receive Offload
  • Partial Generic Segmentation Offload
  • SCTP acceleration with GSO
• Scaling in the Linux Networking Stack
  • Introduction
  • RSS: Receive Side Scaling
  • RPS: Receive Packet Steering
  • RFS: Receive Flow Steering
  • Accelerated RFS
  • XPS: Transmit Packet Steering
  • Per TX Queue rate limitation
  • Further Information
• Kernel TLS
  • Overview
  • User interface
  • Statistics
• Kernel TLS offload
  • Kernel TLS operation
  • Device configuration
  • Normal operation
  • Resync handling
  • Error handling
  • Performance metrics
  • Statistics
  • Notable corner cases, exceptions and additional requirements
• In-Kernel TLS Handshake
  • Overview
  • User handshake agent
  • Kernel Handshake API
  • Handshake Completion
• Linux NFC subsystem
  • Architecture overview
  • Device Driver Interface
  • Userspace interface
• Netdev private dataroom for 6lowpan interfaces
• 6pack Protocol
  • 1. What is 6pack, and what are the advantages to KISS?
  • 2. Who has developed the 6pack protocol?
  • 3. Where can I get the latest version of 6pack for LinuX?
  • 4. Preparing the TNC for 6pack operation
  • 5. Building and installing the 6pack driver
  • How to turn on 6pack support:
  • 6. Known problems
• ARCnet Hardware
  • Introduction to ARCnet
  • Cabling ARCnet Networks
  • Setting the Jumpers
  • Unclassified Stuff
  • Standard Microsystems Corp (SMC)
  • Possibly SMC
  • PureData Corp
  • CNet Technology Inc. (8-bit cards)
  • CNet Technology Inc. (16-bit cards)
  • Lantech
  • Acer
  • Datapoint?
  • Topware
  • Thomas-Conrad
  • Waterloo Microsystems Inc. ??
  • No Name
  • Tiara
  • Other Cards
• ARCnet
  • Where do I discuss these drivers?
  • Other Drivers and Info
  • Installing the Driver
  • Loadable Module Support
  • Using the Driver
  • Multiple Cards in One Computer
  • How do I get it to work with...?
  • Using Multiprotocol ARCnet
  • It works: what now?
  • It doesn’t work: what now?
  • I want to send money: what now?
• ATM
• AX.25
• Linux Ethernet Bonding Driver HOWTO
  • Introduction
  • 1. Bonding Driver Installation
  • 2. Bonding Driver Options
  • 3. Configuring Bonding Devices
  • 4 Querying Bonding Configuration
  • 5. Switch Configuration
  • 6. 802.1q VLAN Support
  • 7. Link Monitoring
  • 8. Potential Sources of Trouble
  • 9. SNMP agents
  • 10. Promiscuous mode
  • 11. Configuring Bonding for High Availability
  • 12. Configuring Bonding for Maximum Throughput
  • 13. Switch Behavior Issues
  • 14. Hardware Specific Considerations
  • 15. Frequently Asked Questions
  • 16. Resources and Links
• cdc_mbim - Driver for CDC MBIM Mobile Broadband modems
  • Command Line Parameters
  • Basic usage
  • MBIM control channel userspace ABI
  • MBIM data channel userspace ABI
  • References
• DCCP protocol
  • Introduction
  • Missing features
  • Socket options
  • Sysctl variables
  • IOCTLS
  • Other tunables
  • Notes
• DCTCP (DataCenter TCP)
• Device Memory TCP
  • Intro
  • Interface
  • Implementation & Caveats
  • Testing
• DNS Resolver Module
  • Overview
  • Compilation
  • Setting up
  • Usage
  • Reading DNS Keys from Userspace
  • Mechanism
  • Debugging
• Softnet Driver Issues
  • Probing guidelines
  • Close/stop guidelines
  • Transmit path guidelines
• EQL Driver: Serial IP Load Balancing HOWTO
  • 1. Introduction
  • 2. Kernel Configuration
  • 3. Network Configuration
  • 4. About the Slave Scheduler Algorithm
  • 5. Testers’ Reports
• LC-trie implementation notes
  • Node types
  • A few concepts explained
  • Comments
  • Locking
  • Main lookup mechanism
• Linux Socket Filtering aka Berkeley Packet Filter (BPF)
  • Notice
  • Introduction
  • Structure
  • Example
  • BPF engine and instruction set
  • JIT compiler
  • BPF kernel internals
  • Testing
  • Misc
  • Written by
• Generic HDLC layer
  • Board-specific issues
• Generic Netlink
• Netlink Family Specifications
  • Family devlink netlink specification
  • Family dpll netlink specification
  • Family ethtool netlink specification
  • Family fou netlink specification
  • Family handshake netlink specification
  • Family mptcp_pm netlink specification
  • Family net-shaper netlink specification
  • Family netdev netlink specification
  • Family nfsd netlink specification
  • Family nftables netlink specification
  • Family nlctrl netlink specification
  • Family ovs_datapath netlink specification
  • Family ovs_flow netlink specification
  • Family ovs_vport netlink specification
  • Family rt-addr netlink specification
  • Family rt-link netlink specification
  • Family rt-neigh netlink specification
  • Family rt-route netlink specification
  • Family rt-rule netlink specification
  • Family tc netlink specification
  • Family tcp_metrics netlink specification
  • Family team netlink specification
• Generic networking statistics for netlink users
  • Collecting:
  • Export to userspace (Dump):
  • TCA_STATS/TCA_XSTATS backward compatibility:
  • Locking:
  • Rate Estimator:
  • Authors:
• The Linux kernel GTP tunneling module
  • What is GTP
  • The Linux GTP tunnelling module
  • Userspace Programs with Linux Kernel GTP-U support
  • Userspace Library / Command Line Utilities
  • Protocol Versions
  • IPv6
  • Mailing List
  • Issue Tracker
  • History / Acknowledgements
  • Architectural Details
  • APN vs. Network Device
• Identifier Locator Addressing (ILA)
  • Introduction
  • ILA terminology
  • Operation
  • Transport checksum handling
  • Identifier types
  • Identifier formats
  • Configuration
  • Some examples
• IOAM6 Sysfs variables
  • /proc/sys/net/conf/<iface>/ioam6_* variables:
• IP dynamic address hack-port v0.03
• IPsec
• IP Sysctl
  • /proc/sys/net/ipv4/* Variables
  • INET peer storage
  • TCP variables
  • UDP variables
  • RAW variables
  • CIPSOv4 Variables
  • IP Variables
  • /proc/sys/net/ipv6/* Variables
  • icmp/*:
  • /proc/sys/net/bridge/* Variables:
  • proc/sys/net/sctp/* Variables:
  • /proc/sys/net/core/*
  • /proc/sys/net/unix/*
• IPv6
• IPVLAN Driver HOWTO
  • 1. Introduction:
  • 2. Building and Installation:
  • 3. Configuration:
  • 4. Operating modes:
  • 5. Mode flags:
  • 6. What to choose (macvlan vs. ipvlan)?
  • 6. Example configuration:
• IPvs-sysctl
  • /proc/sys/net/ipv4/vs/* Variables:
• Kernel Connection Multiplexor
  • KCM sockets
  • Multiplexor
  • TCP sockets & Psocks
  • Connected mode semantics
  • Socket types
  • User interface
  • Use in applications
• L2TP
  • Overview
  • L2TP APIs
  • Internal Implementation
  • Miscellaneous
• The Linux LAPB Module Interface
  • Structures
  • LAPB Initialisation Structure
  • LAPB Parameter Structure
  • Functions
  • Callbacks
• How to use packet injection with mac80211
• Management Component Transport Protocol (MCTP)
  • Structure: interfaces & networks
  • Sockets API
  • Kernel internals
• MPLS Sysfs variables
  • /proc/sys/net/mpls/* Variables:
• Multipath TCP (MPTCP)
  • Introduction
  • Use cases
  • Concepts
  • Sockets API
  • Design choices
• MPTCP Sysfs variables
  • /proc/sys/net/mptcp/* Variables
• HOWTO for multiqueue network device support
  • Section 1: Base driver requirements for implementing multiqueue support
  • Section 2: Qdisc support for multiqueue devices
  • Section 3: Brief howto using MULTIQ for multiqueue devices
• Multi-PF Netdev
  • Contents
  • Background
  • Overview
  • mlx5 implementation
  • Channels distribution
  • Observability
  • Steering
  • Mutually exclusive features
• NAPI
  • Driver API
  • User API
• Common Networking Struct Cachelines
  • inet_connection_sock struct fast path usage breakdown
  • inet_sock struct fast path usage breakdown
  • net_device struct fast path usage breakdown
  • netns_ipv4 struct fast path usage breakdown
  • netns_ipv4 enum fast path usage breakdown
  • tcp_sock struct fast path usage breakdown
• Netconsole
  • Introduction:
  • Sender and receiver configuration:
  • Dynamic reconfiguration:
  • Extended console:
  • Miscellaneous notes:
• Netdev features mess and how to get out from it alive
  • Part I: Feature sets
  • Part II: Controlling enabled features
  • Part III: Implementation hints
  • Part IV: Features
• Network Devices, the Kernel, and You!
  • Introduction
  • struct net_device lifetime rules
  • MTU
  • struct net_device synchronization rules
  • struct napi_struct synchronization rules
• Netfilter Sysfs variables
  • /proc/sys/net/netfilter/* Variables:
• NETIF Msg Level
  • History
• Resilient Next-hop Groups
  • Algorithm
  • Offloading & Driver Feedback
  • Netlink UAPI
  • Usage
  • Netdevsim
• Netfilter Conntrack Sysfs variables
  • /proc/sys/net/netfilter/nf_conntrack_* Variables:
• Netfilter’s flowtable infrastructure
  • Overview
  • Example configuration
  • Layer 2 encapsulation
  • Bridge and IP forwarding
  • Counters
  • Hardware offload
  • Limitations
  • More reading
• OPEN Alliance 10BASE-T1x MAC-PHY Serial Interface (TC6) Framework Support
  • Introduction
  • Overview
  • Protocol Overview
  • Reference
  • Hardware Architecture
  • Software Architecture
  • Implementation
• Open vSwitch datapath developer documentation
  • Flow key compatibility
  • Flow key format
  • Wildcarded flow key format
  • Unique flow identifiers
  • Basic rule for evolving flow keys
  • Handling malformed packets
  • Other rules
• Operational States
  • 1. Introduction
  • 2. Querying from userspace
  • 3. Kernel driver API
  • 4. Setting from userspace
• Packet MMAP
  • Abstract
  • Why use PACKET_MMAP
  • How to use mmap() to improve capture process
  • How to use mmap() directly to improve capture process
  • How to use mmap() directly to improve transmission process
  • PACKET_MMAP settings
  • PACKET_MMAP setting constraints
  • PACKET_MMAP buffer size calculator
  • What TPACKET versions are available and when to use them?
  • AF_PACKET fanout mode
  • AF_PACKET TPACKET_V3 example
  • PACKET_QDISC_BYPASS
  • PACKET_TIMESTAMP
  • Miscellaneous bits
  • THANKS
• Linux Phonet protocol family
  • Introduction
  • Packets format
  • Link layer
  • Network layer
  • Low-level datagram protocol
  • Resource subscription
  • Phonet Pipe protocol
  • Authors
• PHY link topology
  • Overview
  • API
  • UAPI
• HOWTO for the linux packet generator
  • Tuning NIC for max performance
  • Kernel threads
  • Viewing devices
  • Configuring devices
  • Sample scripts
  • Interrupt affinity
  • Enable IPsec
  • Disable shared SKB
  • Current commands and configuration options
• PLIP: The Parallel Line Internet Protocol Device
  • PLIP Introduction
  • PLIP driver details
  • PLIP hardware interconnection
• PPP Generic Driver and Channel Interface
  • PPP channel API
  • Buffering and flow control
  • SMP safety
  • Interface to pppd
• The proc/net/tcp and proc/net/tcp6 variables
• Power Sourcing Equipment (PSE) Documentation
  • Power Sourcing Equipment (PSE) in IEEE 802.3 Standard
  • PSE Power Interface (PSE PI) Documentation
• How to use radiotap headers
  • Pointer to the radiotap include file
  • Structure of the header
  • Requirements for arguments
  • Example valid radiotap header
  • Using the Radiotap Parser
• RDS
  • Overview
  • RDS Architecture
  • Socket Interface
  • RDMA for RDS
  • Congestion Notifications
  • RDS Protocol
  • RDS Transport Layer
  • RDS Kernel Structures
  • Connection management
  • The send path
  • The recv path
  • Multipath RDS (mprds)
• Linux wireless regulatory documentation
  • Keeping regulatory domains in userspace
  • How to get regulatory domains to the kernel
  • How to get regulatory domains to the kernel (old CRDA solution)
  • Who asks for regulatory domains?
  • Example code - drivers hinting an alpha2:
  • Example code - drivers providing a built in regulatory domain:
  • Statically compiled regulatory database
• Network Function Representors
  • Motivation
  • Definitions
  • What does a representor do?
  • What functions should have a representor?
  • How are representors created?
  • How are representors identified?
  • How do representors interact with TC rules?
  • Configuring the representee’s MAC
• RxRPC Network Protocol
  • Overview
  • RxRPC Protocol Summary
  • AF_RXRPC Driver Model
  • Control Messages
• SOCKET OPTIONS
• SECURITY
• EXAMPLE CLIENT USAGE
  • Example Server Usage
  • AF_RXRPC Kernel Interface
  • Configurable Parameters
• Linux Kernel SCTP
  • Caveats
• LSM/SeLinux secid
• Seg6 Sysfs variables
  • /proc/sys/net/conf/<iface>/seg6_* variables:
• struct sk_buff
  • Basic sk_buff geometry
  • Shared skbs and skb clones
  • dataref and headerless skbs
  • Checksum information
• SMC Sysctl
  • /proc/sys/net/smc/* Variables
• NIC SR-IOV APIs
  • Legacy API
• Interface statistics
  • Overview
  • uAPIs
  • struct rtnl_link_stats64
  • Notes for driver authors
• Stream Parser (strparser)
  • Introduction
  • Interface
  • Functions
  • Callbacks
  • Statistics
  • Message assembly limits
  • Author
• Ethernet switch device driver model (switchdev)
  • Include Files
  • Configuration
  • Switch Ports
  • L2 Forwarding Offload
  • L3 Routing Offload
  • Device driver expected behavior
• Sysfs tagging
• TC Actions - Environmental Rules
• TC queue based filtering
• TCP Authentication Option Linux implementation (RFC5925)
  • 1. Introduction
  • 2. In-kernel MKTs database vs database in userspace
  • 3. uAPI
  • 4. setsockopt() vs accept() race
  • 5. Interaction with TCP-MD5
  • 6. SNE Linux implementation
  • 7. Links
• Thin-streams and TCP
  • References
• Team
• Timestamping
  • 1. Control Interfaces
  • 2 Data Interfaces
  • 3. Hardware Timestamping configuration: SIOCSHWTSTAMP and SIOCGHWTSTAMP
• Linux Kernel TIPC
  • Introduction
  • Implementation
• Transparent proxy support
  • 1. Making non-local sockets work
  • 2. Redirecting traffic
  • 3. Iptables and nf_tables extensions
  • 4. Application support
• Universal TUN/TAP device driver
  • 1. Description
  • 2. Configuration
  • 3. Program interface
  • Universal TUN/TAP device driver Frequently Asked Question
• The UDP-Lite protocol (RFC 3828)
  • 1. Applications
  • 2. Programming API
  • 3. Header Files
  • 4. Kernel Behaviour with Regards to the Various Socket Options
  • 5. UDP-Lite Runtime Statistics and their Meaning
  • 6. IPtables
  • 7. Maintainer Address
• Virtual Routing and Forwarding (VRF)
  • The VRF Device
  • Using iproute2 for VRFs
• Virtual eXtensible Local Area Networking documentation
• Linux X.25 Project
• X.25 Device Driver Interface
  • Packet Layer to Device Driver
  • Device Driver to Packet Layer
  • Requirements for the device driver
• XFRM device - offloading the IPsec computations
  • Overview
  • Callbacks to implement
  • Flow
• XFRM proc - /proc/net/xfrm_* files
  • Transformation Statistics
• XFRM
  • 1) Message Structure
  • 2) TLVS reflect the different parameters:
  • 3) Default configurations for the parameters:
  • 4) Message types
  • Exceptions to threshold settings
• XFRM Syscall
  • /proc/sys/net/core/xfrm_* Variables:
• XDP RX Metadata
  • General Design
  • AF_XDP
  • XDP_PASS
  • bpf_redirect_map
  • bpf_tail_call
  • Supported Devices
  • Example
• AF_XDP TX Metadata
  • General Design
  • Software TX Checksum
  • Querying Device Capabilities
  • Example