aboutsummaryrefslogtreecommitdiff
path: root/Documentation/networking/udplite.rst
diff options
context:
space:
mode:
authorLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
committerLibravatar Linus Torvalds <torvalds@linux-foundation.org>2023-02-21 18:24:12 -0800
commit5b7c4cabbb65f5c469464da6c5f614cbd7f730f2 (patch)
treecc5c2d0a898769fd59549594fedb3ee6f84e59a0 /Documentation/networking/udplite.rst
downloadlinux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.tar.gz
linux-5b7c4cabbb65f5c469464da6c5f614cbd7f730f2.zip
Merge tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-nextgrafted
Pull networking updates from Jakub Kicinski: "Core: - Add dedicated kmem_cache for typical/small skb->head, avoid having to access struct page at kfree time, and improve memory use. - Introduce sysctl to set default RPS configuration for new netdevs. - Define Netlink protocol specification format which can be used to describe messages used by each family and auto-generate parsers. Add tools for generating kernel data structures and uAPI headers. - Expose all net/core sysctls inside netns. - Remove 4s sleep in netpoll if carrier is instantly detected on boot. - Add configurable limit of MDB entries per port, and port-vlan. - Continue populating drop reasons throughout the stack. - Retire a handful of legacy Qdiscs and classifiers. Protocols: - Support IPv4 big TCP (TSO frames larger than 64kB). - Add IP_LOCAL_PORT_RANGE socket option, to control local port range on socket by socket basis. - Track and report in procfs number of MPTCP sockets used. - Support mixing IPv4 and IPv6 flows in the in-kernel MPTCP path manager. - IPv6: don't check net.ipv6.route.max_size and rely on garbage collection to free memory (similarly to IPv4). - Support Penultimate Segment Pop (PSP) flavor in SRv6 (RFC8986). - ICMP: add per-rate limit counters. - Add support for user scanning requests in ieee802154. - Remove static WEP support. - Support minimal Wi-Fi 7 Extremely High Throughput (EHT) rate reporting. - WiFi 7 EHT channel puncturing support (client & AP). BPF: - Add a rbtree data structure following the "next-gen data structure" precedent set by recently added linked list, that is, by using kfunc + kptr instead of adding a new BPF map type. - Expose XDP hints via kfuncs with initial support for RX hash and timestamp metadata. - Add BPF_F_NO_TUNNEL_KEY extension to bpf_skb_set_tunnel_key to better support decap on GRE tunnel devices not operating in collect metadata. - Improve x86 JIT's codegen for PROBE_MEM runtime error checks. - Remove the need for trace_printk_lock for bpf_trace_printk and bpf_trace_vprintk helpers. - Extend libbpf's bpf_tracing.h support for tracing arguments of kprobes/uprobes and syscall as a special case. - Significantly reduce the search time for module symbols by livepatch and BPF. - Enable cpumasks to be used as kptrs, which is useful for tracing programs tracking which tasks end up running on which CPUs in different time intervals. - Add support for BPF trampoline on s390x and riscv64. - Add capability to export the XDP features supported by the NIC. - Add __bpf_kfunc tag for marking kernel functions as kfuncs. - Add cgroup.memory=nobpf kernel parameter option to disable BPF memory accounting for container environments. Netfilter: - Remove the CLUSTERIP target. It has been marked as obsolete for years, and we still have WARN splats wrt races of the out-of-band /proc interface installed by this target. - Add 'destroy' commands to nf_tables. They are identical to the existing 'delete' commands, but do not return an error if the referenced object (set, chain, rule...) did not exist. Driver API: - Improve cpumask_local_spread() locality to help NICs set the right IRQ affinity on AMD platforms. - Separate C22 and C45 MDIO bus transactions more clearly. - Introduce new DCB table to control DSCP rewrite on egress. - Support configuration of Physical Layer Collision Avoidance (PLCA) Reconciliation Sublayer (RS) (802.3cg-2019). Modern version of shared medium Ethernet. - Support for MAC Merge layer (IEEE 802.3-2018 clause 99). Allowing preemption of low priority frames by high priority frames. - Add support for controlling MACSec offload using netlink SET. - Rework devlink instance refcounts to allow registration and de-registration under the instance lock. Split the code into multiple files, drop some of the unnecessarily granular locks and factor out common parts of netlink operation handling. - Add TX frame aggregation parameters (for USB drivers). - Add a new attr TCA_EXT_WARN_MSG to report TC (offload) warning messages with notifications for debug. - Allow offloading of UDP NEW connections via act_ct. - Add support for per action HW stats in TC. - Support hardware miss to TC action (continue processing in SW from a specific point in the action chain). - Warn if old Wireless Extension user space interface is used with modern cfg80211/mac80211 drivers. Do not support Wireless Extensions for Wi-Fi 7 devices at all. Everyone should switch to using nl80211 interface instead. - Improve the CAN bit timing configuration. Use extack to return error messages directly to user space, update the SJW handling, including the definition of a new default value that will benefit CAN-FD controllers, by increasing their oscillator tolerance. New hardware / drivers: - Ethernet: - nVidia BlueField-3 support (control traffic driver) - Ethernet support for imx93 SoCs - Motorcomm yt8531 gigabit Ethernet PHY - onsemi NCN26000 10BASE-T1S PHY (with support for PLCA) - Microchip LAN8841 PHY (incl. cable diagnostics and PTP) - Amlogic gxl MDIO mux - WiFi: - RealTek RTL8188EU (rtl8xxxu) - Qualcomm Wi-Fi 7 devices (ath12k) - CAN: - Renesas R-Car V4H Drivers: - Bluetooth: - Set Per Platform Antenna Gain (PPAG) for Intel controllers. - Ethernet NICs: - Intel (1G, igc): - support TSN / Qbv / packet scheduling features of i226 model - Intel (100G, ice): - use GNSS subsystem instead of TTY - multi-buffer XDP support - extend support for GPIO pins to E823 devices - nVidia/Mellanox: - update the shared buffer configuration on PFC commands - implement PTP adjphase function for HW offset control - TC support for Geneve and GRE with VF tunnel offload - more efficient crypto key management method - multi-port eswitch support - Netronome/Corigine: - add DCB IEEE support - support IPsec offloading for NFP3800 - Freescale/NXP (enetc): - support XDP_REDIRECT for XDP non-linear buffers - improve reconfig, avoid link flap and waiting for idle - support MAC Merge layer - Other NICs: - sfc/ef100: add basic devlink support for ef100 - ionic: rx_push mode operation (writing descriptors via MMIO) - bnxt: use the auxiliary bus abstraction for RDMA - r8169: disable ASPM and reset bus in case of tx timeout - cpsw: support QSGMII mode for J721e CPSW9G - cpts: support pulse-per-second output - ngbe: add an mdio bus driver - usbnet: optimize usbnet_bh() by avoiding unnecessary queuing - r8152: handle devices with FW with NCM support - amd-xgbe: support 10Mbps, 2.5GbE speeds and rx-adaptation - virtio-net: support multi buffer XDP - virtio/vsock: replace virtio_vsock_pkt with sk_buff - tsnep: XDP support - Ethernet high-speed switches: - nVidia/Mellanox (mlxsw): - add support for latency TLV (in FW control messages) - Microchip (sparx5): - separate explicit and implicit traffic forwarding rules, make the implicit rules always active - add support for egress DSCP rewrite - IS0 VCAP support (Ingress Classification) - IS2 VCAP filters (protos, L3 addrs, L4 ports, flags, ToS etc.) - ES2 VCAP support (Egress Access Control) - support for Per-Stream Filtering and Policing (802.1Q, 8.6.5.1) - Ethernet embedded switches: - Marvell (mv88e6xxx): - add MAB (port auth) offload support - enable PTP receive for mv88e6390 - NXP (ocelot): - support MAC Merge layer - support for the the vsc7512 internal copper phys - Microchip: - lan9303: convert to PHYLINK - lan966x: support TC flower filter statistics - lan937x: PTP support for KSZ9563/KSZ8563 and LAN937x - lan937x: support Credit Based Shaper configuration - ksz9477: support Energy Efficient Ethernet - other: - qca8k: convert to regmap read/write API, use bulk operations - rswitch: Improve TX timestamp accuracy - Intel WiFi (iwlwifi): - EHT (Wi-Fi 7) rate reporting - STEP equalizer support: transfer some STEP (connection to radio on platforms with integrated wifi) related parameters from the BIOS to the firmware. - Qualcomm 802.11ax WiFi (ath11k): - IPQ5018 support - Fine Timing Measurement (FTM) responder role support - channel 177 support - MediaTek WiFi (mt76): - per-PHY LED support - mt7996: EHT (Wi-Fi 7) support - Wireless Ethernet Dispatch (WED) reset support - switch to using page pool allocator - RealTek WiFi (rtw89): - support new version of Bluetooth co-existance - Mobile: - rmnet: support TX aggregation" * tag 'net-next-6.3' of git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net-next: (1872 commits) page_pool: add a comment explaining the fragment counter usage net: ethtool: fix __ethtool_dev_mm_supported() implementation ethtool: pse-pd: Fix double word in comments xsk: add linux/vmalloc.h to xsk.c sefltests: netdevsim: wait for devlink instance after netns removal selftest: fib_tests: Always cleanup before exit net/mlx5e: Align IPsec ASO result memory to be as required by hardware net/mlx5e: TC, Set CT miss to the specific ct action instance net/mlx5e: Rename CHAIN_TO_REG to MAPPED_OBJ_TO_REG net/mlx5: Refactor tc miss handling to a single function net/mlx5: Kconfig: Make tc offload depend on tc skb extension net/sched: flower: Support hardware miss to tc action net/sched: flower: Move filter handle initialization earlier net/sched: cls_api: Support hardware miss to tc action net/sched: Rename user cookie and act cookie sfc: fix builds without CONFIG_RTC_LIB sfc: clean up some inconsistent indentings net/mlx4_en: Introduce flexible array to silence overflow warning net: lan966x: Fix possible deadlock inside PTP net/ulp: Remove redundant ->clone() test in inet_clone_ulp(). ...
Diffstat (limited to 'Documentation/networking/udplite.rst')
-rw-r--r--Documentation/networking/udplite.rst291
1 files changed, 291 insertions, 0 deletions
diff --git a/Documentation/networking/udplite.rst b/Documentation/networking/udplite.rst
new file mode 100644
index 000000000..2c225f28b
--- /dev/null
+++ b/Documentation/networking/udplite.rst
@@ -0,0 +1,291 @@
+.. SPDX-License-Identifier: GPL-2.0
+
+================================
+The UDP-Lite protocol (RFC 3828)
+================================
+
+
+ UDP-Lite is a Standards-Track IETF transport protocol whose characteristic
+ is a variable-length checksum. This has advantages for transport of multimedia
+ (video, VoIP) over wireless networks, as partly damaged packets can still be
+ fed into the codec instead of being discarded due to a failed checksum test.
+
+ This file briefly describes the existing kernel support and the socket API.
+ For in-depth information, you can consult:
+
+ - The UDP-Lite Homepage:
+ http://web.archive.org/web/%2E/http://www.erg.abdn.ac.uk/users/gerrit/udp-lite/
+
+ From here you can also download some example application source code.
+
+ - The UDP-Lite HOWTO on
+ http://web.archive.org/web/%2E/http://www.erg.abdn.ac.uk/users/gerrit/udp-lite/files/UDP-Lite-HOWTO.txt
+
+ - The Wireshark UDP-Lite WiKi (with capture files):
+ https://wiki.wireshark.org/Lightweight_User_Datagram_Protocol
+
+ - The Protocol Spec, RFC 3828, http://www.ietf.org/rfc/rfc3828.txt
+
+
+1. Applications
+===============
+
+ Several applications have been ported successfully to UDP-Lite. Ethereal
+ (now called wireshark) has UDP-Litev4/v6 support by default.
+
+ Porting applications to UDP-Lite is straightforward: only socket level and
+ IPPROTO need to be changed; senders additionally set the checksum coverage
+ length (default = header length = 8). Details are in the next section.
+
+2. Programming API
+==================
+
+ UDP-Lite provides a connectionless, unreliable datagram service and hence
+ uses the same socket type as UDP. In fact, porting from UDP to UDP-Lite is
+ very easy: simply add ``IPPROTO_UDPLITE`` as the last argument of the
+ socket(2) call so that the statement looks like::
+
+ s = socket(PF_INET, SOCK_DGRAM, IPPROTO_UDPLITE);
+
+ or, respectively,
+
+ ::
+
+ s = socket(PF_INET6, SOCK_DGRAM, IPPROTO_UDPLITE);
+
+ With just the above change you are able to run UDP-Lite services or connect
+ to UDP-Lite servers. The kernel will assume that you are not interested in
+ using partial checksum coverage and so emulate UDP mode (full coverage).
+
+ To make use of the partial checksum coverage facilities requires setting a
+ single socket option, which takes an integer specifying the coverage length:
+
+ * Sender checksum coverage: UDPLITE_SEND_CSCOV
+
+ For example::
+
+ int val = 20;
+ setsockopt(s, SOL_UDPLITE, UDPLITE_SEND_CSCOV, &val, sizeof(int));
+
+ sets the checksum coverage length to 20 bytes (12b data + 8b header).
+ Of each packet only the first 20 bytes (plus the pseudo-header) will be
+ checksummed. This is useful for RTP applications which have a 12-byte
+ base header.
+
+
+ * Receiver checksum coverage: UDPLITE_RECV_CSCOV
+
+ This option is the receiver-side analogue. It is truly optional, i.e. not
+ required to enable traffic with partial checksum coverage. Its function is
+ that of a traffic filter: when enabled, it instructs the kernel to drop
+ all packets which have a coverage _less_ than this value. For example, if
+ RTP and UDP headers are to be protected, a receiver can enforce that only
+ packets with a minimum coverage of 20 are admitted::
+
+ int min = 20;
+ setsockopt(s, SOL_UDPLITE, UDPLITE_RECV_CSCOV, &min, sizeof(int));
+
+ The calls to getsockopt(2) are analogous. Being an extension and not a stand-
+ alone protocol, all socket options known from UDP can be used in exactly the
+ same manner as before, e.g. UDP_CORK or UDP_ENCAP.
+
+ A detailed discussion of UDP-Lite checksum coverage options is in section IV.
+
+3. Header Files
+===============
+
+ The socket API requires support through header files in /usr/include:
+
+ * /usr/include/netinet/in.h
+ to define IPPROTO_UDPLITE
+
+ * /usr/include/netinet/udplite.h
+ for UDP-Lite header fields and protocol constants
+
+ For testing purposes, the following can serve as a ``mini`` header file::
+
+ #define IPPROTO_UDPLITE 136
+ #define SOL_UDPLITE 136
+ #define UDPLITE_SEND_CSCOV 10
+ #define UDPLITE_RECV_CSCOV 11
+
+ Ready-made header files for various distros are in the UDP-Lite tarball.
+
+4. Kernel Behaviour with Regards to the Various Socket Options
+==============================================================
+
+
+ To enable debugging messages, the log level need to be set to 8, as most
+ messages use the KERN_DEBUG level (7).
+
+ 1) Sender Socket Options
+
+ If the sender specifies a value of 0 as coverage length, the module
+ assumes full coverage, transmits a packet with coverage length of 0
+ and according checksum. If the sender specifies a coverage < 8 and
+ different from 0, the kernel assumes 8 as default value. Finally,
+ if the specified coverage length exceeds the packet length, the packet
+ length is used instead as coverage length.
+
+ 2) Receiver Socket Options
+
+ The receiver specifies the minimum value of the coverage length it
+ is willing to accept. A value of 0 here indicates that the receiver
+ always wants the whole of the packet covered. In this case, all
+ partially covered packets are dropped and an error is logged.
+
+ It is not possible to specify illegal values (<0 and <8); in these
+ cases the default of 8 is assumed.
+
+ All packets arriving with a coverage value less than the specified
+ threshold are discarded, these events are also logged.
+
+ 3) Disabling the Checksum Computation
+
+ On both sender and receiver, checksumming will always be performed
+ and cannot be disabled using SO_NO_CHECK. Thus::
+
+ setsockopt(sockfd, SOL_SOCKET, SO_NO_CHECK, ... );
+
+ will always will be ignored, while the value of::
+
+ getsockopt(sockfd, SOL_SOCKET, SO_NO_CHECK, &value, ...);
+
+ is meaningless (as in TCP). Packets with a zero checksum field are
+ illegal (cf. RFC 3828, sec. 3.1) and will be silently discarded.
+
+ 4) Fragmentation
+
+ The checksum computation respects both buffersize and MTU. The size
+ of UDP-Lite packets is determined by the size of the send buffer. The
+ minimum size of the send buffer is 2048 (defined as SOCK_MIN_SNDBUF
+ in include/net/sock.h), the default value is configurable as
+ net.core.wmem_default or via setting the SO_SNDBUF socket(7)
+ option. The maximum upper bound for the send buffer is determined
+ by net.core.wmem_max.
+
+ Given a payload size larger than the send buffer size, UDP-Lite will
+ split the payload into several individual packets, filling up the
+ send buffer size in each case.
+
+ The precise value also depends on the interface MTU. The interface MTU,
+ in turn, may trigger IP fragmentation. In this case, the generated
+ UDP-Lite packet is split into several IP packets, of which only the
+ first one contains the L4 header.
+
+ The send buffer size has implications on the checksum coverage length.
+ Consider the following example::
+
+ Payload: 1536 bytes Send Buffer: 1024 bytes
+ MTU: 1500 bytes Coverage Length: 856 bytes
+
+ UDP-Lite will ship the 1536 bytes in two separate packets::
+
+ Packet 1: 1024 payload + 8 byte header + 20 byte IP header = 1052 bytes
+ Packet 2: 512 payload + 8 byte header + 20 byte IP header = 540 bytes
+
+ The coverage packet covers the UDP-Lite header and 848 bytes of the
+ payload in the first packet, the second packet is fully covered. Note
+ that for the second packet, the coverage length exceeds the packet
+ length. The kernel always re-adjusts the coverage length to the packet
+ length in such cases.
+
+ As an example of what happens when one UDP-Lite packet is split into
+ several tiny fragments, consider the following example::
+
+ Payload: 1024 bytes Send buffer size: 1024 bytes
+ MTU: 300 bytes Coverage length: 575 bytes
+
+ +-+-----------+--------------+--------------+--------------+
+ |8| 272 | 280 | 280 | 280 |
+ +-+-----------+--------------+--------------+--------------+
+ 280 560 840 1032
+ ^
+ *****checksum coverage*************
+
+ The UDP-Lite module generates one 1032 byte packet (1024 + 8 byte
+ header). According to the interface MTU, these are split into 4 IP
+ packets (280 byte IP payload + 20 byte IP header). The kernel module
+ sums the contents of the entire first two packets, plus 15 bytes of
+ the last packet before releasing the fragments to the IP module.
+
+ To see the analogous case for IPv6 fragmentation, consider a link
+ MTU of 1280 bytes and a write buffer of 3356 bytes. If the checksum
+ coverage is less than 1232 bytes (MTU minus IPv6/fragment header
+ lengths), only the first fragment needs to be considered. When using
+ larger checksum coverage lengths, each eligible fragment needs to be
+ checksummed. Suppose we have a checksum coverage of 3062. The buffer
+ of 3356 bytes will be split into the following fragments::
+
+ Fragment 1: 1280 bytes carrying 1232 bytes of UDP-Lite data
+ Fragment 2: 1280 bytes carrying 1232 bytes of UDP-Lite data
+ Fragment 3: 948 bytes carrying 900 bytes of UDP-Lite data
+
+ The first two fragments have to be checksummed in full, of the last
+ fragment only 598 (= 3062 - 2*1232) bytes are checksummed.
+
+ While it is important that such cases are dealt with correctly, they
+ are (annoyingly) rare: UDP-Lite is designed for optimising multimedia
+ performance over wireless (or generally noisy) links and thus smaller
+ coverage lengths are likely to be expected.
+
+5. UDP-Lite Runtime Statistics and their Meaning
+================================================
+
+ Exceptional and error conditions are logged to syslog at the KERN_DEBUG
+ level. Live statistics about UDP-Lite are available in /proc/net/snmp
+ and can (with newer versions of netstat) be viewed using::
+
+ netstat -svu
+
+ This displays UDP-Lite statistics variables, whose meaning is as follows.
+
+ ============ =====================================================
+ InDatagrams The total number of datagrams delivered to users.
+
+ NoPorts Number of packets received to an unknown port.
+ These cases are counted separately (not as InErrors).
+
+ InErrors Number of erroneous UDP-Lite packets. Errors include:
+
+ * internal socket queue receive errors
+ * packet too short (less than 8 bytes or stated
+ coverage length exceeds received length)
+ * xfrm4_policy_check() returned with error
+ * application has specified larger min. coverage
+ length than that of incoming packet
+ * checksum coverage violated
+ * bad checksum
+
+ OutDatagrams Total number of sent datagrams.
+ ============ =====================================================
+
+ These statistics derive from the UDP MIB (RFC 2013).
+
+6. IPtables
+===========
+
+ There is packet match support for UDP-Lite as well as support for the LOG target.
+ If you copy and paste the following line into /etc/protocols::
+
+ udplite 136 UDP-Lite # UDP-Lite [RFC 3828]
+
+ then::
+
+ iptables -A INPUT -p udplite -j LOG
+
+ will produce logging output to syslog. Dropping and rejecting packets also works.
+
+7. Maintainer Address
+=====================
+
+ The UDP-Lite patch was developed at
+
+ University of Aberdeen
+ Electronics Research Group
+ Department of Engineering
+ Fraser Noble Building
+ Aberdeen AB24 3UE; UK
+
+ The current maintainer is Gerrit Renker, <gerrit@erg.abdn.ac.uk>. Initial
+ code was developed by William Stanislaus, <william@erg.abdn.ac.uk>.