IP-XFRM(8)

📦

version 7.3.0 · 4 versions

7.3.0 · alpine 3.24, arch rolling, centos-stream 10, nixos 26.05, nixpkgs unstable, ubuntu resolute, ubuntu stonking (latest)
5.15.0 · ubuntu jammy
6.1.0 · debian bookworm, ubuntu noble
6.17.0 · alpine 3.22, alpine 3.23, centos-stream 9, debian trixie, fedora 43, fedora 44, opensuse-leap 16.0, ubuntu questing

, in alpine 3.24, arch rolling, centos-stream 10, nixos 26.05, nixpkgs unstable, ubuntu resolute, ubuntu stonking

💖 IP-XFRM(8) 💖

okay bestie, this is the ip-xfrm page, and it's literally transform configuration. We're in part 1, so let's vibe.

✨ NAME ✨

ip-xfrm — transform configuration

🌸 SYNOPSIS 🌸

okay so the whole thing kicks off like this:

       ip [ OPTIONS ] xfrm  { COMMAND | help }

       ip xfrm XFRM-OBJECT { COMMAND | help }

       XFRM-OBJECT := state | policy | monitor

🦋 state 🦋

here's the state command menu, no cap:

state commands

       ip xfrm state { add | update } ID [ ALGO-LIST ] [ mode MODE ] [ mark
               MARK [ mask MASK ] ] [ reqid REQID ] [ dir SA-DIR ] [ seq SEQ ]
               [ replay-window SIZE ] [ replay-seq SEQ ] [ replay-oseq SEQ ] [
               replay-seq-hi SEQ ] [ replay-oseq-hi SEQ ] [ flag FLAG-LIST ] [
               sel SELECTOR ] [ LIMIT-LIST ] [ encap ENCAP ] [ coa ADDR[/PLEN]
               ] [ ctx CTX ] [ extra-flag EXTRA-FLAG-LIST ] [ output-mark
               OUTPUT-MARK [ mask MASK ] ] [ if_id IF-ID ] [ offload [
               crypto|packet ] dev DEV dir DIR ] [ tfcpad LENGTH ] [ pcpu-num
               CPUNUM ]

       ip xfrm state allocspi ID [ mode MODE ] [ mark MARK [ mask MASK ] ] [
               reqid REQID ] [ seq SEQ ] [ min SPI max SPI ] [ pcpu-num CPUNUM
               ]

       ip xfrm state { delete | get } ID [ mark MARK [ mask MASK ] ]

       ip [ -4 | -6 ] xfrm state deleteall [ ID ] [ mode MODE ] [ reqid REQID ]
               [ flag FLAG-LIST ]

       ip [ -4 | -6 ] xfrm state list [ ID ] [ nokeys ] [ mode MODE ] [ reqid
               REQID ] [ flag FLAG-LIST ]

       ip xfrm state flush [ proto XFRM-PROTO ]

       ip xfrm state count

state definitions

and the state building blocks are:

       ID := [ src ADDR ] [ dst ADDR ] [ proto XFRM-PROTO ] [ spi SPI ]

       XFRM-PROTO := esp | ah | comp | route2 | hao

       ALGO-LIST := [ ALGO-LIST ] ALGO

       ALGO := { enc | auth } ALGO-NAME ALGO-KEYMAT |
               auth-trunc ALGO-NAME ALGO-KEYMAT ALGO-TRUNC-LEN |
               aead ALGO-NAME ALGO-KEYMAT ALGO-ICV-LEN |
               comp ALGO-NAME

       MODE := transport | tunnel | beet | ro | in_trigger

       SA-DIR := in | out

       FLAG-LIST := [ FLAG-LIST ] FLAG

       FLAG := noecn | decap-dscp | nopmtudisc | wildrecv | icmp | af-unspec |
               align4 | esn

       SELECTOR := [ src ADDR[/PLEN] ] [ dst ADDR[/PLEN] ] [ dev DEV ]
               [ UPSPEC ]

       UPSPEC := proto { PROTO |
               { tcp | udp | sctp | dccp } [ sport PORT ] [ dport PORT ] |
               { icmp | ipv6-icmp | mobility-header } [ type NUMBER ] [ code
               NUMBER ] |
               gre [ key { DOTTED-QUAD | NUMBER } ] }

       LIMIT-LIST := [ LIMIT-LIST ] limit LIMIT

       LIMIT := { time-soft | time-hard | time-use-soft | time-use-hard }
               SECONDS |
               { byte-soft | byte-hard } SIZE |
               { packet-soft | packet-hard } COUNT

       ENCAP := { espinudp | espinudp-nonike | espintcp } SPORT DPORT OADDR

       EXTRA-FLAG-LIST := [ EXTRA-FLAG-LIST ] EXTRA-FLAG

       EXTRA-FLAG := dont-encap-dscp | oseq-may-wrap

💅 policy 💅

next, policy is serving commands too:

policy commands

       ip xfrm policy { add | update } SELECTOR dir DIR [ ctx CTX ] [ mark MARK
               [ mask MASK ] ] [ index INDEX ] [ ptype PTYPE ] [ action ACTION
               ] [ priority PRIORITY ] [ flag FLAG-LIST ] [ if_id IF-ID ] [
               offload packet dev DEV ] [ LIMIT-LIST ] [ TMPL-LIST ]

       ip xfrm policy { delete | get } { SELECTOR | index INDEX } dir DIR [ ctx
               CTX ] [ mark MARK [ mask MASK ] ] [ ptype PTYPE ] [ if_id IF-ID
               ]

       ip [ -4 | -6 ] xfrm policy { deleteall | list } [ nosock ] [ SELECTOR ]
               [ dir DIR ] [ index INDEX ] [ ptype PTYPE ] [ action ACTION ] [
               priority PRIORITY ] [ flag FLAG-LIST]

       ip xfrm policy flush [ ptype PTYPE ]

       ip xfrm policy count

       ip xfrm policy set [ hthresh4 LBITS RBITS ] [ hthresh6 LBITS RBITS ]

       ip xfrm policy setdefault DIR ACTION [ DIR ACTION ] [ DIR ACTION ]

       ip xfrm policy getdefault

policy definitions

and the policy building blocks:

       SELECTOR := [ src ADDR[/PLEN] ] [ dst ADDR[/PLEN] ] [ dev DEV ] [ UPSPEC
               ]

       UPSPEC := proto { PROTO |
               { tcp | udp | sctp | dccp } [ sport PORT ] [ dport PORT ] |
               { icmp | ipv6-icmp | mobility-header } [ type NUMBER ] [ code
               NUMBER ] |
               gre [ key { DOTTED-QUAD | NUMBER } ] }

       DIR := in | out | fwd

       PTYPE := main | sub

       ACTION := allow | block

       FLAG-LIST := [ FLAG-LIST ] FLAG

       FLAG := localok | icmp

       LIMIT-LIST := [ LIMIT-LIST ] limit LIMIT

       LIMIT := { time-soft | time-hard | time-use-soft | time-use-hard }
               SECONDS |
               { byte-soft | byte-hard } SIZE |
               { packet-soft | packet-hard } COUNT

       TMPL-LIST := [ TMPL-LIST ] tmpl TMPL

       TMPL := ID [ mode MODE ] [ reqid REQID ] [ level LEVEL ]

       ID := [ src ADDR ] [ dst ADDR ] [ proto XFRM-PROTO ] [ spi SPI ]

       XFRM-PROTO := esp | ah | comp | route2 | hao

       MODE := transport | tunnel | beet | ro | in_trigger

       LEVEL := required | use

👑 monitor 👑

finally, monitor is the watch vibe:

       ip xfrm monitor [ all-nsid ] [ nokeys ] [ all
                | LISTofXFRM-OBJECTS ]

       LISTofXFRM-OBJECTS := [ LISTofXFRM-OBJECTS ] XFRM-OBJECT

       XFRM-OBJECT := acquire | expire | SA | policy | aevent | report

✨ DESCRIPTION ✨

okay so bestie, xfrm is an IP framework for transforming packets (think encrypting their payloads, that whole situation). This framework is what implements the IPsec protocol suite — the state object works on the Security Association Database, and the policy object works on the Security Policy Database. It's ALSO used for the IP Payload Compression Protocol and for features of Mobile IPv6. multi-purpose queen fr fr 💅

Here's the state command lineup, no cap:

ip xfrm state add         add new state into xfrm
ip xfrm state update      update existing state in xfrm
ip xfrm state allocspi    allocate an SPI value
ip xfrm state delete      delete existing state in xfrm
ip xfrm state get         get existing state in xfrm
ip xfrm state deleteall   delete all existing state in xfrm
ip xfrm state list        print out the list of existing state in xfrm
ip xfrm state flush       flush all state in xfrm
ip xfrm state count       count all existing state in xfrm

Now the vocabulary you're gonna keep seeing, bestie — learn these and you're golden ✨

ID — is specified by a source address, destination address, transform protocol XFRM-PROTO, and/or Security Parameter Index SPI. (For IP Payload Compression, the Compression Parameter Index or CPI is used for SPI.)
XFRM-PROTO — specifies a transform protocol: IPsec Encapsulating Security Payload (esp), IPsec Authentication Header (ah), IP Payload Compression (comp), Mobile IPv6 Type 2 Routing Header (route2), or Mobile IPv6 Home Address Option (hao).
ALGO-LIST — contains one or more algorithms to use. Each algorithm ALGO is specified by:
- the algorithm type: encryption (enc), authentication (auth or auth-trunc), authenticated encryption with associated data (aead), or compression (comp)
- the algorithm name ALGO-NAME (see below)
- (for all except comp) the keying material ALGO-KEYMAT, which may include both a key and a salt or nonce value; refer to the corresponding RFC
- (for auth-trunc only) the truncation length ALGO-TRUNC-LEN in bits
- (for aead only) the Integrity Check Value length ALGO-ICV-LEN in bits

Encryption algorithms include ecb(cipher_null), cbc(des), cbc(des3_ede), cbc(cast5), cbc(blowfish), cbc(aes), cbc(serpent), cbc(camellia), cbc(twofish), and rfc3686(ctr(aes)).

Authentication algorithms include digest_null, hmac(md5), hmac(sha1), hmac(sha256), hmac(sha384), hmac(sha512), hmac(rmd160), and xcbc(aes).

Authenticated encryption with associated data (AEAD) algorithms include rfc4106(gcm(aes)), rfc4309(ccm(aes)), and rfc4543(gcm(aes)).

Compression algorithms include deflate, lzs, and lzjh.

MODE — specifies a mode of operation for the transform protocol. IPsec and IP Payload Compression modes are transport, tunnel, and (for IPsec ESP only) Bound End-to-End Tunnel (beet). Mobile IPv6 modes are route optimization (ro) and inbound trigger (in_trigger).
FLAG-LIST — contains one or more of the following optional flags: noecn, decap-dscp, nopmtudisc, wildrecv, icmp, af-unspec, align4, or esn.
SELECTOR — selects the traffic that will be controlled by the policy, based on the source address, the destination address, the network device, and/or UPSPEC.
UPSPEC — selects traffic by protocol. For the tcp, udp, sctp, or dccp protocols, the source and destination port can optionally be specified. For the icmp, ipv6-icmp, or mobility-header protocols, the type and code numbers can optionally be specified. For the gre protocol, the key can optionally be specified as a dotted-quad or number. Other protocols can be selected by name or number PROTO.
LIMIT-LIST — sets limits in seconds, bytes, or numbers of packets.
ENCAP — encapsulates packets with protocol espinudp, espinudp-nonike, or espintcp, using source port SPORT, destination port DPORT , and original address OADDR.
MARK — used to match xfrm policies and states
OUTPUT-MARK — used to set the output mark to influence the routing of the packets emitted by the state
IF-ID — xfrm interface identifier used to in both xfrm policies and states
DEV — Network interface name used to offload policies and states

🎀 the policy side of things 🎀

policies are their own whole vibe, so here's the roster:

ip xfrm policy add         add a new policy
ip xfrm policy update      update an existing policy
ip xfrm policy delete      delete an existing policy
ip xfrm policy get         get an existing policy
ip xfrm policy deleteall   delete all existing xfrm policies
ip xfrm policy list        print out the list of xfrm policies
ip xfrm policy flush       flush policies

nosock — filter (remove) all socket policies from the output.

And the policy dictionary, bestie:

SELECTOR — selects the traffic that will be controlled by the policy, based on the source address, the destination address, the network device, and/or UPSPEC.
UPSPEC — selects traffic by protocol. For the tcp, udp, sctp, or dccp protocols, the source and destination port can optionally be specified. For the icmp, ipv6-icmp, or mobility-header protocols, the type and code numbers can optionally be specified. For the gre protocol, the key can optionally be specified as a dotted-quad or number. Other protocols can be selected by name or number PROTO.
DIR — selects the policy direction as in, out, or fwd.
CTX — sets the security context.
PTYPE — can be main (default) or sub.
ACTION — can be allow (default) or block.
PRIORITY — is a number that defaults to zero.
FLAG-LIST — contains one or both of the following optional flags: local or icmp.
LIMIT-LIST — sets limits in seconds, bytes, or numbers of packets.
TMPL-LIST — is a template list specified using ID, MODE, REQID, and/or LEVEL.
ID — is specified by a source address, destination address, transform protocol XFRM-PROTO, and/or Security Parameter Index SPI. (For IP Payload Compression, the Compression Parameter Index or CPI is used for SPI.)
XFRM-PROTO — specifies a transform protocol: IPsec Encapsulating Security Payload (esp), IPsec Authentication Header (ah), IP Payload Compression (comp), Mobile IPv6 Type 2 Routing Header (route2), or Mobile IPv6 Home Address Option (hao).
MODE — specifies a mode of operation for the transform protocol. IPsec and IP Payload Compression modes are transport, tunnel, and (for IPsec ESP only) Bound End-to-End Tunnel (beet). Mobile IPv6 modes are route optimization (ro) and inbound trigger (in_trigger).
LEVEL — can be required (default) or use.

counting, hashing & monitoring 💖

ip xfrm policy count — count existing policies

Use one or more -s options to display more details, including policy hash table information.

ip xfrm policy set — configure the policy hash table

Security policies whose address prefix lengths are greater than or equal policy hash table thresholds are hashed. Others are stored in the policy_inexact chained list.

LBITS — specifies the minimum local address prefix length of policies that are stored in the Security Policy Database hash table.
RBITS — specifies the minimum remote address prefix length of policies that are stored in the Security Policy Database hash table.

ip xfrm monitor — state monitoring for xfrm objects

The xfrm objects to monitor can be optionally specified.

If the all-nsid option is set, the program listens to all network namespaces that have a nsid assigned into the network namespace were the program is running. A prefix is displayed to show the network namespace where the message originates. Example:

  [nsid 1]Flushed state proto 0

💜 AUTHOR 💜

Manpage revised by David Ward <david.ward@ll.mit.edu> Manpage revised by Christophe Gouault <christophe.gouault@6wind.com> Manpage revised by Nicolas Dichtel <nicolas.dichtel@6wind.com>

and that's a wrap, bestie!! 🫶 this iconic little page lives in iproute2 and its date is 20 Dec 2011 — yes it's been serving looks since way back, and it's still IP-XFRM(8) through and through. go configure something gorgeous 💅✨

📦 where this page comes from

alpine 3.24: iproute2-doc 7.0.0-r0 · GPL-2.0-or-later
arch rolling: iproute2 7.2.0-1
arch rolling: iproute2 7.3.0-1 · GPL-2.0-or-later
centos-stream 10: iproute 7.0.0-2.el10 · GPL-2.0-or-later AND NIST-PD
nixos 26.05: iproute2 7.0.0
nixpkgs unstable: iproute2 7.2.0
ubuntu resolute: iproute2 6.19.0-1ubuntu1 · GPL-2.0-only
ubuntu resolute: iproute2 6.19.0-1ubuntu1.1 · GPL-2.0-only
ubuntu stonking: iproute2 7.2.0-1ubuntu1 · GPL-2.0-only
💖 girlified by deepseek-ai/DeepSeek-V4.1-Flash on 2026-10-18: a language model's rewrite of the original, under its terms