netlink: specs: add genetlink-legacy spec for GTP

The GTP (GPRS Tunnelling Protocol, user plane) generic netlink family has no YAML specification under Documentation/netlink/specs/, so it cannot be consumed by the ynl tooling used for user-space clients, documentation and selftests. Add a genetlink-legacy spec describing the existing family: the PDP context management commands (NEWPDP, DELPDP, GETPDP) and the GTP-U echo request (ECHOREQ), the GTPA_* attribute set, and the "gtp" multicast group. Command and attribute values are taken from include/uapi/linux/gtp.h and match it one-to-one. The request attributes of each command are the ones its handler in drivers/net/gtp.c reads, and the reply attributes the ones gtp_genl_fill_info() emits. The notifications sent on the "gtp" group are not described: they reuse the command values of the NEWPDP, DELPDP and ECHOREQ requests, which the ynl code generator cannot express with the existing uapi header. The family doc says so. Add the matching CFLAGS_gtp entry to tools/net/ynl/Makefile.deps, so the generated code is built against the tree's gtp.h instead of an older one installed on the host. This only adds the description; there is no kernel code or uapi change. Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com> Link: https://patch.msgid.link/20261016093225.1036375-4-anilkaushikwireless@gmail.com Signed-off-by: Paolo Abeni <pabeni@redhat.com>
2026-11-06 21:58:01 +01:00 · 2026-10-16 09:32:24 +00:00 · 2026-10-16 09:32:24 +00:00 · 8a2f9964fc
commit 8a2f9964fc
parent fe3e1a42fb
3 changed files with 198 additions and 0 deletions
--- a/Documentation/netlink/specs/gtp.yaml
+++ b/Documentation/netlink/specs/gtp.yaml
@ -0,0 +1,196 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+---
+name: gtp
+
+protocol: genetlink-legacy
+
+doc: |
+  GPRS Tunnelling Protocol, user plane (GTP-U).
+
+  The gtp netdevice encapsulates and decapsulates user plane packets in
+  GTP-U tunnels (GTPv0 and GTPv1-U, see 3GPP TS 29.060 and TS 29.281).
+  This family manages the PDP contexts that describe the tunnels and
+  triggers GTP-U echo requests. It is driven by user space control planes
+  such as those built on libgtpnl.
+
+  The kernel registers the family with version 0, which the
+  genetlink-legacy schema cannot express.
+
+  The notifications multicast on the "gtp" group are not described: PDP
+  context additions and deletions, and GTP-U echo responses, reuse the
+  NEWPDP, DELPDP and ECHOREQ command values of the requests.
+
+kernel-policy: global
+
+definitions:
+  -
+    type: enum
+    name: version
+    name-prefix: gtp-
+    enum-name: gtp-version
+    header: linux/gtp.h
+    entries: [v0, v1]
+
+attribute-sets:
+  -
+    name: gtp
+    name-prefix: gtpa-
+    attributes:
+      -
+        name: link
+        type: u32
+        doc: ifindex of the gtp netdevice the context is attached to.
+      -
+        name: version
+        type: u32
+        enum: version
+        doc: GTP version of the context, GTPv0 or GTPv1-U.
+      -
+        name: tid
+        type: u64
+        doc: Tunnel identifier, GTPv0 only.
+      -
+        name: peer-address
+        type: u32
+        byte-order: big-endian
+        display-hint: ipv4
+        doc: |
+          IPv4 address of the remote GSN peer (GGSN or SGSN). Also known
+          as GTPA_SGSN_ADDRESS, kept for legacy user space.
+      -
+        name: ms-address
+        type: u32
+        byte-order: big-endian
+        display-hint: ipv4
+        doc: IPv4 address of the mobile subscriber served by the context.
+      -
+        name: flow
+        type: u16
+        doc: Flow label, GTPv0 only.
+      -
+        name: net-ns-fd
+        type: u32
+        doc: File descriptor of the network namespace of the gtp netdevice.
+      -
+        name: i-tei
+        type: u32
+        doc: Ingress Tunnel Endpoint Identifier, GTPv1-U only.
+      -
+        name: o-tei
+        type: u32
+        doc: Egress Tunnel Endpoint Identifier, GTPv1-U only.
+      -
+        name: pad
+        type: pad
+      -
+        name: peer-addr6
+        type: binary
+        checks:
+          min-len: 16
+        byte-order: big-endian
+        display-hint: ipv6
+        doc: IPv6 address of the remote GSN peer (GGSN or SGSN).
+      -
+        name: ms-addr6
+        type: binary
+        checks:
+          min-len: 16
+        byte-order: big-endian
+        display-hint: ipv6
+        doc: |
+          IPv6 prefix of the mobile subscriber served by the context: a /64
+          prefix, with the lower 64 bits set to zero.
+      -
+        name: family
+        type: u8
+        doc: |
+          Address family (AF_INET or AF_INET6) of ms-address or ms-addr6,
+          AF_INET when absent. The peer address uses the family of the
+          tunnel socket.
+
+operations:
+  list:
+    -
+      name: newpdp
+      doc: Create or update a PDP context.
+      attribute-set: gtp
+      value: 0
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request: &pdp-attrs
+          attributes:
+            - link
+            - version
+            - tid
+            - peer-address
+            - peer-addr6
+            - ms-address
+            - ms-addr6
+            - flow
+            - i-tei
+            - o-tei
+            - family
+            - net-ns-fd
+    -
+      name: delpdp
+      doc: Delete a PDP context.
+      attribute-set: gtp
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request: &pdp-find
+          attributes:
+            - link
+            - version
+            - tid
+            - ms-address
+            - ms-addr6
+            - i-tei
+            - family
+            - net-ns-fd
+    -
+      name: getpdp
+      doc: Get or dump one or more PDP contexts.
+      attribute-set: gtp
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request: *pdp-find
+        reply: &pdp-reply
+          attributes:
+            - link
+            - version
+            - tid
+            - peer-address
+            - peer-addr6
+            - ms-address
+            - ms-addr6
+            - flow
+            - i-tei
+            - o-tei
+            - family
+      dump:
+        reply: *pdp-reply
+    -
+      name: echoreq
+      doc: |
+        Send a GTP-U echo request to a peer. ms-address is not a mobile
+        subscriber address here, but the local IPv4 address used as source
+        of the request.
+      attribute-set: gtp
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request:
+          attributes:
+            - link
+            - version
+            - peer-address
+            - ms-address
+            - net-ns-fd
+
+mcast-groups:
+  list:
+    -
+      name: gtp
--- a/1
+++ b/1
@ -11422,6 +11422,7 @@ M:	Harald Welte <laforge@gnumonks.org>
 L:	osmocom-net-gprs@lists.osmocom.org
 S:	Maintained
 T:	git git://git.kernel.org/pub/scm/linux/kernel/git/pablo/gtp.git
+F:	Documentation/netlink/specs/gtp.yaml
 F:	drivers/net/gtp.c

 GUID PARTITION TABLE (GPT)
--- a/tools/net/ynl/Makefile.deps
+++ b/tools/net/ynl/Makefile.deps
@ -24,6 +24,7 @@ CFLAGS_ethtool:=$(call get_hdr_inc,_LINUX_TYPELIMITS_H,typelimits.h) \
 	$(call get_hdr_inc,_LINUX_ETHTOOL_H,ethtool.h) \
 	$(call get_hdr_inc,_LINUX_ETHTOOL_NETLINK_H_,ethtool_netlink.h) \
 	$(call get_hdr_inc,_LINUX_ETHTOOL_NETLINK_GENERATED_H,ethtool_netlink_generated.h)
+CFLAGS_gtp:=$(call get_hdr_inc,_LINUX_GTP_H_,gtp.h)
 CFLAGS_handshake:=$(call get_hdr_inc,_LINUX_HANDSHAKE_H,handshake.h)
 CFLAGS_lockd_netlink:=$(call get_hdr_inc,_LINUX_LOCKD_NETLINK_H,lockd_netlink.h)
 CFLAGS_mptcp_pm:=$(call get_hdr_inc,_LINUX_MPTCP_PM_H,mptcp_pm.h)