[PATCH net-next v3 0/3] gtp: ynl spec for the GTP netlink family, a reply-command fix, and a selftest

[PATCH net-next v3 0/3] gtp: ynl spec for the GTP netlink family, a reply-command fix, and a selftest

[Anil Kaushik]

This respins the RFC "netlink: specs: add genetlink-legacy spec for GTP"
(netdev, 2026-10-01) as a patch, and adds a driver fix the spec exposed
plus a selftest that uses it.

While writing a ynl-based selftest for the existing gtp family I found
that the GET and dump replies put the genl family id in the command
field instead of a GTP_CMD_* value. libgtpnl ignores the command so it
never mattered, but ynl rejects the reply as an unknown command and
drops it. Patch 1 fixes the driver; patches 2 and 3 then describe and
test the family.

Patch 1 sets a valid command (GTP_CMD_GETPDP) in the get and dump
replies.

Patch 2 adds a genetlink-legacy ynl spec for the gtp family
(NEWPDP/DELPDP/GETPDP/ECHOREQ). Description only, no uapi change.

Patch 3 adds a selftest built on the spec: it creates a gtp device, adds
a PDP context with newpdp, checks getpdp lists it and delpdp removes it.
It skips when the kernel or iproute2 lack GTP support.

Changes since v2:
 - selftest: add CONFIG_GTP to tools/testing/selftests/net/config
   (kept in sorted order).
 - selftest: move gtp.py to its correct alphabetical slot in the net
   Makefile (after the gre_* entries) and mark the script executable.
 - selftest: add docstrings to the three test functions and main();
   ruff check is clean under tools/testing/selftests/net/ruff.toml.
 - selftest: move GtpFamily before PSPFamily in lib/py (import and
   __all__).
 - Patches 1 and 2 are unchanged from v2.

v2: https://lore.kernel.org/netdev/20261008181031.4129029-1-anilkaushikwireless@gmail.com/

Anil Kaushik (3):
  gtp: set a valid genl command in PDP context get and dump replies
  netlink: specs: add genetlink-legacy spec for GTP
  selftests: net: add a test for the gtp netlink family

 Documentation/netlink/specs/gtp.yaml          | 170 ++++++++++++++++++
 MAINTAINERS                                   |   2 +
 drivers/net/gtp.c                             |   4 +-
 tools/testing/selftests/net/Makefile          |   1 +
 tools/testing/selftests/net/config            |   1 +
 tools/testing/selftests/net/gtp.py            |  85 +++++++++
 .../testing/selftests/net/lib/py/__init__.py  |   5 +-
 tools/testing/selftests/net/lib/py/ynl.py     |   8 +-
 8 files changed, 271 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/netlink/specs/gtp.yaml
 create mode 100755 tools/testing/selftests/net/gtp.py

-- 
2.25.1

[PATCH net-next v3 1/3] gtp: set a valid genl command in PDP context get and dump replies

[Anil Kaushik]

gtp_genl_fill_info() stamps the reply with the command its callers pass
in. gtp_genl_get_pdp() and gtp_genl_dump_pdp() pass nlmsg_type, which in
a genl message is the dynamically assigned family id rather than a
GTP_CMD_* value, so replies to a PDP context get or dump carry a
meaningless command number.

libgtpnl ignores the command and is unaffected, but parsers that check
it (for example the ynl tooling) treat the reply as an unknown command
and discard it. Pass GTP_CMD_GETPDP, as gtp_tunnel_notify() already
passes a real command on the notification path. No uapi change.

Fixes: 459aa660eb1d ("gtp: add initial driver for datapath of GPRS Tunneling Protocol (GTP-U)")
Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com>
---
 drivers/net/gtp.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/net/gtp.c b/drivers/net/gtp.c
index 4aff23bcfdd1..99836b773e5c 100644
--- a/drivers/net/gtp.c
+++ b/drivers/net/gtp.c
@@ -2279,7 +2279,7 @@ static int gtp_genl_get_pdp(struct sk_buff *skb, struct genl_info *info)
 	}
 
 	err = gtp_genl_fill_info(skb2, NETLINK_CB(skb).portid, info->snd_seq,
-				 0, info->nlhdr->nlmsg_type, pctx);
+				 0, GTP_CMD_GETPDP, pctx);
 	if (err < 0)
 		goto err_unlock_free;
 
@@ -2326,7 +2326,7 @@ static int gtp_genl_dump_pdp(struct sk_buff *skb,
 					    NETLINK_CB(cb->skb).portid,
 					    cb->nlh->nlmsg_seq,
 					    NLM_F_MULTI,
-					    cb->nlh->nlmsg_type, pctx)) {
+					    GTP_CMD_GETPDP, pctx)) {
 					cb->args[0] = i;
 					cb->args[1] = j;
 					cb->args[2] = (unsigned long)gtp;
-- 
2.25.1

[PATCH net-next v3 2/3] netlink: specs: add genetlink-legacy spec for GTP

[Anil Kaushik]

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. The spec is derived directly from include/uapi/linux/gtp.h and
the gtp_genl_policy / gtp_genl_ops tables in drivers/net/gtp.c; command
and attribute values match the existing uapi one-to-one.

This only adds the description; there is no kernel code or uapi change.

Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com>
---
 Documentation/netlink/specs/gtp.yaml | 170 +++++++++++++++++++++++++++
 MAINTAINERS                          |   1 +
 2 files changed, 171 insertions(+)
 create mode 100644 Documentation/netlink/specs/gtp.yaml

diff --git a/Documentation/netlink/specs/gtp.yaml b/Documentation/netlink/specs/gtp.yaml
new file mode 100644
index 000000000000..7193f5e53a25
--- /dev/null
+++ b/Documentation/netlink/specs/gtp.yaml
@@ -0,0 +1,170 @@
+# 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.
+
+kernel-policy: global
+
+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
+        doc: GTP version of the context, 0 for GTPv0 or 1 for 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:
+          exact-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:
+          exact-len: 16
+        byte-order: big-endian
+        display-hint: ipv6
+        doc: IPv6 address of the mobile subscriber served by the context.
+      -
+        name: family
+        type: u8
+        doc: Address family (AF_INET or AF_INET6) of the context addresses.
+
+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-attrs
+    -
+      name: getpdp
+      doc: Get or dump one or more PDP contexts.
+      attribute-set: gtp
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request:
+          attributes:
+            - link
+            - version
+            - tid
+            - ms-address
+            - ms-addr6
+            - i-tei
+            - family
+            - net-ns-fd
+        reply: &pdp-reply
+          attributes:
+            - 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.
+      attribute-set: gtp
+      dont-validate: [strict, dump]
+      flags: [admin-perm]
+      do:
+        request:
+          attributes:
+            - link
+            - version
+            - peer-address
+            - peer-addr6
+            - family
+
+mcast-groups:
+  list:
+    -
+      name: gtp
diff --git a/MAINTAINERS b/MAINTAINERS
index 51873349ba91..a6e43995ea58 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11421,6 +11421,7 @@ 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)
-- 
2.25.1

[PATCH net-next v3 3/3] selftests: net: add a test for the gtp netlink family

[Anil Kaushik]

Exercise the gtp generic netlink family through its ynl spec: create a
gtp device, add a PDP context with newpdp, check getpdp lists it and
delpdp removes it. Two more cases check that two contexts are dumped and
that deleting an unknown context fails.

Add a GtpFamily ynl wrapper and register the test.

Signed-off-by: Anil Kaushik <anilkaushikwireless@gmail.com>
---
 MAINTAINERS                                   |  1 +
 tools/testing/selftests/net/Makefile          |  1 +
 tools/testing/selftests/net/config            |  1 +
 tools/testing/selftests/net/gtp.py            | 85 +++++++++++++++++++
 .../testing/selftests/net/lib/py/__init__.py  |  5 +-
 tools/testing/selftests/net/lib/py/ynl.py     |  8 +-
 6 files changed, 98 insertions(+), 3 deletions(-)
 create mode 100755 tools/testing/selftests/net/gtp.py

diff --git a/MAINTAINERS b/MAINTAINERS
index a6e43995ea58..8ac817a78bb0 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -11423,6 +11423,7 @@ 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
+F:	tools/testing/selftests/net/gtp.py
 
 GUID PARTITION TABLE (GPT)
 M:	Davidlohr Bueso <dave@stgolabs.net>
diff --git a/tools/testing/selftests/net/Makefile b/tools/testing/selftests/net/Makefile
index d4ca82fec0b4..6b54e04a6430 100644
--- a/tools/testing/selftests/net/Makefile
+++ b/tools/testing/selftests/net/Makefile
@@ -46,6 +46,7 @@ TEST_PROGS := \
 	fq_band_pktlimit.sh \
 	gre_gso.sh \
 	gre_ipv6_lladdr.sh \
+	gtp.py \
 	icmp.sh \
 	icmp_redirect.sh \
 	io_uring_zerocopy_tx.sh \
diff --git a/tools/testing/selftests/net/config b/tools/testing/selftests/net/config
index 737e7e6327b3..c4534e15fb7a 100644
--- a/tools/testing/selftests/net/config
+++ b/tools/testing/selftests/net/config
@@ -15,6 +15,7 @@ CONFIG_DEBUG_INFO_BTF=y
 CONFIG_DEBUG_INFO_BTF_MODULES=n
 CONFIG_DUMMY=y
 CONFIG_GENEVE=m
+CONFIG_GTP=m
 CONFIG_IFB=y
 CONFIG_INET_DIAG=y
 CONFIG_INET_ESP=y
diff --git a/tools/testing/selftests/net/gtp.py b/tools/testing/selftests/net/gtp.py
new file mode 100755
index 000000000000..fcc9bf57a663
--- /dev/null
+++ b/tools/testing/selftests/net/gtp.py
@@ -0,0 +1,85 @@
+#!/usr/bin/env python3
+# SPDX-License-Identifier: GPL-2.0
+
+"""Tests for the gtp netlink family."""
+
+from lib.py import ksft_run, ksft_exit
+from lib.py import ksft_eq, ksft_in, ksft_not_in, ksft_raises
+from lib.py import KsftSkipEx
+from lib.py import NetNS, NetNSEnter
+from lib.py import GtpFamily, NlError
+from lib.py import CmdExitFailure
+from lib.py import ip, defer
+
+
+def _add_gtp_dev(ns):
+    try:
+        ip("link add gtp0 type gtp role ggsn", ns=str(ns))
+    except CmdExitFailure:
+        raise KsftSkipEx("no gtp support (CONFIG_GTP, iproute2)")
+    defer(ip, "link del gtp0", ns=str(ns))
+    ip("link set gtp0 up", ns=str(ns))
+    return ip("-d link show gtp0", ns=str(ns), json=True)[0]["ifindex"]
+
+
+def _iteis(contexts):
+    return [c.get("i-tei") for c in contexts]
+
+
+def add_del_pdp(gtp, ns) -> None:
+    """Add a PDP context, query it, then delete it.
+
+    The query must return the context with the TEIDs and addresses
+    it was created with, and it must be gone after the delete.
+    """
+    link = _add_gtp_dev(ns)
+
+    gtp.newpdp({"link": link, "version": 1,
+                "i-tei": 0x100, "o-tei": 0x200,
+                "ms-address": "10.0.0.1", "peer-address": "192.0.2.1"})
+
+    pdp = [c for c in gtp.getpdp({}, dump=True) if c.get("i-tei") == 0x100]
+    ksft_eq(len(pdp), 1)
+    ksft_eq(pdp[0]["o-tei"], 0x200)
+    ksft_eq(pdp[0]["ms-address"], "10.0.0.1")
+    ksft_eq(pdp[0]["peer-address"], "192.0.2.1")
+
+    gtp.delpdp({"link": link, "version": 1,
+                "i-tei": 0x100, "ms-address": "10.0.0.1"})
+    ksft_not_in(0x100, _iteis(gtp.getpdp({}, dump=True)))
+
+
+def add_two_pdp(gtp, ns) -> None:
+    """Add two PDP contexts and check both are returned."""
+    link = _add_gtp_dev(ns)
+
+    for i_tei, o_tei, ms in ((0x111, 0x211, "10.0.1.1"),
+                             (0x112, 0x212, "10.0.1.2")):
+        gtp.newpdp({"link": link, "version": 1,
+                    "i-tei": i_tei, "o-tei": o_tei,
+                    "ms-address": ms, "peer-address": "192.0.2.5"})
+
+    iteis = _iteis(gtp.getpdp({}, dump=True))
+    ksft_in(0x111, iteis)
+    ksft_in(0x112, iteis)
+
+
+def del_unknown_pdp(gtp, ns) -> None:
+    """Deleting a context that was never added must fail."""
+    link = _add_gtp_dev(ns)
+    with ksft_raises(NlError):
+        gtp.delpdp({"link": link, "version": 1,
+                    "i-tei": 0x999, "ms-address": "10.9.9.9"})
+
+
+def main() -> None:
+    """Run the PDP context tests in a temporary netns."""
+    with NetNS() as ns:
+        with NetNSEnter(str(ns)):
+            gtp = GtpFamily()
+        ksft_run([add_del_pdp, add_two_pdp, del_unknown_pdp], args=(gtp, ns))
+    ksft_exit()
+
+
+if __name__ == "__main__":
+    main()
diff --git a/tools/testing/selftests/net/lib/py/__init__.py b/tools/testing/selftests/net/lib/py/__init__.py
index 71df5880b356..e269a260d58e 100644
--- a/tools/testing/selftests/net/lib/py/__init__.py
+++ b/tools/testing/selftests/net/lib/py/__init__.py
@@ -18,7 +18,7 @@ from .utils import CmdExitFailure, fd_read_timeout, cmd, bkg, defer, \
 from .bpf import bpf_map_set, bpf_map_dump, bpf_prog_map_ids
 from .ynl import NlError, NlctrlFamily, YnlFamily, \
     EthtoolFamily, NetdevFamily, RtnlFamily, RtnlAddrFamily, RtnlRouteFamily
-from .ynl import NetshaperFamily, DevlinkFamily, PSPFamily, Netlink
+from .ynl import NetshaperFamily, DevlinkFamily, GtpFamily, PSPFamily, Netlink
 
 __all__ = ["KSRC",
            "KsftFailEx", "KsftSkipEx", "KsftXfailEx", "ksft_pr", "ksft_eq",
@@ -32,6 +32,7 @@ __all__ = ["KSRC",
            "wait_port_listen", "ctl_file_write", "wait_file", "tool", "tc",
            "bpf_map_set", "bpf_map_dump", "bpf_prog_map_ids",
            "NetdevSim", "NetdevSimDev",
-           "NetshaperFamily", "DevlinkFamily", "PSPFamily", "NlError",
+           "NetshaperFamily", "DevlinkFamily", "GtpFamily", "PSPFamily",
+           "NlError",
            "YnlFamily", "EthtoolFamily", "NetdevFamily", "RtnlFamily",
            "NlctrlFamily", "RtnlAddrFamily", "RtnlRouteFamily", "Netlink"]
diff --git a/tools/testing/selftests/net/lib/py/ynl.py b/tools/testing/selftests/net/lib/py/ynl.py
index 08deff756f29..7edb74971023 100644
--- a/tools/testing/selftests/net/lib/py/ynl.py
+++ b/tools/testing/selftests/net/lib/py/ynl.py
@@ -31,7 +31,7 @@ __all__ = [
     "NlError", "NlPolicy", "Netlink", "YnlFamily", "SPEC_PATH",
     "EthtoolFamily", "RtnlFamily", "RtnlAddrFamily", "RtnlRouteFamily",
     "NetdevFamily", "NetshaperFamily", "NlctrlFamily", "DevlinkFamily",
-    "PSPFamily",
+    "GtpFamily", "PSPFamily",
 ]
 
 #
@@ -85,3 +85,9 @@ class PSPFamily(YnlFamily):
     def __init__(self, recv_size=0):
         super().__init__((SPEC_PATH / Path('psp.yaml')).as_posix(),
                          schema='', recv_size=recv_size)
+
+
+class GtpFamily(YnlFamily):
+    def __init__(self, recv_size=0):
+        super().__init__((SPEC_PATH / Path('gtp.yaml')).as_posix(),
+                         schema='', recv_size=recv_size)
-- 
2.25.1