[PATCH bpf-next v4 0/6] XDP metadata support for tun driver

[PATCH bpf-next v4 0/6] XDP metadata support for tun driver

[Marcus Wichelmann]

Hi all,

this series contains some improvements for the selftest patches. The other
patches remain unchanged. Please check the changelist below.

I have reverted the addition of the NOARP flag from the previous version,
as it was not effective and the CI was still failing occasionally because
of the race condition caused by foreign packets interfering with the veth
tests. This series contains an alternative solution by filtering all but
the test packets using the attached XDP program.

Successful pipeline:
https://github.com/kernel-patches/bpf/actions/runs/13552017584

---

v4:
- strip unrelated changes from the selftest patches
- extend commit message for "selftests/bpf: refactor xdp_context_functional
  test and bpf program"
- the NOARP flag was not effective to prevent other packets from
  interfering with the tests, add a filter to the XDP program instead
- run xdp_context_tuntap in a separate namespace to avoid conflicts with
  other tests

v3: https://lore.kernel.org/bpf/20250224152909.3911544-1-marcus.wichelmann@hetzner-cloud.de/
- change the condition to handle xdp_buffs without metadata support, as
  suggested by Willem de Bruijn <willemb@google.com>
- add clarifying comment why that condition is needed
- set NOARP flag in selftests to ensure that the kernel does not send
  packets on the test interfaces that may interfere with the tests

v2: https://lore.kernel.org/bpf/20250217172308.3291739-1-marcus.wichelmann@hetzner-cloud.de/
- submit against bpf-next subtree
- split commits and improved commit messages
- remove redundant metasize check and add clarifying comment instead
- use max() instead of ternary operator
- add selftest for metadata support in the tun driver

v1: https://lore.kernel.org/all/20250130171614.1657224-1-marcus.wichelmann@hetzner-cloud.de/

Marcus Wichelmann (6):
  net: tun: enable XDP metadata support
  net: tun: enable transfer of XDP metadata to skb
  selftests/bpf: move open_tuntap to network helpers
  selftests/bpf: refactor xdp_context_functional test and bpf program
  selftests/bpf: add test for XDP metadata support in tun driver
  selftests/bpf: fix file descriptor assertion in open_tuntap helper

 drivers/net/tun.c                             |  28 +++-
 tools/testing/selftests/bpf/network_helpers.c |  28 ++++
 tools/testing/selftests/bpf/network_helpers.h |   3 +
 .../selftests/bpf/prog_tests/lwt_helpers.h    |  29 ----
 .../bpf/prog_tests/xdp_context_test_run.c     | 138 +++++++++++++++++-
 .../selftests/bpf/progs/test_xdp_meta.c       |  53 +++++--
 6 files changed, 223 insertions(+), 56 deletions(-)

-- 
2.43.0

[PATCH bpf-next v4 1/6] net: tun: enable XDP metadata support

[Marcus Wichelmann]

Enable the support for the bpf_xdp_adjust_meta helper function for XDP
buffers initialized by the tun driver. This allows to reserve a metadata
area that is useful to pass any information from one XDP program to
another one, for example when using tail-calls.

Whether this helper function can be used in an XDP program depends on
how the xdp_buff was initialized. Most net drivers initialize the
xdp_buff in a way, that allows bpf_xdp_adjust_meta to be used. In case
of the tun driver, this is currently not the case.

There are two code paths in the tun driver that lead to a
bpf_prog_run_xdp and where metadata support should be enabled:

1. tun_build_skb, which is called by tun_get_user and is used when
   writing packets from userspace into the device. In this case, the
   xdp_buff created in tun_build_skb has no support for
   bpf_xdp_adjust_meta and calls of that helper function result in
   ENOTSUPP.

   For this code path, it's sufficient to set the meta_valid argument of
   the xdp_prepare_buff call. The reserved headroom is large enough
   already.

2. tun_xdp_one, which is called by tun_sendmsg which again is called by
   other drivers (e.g. vhost_net). When the TUN_MSG_PTR mode is used,
   another driver may pass a batch of xdp_buffs to the tun driver. In
   this case, that other driver is the one initializing the xdp_buff.

   See commit 043d222f93ab ("tuntap: accept an array of XDP buffs
   through sendmsg()") for details.

   For now, the vhost_net driver is the only one using TUN_MSG_PTR and
   it already initializes the xdp_buffs with metadata support and
   sufficient headroom. But the tun driver disables it again, so the
   xdp_set_data_meta_invalid call has to be removed.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/tun.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index acf96f262488..4ec8fbd93c8d 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1709,7 +1709,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 		u32 act;
 
 		xdp_init_buff(&xdp, buflen, &tfile->xdp_rxq);
-		xdp_prepare_buff(&xdp, buf, pad, len, false);
+		xdp_prepare_buff(&xdp, buf, pad, len, true);
 
 		act = bpf_prog_run_xdp(xdp_prog, &xdp);
 		if (act == XDP_REDIRECT || act == XDP_TX) {
@@ -2467,7 +2467,6 @@ static int tun_xdp_one(struct tun_struct *tun,
 		}
 
 		xdp_init_buff(xdp, buflen, &tfile->xdp_rxq);
-		xdp_set_data_meta_invalid(xdp);
 
 		act = bpf_prog_run_xdp(xdp_prog, xdp);
 		ret = tun_xdp_act(tun, xdp_prog, xdp, act);
-- 
2.43.0

[PATCH bpf-next v4 2/6] net: tun: enable transfer of XDP metadata to skb

[Marcus Wichelmann]

When the XDP metadata area was used, it is expected that the same
metadata can also be accessed from TC, as can be read in the description
of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
not yet implemented.

To make this work, the skb that is being built on XDP_PASS should know
of the current size of the metadata area. This is ensured by adding
calls to skb_metadata_set. For the tun_xdp_one code path, an additional
check is necessary to handle the case where the externally initialized
xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).

More information about this feature can be found in the commit message
of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 drivers/net/tun.c | 25 ++++++++++++++++++++++---
 1 file changed, 22 insertions(+), 3 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 4ec8fbd93c8d..70208b3a2e93 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -1600,7 +1600,8 @@ static bool tun_can_build_skb(struct tun_struct *tun, struct tun_file *tfile,
 
 static struct sk_buff *__tun_build_skb(struct tun_file *tfile,
 				       struct page_frag *alloc_frag, char *buf,
-				       int buflen, int len, int pad)
+				       int buflen, int len, int pad,
+				       int metasize)
 {
 	struct sk_buff *skb = build_skb(buf, buflen);
 
@@ -1609,6 +1610,8 @@ static struct sk_buff *__tun_build_skb(struct tun_file *tfile,
 
 	skb_reserve(skb, pad);
 	skb_put(skb, len);
+	if (metasize)
+		skb_metadata_set(skb, metasize);
 	skb_set_owner_w(skb, tfile->socket.sk);
 
 	get_page(alloc_frag->page);
@@ -1668,6 +1671,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 	char *buf;
 	size_t copied;
 	int pad = TUN_RX_PAD;
+	int metasize = 0;
 	int err = 0;
 
 	rcu_read_lock();
@@ -1695,7 +1699,7 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 	if (hdr->gso_type || !xdp_prog) {
 		*skb_xdp = 1;
 		return __tun_build_skb(tfile, alloc_frag, buf, buflen, len,
-				       pad);
+				       pad, metasize);
 	}
 
 	*skb_xdp = 0;
@@ -1730,12 +1734,18 @@ static struct sk_buff *tun_build_skb(struct tun_struct *tun,
 
 		pad = xdp.data - xdp.data_hard_start;
 		len = xdp.data_end - xdp.data;
+
+		/* It is known that the xdp_buff was prepared with metadata
+		 * support, so the metasize will never be negative.
+		 */
+		metasize = xdp.data - xdp.data_meta;
 	}
 	bpf_net_ctx_clear(bpf_net_ctx);
 	rcu_read_unlock();
 	local_bh_enable();
 
-	return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad);
+	return __tun_build_skb(tfile, alloc_frag, buf, buflen, len, pad,
+			       metasize);
 
 out:
 	bpf_net_ctx_clear(bpf_net_ctx);
@@ -2452,6 +2462,7 @@ static int tun_xdp_one(struct tun_struct *tun,
 	struct sk_buff_head *queue;
 	u32 rxhash = 0, act;
 	int buflen = hdr->buflen;
+	int metasize = 0;
 	int ret = 0;
 	bool skb_xdp = false;
 	struct page *page;
@@ -2506,6 +2517,14 @@ static int tun_xdp_one(struct tun_struct *tun,
 	skb_reserve(skb, xdp->data - xdp->data_hard_start);
 	skb_put(skb, xdp->data_end - xdp->data);
 
+	/* The externally provided xdp_buff may have no metadata support, which
+	 * is marked by xdp->data_meta being xdp->data + 1. This will lead to a
+	 * metasize of -1 and is the reason why the condition checks for > 0.
+	 */
+	metasize = xdp->data - xdp->data_meta;
+	if (metasize > 0)
+		skb_metadata_set(skb, metasize);
+
 	if (virtio_net_hdr_to_skb(skb, gso, tun_is_little_endian(tun))) {
 		atomic_long_inc(&tun->rx_frame_errors);
 		kfree_skb(skb);
-- 
2.43.0

[PATCH bpf-next v4 3/6] selftests/bpf: move open_tuntap to network helpers

[Marcus Wichelmann]

To test the XDP metadata functionality of the tun driver, it's necessary
to create a new tap device first. A helper function for this already
exists in lwt_helpers.h. Move it to the common network helpers header,
so it can be reused in other tests.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 tools/testing/selftests/bpf/network_helpers.c | 28 ++++++++++++++++++
 tools/testing/selftests/bpf/network_helpers.h |  3 ++
 .../selftests/bpf/prog_tests/lwt_helpers.h    | 29 -------------------
 3 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 737a952dcf80..e1cfa1b37754 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -565,6 +565,34 @@ void close_netns(struct nstoken *token)
 	free(token);
 }
 
+int open_tuntap(const char *dev_name, bool need_mac)
+{
+	int err = 0;
+	struct ifreq ifr;
+	int fd = open("/dev/net/tun", O_RDWR);
+
+	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+		return -1;
+
+	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
+	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
+	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
+
+	err = ioctl(fd, TUNSETIFF, &ifr);
+	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
+		close(fd);
+		return -1;
+	}
+
+	err = fcntl(fd, F_SETFL, O_NONBLOCK);
+	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
 int get_socket_local_port(int sock_fd)
 {
 	struct sockaddr_storage addr;
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index 9f6e05d886c5..99d1417c1d8b 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -8,6 +8,7 @@
 typedef __u16 __sum16;
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
+#include <linux/if_tun.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/ethtool.h>
@@ -98,6 +99,8 @@ int send_recv_data(int lfd, int fd, uint32_t total_bytes);
 int make_netns(const char *name);
 int remove_netns(const char *name);
 
+int open_tuntap(const char *dev_name, bool need_mac);
+
 /**
  * append_tid() - Append thread ID to the given string.
  *
diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
index fb1eb8c67361..ccec0fcdabc1 100644
--- a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
@@ -5,7 +5,6 @@
 
 #include <time.h>
 #include <net/if.h>
-#include <linux/if_tun.h>
 #include <linux/icmp.h>
 
 #include "test_progs.h"
@@ -37,34 +36,6 @@ static inline int netns_delete(void)
 	return system("ip netns del " NETNS ">/dev/null 2>&1");
 }
 
-static int open_tuntap(const char *dev_name, bool need_mac)
-{
-	int err = 0;
-	struct ifreq ifr;
-	int fd = open("/dev/net/tun", O_RDWR);
-
-	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
-		return -1;
-
-	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
-	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
-
-	err = ioctl(fd, TUNSETIFF, &ifr);
-	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
-		close(fd);
-		return -1;
-	}
-
-	err = fcntl(fd, F_SETFL, O_NONBLOCK);
-	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
-		close(fd);
-		return -1;
-	}
-
-	return fd;
-}
-
 #define ICMP_PAYLOAD_SIZE     100
 
 /* Match an ICMP packet with payload len ICMP_PAYLOAD_SIZE */
-- 
2.43.0

[PATCH bpf-next v4 4/6] selftests/bpf: refactor xdp_context_functional test and bpf program

[Marcus Wichelmann]

The existing XDP metadata test works by creating a veth pair and
attaching XDP & TC programs that drop the packet when the condition of
the test isn't fulfilled. The test then pings through the veth pair and
succeeds when the ping comes through.

While this test works great for a veth pair, it is hard to replicate for
tap devices to test the XDP metadata support of them. A similar test for
the tun driver would either involve logic to reply to the ping request,
or would have to capture the packet to check if it was dropped or not.

To make the testing of other drivers easier while still maximizing code
reuse, this commit refactors the existing xdp_context_functional test to
use a test_result map. Instead of conditionally passing or dropping the
packet, the TC program is changed to copy the received metadata into the
value of that single-entry array map. Tests can then verify that the map
value matches the expectation.

This testing logic is easy to adapt to other network drivers as the only
remaining requirement is that there is some way to send a custom
Ethernet packet through it that triggers the XDP & TC programs.

The Ethernet header of that custom packet is all-zero, because it is not
required to be valid for the test to work. The zero ethertype also helps
to filter out packets that are not related to the test and would
otherwise interfere with it.

The payload of the Ethernet packet is used as the test data that is
expected to be passed as metadata from the XDP to the TC program and
written to the map. It has a fixed size of 32 bytes which is a
reasonable size that should be supported by both drivers. Additional
packet headers are not necessary for the test and were therefore skipped
to keep the testing code short.

This new testing methodology no longer requires the veth interfaces to
have IP addresses assigned, therefore these were removed.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
---
 .../bpf/prog_tests/xdp_context_test_run.c     | 79 +++++++++++++++++--
 .../selftests/bpf/progs/test_xdp_meta.c       | 53 +++++++++----
 2 files changed, 110 insertions(+), 22 deletions(-)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
index 937da9b7532a..78ca01edb050 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
@@ -4,13 +4,19 @@
 #include "test_xdp_context_test_run.skel.h"
 #include "test_xdp_meta.skel.h"
 
-#define TX_ADDR "10.0.0.1"
-#define RX_ADDR "10.0.0.2"
 #define RX_NAME "veth0"
 #define TX_NAME "veth1"
 #define TX_NETNS "xdp_context_tx"
 #define RX_NETNS "xdp_context_rx"
 
+#define TEST_PAYLOAD_LEN 32
+static const __u8 test_payload[TEST_PAYLOAD_LEN] = {
+	0x01, 0x02, 0x03, 0x04, 0x05, 0x06, 0x07, 0x08,
+	0x11, 0x12, 0x13, 0x14, 0x15, 0x16, 0x17, 0x18,
+	0x21, 0x22, 0x23, 0x24, 0x25, 0x26, 0x27, 0x28,
+	0x31, 0x32, 0x33, 0x34, 0x35, 0x36, 0x37, 0x38,
+};
+
 void test_xdp_context_error(int prog_fd, struct bpf_test_run_opts opts,
 			    __u32 data_meta, __u32 data, __u32 data_end,
 			    __u32 ingress_ifindex, __u32 rx_queue_index,
@@ -112,7 +118,59 @@ void test_xdp_context_test_run(void)
 	test_xdp_context_test_run__destroy(skel);
 }
 
-void test_xdp_context_functional(void)
+static int send_test_packet(int ifindex)
+{
+	int n, sock = -1;
+	__u8 packet[sizeof(struct ethhdr) + TEST_PAYLOAD_LEN];
+
+	/* The ethernet header is not relevant for this test and doesn't need to
+	 * be meaningful.
+	 */
+	struct ethhdr eth = { 0 };
+
+	memcpy(packet, &eth, sizeof(eth));
+	memcpy(packet + sizeof(eth), test_payload, TEST_PAYLOAD_LEN);
+
+	sock = socket(AF_PACKET, SOCK_RAW, IPPROTO_RAW);
+	if (!ASSERT_GE(sock, 0, "socket"))
+		goto err;
+
+	struct sockaddr_ll saddr = {
+		.sll_family = PF_PACKET,
+		.sll_ifindex = ifindex,
+		.sll_halen = ETH_ALEN
+	};
+	n = sendto(sock, packet, sizeof(packet), 0, (struct sockaddr *)&saddr,
+		   sizeof(saddr));
+	if (!ASSERT_EQ(n, sizeof(packet), "sendto"))
+		goto err;
+
+	close(sock);
+	return 0;
+
+err:
+	if (sock >= 0)
+		close(sock);
+	return -1;
+}
+
+static void assert_test_result(struct test_xdp_meta *skel)
+{
+	int err;
+	__u32 map_key = 0;
+	__u8 map_value[TEST_PAYLOAD_LEN];
+
+	err = bpf_map__lookup_elem(skel->maps.test_result, &map_key,
+				   sizeof(map_key), &map_value,
+				   TEST_PAYLOAD_LEN, BPF_ANY);
+	if (!ASSERT_OK(err, "lookup test_result"))
+		return;
+
+	ASSERT_MEMEQ(&map_value, &test_payload, TEST_PAYLOAD_LEN,
+		     "test_result map contains test payload");
+}
+
+void test_xdp_context_veth(void)
 {
 	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
 	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
@@ -120,7 +178,7 @@ void test_xdp_context_functional(void)
 	struct bpf_program *tc_prog, *xdp_prog;
 	struct test_xdp_meta *skel = NULL;
 	struct nstoken *nstoken = NULL;
-	int rx_ifindex;
+	int rx_ifindex, tx_ifindex;
 	int ret;
 
 	tx_ns = netns_new(TX_NETNS, false);
@@ -138,7 +196,6 @@ void test_xdp_context_functional(void)
 	if (!ASSERT_OK_PTR(nstoken, "setns rx_ns"))
 		goto close;
 
-	SYS(close, "ip addr add " RX_ADDR "/24 dev " RX_NAME);
 	SYS(close, "ip link set dev " RX_NAME " up");
 
 	skel = test_xdp_meta__open_and_load();
@@ -179,9 +236,17 @@ void test_xdp_context_functional(void)
 	if (!ASSERT_OK_PTR(nstoken, "setns tx_ns"))
 		goto close;
 
-	SYS(close, "ip addr add " TX_ADDR "/24 dev " TX_NAME);
 	SYS(close, "ip link set dev " TX_NAME " up");
-	ASSERT_OK(SYS_NOFAIL("ping -c 1 " RX_ADDR), "ping");
+
+	tx_ifindex = if_nametoindex(TX_NAME);
+	if (!ASSERT_GE(tx_ifindex, 0, "if_nametoindex tx"))
+		goto close;
+
+	ret = send_test_packet(tx_ifindex);
+	if (!ASSERT_OK(ret, "send_test_packet"))
+		goto close;
+
+	assert_test_result(skel);
 
 close:
 	close_netns(nstoken);
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_meta.c b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
index fe2d71ae0e71..fcf6ca14f2ea 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_meta.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_meta.c
@@ -4,37 +4,50 @@
 
 #include <bpf/bpf_helpers.h>
 
-#define __round_mask(x, y) ((__typeof__(x))((y) - 1))
-#define round_up(x, y) ((((x) - 1) | __round_mask(x, y)) + 1)
+#define META_SIZE 32
+
 #define ctx_ptr(ctx, mem) (void *)(unsigned long)ctx->mem
 
+/* Demonstrates how metadata can be passed from an XDP program to a TC program
+ * using bpf_xdp_adjust_meta.
+ * For the sake of testing the metadata support in drivers, the XDP program uses
+ * a fixed-size payload after the Ethernet header as metadata. The TC program
+ * copies the metadata it receives into a map so it can be checked from
+ * userspace.
+ */
+
+struct {
+	__uint(type, BPF_MAP_TYPE_ARRAY);
+	__uint(max_entries, 1);
+	__type(key, __u32);
+	__uint(value_size, META_SIZE);
+} test_result SEC(".maps");
+
 SEC("tc")
 int ing_cls(struct __sk_buff *ctx)
 {
-	__u8 *data, *data_meta, *data_end;
-	__u32 diff = 0;
+	__u8 *data, *data_meta;
+	__u32 key = 0;
 
 	data_meta = ctx_ptr(ctx, data_meta);
-	data_end  = ctx_ptr(ctx, data_end);
 	data      = ctx_ptr(ctx, data);
 
-	if (data + ETH_ALEN > data_end ||
-	    data_meta + round_up(ETH_ALEN, 4) > data)
+	if (data_meta + META_SIZE > data)
 		return TC_ACT_SHOT;
 
-	diff |= ((__u32 *)data_meta)[0] ^ ((__u32 *)data)[0];
-	diff |= ((__u16 *)data_meta)[2] ^ ((__u16 *)data)[2];
+	bpf_map_update_elem(&test_result, &key, data_meta, BPF_ANY);
 
-	return diff ? TC_ACT_SHOT : TC_ACT_OK;
+	return TC_ACT_SHOT;
 }
 
 SEC("xdp")
 int ing_xdp(struct xdp_md *ctx)
 {
-	__u8 *data, *data_meta, *data_end;
+	__u8 *data, *data_meta, *data_end, *payload;
+	struct ethhdr *eth;
 	int ret;
 
-	ret = bpf_xdp_adjust_meta(ctx, -round_up(ETH_ALEN, 4));
+	ret = bpf_xdp_adjust_meta(ctx, -META_SIZE);
 	if (ret < 0)
 		return XDP_DROP;
 
@@ -42,11 +55,21 @@ int ing_xdp(struct xdp_md *ctx)
 	data_end  = ctx_ptr(ctx, data_end);
 	data      = ctx_ptr(ctx, data);
 
-	if (data + ETH_ALEN > data_end ||
-	    data_meta + round_up(ETH_ALEN, 4) > data)
+	eth = (struct ethhdr *)data;
+	payload = data + sizeof(struct ethhdr);
+
+	if (payload + META_SIZE > data_end ||
+	    data_meta + META_SIZE > data)
+		return XDP_DROP;
+
+	/* The Linux networking stack may send other packets on the test
+	 * interface that interfere with the test. Just drop them.
+	 * The test packets can be recognized by their ethertype of zero.
+	 */
+	if (eth->h_proto != 0)
 		return XDP_DROP;
 
-	__builtin_memcpy(data_meta, data, ETH_ALEN);
+	__builtin_memcpy(data_meta, payload, META_SIZE);
 	return XDP_PASS;
 }
 
-- 
2.43.0

[PATCH bpf-next v4 5/6] selftests/bpf: add test for XDP metadata support in tun driver

[Marcus Wichelmann]

Add a selftest that creates a tap device, attaches XDP and TC programs,
writes a packet with a test payload into the tap device and checks the
test result. This test ensures that the XDP metadata support in the tun
driver is enabled and that the metadata size is correctly passed to the
skb.

See the previous commit ("selftests/bpf: refactor xdp_context_functional
test and bpf program") for details about the test design.

The test runs in its own network namespace using the feature introduced
with commit c047e0e0e435 ("selftests/bpf: Optionally open a dedicated
namespace to run test in it"). This provides some extra safety against
conflicting interface names.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
---
 .../bpf/prog_tests/xdp_context_test_run.c     | 59 +++++++++++++++++++
 1 file changed, 59 insertions(+)

diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
index 78ca01edb050..ce3e82cc69d1 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_context_test_run.c
@@ -8,6 +8,7 @@
 #define TX_NAME "veth1"
 #define TX_NETNS "xdp_context_tx"
 #define RX_NETNS "xdp_context_rx"
+#define TAP_NAME "tap0"
 
 #define TEST_PAYLOAD_LEN 32
 static const __u8 test_payload[TEST_PAYLOAD_LEN] = {
@@ -255,3 +256,61 @@ void test_xdp_context_veth(void)
 	netns_free(tx_ns);
 }
 
+void test_ns_xdp_context_tuntap(void)
+{
+	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .attach_point = BPF_TC_INGRESS);
+	LIBBPF_OPTS(bpf_tc_opts, tc_opts, .handle = 1, .priority = 1);
+	struct test_xdp_meta *skel = NULL;
+	__u8 packet[sizeof(struct ethhdr) + TEST_PAYLOAD_LEN];
+	int tap_fd = -1;
+	int tap_ifindex;
+	int ret;
+
+	tap_fd = open_tuntap(TAP_NAME, true);
+	if (!ASSERT_GE(tap_fd, 0, "open_tuntap"))
+		goto close;
+
+	SYS(close, "ip link set dev " TAP_NAME " up");
+
+	skel = test_xdp_meta__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "open and load skeleton"))
+		goto close;
+
+	tap_ifindex = if_nametoindex(TAP_NAME);
+	if (!ASSERT_GE(tap_ifindex, 0, "if_nametoindex"))
+		goto close;
+
+	tc_hook.ifindex = tap_ifindex;
+	ret = bpf_tc_hook_create(&tc_hook);
+	if (!ASSERT_OK(ret, "bpf_tc_hook_create"))
+		goto close;
+
+	tc_opts.prog_fd = bpf_program__fd(skel->progs.ing_cls);
+	ret = bpf_tc_attach(&tc_hook, &tc_opts);
+	if (!ASSERT_OK(ret, "bpf_tc_attach"))
+		goto close;
+
+	ret = bpf_xdp_attach(tap_ifindex, bpf_program__fd(skel->progs.ing_xdp),
+			     0, NULL);
+	if (!ASSERT_GE(ret, 0, "bpf_xdp_attach"))
+		goto close;
+
+	/* The ethernet header is not relevant for this test and doesn't need to
+	 * be meaningful.
+	 */
+	struct ethhdr eth = { 0 };
+
+	memcpy(packet, &eth, sizeof(eth));
+	memcpy(packet + sizeof(eth), test_payload, TEST_PAYLOAD_LEN);
+
+	ret = write(tap_fd, packet, sizeof(packet));
+	if (!ASSERT_EQ(ret, sizeof(packet), "write packet"))
+		goto close;
+
+	assert_test_result(skel);
+
+close:
+	if (tap_fd >= 0)
+		close(tap_fd);
+	test_xdp_meta__destroy(skel);
+}
-- 
2.43.0

[PATCH bpf-next v4 6/6] selftests/bpf: fix file descriptor assertion in open_tuntap helper

[Marcus Wichelmann]

The open_tuntap helper function uses open() to get a file descriptor for
/dev/net/tun.

The open(2) manpage writes this about its return value:

  On success, open(), openat(), and creat() return the new file
  descriptor (a nonnegative integer).  On error, -1 is returned and
  errno is set to indicate the error.

This means that the fd > 0 assertion in the open_tuntap helper is
incorrect and should rather check for fd >= 0.

When running the BPF selftests locally, this incorrect assertion was not
an issue, but the BPF kernel-patches CI failed because of this:

  open_tuntap:FAIL:open(/dev/net/tun) unexpected open(/dev/net/tun):
  actual 0 <= expected 0

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
---
 tools/testing/selftests/bpf/network_helpers.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index e1cfa1b37754..9b59bfd5d912 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -571,7 +571,7 @@ int open_tuntap(const char *dev_name, bool need_mac)
 	struct ifreq ifr;
 	int fd = open("/dev/net/tun", O_RDWR);
 
-	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+	if (!ASSERT_GE(fd, 0, "open(/dev/net/tun)"))
 		return -1;
 
 	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-- 
2.43.0

Re: [PATCH bpf-next v4 4/6] selftests/bpf: refactor xdp_context_functional test and bpf program

[Willem de Bruijn]

Marcus Wichelmann wrote:
> The existing XDP metadata test works by creating a veth pair and
> attaching XDP & TC programs that drop the packet when the condition of
> the test isn't fulfilled. The test then pings through the veth pair and
> succeeds when the ping comes through.
> 
> While this test works great for a veth pair, it is hard to replicate for
> tap devices to test the XDP metadata support of them. A similar test for
> the tun driver would either involve logic to reply to the ping request,
> or would have to capture the packet to check if it was dropped or not.
> 
> To make the testing of other drivers easier while still maximizing code
> reuse, this commit refactors the existing xdp_context_functional test to
> use a test_result map. Instead of conditionally passing or dropping the
> packet, the TC program is changed to copy the received metadata into the
> value of that single-entry array map. Tests can then verify that the map
> value matches the expectation.
> 
> This testing logic is easy to adapt to other network drivers as the only
> remaining requirement is that there is some way to send a custom
> Ethernet packet through it that triggers the XDP & TC programs.
> 
> The Ethernet header of that custom packet is all-zero, because it is not
> required to be valid for the test to work. The zero ethertype also helps
> to filter out packets that are not related to the test and would
> otherwise interfere with it.
> 
> The payload of the Ethernet packet is used as the test data that is
> expected to be passed as metadata from the XDP to the TC program and
> written to the map. It has a fixed size of 32 bytes which is a
> reasonable size that should be supported by both drivers. Additional
> packet headers are not necessary for the test and were therefore skipped
> to keep the testing code short.
> 
> This new testing methodology no longer requires the veth interfaces to
> have IP addresses assigned, therefore these were removed.
> 
> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>

Reviewed-by: Willem de Bruijn <willemb@google.com>

Re: [PATCH bpf-next v4 5/6] selftests/bpf: add test for XDP metadata support in tun driver

[Stanislav Fomichev]

On 02/27, Marcus Wichelmann wrote:
> Add a selftest that creates a tap device, attaches XDP and TC programs,
> writes a packet with a test payload into the tap device and checks the
> test result. This test ensures that the XDP metadata support in the tun
> driver is enabled and that the metadata size is correctly passed to the
> skb.
> 
> See the previous commit ("selftests/bpf: refactor xdp_context_functional
> test and bpf program") for details about the test design.
> 
> The test runs in its own network namespace using the feature introduced
> with commit c047e0e0e435 ("selftests/bpf: Optionally open a dedicated
> namespace to run test in it"). This provides some extra safety against
> conflicting interface names.
> 
> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>

Acked-by: Stanislav Fomichev <sdf@fomichev.me>

Re: [PATCH bpf-next v4 0/6] XDP metadata support for tun driver

[Lei Yang]

[-- Attachment #1: Type: text/plain, Size: 3506 bytes --]

Hi Marcus

Since your patches are about the virtual network, I'd like to test it,
but it conflicts (Please review the attachment to review more details)
when I apply it to the master branch.
My test based on this commit:
commit 1e15510b71c99c6e49134d756df91069f7d18141 (origin/master, origin/HEAD)
Merge: f09d694cf799 54e1b4becf5e
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu Feb 27 09:32:42 2025 -0800

    Merge tag 'net-6.14-rc5' of
git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net

    Pull networking fixes from Jakub Kicinski:
     "Including fixes from bluetooth.

Thanks
Lei

On Thu, Feb 27, 2025 at 10:28 PM Marcus Wichelmann
<marcus.wichelmann@hetzner-cloud.de> wrote:
>
> Hi all,
>
> this series contains some improvements for the selftest patches. The other
> patches remain unchanged. Please check the changelist below.
>
> I have reverted the addition of the NOARP flag from the previous version,
> as it was not effective and the CI was still failing occasionally because
> of the race condition caused by foreign packets interfering with the veth
> tests. This series contains an alternative solution by filtering all but
> the test packets using the attached XDP program.
>
> Successful pipeline:
> https://github.com/kernel-patches/bpf/actions/runs/13552017584
>
> ---
>
> v4:
> - strip unrelated changes from the selftest patches
> - extend commit message for "selftests/bpf: refactor xdp_context_functional
>   test and bpf program"
> - the NOARP flag was not effective to prevent other packets from
>   interfering with the tests, add a filter to the XDP program instead
> - run xdp_context_tuntap in a separate namespace to avoid conflicts with
>   other tests
>
> v3: https://lore.kernel.org/bpf/20250224152909.3911544-1-marcus.wichelmann@hetzner-cloud.de/
> - change the condition to handle xdp_buffs without metadata support, as
>   suggested by Willem de Bruijn <willemb@google.com>
> - add clarifying comment why that condition is needed
> - set NOARP flag in selftests to ensure that the kernel does not send
>   packets on the test interfaces that may interfere with the tests
>
> v2: https://lore.kernel.org/bpf/20250217172308.3291739-1-marcus.wichelmann@hetzner-cloud.de/
> - submit against bpf-next subtree
> - split commits and improved commit messages
> - remove redundant metasize check and add clarifying comment instead
> - use max() instead of ternary operator
> - add selftest for metadata support in the tun driver
>
> v1: https://lore.kernel.org/all/20250130171614.1657224-1-marcus.wichelmann@hetzner-cloud.de/
>
> Marcus Wichelmann (6):
>   net: tun: enable XDP metadata support
>   net: tun: enable transfer of XDP metadata to skb
>   selftests/bpf: move open_tuntap to network helpers
>   selftests/bpf: refactor xdp_context_functional test and bpf program
>   selftests/bpf: add test for XDP metadata support in tun driver
>   selftests/bpf: fix file descriptor assertion in open_tuntap helper
>
>  drivers/net/tun.c                             |  28 +++-
>  tools/testing/selftests/bpf/network_helpers.c |  28 ++++
>  tools/testing/selftests/bpf/network_helpers.h |   3 +
>  .../selftests/bpf/prog_tests/lwt_helpers.h    |  29 ----
>  .../bpf/prog_tests/xdp_context_test_run.c     | 138 +++++++++++++++++-
>  .../selftests/bpf/progs/test_xdp_meta.c       |  53 +++++--
>  6 files changed, 223 insertions(+), 56 deletions(-)
>
> --
> 2.43.0
>
>

[-- Attachment #2: conflict --]
[-- Type: application/octet-stream, Size: 3595 bytes --]

# git am --show-current-patch=diff
---
 tools/testing/selftests/bpf/network_helpers.c | 28 ++++++++++++++++++
 tools/testing/selftests/bpf/network_helpers.h |  3 ++
 .../selftests/bpf/prog_tests/lwt_helpers.h    | 29 -------------------
 3 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 737a952dcf80..e1cfa1b37754 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -565,6 +565,34 @@ void close_netns(struct nstoken *token)
        free(token);
 }
 
+int open_tuntap(const char *dev_name, bool need_mac)
+{
+       int err = 0;
+       struct ifreq ifr;
+       int fd = open("/dev/net/tun", O_RDWR);
+
+       if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+               return -1;
+
+       ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
+       strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
+       ifr.ifr_name[IFNAMSIZ - 1] = '\0';
+
+       err = ioctl(fd, TUNSETIFF, &ifr);
+       if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
+               close(fd);
+               return -1;
+       }
+
+       err = fcntl(fd, F_SETFL, O_NONBLOCK);
+       if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
+               close(fd);
+               return -1;
+       }
+
+       return fd;
+}
+
 int get_socket_local_port(int sock_fd)
 {
        struct sockaddr_storage addr;
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index 9f6e05d886c5..99d1417c1d8b 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -8,6 +8,7 @@
 typedef __u16 __sum16;
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
+#include <linux/if_tun.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/ethtool.h>
@@ -98,6 +99,8 @@ int send_recv_data(int lfd, int fd, uint32_t total_bytes);
 int make_netns(const char *name);
 int remove_netns(const char *name);
 
+int open_tuntap(const char *dev_name, bool need_mac);
+
 /**
  * append_tid() - Append thread ID to the given string.
  *
diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
index fb1eb8c67361..ccec0fcdabc1 100644
--- a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
@@ -5,7 +5,6 @@
 
 #include <time.h>
 #include <net/if.h>
-#include <linux/if_tun.h>
 #include <linux/icmp.h>
 
 #include "test_progs.h"
@@ -37,34 +36,6 @@ static inline int netns_delete(void)
        return system("ip netns del " NETNS ">/dev/null 2>&1");
 }
 
-static int open_tuntap(const char *dev_name, bool need_mac)
-{
-       int err = 0;
-       struct ifreq ifr;
-       int fd = open("/dev/net/tun", O_RDWR);
-
-       if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
-               return -1;
-
-       ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-       strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
-       ifr.ifr_name[IFNAMSIZ - 1] = '\0';
-
-       err = ioctl(fd, TUNSETIFF, &ifr);
-       if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
-               close(fd);
-               return -1;
-       }
-
-       err = fcntl(fd, F_SETFL, O_NONBLOCK);
-       if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
-               close(fd);
-               return -1;
-       }
-
-       return fd;
-}
-
 #define ICMP_PAYLOAD_SIZE     100
 
 /* Match an ICMP packet with payload len ICMP_PAYLOAD_SIZE */
-- 
2.43.0

Re: [PATCH bpf-next v4 0/6] XDP metadata support for tun driver

[Marcus Wichelmann]

Am 28.02.25 um 06:43 schrieb Lei Yang:
> Hi Marcus
> 
> Since your patches are about the virtual network, I'd like to test it,
> but it conflicts (Please review the attachment to review more details)
> when I apply it to the master branch.
> My test based on this commit:
> commit 1e15510b71c99c6e49134d756df91069f7d18141 (origin/master, origin/HEAD)
> Merge: f09d694cf799 54e1b4becf5e
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Thu Feb 27 09:32:42 2025 -0800
> 
>      Merge tag 'net-6.14-rc5' of
> git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
> 
>      Pull networking fixes from Jakub Kicinski:
>       "Including fixes from bluetooth.
> 

Hi,

thank you for including it in your tests.

The mentioned commit is not yet in bpf-next, but I rebased my patch on
latest mainline and attached the updated patch for the conflicting
commit.

The conflict was just about a section that was removed right below
my added line in network_helpers.h, so no functional change.

---

 From c7182e5a4d21696b9e8cd25f92e64e28129e2c6e Mon Sep 17 00:00:00 2001
From: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Date: Thu, 13 Feb 2025 16:28:19 +0000
Subject: [PATCH] selftests/bpf: move open_tuntap to network helpers

To test the XDP metadata functionality of the tun driver, it's necessary
to create a new tap device first. A helper function for this already
exists in lwt_helpers.h. Move it to the common network helpers header,
so it can be reused in other tests.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
  tools/testing/selftests/bpf/network_helpers.c | 28 ++++++++++++++++++
  tools/testing/selftests/bpf/network_helpers.h |  3 ++
  .../selftests/bpf/prog_tests/lwt_helpers.h    | 29 -------------------
  3 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 80844a5fb1fe..fcee2c4a637a 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -548,6 +548,34 @@ void close_netns(struct nstoken *token)
  	free(token);
  }
  
+int open_tuntap(const char *dev_name, bool need_mac)
+{
+	int err = 0;
+	struct ifreq ifr;
+	int fd = open("/dev/net/tun", O_RDWR);
+
+	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+		return -1;
+
+	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
+	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
+	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
+
+	err = ioctl(fd, TUNSETIFF, &ifr);
+	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
+		close(fd);
+		return -1;
+	}
+
+	err = fcntl(fd, F_SETFL, O_NONBLOCK);
+	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
  int get_socket_local_port(int sock_fd)
  {
  	struct sockaddr_storage addr;
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index ebec8a8d6f81..175dd547849f 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -8,6 +8,7 @@
  typedef __u16 __sum16;
  #include <linux/if_ether.h>
  #include <linux/if_packet.h>
+#include <linux/if_tun.h>
  #include <linux/ip.h>
  #include <linux/ipv6.h>
  #include <linux/ethtool.h>
@@ -98,6 +99,8 @@ int send_recv_data(int lfd, int fd, uint32_t total_bytes);
  int make_netns(const char *name);
  int remove_netns(const char *name);
  
+int open_tuntap(const char *dev_name, bool need_mac);
+
  static __u16 csum_fold(__u32 csum)
  {
  	csum = (csum & 0xffff) + (csum >> 16);
diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
index fb1eb8c67361..ccec0fcdabc1 100644
--- a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
@@ -5,7 +5,6 @@
  
  #include <time.h>
  #include <net/if.h>
-#include <linux/if_tun.h>
  #include <linux/icmp.h>
  
  #include "test_progs.h"
@@ -37,34 +36,6 @@ static inline int netns_delete(void)
  	return system("ip netns del " NETNS ">/dev/null 2>&1");
  }
  
-static int open_tuntap(const char *dev_name, bool need_mac)
-{
-	int err = 0;
-	struct ifreq ifr;
-	int fd = open("/dev/net/tun", O_RDWR);
-
-	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
-		return -1;
-
-	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
-	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
-
-	err = ioctl(fd, TUNSETIFF, &ifr);
-	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
-		close(fd);
-		return -1;
-	}
-
-	err = fcntl(fd, F_SETFL, O_NONBLOCK);
-	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
-		close(fd);
-		return -1;
-	}
-
-	return fd;
-}
-
  #define ICMP_PAYLOAD_SIZE     100
  
  /* Match an ICMP packet with payload len ICMP_PAYLOAD_SIZE */
-- 
2.43.0

Re: [PATCH bpf-next v4 0/6] XDP metadata support for tun driver

[Marcus Wichelmann]

Am 28.02.25 um 06:43 schrieb Lei Yang:
> Hi Marcus
> 
> Since your patches are about the virtual network, I'd like to test it,
> but it conflicts (Please review the attachment to review more details)
> when I apply it to the master branch.
> My test based on this commit:
> commit 1e15510b71c99c6e49134d756df91069f7d18141 (origin/master, origin/HEAD)
> Merge: f09d694cf799 54e1b4becf5e
> Author: Linus Torvalds <torvalds@linux-foundation.org>
> Date:   Thu Feb 27 09:32:42 2025 -0800
> 
>     Merge tag 'net-6.14-rc5' of
> git://git.kernel.org/pub/scm/linux/kernel/git/netdev/net
> 
>     Pull networking fixes from Jakub Kicinski:
>      "Including fixes from bluetooth.
> 

Hi,

thank you for including it in your tests.

The mentioned commit is not yet in bpf-next, but I rebased my patch on
latest mainline and attached the updated patch for the conflicting
commit (now with proper formatting, hopefully).

The conflict was just about a section that was removed right below
my added line in network_helpers.h, so no functional change.

---

From c7182e5a4d21696b9e8cd25f92e64e28129e2c6e Mon Sep 17 00:00:00 2001
From: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Date: Thu, 13 Feb 2025 16:28:19 +0000
Subject: [PATCH] selftests/bpf: move open_tuntap to network helpers

To test the XDP metadata functionality of the tun driver, it's necessary
to create a new tap device first. A helper function for this already
exists in lwt_helpers.h. Move it to the common network helpers header,
so it can be reused in other tests.

Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
Reviewed-by: Willem de Bruijn <willemb@google.com>
Acked-by: Jason Wang <jasowang@redhat.com>
---
 tools/testing/selftests/bpf/network_helpers.c | 28 ++++++++++++++++++
 tools/testing/selftests/bpf/network_helpers.h |  3 ++
 .../selftests/bpf/prog_tests/lwt_helpers.h    | 29 -------------------
 3 files changed, 31 insertions(+), 29 deletions(-)

diff --git a/tools/testing/selftests/bpf/network_helpers.c b/tools/testing/selftests/bpf/network_helpers.c
index 80844a5fb1fe..fcee2c4a637a 100644
--- a/tools/testing/selftests/bpf/network_helpers.c
+++ b/tools/testing/selftests/bpf/network_helpers.c
@@ -548,6 +548,34 @@ void close_netns(struct nstoken *token)
 	free(token);
 }
 
+int open_tuntap(const char *dev_name, bool need_mac)
+{
+	int err = 0;
+	struct ifreq ifr;
+	int fd = open("/dev/net/tun", O_RDWR);
+
+	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
+		return -1;
+
+	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
+	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
+	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
+
+	err = ioctl(fd, TUNSETIFF, &ifr);
+	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
+		close(fd);
+		return -1;
+	}
+
+	err = fcntl(fd, F_SETFL, O_NONBLOCK);
+	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
+		close(fd);
+		return -1;
+	}
+
+	return fd;
+}
+
 int get_socket_local_port(int sock_fd)
 {
 	struct sockaddr_storage addr;
diff --git a/tools/testing/selftests/bpf/network_helpers.h b/tools/testing/selftests/bpf/network_helpers.h
index ebec8a8d6f81..175dd547849f 100644
--- a/tools/testing/selftests/bpf/network_helpers.h
+++ b/tools/testing/selftests/bpf/network_helpers.h
@@ -8,6 +8,7 @@
 typedef __u16 __sum16;
 #include <linux/if_ether.h>
 #include <linux/if_packet.h>
+#include <linux/if_tun.h>
 #include <linux/ip.h>
 #include <linux/ipv6.h>
 #include <linux/ethtool.h>
@@ -98,6 +99,8 @@ int send_recv_data(int lfd, int fd, uint32_t total_bytes);
 int make_netns(const char *name);
 int remove_netns(const char *name);
 
+int open_tuntap(const char *dev_name, bool need_mac);
+
 static __u16 csum_fold(__u32 csum)
 {
 	csum = (csum & 0xffff) + (csum >> 16);
diff --git a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
index fb1eb8c67361..ccec0fcdabc1 100644
--- a/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
+++ b/tools/testing/selftests/bpf/prog_tests/lwt_helpers.h
@@ -5,7 +5,6 @@
 
 #include <time.h>
 #include <net/if.h>
-#include <linux/if_tun.h>
 #include <linux/icmp.h>
 
 #include "test_progs.h"
@@ -37,34 +36,6 @@ static inline int netns_delete(void)
 	return system("ip netns del " NETNS ">/dev/null 2>&1");
 }
 
-static int open_tuntap(const char *dev_name, bool need_mac)
-{
-	int err = 0;
-	struct ifreq ifr;
-	int fd = open("/dev/net/tun", O_RDWR);
-
-	if (!ASSERT_GT(fd, 0, "open(/dev/net/tun)"))
-		return -1;
-
-	ifr.ifr_flags = IFF_NO_PI | (need_mac ? IFF_TAP : IFF_TUN);
-	strncpy(ifr.ifr_name, dev_name, IFNAMSIZ - 1);
-	ifr.ifr_name[IFNAMSIZ - 1] = '\0';
-
-	err = ioctl(fd, TUNSETIFF, &ifr);
-	if (!ASSERT_OK(err, "ioctl(TUNSETIFF)")) {
-		close(fd);
-		return -1;
-	}
-
-	err = fcntl(fd, F_SETFL, O_NONBLOCK);
-	if (!ASSERT_OK(err, "fcntl(O_NONBLOCK)")) {
-		close(fd);
-		return -1;
-	}
-
-	return fd;
-}
-
 #define ICMP_PAYLOAD_SIZE     100
 
 /* Match an ICMP packet with payload len ICMP_PAYLOAD_SIZE */
-- 
2.43.0

Re: [PATCH bpf-next v4 2/6] net: tun: enable transfer of XDP metadata to skb

[Martin KaFai Lau]

On 2/27/25 6:23 AM, Marcus Wichelmann wrote:
> When the XDP metadata area was used, it is expected that the same
> metadata can also be accessed from TC, as can be read in the description
> of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
> not yet implemented.
> 
> To make this work, the skb that is being built on XDP_PASS should know
> of the current size of the metadata area. This is ensured by adding
> calls to skb_metadata_set. For the tun_xdp_one code path, an additional
> check is necessary to handle the case where the externally initialized
> xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).
> 
> More information about this feature can be found in the commit message
> of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").
> > Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
> Reviewed-by: Willem de Bruijn <willemb@google.com>
> Acked-by: Jason Wang <jasowang@redhat.com>
> ---
>   drivers/net/tun.c | 25 ++++++++++++++++++++++---
>   1 file changed, 22 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
> index 4ec8fbd93c8d..70208b3a2e93 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c

The changes have conflicts with the commit 2506251e81d1 ("tun: Decouple vnet handling").

It is better to rebase the works onto the bpf-next/net,
i.e. the "net" branch instead of the "master" branch.

Re: [PATCH bpf-next v4 2/6] net: tun: enable transfer of XDP metadata to skb

[Marcus Wichelmann]

Am 28.02.25 um 20:49 schrieb Martin KaFai Lau:
> On 2/27/25 6:23 AM, Marcus Wichelmann wrote:
>> When the XDP metadata area was used, it is expected that the same
>> metadata can also be accessed from TC, as can be read in the description
>> of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
>> not yet implemented.
>>
>> To make this work, the skb that is being built on XDP_PASS should know
>> of the current size of the metadata area. This is ensured by adding
>> calls to skb_metadata_set. For the tun_xdp_one code path, an additional
>> check is necessary to handle the case where the externally initialized
>> xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).
>>
>> More information about this feature can be found in the commit message
>> of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").
>> > Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
>> Reviewed-by: Willem de Bruijn <willemb@google.com>
>> Acked-by: Jason Wang <jasowang@redhat.com>
>> ---
>>   drivers/net/tun.c | 25 ++++++++++++++++++++++---
>>   1 file changed, 22 insertions(+), 3 deletions(-)
>>
>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>> index 4ec8fbd93c8d..70208b3a2e93 100644
>> --- a/drivers/net/tun.c
>> +++ b/drivers/net/tun.c
> 
> The changes have conflicts with the commit 2506251e81d1 ("tun: Decouple vnet handling").
> 
> It is better to rebase the works onto the bpf-next/net,
> i.e. the "net" branch instead of the "master" branch.

Alright, will do that. Should I send it as a v5 and still with "PATCH bpf-next"
in the header or something else?

Thanks!
Marcus

Re: [PATCH bpf-next v4 2/6] net: tun: enable transfer of XDP metadata to skb

[Martin KaFai Lau]

On 3/3/25 8:13 AM, Marcus Wichelmann wrote:
> Am 28.02.25 um 20:49 schrieb Martin KaFai Lau:
>> On 2/27/25 6:23 AM, Marcus Wichelmann wrote:
>>> When the XDP metadata area was used, it is expected that the same
>>> metadata can also be accessed from TC, as can be read in the description
>>> of the bpf_xdp_adjust_meta helper function. In the tun driver, this was
>>> not yet implemented.
>>>
>>> To make this work, the skb that is being built on XDP_PASS should know
>>> of the current size of the metadata area. This is ensured by adding
>>> calls to skb_metadata_set. For the tun_xdp_one code path, an additional
>>> check is necessary to handle the case where the externally initialized
>>> xdp_buff has no metadata support (xdp->data_meta == xdp->data + 1).
>>>
>>> More information about this feature can be found in the commit message
>>> of commit de8f3a83b0a0 ("bpf: add meta pointer for direct access").
>>>> Signed-off-by: Marcus Wichelmann <marcus.wichelmann@hetzner-cloud.de>
>>> Reviewed-by: Willem de Bruijn <willemb@google.com>
>>> Acked-by: Jason Wang <jasowang@redhat.com>
>>> ---
>>>    drivers/net/tun.c | 25 ++++++++++++++++++++++---
>>>    1 file changed, 22 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c
>>> index 4ec8fbd93c8d..70208b3a2e93 100644
>>> --- a/drivers/net/tun.c
>>> +++ b/drivers/net/tun.c
>>
>> The changes have conflicts with the commit 2506251e81d1 ("tun: Decouple vnet handling").
>>
>> It is better to rebase the works onto the bpf-next/net,
>> i.e. the "net" branch instead of the "master" branch.
> 
> Alright, will do that. Should I send it as a v5 and still with "PATCH bpf-next"
> in the header or something else?

That should do. The bpf CI should pick up the bpf-next/net if it fails to apply 
to the bpf-next/master because of the conflict mentioned above.

For patch 3, it should help to avoid the future merge conflict if the 
open_tuntap() is added a few lines above in the network_helpers.h. For patch 6, 
the "test_ns_" naming is not in bpf-next/net yet. Other tests in the same file 
is doing netns_new. May be just do the same and cleanup all at once of this file 
later.