[xdp-hints] [PATCH bpf-next v5 0/4] xsk: TX metadata Launch Time support

[xdp-hints] [PATCH bpf-next v5 0/4] xsk: TX metadata Launch Time support

[Song Yoong Siang]

This series expands the XDP TX metadata framework to allow user
applications to pass per packet 64-bit launch time directly to the kernel
driver, requesting launch time hardware offload support. The XDP TX
metadata framework will not perform any clock conversion or packet
reordering.

Please note that the role of Tx metadata is just to pass the launch time,
not to enable the offload feature. Users will need to enable the launch
time hardware offload feature of the device by using the respective
command, such as the tc-etf command.

Although some devices use the tc-etf command to enable their launch time
hardware offload feature, xsk packets will not go through the etf qdisc.
Therefore, in my opinion, the launch time should always be based on the PTP
Hardware Clock (PHC). Thus, i did not include a clock ID to indicate the
clock source.

To simplify the test steps, I modified the xdp_hw_metadata bpf self-test
tool in such a way that it will set the launch time based on the offset
provided by the user and the value of the Receive Hardware Timestamp, which
is against the PHC. This will eliminate the need to discipline System Clock
with the PHC and then use clock_gettime() to get the time.

Please note that AF_XDP lacks a feedback mechanism to inform the
application if the requested launch time is invalid. So, users are expected
to familiar with the horizon of the launch time of the device they use and
not request a launch time that is beyond the horizon. Otherwise, the driver
might interpret the launch time incorrectly and react wrongly. For stmmac
and igc, where modulo computation is used, a launch time larger than the
horizon will cause the device to transmit the packet earlier that the
requested launch time.

Although there is no feedback mechanism for the launch time request
for now, user still can check whether the requested launch time is
working or not, by requesting the Transmit Completion Hardware Timestamp.

Changes since v1:
- renamed to use Earliest TxTime First (Willem)
- renamed to use txtime (Willem)

Changes since v2:
- renamed to use launch time (Jesper & Willem)
- changed the default launch time in xdp_hw_metadata apps from 1s to 0.1s
  because some NICs do not support such a large future time.

Changes since v3:
- added XDP launch time support to the igc driver (Jesper & Florian)
- added per-driver launch time limitation on xsk-tx-metadata.rst (Jesper)
- added explanation on FIFO behavior on xsk-tx-metadata.rst (Jakub)
- added step to enable launch time in the commit message (Jesper & Willem)
- explicitly documented the type of launch_time and which clock source
  it is against (Willem)

Changes since v4:
- change netdev feature name from tx-launch-time to tx-launch-time-fifo
  to explicitly state the FIFO behaviour (Stanislav)
- improve the looping of xdp_hw_metadata app to wait for packet tx
  completion to be more readable by using clock_gettime() (Stanislav)
- add launch time setup steps into xdp_hw_metadata app (Stanislav)

v1: https://patchwork.kernel.org/project/netdevbpf/cover/20231130162028.852006-1-yoong.siang.song@intel.com/
v2: https://patchwork.kernel.org/project/netdevbpf/cover/20231201062421.1074768-1-yoong.siang.song@intel.com/
v3: https://patchwork.kernel.org/project/netdevbpf/cover/20231203165129.1740512-1-yoong.siang.song@intel.com/
v4: https://patchwork.kernel.org/project/netdevbpf/cover/20250106135506.9687-1-yoong.siang.song@intel.com/

Song Yoong Siang (4):
  xsk: Add launch time hardware offload support to XDP Tx metadata
  selftests/bpf: Add launch time request to xdp_hw_metadata
  net: stmmac: Add launch time support to XDP ZC
  igc: Add launch time support to XDP ZC

 Documentation/netlink/specs/netdev.yaml       |   4 +
 Documentation/networking/xsk-tx-metadata.rst  |  62 +++++++++
 drivers/net/ethernet/intel/igc/igc_main.c     |  78 +++++++----
 drivers/net/ethernet/stmicro/stmmac/stmmac.h  |   2 +
 .../net/ethernet/stmicro/stmmac/stmmac_main.c |  13 ++
 include/net/xdp_sock.h                        |  10 ++
 include/net/xdp_sock_drv.h                    |   1 +
 include/uapi/linux/if_xdp.h                   |  10 ++
 include/uapi/linux/netdev.h                   |   3 +
 net/core/netdev-genl.c                        |   2 +
 net/xdp/xsk.c                                 |   3 +
 tools/include/uapi/linux/if_xdp.h             |  10 ++
 tools/include/uapi/linux/netdev.h             |   3 +
 tools/testing/selftests/bpf/xdp_hw_metadata.c | 121 +++++++++++++++++-
 14 files changed, 298 insertions(+), 24 deletions(-)

-- 
2.34.1

[xdp-hints] [PATCH bpf-next v5 1/4] xsk: Add launch time hardware offload support to XDP Tx metadata

[Song Yoong Siang]

Extend the XDP Tx metadata framework so that user can requests launch time
hardware offload, where the Ethernet device will schedule the packet for
transmission at a pre-determined time called launch time. The value of
launch time is communicated from user space to Ethernet driver via
launch_time field of struct xsk_tx_metadata.

Suggested-by: Stanislav Fomichev <sdf@fomichev.me>
Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
---
 Documentation/netlink/specs/netdev.yaml      |  4 ++
 Documentation/networking/xsk-tx-metadata.rst | 62 ++++++++++++++++++++
 include/net/xdp_sock.h                       | 10 ++++
 include/net/xdp_sock_drv.h                   |  1 +
 include/uapi/linux/if_xdp.h                  | 10 ++++
 include/uapi/linux/netdev.h                  |  3 +
 net/core/netdev-genl.c                       |  2 +
 net/xdp/xsk.c                                |  3 +
 tools/include/uapi/linux/if_xdp.h            | 10 ++++
 tools/include/uapi/linux/netdev.h            |  3 +
 10 files changed, 108 insertions(+)

diff --git a/Documentation/netlink/specs/netdev.yaml b/Documentation/netlink/specs/netdev.yaml
index cbb544bd6c84..901b5afb3df0 100644
--- a/Documentation/netlink/specs/netdev.yaml
+++ b/Documentation/netlink/specs/netdev.yaml
@@ -70,6 +70,10 @@ definitions:
         name: tx-checksum
         doc:
           L3 checksum HW offload is supported by the driver.
+      -
+        name: tx-launch-time-fifo
+        doc:
+          Launch time HW offload is supported by the driver.
   -
     name: queue-type
     type: enum
diff --git a/Documentation/networking/xsk-tx-metadata.rst b/Documentation/networking/xsk-tx-metadata.rst
index e76b0cfc32f7..df53a10ccac3 100644
--- a/Documentation/networking/xsk-tx-metadata.rst
+++ b/Documentation/networking/xsk-tx-metadata.rst
@@ -50,6 +50,10 @@ The flags field enables the particular offload:
   checksum. ``csum_start`` specifies byte offset of where the checksumming
   should start and ``csum_offset`` specifies byte offset where the
   device should store the computed checksum.
+- ``XDP_TXMD_FLAGS_LAUNCH_TIME``: requests the device to schedule the
+  packet for transmission at a pre-determined time called launch time. The
+  value of launch time is indicated by ``launch_time`` field of
+  ``union xsk_tx_metadata``.
 
 Besides the flags above, in order to trigger the offloads, the first
 packet's ``struct xdp_desc`` descriptor should set ``XDP_TX_METADATA``
@@ -65,6 +69,63 @@ In this case, when running in ``XDK_COPY`` mode, the TX checksum
 is calculated on the CPU. Do not enable this option in production because
 it will negatively affect performance.
 
+Launch Time
+===========
+
+The value of the requested launch time should be based on the device's PTP
+Hardware Clock (PHC) to ensure accuracy. AF_XDP takes a different data path
+compared to the ETF queuing discipline, which organizes packets and delays
+their transmission. Instead, AF_XDP immediately hands off the packets to
+the device driver without rearranging their order or holding them prior to
+transmission. Since the driver maintains FIFO behavior and does not perform
+packet reordering, a packet with a launch time request will block other
+packets in the same Tx Queue until it is sent. Therefore, it is recommended
+to allocate separate queue for scheduling traffic that is intended for
+future transmission.
+
+In scenarios where the launch time offload feature is disabled, the device
+driver is expected to disregard the launch time request. For correct
+interpretation and meaningful operation, the launch time should never be
+set to a value larger than the farthest programmable time in the future
+(the horizon). Different devices have different hardware limitations on the
+launch time offload feature.
+
+stmmac driver
+-------------
+
+For stmmac, TSO and launch time (TBS) features are mutually exclusive for
+each individual Tx Queue. By default, the driver configures Tx Queue 0 to
+support TSO and the rest of the Tx Queues to support TBS. The launch time
+hardware offload feature can be enabled or disabled by using the tc-etf
+command to call the driver's ndo_setup_tc() callback.
+
+The value of the launch time that is programmed in the Enhanced Normal
+Transmit Descriptors is a 32-bit value, where the most significant 8 bits
+represent the time in seconds and the remaining 24 bits represent the time
+in 256 ns increments. The programmed launch time is compared against the
+PTP time (bits[39:8]) and rolls over after 256 seconds. Therefore, the
+horizon of the launch time for dwmac4 and dwxlgmac2 is 128 seconds in the
+future.
+
+igc driver
+----------
+
+For igc, all four Tx Queues support the launch time feature. The launch
+time hardware offload feature can be enabled or disabled by using the
+tc-etf command to call the driver's ndo_setup_tc() callback. When entering
+TSN mode, the igc driver will reset the device and create a default Qbv
+schedule with a 1-second cycle time, with all Tx Queues open at all times.
+
+The value of the launch time that is programmed in the Advanced Transmit
+Context Descriptor is a relative offset to the starting time of the Qbv
+transmission window of the queue. The Frst flag of the descriptor can be
+set to schedule the packet for the next Qbv cycle. Therefore, the horizon
+of the launch time for i225 and i226 is the ending time of the next cycle
+of the Qbv transmission window of the queue. For example, when the Qbv
+cycle time is set to 1 second, the horizon of the launch time ranges
+from 1 second to 2 seconds, depending on where the Qbv cycle is currently
+running.
+
 Querying Device Capabilities
 ============================
 
@@ -74,6 +135,7 @@ Refer to ``xsk-flags`` features bitmask in
 
 - ``tx-timestamp``: device supports ``XDP_TXMD_FLAGS_TIMESTAMP``
 - ``tx-checksum``: device supports ``XDP_TXMD_FLAGS_CHECKSUM``
+- ``tx-launch-time-fifo``: device supports ``XDP_TXMD_FLAGS_LAUNCH_TIME``
 
 See ``tools/net/ynl/samples/netdev.c`` on how to query this information.
 
diff --git a/include/net/xdp_sock.h b/include/net/xdp_sock.h
index bfe625b55d55..a58ae7589d12 100644
--- a/include/net/xdp_sock.h
+++ b/include/net/xdp_sock.h
@@ -110,11 +110,16 @@ struct xdp_sock {
  *     indicates position where checksumming should start.
  *     csum_offset indicates position where checksum should be stored.
  *
+ * void (*tmo_request_launch_time)(u64 launch_time, void *priv)
+ *     Called when AF_XDP frame requested launch time HW offload support.
+ *     launch_time indicates the PTP time at which the device can schedule the
+ *     packet for transmission.
  */
 struct xsk_tx_metadata_ops {
 	void	(*tmo_request_timestamp)(void *priv);
 	u64	(*tmo_fill_timestamp)(void *priv);
 	void	(*tmo_request_checksum)(u16 csum_start, u16 csum_offset, void *priv);
+	void	(*tmo_request_launch_time)(u64 launch_time, void *priv);
 };
 
 #ifdef CONFIG_XDP_SOCKETS
@@ -162,6 +167,11 @@ static inline void xsk_tx_metadata_request(const struct xsk_tx_metadata *meta,
 	if (!meta)
 		return;
 
+	if (ops->tmo_request_launch_time)
+		if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME)
+			ops->tmo_request_launch_time(meta->request.launch_time,
+						     priv);
+
 	if (ops->tmo_request_timestamp)
 		if (meta->flags & XDP_TXMD_FLAGS_TIMESTAMP)
 			ops->tmo_request_timestamp(priv);
diff --git a/include/net/xdp_sock_drv.h b/include/net/xdp_sock_drv.h
index 86620c818965..8c005b50dfd9 100644
--- a/include/net/xdp_sock_drv.h
+++ b/include/net/xdp_sock_drv.h
@@ -208,6 +208,7 @@ static inline void *xsk_buff_raw_get_data(struct xsk_buff_pool *pool, u64 addr)
 #define XDP_TXMD_FLAGS_VALID ( \
 		XDP_TXMD_FLAGS_TIMESTAMP | \
 		XDP_TXMD_FLAGS_CHECKSUM | \
+		XDP_TXMD_FLAGS_LAUNCH_TIME | \
 	0)
 
 static inline bool
diff --git a/include/uapi/linux/if_xdp.h b/include/uapi/linux/if_xdp.h
index 42ec5ddaab8d..42869770776e 100644
--- a/include/uapi/linux/if_xdp.h
+++ b/include/uapi/linux/if_xdp.h
@@ -127,6 +127,12 @@ struct xdp_options {
  */
 #define XDP_TXMD_FLAGS_CHECKSUM			(1 << 1)
 
+/* Request launch time hardware offload. The device will schedule the packet for
+ * transmission at a pre-determined time called launch time. The value of
+ * launch time is communicated via launch_time field of struct xsk_tx_metadata.
+ */
+#define XDP_TXMD_FLAGS_LAUNCH_TIME		(1 << 2)
+
 /* AF_XDP offloads request. 'request' union member is consumed by the driver
  * when the packet is being transmitted. 'completion' union member is
  * filled by the driver when the transmit completion arrives.
@@ -142,6 +148,10 @@ struct xsk_tx_metadata {
 			__u16 csum_start;
 			/* Offset from csum_start where checksum should be stored. */
 			__u16 csum_offset;
+
+			/* XDP_TXMD_FLAGS_LAUNCH_TIME */
+			/* Launch time in nanosecond against the PTP HW Clock */
+			__u64 launch_time;
 		} request;
 
 		struct {
diff --git a/include/uapi/linux/netdev.h b/include/uapi/linux/netdev.h
index e4be227d3ad6..5ab85f4af009 100644
--- a/include/uapi/linux/netdev.h
+++ b/include/uapi/linux/netdev.h
@@ -59,10 +59,13 @@ enum netdev_xdp_rx_metadata {
  *   by the driver.
  * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum HW offload is supported by the
  *   driver.
+ * @NETDEV_XSK_FLAGS_LAUNCH_TIME: Launch Time HW offload is supported by the
+ *   driver.
  */
 enum netdev_xsk_flags {
 	NETDEV_XSK_FLAGS_TX_TIMESTAMP = 1,
 	NETDEV_XSK_FLAGS_TX_CHECKSUM = 2,
+	NETDEV_XSK_FLAGS_LAUNCH_TIME = 4,
 };
 
 enum netdev_queue_type {
diff --git a/net/core/netdev-genl.c b/net/core/netdev-genl.c
index b0772d135efb..586cd485045d 100644
--- a/net/core/netdev-genl.c
+++ b/net/core/netdev-genl.c
@@ -52,6 +52,8 @@ XDP_METADATA_KFUNC_xxx
 			xsk_features |= NETDEV_XSK_FLAGS_TX_TIMESTAMP;
 		if (netdev->xsk_tx_metadata_ops->tmo_request_checksum)
 			xsk_features |= NETDEV_XSK_FLAGS_TX_CHECKSUM;
+		if (netdev->xsk_tx_metadata_ops->tmo_request_launch_time)
+			xsk_features |= NETDEV_XSK_FLAGS_LAUNCH_TIME;
 	}
 
 	if (nla_put_u32(rsp, NETDEV_A_DEV_IFINDEX, netdev->ifindex) ||
diff --git a/net/xdp/xsk.c b/net/xdp/xsk.c
index 3fa70286c846..8feaa0e86f07 100644
--- a/net/xdp/xsk.c
+++ b/net/xdp/xsk.c
@@ -743,6 +743,9 @@ static struct sk_buff *xsk_build_skb(struct xdp_sock *xs,
 						goto free_err;
 				}
 			}
+
+			if (meta->flags & XDP_TXMD_FLAGS_LAUNCH_TIME)
+				skb->skb_mstamp_ns = meta->request.launch_time;
 		}
 	}
 
diff --git a/tools/include/uapi/linux/if_xdp.h b/tools/include/uapi/linux/if_xdp.h
index 2f082b01ff22..67719f8966c2 100644
--- a/tools/include/uapi/linux/if_xdp.h
+++ b/tools/include/uapi/linux/if_xdp.h
@@ -127,6 +127,12 @@ struct xdp_options {
  */
 #define XDP_TXMD_FLAGS_CHECKSUM			(1 << 1)
 
+/* Request launch time hardware offload. The device will schedule the packet for
+ * transmission at a pre-determined time called launch time. The value of
+ * launch time is communicated via launch_time field of struct xsk_tx_metadata.
+ */
+#define XDP_TXMD_FLAGS_LAUNCH_TIME		(1 << 2)
+
 /* AF_XDP offloads request. 'request' union member is consumed by the driver
  * when the packet is being transmitted. 'completion' union member is
  * filled by the driver when the transmit completion arrives.
@@ -142,6 +148,10 @@ struct xsk_tx_metadata {
 			__u16 csum_start;
 			/* Offset from csum_start where checksum should be stored. */
 			__u16 csum_offset;
+
+			/* XDP_TXMD_FLAGS_LAUNCH_TIME */
+			/* Launch time in nanosecond against the PTP HW Clock */
+			__u64 launch_time;
 		} request;
 
 		struct {
diff --git a/tools/include/uapi/linux/netdev.h b/tools/include/uapi/linux/netdev.h
index e4be227d3ad6..5ab85f4af009 100644
--- a/tools/include/uapi/linux/netdev.h
+++ b/tools/include/uapi/linux/netdev.h
@@ -59,10 +59,13 @@ enum netdev_xdp_rx_metadata {
  *   by the driver.
  * @NETDEV_XSK_FLAGS_TX_CHECKSUM: L3 checksum HW offload is supported by the
  *   driver.
+ * @NETDEV_XSK_FLAGS_LAUNCH_TIME: Launch Time HW offload is supported by the
+ *   driver.
  */
 enum netdev_xsk_flags {
 	NETDEV_XSK_FLAGS_TX_TIMESTAMP = 1,
 	NETDEV_XSK_FLAGS_TX_CHECKSUM = 2,
+	NETDEV_XSK_FLAGS_LAUNCH_TIME = 4,
 };
 
 enum netdev_queue_type {
-- 
2.34.1

[xdp-hints] [PATCH bpf-next v5 2/4] selftests/bpf: Add launch time request to xdp_hw_metadata

[Song Yoong Siang]

Add launch time hardware offload request to xdp_hw_metadata. Users can
configure the delta of launch time relative to HW RX-time using the "-l"
argument. By default, the delta is set to 0 ns, which means the launch time
is disabled. By setting the delta to a non-zero value, the launch time
hardware offload feature will be enabled and requested. Additionally, users
can configure the Tx Queue to be enabled with the launch time hardware
offload using the "-L" argument. By default, Tx Queue 0 will be used.

Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
---
 tools/testing/selftests/bpf/xdp_hw_metadata.c | 121 +++++++++++++++++-
 1 file changed, 119 insertions(+), 2 deletions(-)

diff --git a/tools/testing/selftests/bpf/xdp_hw_metadata.c b/tools/testing/selftests/bpf/xdp_hw_metadata.c
index 6f7b15d6c6ed..1b2e5c241bd8 100644
--- a/tools/testing/selftests/bpf/xdp_hw_metadata.c
+++ b/tools/testing/selftests/bpf/xdp_hw_metadata.c
@@ -13,6 +13,7 @@
  * - UDP 9091 packets trigger TX reply
  * - TX HW timestamp is requested and reported back upon completion
  * - TX checksum is requested
+ * - TX launch time HW offload is requested for transmission
  */
 
 #include <test_progs.h>
@@ -37,6 +38,15 @@
 #include <time.h>
 #include <unistd.h>
 #include <libgen.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <linux/pkt_sched.h>
+#include <linux/pkt_cls.h>
+#include <linux/ethtool.h>
+#include <sys/socket.h>
+#include <arpa/inet.h>
 
 #include "xdp_metadata.h"
 
@@ -64,6 +74,18 @@ int rxq;
 bool skip_tx;
 __u64 last_hw_rx_timestamp;
 __u64 last_xdp_rx_timestamp;
+__u64 last_launch_time;
+__u64 launch_time_delta_to_hw_rx_timestamp;
+int launch_time_queue;
+
+#define run_command(cmd, ...)					\
+({								\
+	char command[1024];					\
+	memset(command, 0, sizeof(command));			\
+	snprintf(command, sizeof(command), cmd, ##__VA_ARGS__);	\
+	fprintf(stderr, "Running: %s\n", command);		\
+	system(command);					\
+})
 
 void test__fail(void) { /* for network_helpers.c */ }
 
@@ -298,6 +320,12 @@ static bool complete_tx(struct xsk *xsk, clockid_t clock_id)
 	if (meta->completion.tx_timestamp) {
 		__u64 ref_tstamp = gettime(clock_id);
 
+		if (launch_time_delta_to_hw_rx_timestamp) {
+			print_tstamp_delta("HW Launch-time",
+					   "HW TX-complete-time",
+					   last_launch_time,
+					   meta->completion.tx_timestamp);
+		}
 		print_tstamp_delta("HW TX-complete-time", "User TX-complete-time",
 				   meta->completion.tx_timestamp, ref_tstamp);
 		print_tstamp_delta("XDP RX-time", "User TX-complete-time",
@@ -395,6 +423,17 @@ static void ping_pong(struct xsk *xsk, void *rx_packet, clockid_t clock_id)
 	       xsk, ntohs(udph->check), ntohs(want_csum),
 	       meta->request.csum_start, meta->request.csum_offset);
 
+	/* Set the value of launch time */
+	if (launch_time_delta_to_hw_rx_timestamp) {
+		meta->flags |= XDP_TXMD_FLAGS_LAUNCH_TIME;
+		meta->request.launch_time = last_hw_rx_timestamp +
+					    launch_time_delta_to_hw_rx_timestamp;
+		last_launch_time = meta->request.launch_time;
+		print_tstamp_delta("HW RX-time", "HW Launch-time",
+				   last_hw_rx_timestamp,
+				   meta->request.launch_time);
+	}
+
 	memcpy(data, rx_packet, len); /* don't share umem chunk for simplicity */
 	tx_desc->options |= XDP_TX_METADATA;
 	tx_desc->len = len;
@@ -407,6 +446,7 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t
 	const struct xdp_desc *rx_desc;
 	struct pollfd fds[rxq + 1];
 	__u64 comp_addr;
+	__u64 deadline;
 	__u64 addr;
 	__u32 idx = 0;
 	int ret;
@@ -477,9 +517,15 @@ static int verify_metadata(struct xsk *rx_xsk, int rxq, int server_fd, clockid_t
 					if (ret)
 						printf("kick_tx ret=%d\n", ret);
 
-					for (int j = 0; j < 500; j++) {
+					/* wait 1 second + cover launch time */
+					deadline = gettime(clock_id) +
+						   NANOSEC_PER_SEC +
+						   launch_time_delta_to_hw_rx_timestamp;
+					while (true) {
 						if (complete_tx(xsk, clock_id))
 							break;
+						if (gettime(clock_id) >= deadline)
+							break;
 						usleep(10);
 					}
 				}
@@ -608,6 +654,10 @@ static void print_usage(void)
 		"  -h    Display this help and exit\n\n"
 		"  -m    Enable multi-buffer XDP for larger MTU\n"
 		"  -r    Don't generate AF_XDP reply (rx metadata only)\n"
+		"  -l    Delta of launch time relative to HW RX-time in ns\n"
+		"        default: 0 ns (launch time request is disabled)\n"
+		"  -L    Tx Queue to be enabled with launch time offload\n"
+		"        default: 0 (Tx Queue 0)\n"
 		"Generate test packets on the other machine with:\n"
 		"  echo -n xdp | nc -u -q1 <dst_ip> 9091\n";
 
@@ -618,7 +668,7 @@ static void read_args(int argc, char *argv[])
 {
 	int opt;
 
-	while ((opt = getopt(argc, argv, "chmr")) != -1) {
+	while ((opt = getopt(argc, argv, "chmrl:L:")) != -1) {
 		switch (opt) {
 		case 'c':
 			bind_flags &= ~XDP_USE_NEED_WAKEUP;
@@ -634,6 +684,12 @@ static void read_args(int argc, char *argv[])
 		case 'r':
 			skip_tx = true;
 			break;
+		case 'l':
+			launch_time_delta_to_hw_rx_timestamp = atoll(optarg);
+			break;
+		case 'L':
+			launch_time_queue = atoll(optarg);
+			break;
 		case '?':
 			if (isprint(optopt))
 				fprintf(stderr, "Unknown option: -%c\n", optopt);
@@ -657,6 +713,23 @@ static void read_args(int argc, char *argv[])
 		error(-1, errno, "Invalid interface name");
 }
 
+void clean_existing_configurations(void)
+{
+	/* Check and delete root qdisc if exists */
+	if (run_command("sudo tc qdisc show dev %s | grep -q 'qdisc mqprio 8001:'", ifname) == 0)
+		run_command("sudo tc qdisc del dev %s root", ifname);
+
+	/* Check and delete ingress qdisc if exists */
+	if (run_command("sudo tc qdisc show dev %s | grep -q 'qdisc ingress ffff:'", ifname) == 0)
+		run_command("sudo tc qdisc del dev %s ingress", ifname);
+
+	/* Check and delete ethtool filters if any exist */
+	if (run_command("sudo ethtool -n %s | grep -q 'Filter:'", ifname) == 0) {
+		run_command("sudo ethtool -n %s | grep 'Filter:' | awk '{print $2}' | xargs -n1 sudo ethtool -N %s delete >&2",
+			    ifname, ifname);
+	}
+}
+
 int main(int argc, char *argv[])
 {
 	clockid_t clock_id = CLOCK_TAI;
@@ -672,8 +745,50 @@ int main(int argc, char *argv[])
 
 	printf("rxq: %d\n", rxq);
 
+	if (launch_time_queue >= rxq || launch_time_queue < 0)
+		error(1, 0, "Invalid launch_time_queue.\n");
+
+	clean_existing_configurations();
+	sleep(1);
+
+	/* Enable tx and rx hardware timestamping */
 	hwtstamp_enable(ifname);
 
+	/* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
+	char map[256] = {0};
+	char queues[256] = {0};
+
+	for (i = 0; i < rxq; i++) {
+		char buf[8];
+
+		snprintf(buf, sizeof(buf), "%d ", i);
+		strcat(map, buf);
+
+		snprintf(buf, sizeof(buf), "1@%d ", i);
+		strcat(queues, buf);
+	}
+	run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio num_tc %d map %s queues %s hw 0",
+		    ifname, rxq, map, queues);
+
+	/* To test launch time, send UDP packet with VLAN priority 1 to port 9091 */
+	if (launch_time_delta_to_hw_rx_timestamp) {
+		/* Enable launch time hardware offload on launch_time_queue */
+		run_command("sudo tc qdisc replace dev %s parent 8001:%d etf offload clockid CLOCK_TAI delta 500000",
+			    ifname, launch_time_queue + 1);
+		sleep(1);
+
+		/* Route incoming packet with VLAN priority 1 into launch_time_queue */
+		if (run_command("sudo ethtool -N %s flow-type ether vlan 0x2000 vlan-mask 0x1FFF action %d",
+				ifname, launch_time_queue)) {
+			run_command("sudo tc qdisc add dev %s ingress", ifname);
+			run_command("sudo tc filter add dev %s parent ffff: protocol 802.1Q flower vlan_prio 1 hw_tc %d",
+				    ifname, launch_time_queue);
+		}
+
+		/* Enable VLAN tag stripping offload */
+		run_command("sudo ethtool -K %s rxvlan on", ifname);
+	}
+
 	rx_xsk = malloc(sizeof(struct xsk) * rxq);
 	if (!rx_xsk)
 		error(1, ENOMEM, "malloc");
@@ -733,4 +848,6 @@ int main(int argc, char *argv[])
 	cleanup();
 	if (ret)
 		error(1, -ret, "verify_metadata");
+
+	clean_existing_configurations();
 }
-- 
2.34.1

[xdp-hints] [PATCH bpf-next v5 3/4] net: stmmac: Add launch time support to XDP ZC

[Song Yoong Siang]

Enable launch time (Time-Based Scheduling) support to XDP zero copy via XDP
Tx metadata framework.

This patch is tested with tools/testing/selftests/bpf/xdp_hw_metadata on
Intel Tiger Lake platform. Below are the test steps and result.

Test Steps:
1. At DUT, start xdp_hw_metadata selftest application:
   $ sudo ./xdp_hw_metadata enp0s30f4 -l 1000000000 -L 1

2. At Link Partner, send an UDP packet with VLAN priority 1 to port 9091 of
   DUT.

When launch time is set to 1s in the future, the delta between launch time
and transmit hardware timestamp is equal to 16.963us, as shown in result
below:
  0x55b5864717a8: rx_desc[4]->addr=88100 addr=88100 comp_addr=88100 EoP
  No rx_hash, err=-95
  HW RX-time:   1734579065767717328 (sec:1734579065.7677) delta to User RX-time sec:0.0004 (375.624 usec)
  XDP RX-time:   1734579065768004454 (sec:1734579065.7680) delta to User RX-time sec:0.0001 (88.498 usec)
  No rx_vlan_tci or rx_vlan_proto, err=-95
  0x55b5864717a8: ping-pong with csum=5619 (want 0000) csum_start=34 csum_offset=6
  HW RX-time:   1734579065767717328 (sec:1734579065.7677) delta to HW Launch-time sec:1.0000 (1000000.000 usec)
  0x55b5864717a8: complete tx idx=4 addr=4018
  HW Launch-time:   1734579066767717328 (sec:1734579066.7677) delta to HW TX-complete-time sec:0.0000 (16.963 usec)
  HW TX-complete-time:   1734579066767734291 (sec:1734579066.7677) delta to User TX-complete-time sec:0.0001 (130.408 usec)
  XDP RX-time:   1734579065768004454 (sec:1734579065.7680) delta to User TX-complete-time sec:0.9999 (999860.245 usec)
  HW RX-time:   1734579065767717328 (sec:1734579065.7677) delta to HW TX-complete-time sec:1.0000 (1000016.963 usec)
  0x55b5864717a8: complete rx idx=132 addr=88100

Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
---
 drivers/net/ethernet/stmicro/stmmac/stmmac.h      |  2 ++
 drivers/net/ethernet/stmicro/stmmac/stmmac_main.c | 13 +++++++++++++
 2 files changed, 15 insertions(+)

diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac.h b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
index b8d631e559c0..11f7b539c4b5 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac.h
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac.h
@@ -106,6 +106,8 @@ struct stmmac_metadata_request {
 	struct stmmac_priv *priv;
 	struct dma_desc *tx_desc;
 	bool *set_ic;
+	struct dma_edesc *edesc;
+	int tbs;
 };
 
 struct stmmac_xsk_tx_complete {
diff --git a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
index 70c8f60d34f2..1c08e913f526 100644
--- a/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
+++ b/drivers/net/ethernet/stmicro/stmmac/stmmac_main.c
@@ -2453,9 +2453,20 @@ static u64 stmmac_xsk_fill_timestamp(void *_priv)
 	return 0;
 }
 
+static void stmmac_xsk_request_launch_time(u64 launch_time, void *_priv)
+{
+	struct stmmac_metadata_request *meta_req = _priv;
+	struct timespec64 ts = ns_to_timespec64(launch_time);
+
+	if (meta_req->tbs & STMMAC_TBS_EN)
+		stmmac_set_desc_tbs(meta_req->priv, meta_req->edesc, ts.tv_sec,
+				    ts.tv_nsec);
+}
+
 static const struct xsk_tx_metadata_ops stmmac_xsk_tx_metadata_ops = {
 	.tmo_request_timestamp		= stmmac_xsk_request_timestamp,
 	.tmo_fill_timestamp		= stmmac_xsk_fill_timestamp,
+	.tmo_request_launch_time	= stmmac_xsk_request_launch_time,
 };
 
 static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
@@ -2539,6 +2550,8 @@ static bool stmmac_xdp_xmit_zc(struct stmmac_priv *priv, u32 queue, u32 budget)
 		meta_req.priv = priv;
 		meta_req.tx_desc = tx_desc;
 		meta_req.set_ic = &set_ic;
+		meta_req.tbs = tx_q->tbs;
+		meta_req.edesc = &tx_q->dma_entx[entry];
 		xsk_tx_metadata_request(meta, &stmmac_xsk_tx_metadata_ops,
 					&meta_req);
 		if (set_ic) {
-- 
2.34.1

[xdp-hints] [PATCH bpf-next v5 4/4] igc: Add launch time support to XDP ZC

[Song Yoong Siang]

Enable Launch Time Control (LTC) support to XDP zero copy via XDP Tx
metadata framework.

This patch is tested with tools/testing/selftests/bpf/xdp_hw_metadata on
Intel I225-LM Ethernet controller. Below are the test steps and result.

Test Steps:
1. At DUT, start xdp_hw_metadata selftest application:
   $ sudo ./xdp_hw_metadata enp2s0 -l 1000000000 -L 1

2. At Link Partner, send an UDP packet with VLAN priority 1 to port 9091 of
   DUT.

When launch time is set to 1s in the future, the delta between launch time
and transmit hardware timestamp is equal to 0.016us, as shown in result
below:
  0x562ff5dc8880: rx_desc[4]->addr=84110 addr=84110 comp_addr=84110 EoP
  rx_hash: 0xE343384 with RSS type:0x1
  HW RX-time:   1734578015467548904 (sec:1734578015.4675) delta to User RX-time sec:0.0002 (183.103 usec)
  XDP RX-time:   1734578015467651698 (sec:1734578015.4677) delta to User RX-time sec:0.0001 (80.309 usec)
  No rx_vlan_tci or rx_vlan_proto, err=-95
  0x562ff5dc8880: ping-pong with csum=561c (want c7dd) csum_start=34 csum_offset=6
  HW RX-time:   1734578015467548904 (sec:1734578015.4675) delta to HW Launch-time sec:1.0000 (1000000.000 usec)
  0x562ff5dc8880: complete tx idx=4 addr=4018
  HW Launch-time:   1734578016467548904 (sec:1734578016.4675) delta to HW TX-complete-time sec:0.0000 (0.016 usec)
  HW TX-complete-time:   1734578016467548920 (sec:1734578016.4675) delta to User TX-complete-time sec:0.0000 (32.546 usec)
  XDP RX-time:   1734578015467651698 (sec:1734578015.4677) delta to User TX-complete-time sec:0.9999 (999929.768 usec)
  HW RX-time:   1734578015467548904 (sec:1734578015.4675) delta to HW TX-complete-time sec:1.0000 (1000000.016 usec)
  0x562ff5dc8880: complete rx idx=132 addr=84110

Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>
---
 drivers/net/ethernet/intel/igc/igc_main.c | 78 ++++++++++++++++-------
 1 file changed, 56 insertions(+), 22 deletions(-)

diff --git a/drivers/net/ethernet/intel/igc/igc_main.c b/drivers/net/ethernet/intel/igc/igc_main.c
index 56a35d58e7a6..3c7015cb5cb5 100644
--- a/drivers/net/ethernet/intel/igc/igc_main.c
+++ b/drivers/net/ethernet/intel/igc/igc_main.c
@@ -1566,6 +1566,26 @@ static bool igc_request_tx_tstamp(struct igc_adapter *adapter, struct sk_buff *s
 	return false;
 }
 
+static void igc_insert_empty_packet(struct igc_ring *tx_ring)
+{
+	struct igc_tx_buffer *empty_info;
+	struct sk_buff *empty;
+	void *data;
+
+	empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
+	empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
+	if (!empty)
+		return;
+
+	data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
+	memset(data, 0, IGC_EMPTY_FRAME_SIZE);
+
+	igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
+
+	if (igc_init_tx_empty_descriptor(tx_ring, empty, empty_info) < 0)
+		dev_kfree_skb_any(empty);
+}
+
 static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
 				       struct igc_ring *tx_ring)
 {
@@ -1603,26 +1623,8 @@ static netdev_tx_t igc_xmit_frame_ring(struct sk_buff *skb,
 	skb->tstamp = ktime_set(0, 0);
 	launch_time = igc_tx_launchtime(tx_ring, txtime, &first_flag, &insert_empty);
 
-	if (insert_empty) {
-		struct igc_tx_buffer *empty_info;
-		struct sk_buff *empty;
-		void *data;
-
-		empty_info = &tx_ring->tx_buffer_info[tx_ring->next_to_use];
-		empty = alloc_skb(IGC_EMPTY_FRAME_SIZE, GFP_ATOMIC);
-		if (!empty)
-			goto done;
-
-		data = skb_put(empty, IGC_EMPTY_FRAME_SIZE);
-		memset(data, 0, IGC_EMPTY_FRAME_SIZE);
-
-		igc_tx_ctxtdesc(tx_ring, 0, false, 0, 0, 0);
-
-		if (igc_init_tx_empty_descriptor(tx_ring,
-						 empty,
-						 empty_info) < 0)
-			dev_kfree_skb_any(empty);
-	}
+	if (insert_empty)
+		igc_insert_empty_packet(tx_ring);
 
 done:
 	/* record the location of the first descriptor for this packet */
@@ -2949,9 +2951,33 @@ static u64 igc_xsk_fill_timestamp(void *_priv)
 	return *(u64 *)_priv;
 }
 
+static void igc_xsk_request_launch_time(u64 launch_time, void *_priv)
+{
+	struct igc_metadata_request *meta_req = _priv;
+	struct igc_ring *tx_ring = meta_req->tx_ring;
+	__le32 launch_time_offset;
+	bool insert_empty = false;
+	bool first_flag = false;
+
+	if (!tx_ring->launchtime_enable)
+		return;
+
+	launch_time_offset = igc_tx_launchtime(tx_ring,
+					       ns_to_ktime(launch_time),
+					       &first_flag, &insert_empty);
+	if (insert_empty) {
+		igc_insert_empty_packet(tx_ring);
+		meta_req->tx_buffer =
+			&tx_ring->tx_buffer_info[tx_ring->next_to_use];
+	}
+
+	igc_tx_ctxtdesc(tx_ring, launch_time_offset, first_flag, 0, 0, 0);
+}
+
 const struct xsk_tx_metadata_ops igc_xsk_tx_metadata_ops = {
 	.tmo_request_timestamp		= igc_xsk_request_timestamp,
 	.tmo_fill_timestamp		= igc_xsk_fill_timestamp,
+	.tmo_request_launch_time	= igc_xsk_request_launch_time,
 };
 
 static void igc_xdp_xmit_zc(struct igc_ring *ring)
@@ -2974,7 +3000,7 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
 	ntu = ring->next_to_use;
 	budget = igc_desc_unused(ring);
 
-	while (xsk_tx_peek_desc(pool, &xdp_desc) && budget--) {
+	while (xsk_tx_peek_desc(pool, &xdp_desc) && budget >= 4) {
 		struct igc_metadata_request meta_req;
 		struct xsk_tx_metadata *meta = NULL;
 		struct igc_tx_buffer *bi;
@@ -2998,6 +3024,12 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
 		xsk_tx_metadata_request(meta, &igc_xsk_tx_metadata_ops,
 					&meta_req);
 
+		/* xsk_tx_metadata_request() may have updated next_to_use */
+		ntu = ring->next_to_use;
+
+		/* xsk_tx_metadata_request() may have updated Tx buffer info */
+		bi = meta_req.tx_buffer;
+
 		tx_desc = IGC_TX_DESC(ring, ntu);
 		tx_desc->read.cmd_type_len = cpu_to_le32(meta_req.cmd_type);
 		tx_desc->read.olinfo_status = cpu_to_le32(olinfo_status);
@@ -3015,9 +3047,11 @@ static void igc_xdp_xmit_zc(struct igc_ring *ring)
 		ntu++;
 		if (ntu == ring->count)
 			ntu = 0;
+
+		ring->next_to_use = ntu;
+		budget = igc_desc_unused(ring);
 	}
 
-	ring->next_to_use = ntu;
 	if (tx_desc) {
 		igc_flush_tx_descriptors(ring);
 		xsk_tx_release(pool);
-- 
2.34.1

[xdp-hints] Re: [PATCH bpf-next v5 2/4] selftests/bpf: Add launch time request to xdp_hw_metadata

[Daniel Borkmann]

On 1/14/25 4:27 PM, Song Yoong Siang wrote:
[...]
> +	/* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
> +	char map[256] = {0};
> +	char queues[256] = {0};
> +
> +	for (i = 0; i < rxq; i++) {
> +		char buf[8];
> +
> +		snprintf(buf, sizeof(buf), "%d ", i);
> +		strcat(map, buf);
> +
> +		snprintf(buf, sizeof(buf), "1@%d ", i);
> +		strcat(queues, buf);
> +	}
> +	run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio num_tc %d map %s queues %s hw 0",
> +		    ifname, rxq, map, queues);

Fyi, above triggers selftest build errors:

   xdp_hw_metadata.c: In function ‘main’:
   xdp_hw_metadata.c:763:45: error: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size 8 [-Werror=format-truncation=]
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                                             ^~
     TEST-OBJ [test_progs] arg_parsing.test.o
   xdp_hw_metadata.c:763:44: note: directive argument in the range [0, 2147483646]
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                                            ^~~~~
   xdp_hw_metadata.c:763:17: note: ‘snprintf’ output between 3 and 12 bytes into a destination of size 8
     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
   xdp_hw_metadata.c:766:47: error: ‘%d’ directive output may be truncated writing between 1 and 10 bytes into a region of size 6 [-Werror=format-truncation=]
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                                               ^~
   xdp_hw_metadata.c:766:44: note: directive argument in the range [0, 2147483646]
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                                            ^~~~~~~
   xdp_hw_metadata.c:766:17: note: ‘snprintf’ output between 5 and 14 bytes into a destination of size 8
     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

[xdp-hints] Re: [PATCH bpf-next v5 2/4] selftests/bpf: Add launch time request to xdp_hw_metadata

[Song, Yoong Siang]

On Wednesday, January 15, 2025 10:57 PM, Daniel Borkmann <daniel@iogearbox.net> wrote:
>On 1/14/25 4:27 PM, Song Yoong Siang wrote:
>[...]
>> +	/* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
>> +	char map[256] = {0};
>> +	char queues[256] = {0};
>> +
>> +	for (i = 0; i < rxq; i++) {
>> +		char buf[8];
>> +
>> +		snprintf(buf, sizeof(buf), "%d ", i);
>> +		strcat(map, buf);
>> +
>> +		snprintf(buf, sizeof(buf), "1@%d ", i);
>> +		strcat(queues, buf);
>> +	}
>> +	run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio
>num_tc %d map %s queues %s hw 0",
>> +		    ifname, rxq, map, queues);
>
>Fyi, above triggers selftest build errors:
>
>   xdp_hw_metadata.c: In function ‘main’:
>   xdp_hw_metadata.c:763:45: error: ‘%d’ directive output may be truncated
>writing between 1 and 10 bytes into a region of size 8 [-Werror=format-
>truncation=]
>     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
>         |                                             ^~
>     TEST-OBJ [test_progs] arg_parsing.test.o
>   xdp_hw_metadata.c:763:44: note: directive argument in the range [0,
>2147483646]
>     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
>         |                                            ^~~~~
>   xdp_hw_metadata.c:763:17: note: ‘snprintf’ output between 3 and 12 bytes into
>a destination of size 8
>     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
>         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>   xdp_hw_metadata.c:766:47: error: ‘%d’ directive output may be truncated
>writing between 1 and 10 bytes into a region of size 6 [-Werror=format-
>truncation=]
>     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
>         |                                               ^~
>   xdp_hw_metadata.c:766:44: note: directive argument in the range [0,
>2147483646]
>     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
>         |                                            ^~~~~~~
>   xdp_hw_metadata.c:766:17: note: ‘snprintf’ output between 5 and 14 bytes into
>a destination of size 8
>     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
>         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

Thanks for pointing this out.
Btw, do you know which build command will trigger these errors?
I am using "make -C tools/testing/selftests/bpf" but cannot
reproduce the build error.

Thanks & Regards
Siang

[xdp-hints] Re: [PATCH bpf-next v5 1/4] xsk: Add launch time hardware offload support to XDP Tx metadata

[Stanislav Fomichev]

On 01/14, Song Yoong Siang wrote:
> Extend the XDP Tx metadata framework so that user can requests launch time
> hardware offload, where the Ethernet device will schedule the packet for
> transmission at a pre-determined time called launch time. The value of
> launch time is communicated from user space to Ethernet driver via
> launch_time field of struct xsk_tx_metadata.
> 
> Suggested-by: Stanislav Fomichev <sdf@fomichev.me>
> Signed-off-by: Song Yoong Siang <yoong.siang.song@intel.com>

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

[xdp-hints] Re: [PATCH bpf-next v5 2/4] selftests/bpf: Add launch time request to xdp_hw_metadata

[Stanislav Fomichev]

On 01/15, Song, Yoong Siang wrote:
> On Wednesday, January 15, 2025 10:57 PM, Daniel Borkmann <daniel@iogearbox.net> wrote:
> >On 1/14/25 4:27 PM, Song Yoong Siang wrote:
> >[...]
> >> +	/* Add mqprio qdisc with TC and hardware queue one-to-one mapping */
> >> +	char map[256] = {0};
> >> +	char queues[256] = {0};
> >> +
> >> +	for (i = 0; i < rxq; i++) {
> >> +		char buf[8];
> >> +
> >> +		snprintf(buf, sizeof(buf), "%d ", i);
> >> +		strcat(map, buf);
> >> +
> >> +		snprintf(buf, sizeof(buf), "1@%d ", i);
> >> +		strcat(queues, buf);
> >> +	}
> >> +	run_command("sudo tc qdisc add dev %s handle 8001: parent root mqprio
> >num_tc %d map %s queues %s hw 0",
> >> +		    ifname, rxq, map, queues);
> >
> >Fyi, above triggers selftest build errors:
> >
> >   xdp_hw_metadata.c: In function ‘main’:
> >   xdp_hw_metadata.c:763:45: error: ‘%d’ directive output may be truncated
> >writing between 1 and 10 bytes into a region of size 8 [-Werror=format-
> >truncation=]
> >     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
> >         |                                             ^~
> >     TEST-OBJ [test_progs] arg_parsing.test.o
> >   xdp_hw_metadata.c:763:44: note: directive argument in the range [0,
> >2147483646]
> >     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
> >         |                                            ^~~~~
> >   xdp_hw_metadata.c:763:17: note: ‘snprintf’ output between 3 and 12 bytes into
> >a destination of size 8
> >     763 |                 snprintf(buf, sizeof(buf), "%d ", i);
> >         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >   xdp_hw_metadata.c:766:47: error: ‘%d’ directive output may be truncated
> >writing between 1 and 10 bytes into a region of size 6 [-Werror=format-
> >truncation=]
> >     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
> >         |                                               ^~
> >   xdp_hw_metadata.c:766:44: note: directive argument in the range [0,
> >2147483646]
> >     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
> >         |                                            ^~~~~~~
> >   xdp_hw_metadata.c:766:17: note: ‘snprintf’ output between 5 and 14 bytes into
> >a destination of size 8
> >     766 |                 snprintf(buf, sizeof(buf), "1@%d ", i);
> >         |                 ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> 
> Thanks for pointing this out.
> Btw, do you know which build command will trigger these errors?
> I am using "make -C tools/testing/selftests/bpf" but cannot
> reproduce the build error.
> 
> Thanks & Regards
> Siang

Last time I used the following to reproduce similar issues on my side:

make -C tools/testing/selftests TARGETS="bpf" LLVM=1 USERCFLAGS="-Wformat-truncation"

You can also try to use something like asprintf instead of managing the buffer
sizes manually.