selftests/bpf: Test bpf_xdp_pull_data

Test bpf_xdp_pull_data() with xdp packets with different layouts. The
xdp bpf program first checks if the layout is as expected. Then, it
calls bpf_xdp_pull_data(). Finally, it checks the 0xbb marker at offset
1024 using directly packet access.

Signed-off-by: Amery Hung <ameryhung@gmail.com>
Signed-off-by: Martin KaFai Lau <martin.lau@kernel.org>
Link: https://patch.msgid.link/20250922233356.3356453-8-ameryhung@gmail.com

tools/testing/selftests/bpf/prog_tests/xdp_pull_data.c

@@ -0,0 +1,179 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include <test_progs.h>
+#include <network_helpers.h>
+#include "test_xdp_pull_data.skel.h"
+
+#define PULL_MAX	(1 << 31)
+#define PULL_PLUS_ONE	(1 << 30)
+
+#define XDP_PACKET_HEADROOM 256
+
+/* Find headroom and tailroom occupied by struct xdp_frame and struct
+ * skb_shared_info so that we can calculate the maximum pull lengths for
+ * test cases. They might not be the real size of the structures due to
+ * cache alignment.
+ */
+static int find_xdp_sizes(struct test_xdp_pull_data *skel, int frame_sz)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct xdp_md ctx = {};
+	int prog_fd, err;
+	__u8 *buf;
+
+	buf = calloc(frame_sz, sizeof(__u8));
+	if (!ASSERT_OK_PTR(buf, "calloc buf"))
+		return -ENOMEM;
+
+	topts.data_in = buf;
+	topts.data_out = buf;
+	topts.data_size_in = frame_sz;
+	topts.data_size_out = frame_sz;
+	/* Pass a data_end larger than the linear space available to make sure
+	 * bpf_prog_test_run_xdp() will fill the linear data area so that
+	 * xdp_find_sizes can infer the size of struct skb_shared_info
+	 */
+	ctx.data_end = frame_sz;
+	topts.ctx_in = &ctx;
+	topts.ctx_out = &ctx;
+	topts.ctx_size_in = sizeof(ctx);
+	topts.ctx_size_out = sizeof(ctx);
+
+	prog_fd = bpf_program__fd(skel->progs.xdp_find_sizes);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "bpf_prog_test_run_opts");
+
+	free(buf);
+
+	return err;
+}
+
+/* xdp_pull_data_prog will directly read a marker 0xbb stored at buf[1024]
+ * so caller expecting XDP_PASS should always pass pull_len no less than 1024
+ */
+static void run_test(struct test_xdp_pull_data *skel, int retval,
+		     int frame_sz, int buff_len, int meta_len, int data_len,
+		     int pull_len)
+{
+	LIBBPF_OPTS(bpf_test_run_opts, topts);
+	struct xdp_md ctx = {};
+	int prog_fd, err;
+	__u8 *buf;
+
+	buf = calloc(buff_len, sizeof(__u8));
+	if (!ASSERT_OK_PTR(buf, "calloc buf"))
+		return;
+
+	buf[meta_len + 1023] = 0xaa;
+	buf[meta_len + 1024] = 0xbb;
+	buf[meta_len + 1025] = 0xcc;
+
+	topts.data_in = buf;
+	topts.data_out = buf;
+	topts.data_size_in = buff_len;
+	topts.data_size_out = buff_len;
+	ctx.data = meta_len;
+	ctx.data_end = meta_len + data_len;
+	topts.ctx_in = &ctx;
+	topts.ctx_out = &ctx;
+	topts.ctx_size_in = sizeof(ctx);
+	topts.ctx_size_out = sizeof(ctx);
+
+	skel->bss->data_len = data_len;
+	if (pull_len & PULL_MAX) {
+		int headroom = XDP_PACKET_HEADROOM - meta_len - skel->bss->xdpf_sz;
+		int tailroom = frame_sz - XDP_PACKET_HEADROOM -
+			       data_len - skel->bss->sinfo_sz;
+
+		pull_len = pull_len & PULL_PLUS_ONE ? 1 : 0;
+		pull_len += headroom + tailroom + data_len;
+	}
+	skel->bss->pull_len = pull_len;
+
+	prog_fd = bpf_program__fd(skel->progs.xdp_pull_data_prog);
+	err = bpf_prog_test_run_opts(prog_fd, &topts);
+	ASSERT_OK(err, "bpf_prog_test_run_opts");
+	ASSERT_EQ(topts.retval, retval, "xdp_pull_data_prog retval");
+
+	if (retval == XDP_DROP)
+		goto out;
+
+	ASSERT_EQ(ctx.data_end, meta_len + pull_len, "linear data size");
+	ASSERT_EQ(topts.data_size_out, buff_len, "linear + non-linear data size");
+	/* Make sure data around xdp->data_end was not messed up by
+	 * bpf_xdp_pull_data()
+	 */
+	ASSERT_EQ(buf[meta_len + 1023], 0xaa, "data[1023]");
+	ASSERT_EQ(buf[meta_len + 1024], 0xbb, "data[1024]");
+	ASSERT_EQ(buf[meta_len + 1025], 0xcc, "data[1025]");
+out:
+	free(buf);
+}
+
+static void test_xdp_pull_data_basic(void)
+{
+	u32 pg_sz, max_meta_len, max_data_len;
+	struct test_xdp_pull_data *skel;
+
+	skel = test_xdp_pull_data__open_and_load();
+	if (!ASSERT_OK_PTR(skel, "test_xdp_pull_data__open_and_load"))
+		return;
+
+	pg_sz = sysconf(_SC_PAGE_SIZE);
+
+	if (find_xdp_sizes(skel, pg_sz))
+		goto out;
+
+	max_meta_len = XDP_PACKET_HEADROOM - skel->bss->xdpf_sz;
+	max_data_len = pg_sz - XDP_PACKET_HEADROOM - skel->bss->sinfo_sz;
+
+	/* linear xdp pkt, pull 0 byte */
+	run_test(skel, XDP_PASS, pg_sz, 2048, 0, 2048, 2048);
+
+	/* multi-buf pkt, pull results in linear xdp pkt */
+	run_test(skel, XDP_PASS, pg_sz, 2048, 0, 1024, 2048);
+
+	/* multi-buf pkt, pull 1 byte to linear data area */
+	run_test(skel, XDP_PASS, pg_sz, 9000, 0, 1024, 1025);
+
+	/* multi-buf pkt, pull 0 byte to linear data area */
+	run_test(skel, XDP_PASS, pg_sz, 9000, 0, 1025, 1025);
+
+	/* multi-buf pkt, empty linear data area, pull requires memmove */
+	run_test(skel, XDP_PASS, pg_sz, 9000, 0, 0, PULL_MAX);
+
+	/* multi-buf pkt, no headroom */
+	run_test(skel, XDP_PASS, pg_sz, 9000, max_meta_len, 1024, PULL_MAX);
+
+	/* multi-buf pkt, no tailroom, pull requires memmove */
+	run_test(skel, XDP_PASS, pg_sz, 9000, 0, max_data_len, PULL_MAX);
+
+	/* Test cases with invalid pull length */
+
+	/* linear xdp pkt, pull more than total data len */
+	run_test(skel, XDP_DROP, pg_sz, 2048, 0, 2048, 2049);
+
+	/* multi-buf pkt with no space left in linear data area */
+	run_test(skel, XDP_DROP, pg_sz, 9000, max_meta_len, max_data_len,
+		 PULL_MAX | PULL_PLUS_ONE);
+
+	/* multi-buf pkt, empty linear data area */
+	run_test(skel, XDP_DROP, pg_sz, 9000, 0, 0, PULL_MAX | PULL_PLUS_ONE);
+
+	/* multi-buf pkt, no headroom */
+	run_test(skel, XDP_DROP, pg_sz, 9000, max_meta_len, 1024,
+		 PULL_MAX | PULL_PLUS_ONE);
+
+	/* multi-buf pkt, no tailroom */
+	run_test(skel, XDP_DROP, pg_sz, 9000, 0, max_data_len,
+		 PULL_MAX | PULL_PLUS_ONE);
+
+out:
+	test_xdp_pull_data__destroy(skel);
+}
+
+void test_xdp_pull_data(void)
+{
+	if (test__start_subtest("xdp_pull_data"))
+		test_xdp_pull_data_basic();
+}

tools/testing/selftests/bpf/progs/test_xdp_pull_data.c

@@ -0,0 +1,48 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#include "vmlinux.h"
+#include <bpf/bpf_helpers.h>
+
+int xdpf_sz;
+int sinfo_sz;
+int data_len;
+int pull_len;
+
+#define XDP_PACKET_HEADROOM 256
+
+SEC("xdp.frags")
+int xdp_find_sizes(struct xdp_md *ctx)
+{
+	xdpf_sz = sizeof(struct xdp_frame);
+	sinfo_sz = __PAGE_SIZE - XDP_PACKET_HEADROOM -
+		   (ctx->data_end - ctx->data);
+
+	return XDP_PASS;
+}
+
+SEC("xdp.frags")
+int xdp_pull_data_prog(struct xdp_md *ctx)
+{
+	__u8 *data_end = (void *)(long)ctx->data_end;
+	__u8 *data = (void *)(long)ctx->data;
+	__u8 *val_p;
+	int err;
+
+	if (data_len != data_end - data)
+		return XDP_DROP;
+
+	err = bpf_xdp_pull_data(ctx, pull_len);
+	if (err)
+		return XDP_DROP;
+
+	val_p = (void *)(long)ctx->data + 1024;
+	if (val_p + 1 > (void *)(long)ctx->data_end)
+		return XDP_DROP;
+
+	if (*val_p != 0xbb)
+		return XDP_DROP;
+
+	return XDP_PASS;
+}
+
+char _license[] SEC("license") = "GPL";