[PATCH v8 bpf-next 09/14] bpd: add multi-buffer support to xdp copy helpers

[Lorenzo Bianconi <lorenzo@kernel.org>]

From: Eelco Chaudron <echaudro@redhat.com>

This patch adds support for multi-buffer for the following helpers:
  - bpf_xdp_output()
  - bpf_perf_event_output()

Signed-off-by: Eelco Chaudron <echaudro@redhat.com>
Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
---
 net/core/filter.c                             |  63 ++++++++-
 .../selftests/bpf/prog_tests/xdp_bpf2bpf.c    | 127 ++++++++++++------
 .../selftests/bpf/progs/test_xdp_bpf2bpf.c    |   3 +-
 3 files changed, 149 insertions(+), 44 deletions(-)

diff --git a/net/core/filter.c b/net/core/filter.c
index c4eb1392f88e..c00f52ab2532 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4549,10 +4549,56 @@ static const struct bpf_func_proto bpf_sk_ancestor_cgroup_id_proto = {
 };
 #endif
 
-static unsigned long bpf_xdp_copy(void *dst_buff, const void *src_buff,
+static unsigned long bpf_xdp_copy(void *dst_buff, const void *ctx,
 				  unsigned long off, unsigned long len)
 {
-	memcpy(dst_buff, src_buff + off, len);
+	struct xdp_buff *xdp = (struct xdp_buff *)ctx;
+	struct xdp_shared_info *xdp_sinfo;
+	unsigned long base_len;
+
+	if (likely(!xdp->mb)) {
+		memcpy(dst_buff, xdp->data + off, len);
+		return 0;
+	}
+
+	base_len = xdp->data_end - xdp->data;
+	xdp_sinfo = xdp_get_shared_info_from_buff(xdp);
+	do {
+		const void *src_buff = NULL;
+		unsigned long copy_len = 0;
+
+		if (off < base_len) {
+			src_buff = xdp->data + off;
+			copy_len = min(len, base_len - off);
+		} else {
+			unsigned long frag_off_total = base_len;
+			int i;
+
+			for (i = 0; i < xdp_sinfo->nr_frags; i++) {
+				skb_frag_t *frag = &xdp_sinfo->frags[i];
+				unsigned long frag_len, frag_off;
+
+				frag_len = xdp_get_frag_size(frag);
+				frag_off = off - frag_off_total;
+				if (frag_off < frag_len) {
+					src_buff = xdp_get_frag_address(frag) +
+						   frag_off;
+					copy_len = min(len,
+						       frag_len - frag_off);
+					break;
+				}
+				frag_off_total += frag_len;
+			}
+		}
+		if (!src_buff)
+			break;
+
+		memcpy(dst_buff, src_buff, copy_len);
+		off += copy_len;
+		len -= copy_len;
+		dst_buff += copy_len;
+	} while (len);
+
 	return 0;
 }
 
@@ -4564,10 +4610,19 @@ BPF_CALL_5(bpf_xdp_event_output, struct xdp_buff *, xdp, struct bpf_map *, map,
 	if (unlikely(flags & ~(BPF_F_CTXLEN_MASK | BPF_F_INDEX_MASK)))
 		return -EINVAL;
 	if (unlikely(!xdp ||
-		     xdp_size > (unsigned long)(xdp->data_end - xdp->data)))
+		     (likely(!xdp->mb) &&
+		      xdp_size > (unsigned long)(xdp->data_end - xdp->data))))
 		return -EFAULT;
+	if (unlikely(xdp->mb)) {
+		struct xdp_shared_info *xdp_sinfo;
+
+		xdp_sinfo = xdp_get_shared_info_from_buff(xdp);
+		if (unlikely(xdp_size > ((int)(xdp->data_end - xdp->data) +
+					 xdp_sinfo->data_length)))
+			return -EFAULT;
+	}
 
-	return bpf_event_output(map, flags, meta, meta_size, xdp->data,
+	return bpf_event_output(map, flags, meta, meta_size, xdp,
 				xdp_size, bpf_xdp_copy);
 }
 
diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c b/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
index 2c6c570b21f8..355e64526f3f 100644
--- a/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/prog_tests/xdp_bpf2bpf.c
@@ -10,11 +10,20 @@ struct meta {
 	int pkt_len;
 };
 
+struct test_ctx_s {
+	bool passed;
+	int pkt_size;
+};
+
+struct test_ctx_s test_ctx;
+
 static void on_sample(void *ctx, int cpu, void *data, __u32 size)
 {
-	int duration = 0;
 	struct meta *meta = (struct meta *)data;
 	struct ipv4_packet *trace_pkt_v4 = data + sizeof(*meta);
+	unsigned char *raw_pkt = data + sizeof(*meta);
+	struct test_ctx_s *tst_ctx = ctx;
+	int duration = 0;
 
 	if (CHECK(size < sizeof(pkt_v4) + sizeof(*meta),
 		  "check_size", "size %u < %zu\n",
@@ -25,25 +34,90 @@ static void on_sample(void *ctx, int cpu, void *data, __u32 size)
 		  "meta->ifindex = %d\n", meta->ifindex))
 		return;
 
-	if (CHECK(meta->pkt_len != sizeof(pkt_v4), "check_meta_pkt_len",
-		  "meta->pkt_len = %zd\n", sizeof(pkt_v4)))
+	if (CHECK(meta->pkt_len != tst_ctx->pkt_size, "check_meta_pkt_len",
+		  "meta->pkt_len = %d\n", tst_ctx->pkt_size))
 		return;
 
 	if (CHECK(memcmp(trace_pkt_v4, &pkt_v4, sizeof(pkt_v4)),
 		  "check_packet_content", "content not the same\n"))
 		return;
 
-	*(bool *)ctx = true;
+	if (meta->pkt_len > sizeof(pkt_v4)) {
+		for (int i = 0; i < (meta->pkt_len - sizeof(pkt_v4)); i++) {
+			if (raw_pkt[i + sizeof(pkt_v4)] != (unsigned char)i) {
+				CHECK(true, "check_packet_content",
+				      "byte %zu does not match %u != %u\n",
+				      i + sizeof(pkt_v4),
+				      raw_pkt[i + sizeof(pkt_v4)],
+				      (unsigned char)i);
+				break;
+			}
+		}
+	}
+
+	tst_ctx->passed = true;
 }
 
-void test_xdp_bpf2bpf(void)
+static int run_xdp_bpf2bpf_pkt_size(int pkt_fd, struct perf_buffer *pb,
+				    struct test_xdp_bpf2bpf *ftrace_skel,
+				    int pkt_size)
 {
 	__u32 duration = 0, retval, size;
-	char buf[128];
+	unsigned char buf_in[9000];
+	unsigned char buf[9000];
+	int err;
+
+	if (pkt_size > sizeof(buf_in) || pkt_size < sizeof(pkt_v4))
+		return -EINVAL;
+
+	test_ctx.passed = false;
+	test_ctx.pkt_size = pkt_size;
+
+	memcpy(buf_in, &pkt_v4, sizeof(pkt_v4));
+	if (pkt_size > sizeof(pkt_v4)) {
+		for (int i = 0; i < (pkt_size - sizeof(pkt_v4)); i++)
+			buf_in[i + sizeof(pkt_v4)] = i;
+	}
+
+	/* Run test program */
+	err = bpf_prog_test_run(pkt_fd, 1, buf_in, pkt_size,
+				buf, &size, &retval, &duration);
+
+	if (CHECK(err || retval != XDP_PASS || size != pkt_size,
+		  "ipv4", "err %d errno %d retval %d size %d\n",
+		  err, errno, retval, size))
+		return -1;
+
+	/* Make sure bpf_xdp_output() was triggered and it sent the expected
+	 * data to the perf ring buffer.
+	 */
+	err = perf_buffer__poll(pb, 100);
+	if (CHECK(err <= 0, "perf_buffer__poll", "err %d\n", err))
+		return -1;
+
+	if (CHECK_FAIL(!test_ctx.passed))
+		return -1;
+
+	/* Verify test results */
+	if (CHECK(ftrace_skel->bss->test_result_fentry != if_nametoindex("lo"),
+		  "result", "fentry failed err %llu\n",
+		  ftrace_skel->bss->test_result_fentry))
+		return -1;
+
+	if (CHECK(ftrace_skel->bss->test_result_fexit != XDP_PASS, "result",
+		  "fexit failed err %llu\n",
+		  ftrace_skel->bss->test_result_fexit))
+		return -1;
+
+	return 0;
+}
+
+void test_xdp_bpf2bpf(void)
+{
 	int err, pkt_fd, map_fd;
-	bool passed = false;
-	struct iphdr *iph = (void *)buf + sizeof(struct ethhdr);
-	struct iptnl_info value4 = {.family = AF_INET};
+	__u32 duration = 0;
+	int pkt_sizes[] = {sizeof(pkt_v4), 1024, 4100, 8200};
+	struct iptnl_info value4 = {.family = AF_INET6};
 	struct test_xdp *pkt_skel = NULL;
 	struct test_xdp_bpf2bpf *ftrace_skel = NULL;
 	struct vip key4 = {.protocol = 6, .family = AF_INET};
@@ -87,40 +161,15 @@ void test_xdp_bpf2bpf(void)
 
 	/* Set up perf buffer */
 	pb_opts.sample_cb = on_sample;
-	pb_opts.ctx = &passed;
+	pb_opts.ctx = &test_ctx;
 	pb = perf_buffer__new(bpf_map__fd(ftrace_skel->maps.perf_buf_map),
-			      1, &pb_opts);
+			      8, &pb_opts);
 	if (CHECK(IS_ERR(pb), "perf_buf__new", "err %ld\n", PTR_ERR(pb)))
 		goto out;
 
-	/* Run test program */
-	err = bpf_prog_test_run(pkt_fd, 1, &pkt_v4, sizeof(pkt_v4),
-				buf, &size, &retval, &duration);
-
-	if (CHECK(err || retval != XDP_TX || size != 74 ||
-		  iph->protocol != IPPROTO_IPIP, "ipv4",
-		  "err %d errno %d retval %d size %d\n",
-		  err, errno, retval, size))
-		goto out;
-
-	/* Make sure bpf_xdp_output() was triggered and it sent the expected
-	 * data to the perf ring buffer.
-	 */
-	err = perf_buffer__poll(pb, 100);
-	if (CHECK(err < 0, "perf_buffer__poll", "err %d\n", err))
-		goto out;
-
-	CHECK_FAIL(!passed);
-
-	/* Verify test results */
-	if (CHECK(ftrace_skel->bss->test_result_fentry != if_nametoindex("lo"),
-		  "result", "fentry failed err %llu\n",
-		  ftrace_skel->bss->test_result_fentry))
-		goto out;
-
-	CHECK(ftrace_skel->bss->test_result_fexit != XDP_TX, "result",
-	      "fexit failed err %llu\n", ftrace_skel->bss->test_result_fexit);
-
+	for (int i = 0; i < ARRAY_SIZE(pkt_sizes); i++)
+		run_xdp_bpf2bpf_pkt_size(pkt_fd, pb, ftrace_skel,
+					 pkt_sizes[i]);
 out:
 	if (pb)
 		perf_buffer__free(pb);
diff --git a/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c b/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
index a038e827f850..d5a5f603d252 100644
--- a/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
+++ b/tools/testing/selftests/bpf/progs/test_xdp_bpf2bpf.c
@@ -27,6 +27,7 @@ struct xdp_buff {
 	void *data_hard_start;
 	unsigned long handle;
 	struct xdp_rxq_info *rxq;
+	__u32 frame_length;
 } __attribute__((preserve_access_index));
 
 struct meta {
@@ -49,7 +50,7 @@ int BPF_PROG(trace_on_entry, struct xdp_buff *xdp)
 	void *data = (void *)(long)xdp->data;
 
 	meta.ifindex = xdp->rxq->dev->ifindex;
-	meta.pkt_len = data_end - data;
+	meta.pkt_len = xdp->frame_length;
 	bpf_xdp_output(xdp, &perf_buf_map,
 		       ((__u64) meta.pkt_len << 32) |
 		       BPF_F_CURRENT_CPU,
-- 
2.30.2