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Date:   Mon, 13 Jul 2020 09:17:48 -0700
From:   Yonghong Song <yhs@...com>
To:     <bpf@...r.kernel.org>, <netdev@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>, <kernel-team@...com>,
        Martin KaFai Lau <kafai@...com>
Subject: [PATCH bpf-next 08/13] tools/libbpf: add support for bpf map element iterator

Add map_fd to bpf_iter_attach_opts and flags to
bpf_link_create_opts. Later on, bpftool or selftest
will be able to create a bpf map element iterator
by passing map_fd to the kernel during link
creation time.

Signed-off-by: Yonghong Song <yhs@...com>
---
 tools/lib/bpf/bpf.c    |  1 +
 tools/lib/bpf/bpf.h    |  3 ++-
 tools/lib/bpf/libbpf.c | 10 +++++++++-
 tools/lib/bpf/libbpf.h |  3 ++-
 4 files changed, 14 insertions(+), 3 deletions(-)

diff --git a/tools/lib/bpf/bpf.c b/tools/lib/bpf/bpf.c
index a7329b671c41..e1bdf214f75f 100644
--- a/tools/lib/bpf/bpf.c
+++ b/tools/lib/bpf/bpf.c
@@ -598,6 +598,7 @@ int bpf_link_create(int prog_fd, int target_fd,
 	attr.link_create.prog_fd = prog_fd;
 	attr.link_create.target_fd = target_fd;
 	attr.link_create.attach_type = attach_type;
+	attr.link_create.flags = OPTS_GET(opts, flags, 0);
 
 	return sys_bpf(BPF_LINK_CREATE, &attr, sizeof(attr));
 }
diff --git a/tools/lib/bpf/bpf.h b/tools/lib/bpf/bpf.h
index 1b6015b21ba8..329a8db5526b 100644
--- a/tools/lib/bpf/bpf.h
+++ b/tools/lib/bpf/bpf.h
@@ -170,8 +170,9 @@ LIBBPF_API int bpf_prog_detach2(int prog_fd, int attachable_fd,
 
 struct bpf_link_create_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
+	__u32 flags;
 };
-#define bpf_link_create_opts__last_field sz
+#define bpf_link_create_opts__last_field flags
 
 LIBBPF_API int bpf_link_create(int prog_fd, int target_fd,
 			       enum bpf_attach_type attach_type,
diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 25e4f77be8d7..35ed8fbe6502 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -8271,13 +8271,20 @@ struct bpf_link *
 bpf_program__attach_iter(struct bpf_program *prog,
 			 const struct bpf_iter_attach_opts *opts)
 {
+	DECLARE_LIBBPF_OPTS(bpf_link_create_opts, link_create_opts);
 	char errmsg[STRERR_BUFSIZE];
 	struct bpf_link *link;
 	int prog_fd, link_fd;
+	__u32 target_fd = 0;
 
 	if (!OPTS_VALID(opts, bpf_iter_attach_opts))
 		return ERR_PTR(-EINVAL);
 
+	if (OPTS_HAS(opts, map_fd)) {
+		target_fd = opts->map_fd;
+		link_create_opts.flags = BPF_ITER_LINK_MAP_FD;
+	}
+
 	prog_fd = bpf_program__fd(prog);
 	if (prog_fd < 0) {
 		pr_warn("program '%s': can't attach before loaded\n",
@@ -8290,7 +8297,8 @@ bpf_program__attach_iter(struct bpf_program *prog,
 		return ERR_PTR(-ENOMEM);
 	link->detach = &bpf_link__detach_fd;
 
-	link_fd = bpf_link_create(prog_fd, 0, BPF_TRACE_ITER, NULL);
+	link_fd = bpf_link_create(prog_fd, target_fd, BPF_TRACE_ITER,
+				  &link_create_opts);
 	if (link_fd < 0) {
 		link_fd = -errno;
 		free(link);
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 2335971ed0bd..9b883fa7724a 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -264,8 +264,9 @@ LIBBPF_API struct bpf_link *bpf_map__attach_struct_ops(struct bpf_map *map);
 
 struct bpf_iter_attach_opts {
 	size_t sz; /* size of this struct for forward/backward compatibility */
+	__u32 map_fd;
 };
-#define bpf_iter_attach_opts__last_field sz
+#define bpf_iter_attach_opts__last_field map_fd
 
 LIBBPF_API struct bpf_link *
 bpf_program__attach_iter(struct bpf_program *prog,
-- 
2.24.1

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