netdev - [PATCH bpf-next v2 1/8] libbpf: Add a helper for retrieving a map fd for a given name

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Date:   Mon, 21 Jan 2019 10:10:34 +0100
From:   Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
To:     daniel@...earbox.net, ast@...nel.org
Cc:     netdev@...r.kernel.org, jakub.kicinski@...ronome.com,
        brouer@...hat.com
Subject: [PATCH bpf-next v2 1/8] libbpf: Add a helper for retrieving a map fd for a given name

XDP samples are mostly cooperating with eBPF maps through their file
descriptors. In case of a eBPF program that contains multiple maps it
might be tiresome to iterate through them and call bpf_map__fd for each
one. Add a helper mostly based on bpf_object__find_map_by_name, but
instead of returning the struct bpf_map pointer, return map fd.

Bump libbpf ABI version to 0.0.2.

Suggested-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
Signed-off-by: Maciej Fijalkowski <maciejromanfijalkowski@...il.com>
Reviewed-by: Jakub Kicinski <jakub.kicinski@...ronome.com>
---
 tools/lib/bpf/libbpf.c   | 12 ++++++++++++
 tools/lib/bpf/libbpf.h   |  3 +++
 tools/lib/bpf/libbpf.map |  4 ++++
 3 files changed, 19 insertions(+)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 169e347c76f6..dc838bea403f 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -2840,6 +2840,18 @@ bpf_object__find_map_by_name(struct bpf_object *obj, const char *name)
 	return NULL;
 }
 
+int
+bpf_object__find_map_fd_by_name(struct bpf_object *obj, const char *name)
+{
+	struct bpf_map *pos;
+
+	bpf_map__for_each(pos, obj) {
+		if (pos->name && !strcmp(pos->name, name))
+			return bpf_map__fd(pos);
+	}
+	return -ENOENT;
+}
+
 struct bpf_map *
 bpf_object__find_map_by_offset(struct bpf_object *obj, size_t offset)
 {
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 5f68d7b75215..7f10d36abdde 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -264,6 +264,9 @@ struct bpf_map;
 LIBBPF_API struct bpf_map *
 bpf_object__find_map_by_name(struct bpf_object *obj, const char *name);
 
+LIBBPF_API int
+bpf_object__find_map_fd_by_name(struct bpf_object *obj, const char *name);
+
 /*
  * Get bpf_map through the offset of corresponding struct bpf_map_def
  * in the BPF object file.
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index cd02cd4e2cc3..7c59e4f64082 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -124,3 +124,7 @@ LIBBPF_0.0.1 {
 	local:
 		*;
 };
+LIBBPF_0.0.2 {
+	global:
+		bpf_object__find_map_fd_by_name;
+} LIBBPF_0.0.1;
-- 
2.16.1