[PATCH bpf-next 6/8] libbpf: Add support for bpf_link-based netns attachment

[Jakub Sitnicki <jakub@cloudflare.com>]

Add bpf_program__attach_nets(), which uses LINK_CREATE subcommand to create
an FD-based kernel bpf_link, for attach types tied to network namespace,
that is BPF_FLOW_DISSECTOR for the moment.

Signed-off-by: Jakub Sitnicki <jakub@cloudflare.com>
---
 tools/lib/bpf/libbpf.c   | 20 ++++++++++++++++----
 tools/lib/bpf/libbpf.h   |  2 ++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 19 insertions(+), 4 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 5d60de6fd818..a49c1eb5db64 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7894,8 +7894,8 @@ static struct bpf_link *attach_iter(const struct bpf_sec_def *sec,
 	return bpf_program__attach_iter(prog, NULL);
 }
 
-struct bpf_link *
-bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
+static struct bpf_link *
+bpf_program__attach_fd(struct bpf_program *prog, int target_fd)
 {
 	enum bpf_attach_type attach_type;
 	char errmsg[STRERR_BUFSIZE];
@@ -7915,11 +7915,11 @@ bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
 	link->detach = &bpf_link__detach_fd;
 
 	attach_type = bpf_program__get_expected_attach_type(prog);
-	link_fd = bpf_link_create(prog_fd, cgroup_fd, attach_type, NULL);
+	link_fd = bpf_link_create(prog_fd, target_fd, attach_type, NULL);
 	if (link_fd < 0) {
 		link_fd = -errno;
 		free(link);
-		pr_warn("program '%s': failed to attach to cgroup: %s\n",
+		pr_warn("program '%s': failed to attach to cgroup/netns: %s\n",
 			bpf_program__title(prog, false),
 			libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
 		return ERR_PTR(link_fd);
@@ -7928,6 +7928,18 @@ bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
 	return link;
 }
 
+struct bpf_link *
+bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd)
+{
+	return bpf_program__attach_fd(prog, cgroup_fd);
+}
+
+struct bpf_link *
+bpf_program__attach_netns(struct bpf_program *prog, int netns_fd)
+{
+	return bpf_program__attach_fd(prog, netns_fd);
+}
+
 struct bpf_link *
 bpf_program__attach_iter(struct bpf_program *prog,
 			 const struct bpf_iter_attach_opts *opts)
diff --git a/tools/lib/bpf/libbpf.h b/tools/lib/bpf/libbpf.h
index 1e2e399a5f2c..adf6fd9b6fe8 100644
--- a/tools/lib/bpf/libbpf.h
+++ b/tools/lib/bpf/libbpf.h
@@ -253,6 +253,8 @@ LIBBPF_API struct bpf_link *
 bpf_program__attach_lsm(struct bpf_program *prog);
 LIBBPF_API struct bpf_link *
 bpf_program__attach_cgroup(struct bpf_program *prog, int cgroup_fd);
+LIBBPF_API struct bpf_link *
+bpf_program__attach_netns(struct bpf_program *prog, int netns_fd);
 
 struct bpf_map;
 
diff --git a/tools/lib/bpf/libbpf.map b/tools/lib/bpf/libbpf.map
index 381a7342ecfc..7ad21ba1feb6 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -263,4 +263,5 @@ LIBBPF_0.0.9 {
 		bpf_link_get_next_id;
 		bpf_program__attach_iter;
 		perf_buffer__consume;
+		bpf_program__attach_netns;
 } LIBBPF_0.0.8;
-- 
2.25.4