[PATCH bpf-next v2 06/12] libbpf: Add support for bpf_link-based netns attachment

[Jakub Sitnicki]

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 <ja...@cloudflare.com>
---
 tools/lib/bpf/libbpf.c   | 23 ++++++++++++++++++-----
 tools/lib/bpf/libbpf.h   |  2 ++
 tools/lib/bpf/libbpf.map |  1 +
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index 74d967619dcf..b8af2f91b7c3 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -7894,8 +7894,9 @@ 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,
+                      const char *target_name)
 {
        enum bpf_attach_type attach_type;
        char errmsg[STRERR_BUFSIZE];
@@ -7915,12 +7916,12 @@ 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",
-                       bpf_program__title(prog, false),
+               pr_warn("program '%s': failed to attach to %s: %s\n",
+                       bpf_program__title(prog, false), target_name,
                        libbpf_strerror_r(link_fd, errmsg, sizeof(errmsg)));
                return ERR_PTR(link_fd);
        }
@@ -7928,6 +7929,18 @@ 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, "cgroup");
+}
+
+struct bpf_link *
+bpf_program__attach_netns(struct bpf_program *prog, int netns_fd)
+{
+       return bpf_program__attach_fd(prog, netns_fd, "netns");
+}
+
 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 8528a02d5af8..334437af3014 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 c18860200abb..f732c77b7ed0 100644
--- a/tools/lib/bpf/libbpf.map
+++ b/tools/lib/bpf/libbpf.map
@@ -262,6 +262,7 @@ LIBBPF_0.0.9 {
                bpf_link_get_fd_by_id;
                bpf_link_get_next_id;
                bpf_program__attach_iter;
+               bpf_program__attach_netns;
                perf_buffer__consume;
                ring_buffer__add;
                ring_buffer__consume;
-- 
2.25.4