shared, bpf: add bpf link serialization

core: serialize socket_bind bpf links

src/shared/bpf-link.c

@@ -1,6 +1,7 @@
 /* SPDX-License-Identifier: LGPL-2.1+ */
 
 #include "bpf-link.h"
+#include "serialize.h"
 
 bool can_link_bpf_program(struct bpf_program *prog) {
         _cleanup_(bpf_link_freep) struct bpf_link *link = NULL;
@@ -14,6 +15,21 @@ bool can_link_bpf_program(struct bpf_program *prog) {
         return libbpf_get_error(link) == -EBADF;
 }
 
+int serialize_bpf_link(FILE *f, FDSet *fds, const char *key, struct bpf_link *link) {
+        int fd;
+
+        assert(key);
+
+        if (!link)
+                return -ENOENT;
+
+        if (libbpf_get_error(link) != 0)
+                return -EINVAL;
+
+        fd = bpf_link__fd(link);
+        return serialize_fd(f, fds, key, fd);
+}
+
 struct bpf_link *bpf_link_free(struct bpf_link *link) {
         /* bpf_link__destroy handles link == NULL case */
         (void) bpf_link__destroy(link);

src/shared/bpf-link.h

@@ -3,10 +3,14 @@
 #pragma once
 
 #include <bpf/libbpf.h>
+#include <stdio.h>
 
+#include "fdset.h"
 #include "macro.h"
 
 bool can_link_bpf_program(struct bpf_program *prog);
 
+int serialize_bpf_link(FILE *f, FDSet *fds, const char *key, struct bpf_link *link);
+
 struct bpf_link *bpf_link_free(struct bpf_link *p);
 DEFINE_TRIVIAL_CLEANUP_FUNC(struct bpf_link *, bpf_link_free);