tools: bpftool: allow reuse of maps with bpftool prog load

Add map parameter to prog load which will allow reuse of existing
maps instead of creating new ones.

We need feature detection and compat code for reallocarray, since
it's not available in many libc versions.

Signed-off-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Reviewed-by: Quentin Monnet <quentin.monnet@netronome.com>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

1 files changed, 135 insertions, 13 deletions

diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c
index 2bdd5ecd1aad..dce960d22106 100644
--- a/tools/bpf/bpftool/prog.c
+++ b/tools/bpf/bpftool/prog.c
@@ -31,6 +31,7 @@
  * SOFTWARE.
  */
 
+#define _GNU_SOURCE
 #include <errno.h>
 #include <fcntl.h>
 #include <stdarg.h>
@@ -682,18 +683,34 @@ static int do_pin(int argc, char **argv)
 	return err;
 }
 
+struct map_replace {
+	int idx;
+	int fd;
+	char *name;
+};
+
+int map_replace_compar(const void *p1, const void *p2)
+{
+	const struct map_replace *a = p1, *b = p2;
+
+	return a->idx - b->idx;
+}
+
 static int do_load(int argc, char **argv)
 {
 	enum bpf_attach_type expected_attach_type;
 	struct bpf_object_open_attr attr = {
 		.prog_type	= BPF_PROG_TYPE_UNSPEC,
 	};
+	struct map_replace *map_replace = NULL;
+	unsigned int old_map_fds = 0;
 	struct bpf_program *prog;
 	struct bpf_object *obj;
 	struct bpf_map *map;
 	const char *pinfile;
+	unsigned int i, j;
 	__u32 ifindex = 0;
-	int err;
+	int idx, err;
 
 	if (!REQ_ARGS(2))
 		return -1;
@@ -708,16 +725,16 @@ static int do_load(int argc, char **argv)
 
 			if (attr.prog_type != BPF_PROG_TYPE_UNSPEC) {
 				p_err("program type already specified");
-				return -1;
+				goto err_free_reuse_maps;
 			}
 			if (!REQ_ARGS(1))
-				return -1;
+				goto err_free_reuse_maps;
 
 			/* Put a '/' at the end of type to appease libbpf */
 			type = malloc(strlen(*argv) + 2);
 			if (!type) {
 				p_err("mem alloc failed");
-				return -1;
+				goto err_free_reuse_maps;
 			}
 			*type = 0;
 			strcat(type, *argv);
@@ -728,37 +745,81 @@ static int do_load(int argc, char **argv)
 			free(type);
 			if (err < 0) {
 				p_err("unknown program type '%s'", *argv);
-				return err;
+				goto err_free_reuse_maps;
 			}
 			NEXT_ARG();
+		} else if (is_prefix(*argv, "map")) {
+			char *endptr, *name;
+			int fd;
+
+			NEXT_ARG();
+
+			if (!REQ_ARGS(4))
+				goto err_free_reuse_maps;
+
+			if (is_prefix(*argv, "idx")) {
+				NEXT_ARG();
+
+				idx = strtoul(*argv, &endptr, 0);
+				if (*endptr) {
+					p_err("can't parse %s as IDX", *argv);
+					goto err_free_reuse_maps;
+				}
+				name = NULL;
+			} else if (is_prefix(*argv, "name")) {
+				NEXT_ARG();
+
+				name = *argv;
+				idx = -1;
+			} else {
+				p_err("expected 'idx' or 'name', got: '%s'?",
+				      *argv);
+				goto err_free_reuse_maps;
+			}
+			NEXT_ARG();
+
+			fd = map_parse_fd(&argc, &argv);
+			if (fd < 0)
+				goto err_free_reuse_maps;
+
+			map_replace = reallocarray(map_replace, old_map_fds + 1,
+						   sizeof(*map_replace));
+			if (!map_replace) {
+				p_err("mem alloc failed");
+				goto err_free_reuse_maps;
+			}
+			map_replace[old_map_fds].idx = idx;
+			map_replace[old_map_fds].name = name;
+			map_replace[old_map_fds].fd = fd;
+			old_map_fds++;
 		} else if (is_prefix(*argv, "dev")) {
 			NEXT_ARG();
 
 			if (ifindex) {
 				p_err("offload device already specified");
-				return -1;
+				goto err_free_reuse_maps;
 			}
 			if (!REQ_ARGS(1))
-				return -1;
+				goto err_free_reuse_maps;
 
 			ifindex = if_nametoindex(*argv);
 			if (!ifindex) {
 				p_err("unrecognized netdevice '%s': %s",
 				      *argv, strerror(errno));
-				return -1;
+				goto err_free_reuse_maps;
 			}
 			NEXT_ARG();
 		} else {
-			p_err("expected no more arguments, 'type' or 'dev', got: '%s'?",
+			p_err("expected no more arguments, 'type', 'map' or 'dev', got: '%s'?",
 			      *argv);
-			return -1;
+			goto err_free_reuse_maps;
 		}
 	}
 
 	obj = bpf_object__open_xattr(&attr);
 	if (IS_ERR_OR_NULL(obj)) {
 		p_err("failed to open object file");
-		return -1;
+		goto err_free_reuse_maps;
 	}
 
 	prog = bpf_program__next(NULL, obj);
@@ -782,10 +843,62 @@ static int do_load(int argc, char **argv)
 	bpf_program__set_type(prog, attr.prog_type);
 	bpf_program__set_expected_attach_type(prog, expected_attach_type);
 
-	bpf_map__for_each(map, obj)
+	qsort(map_replace, old_map_fds, sizeof(*map_replace),
+	      map_replace_compar);
+
+	/* After the sort maps by name will be first on the list, because they
+	 * have idx == -1.  Resolve them.
+	 */
+	j = 0;
+	while (j < old_map_fds && map_replace[j].name) {
+		i = 0;
+		bpf_map__for_each(map, obj) {
+			if (!strcmp(bpf_map__name(map), map_replace[j].name)) {
+				map_replace[j].idx = i;
+				break;
+			}
+			i++;
+		}
+		if (map_replace[j].idx == -1) {
+			p_err("unable to find map '%s'", map_replace[j].name);
+			goto err_close_obj;
+		}
+		j++;
+	}
+	/* Resort if any names were resolved */
+	if (j)
+		qsort(map_replace, old_map_fds, sizeof(*map_replace),
+		      map_replace_compar);
+
+	/* Set ifindex and name reuse */
+	j = 0;
+	idx = 0;
+	bpf_map__for_each(map, obj) {
 		if (!bpf_map__is_offload_neutral(map))
 			bpf_map__set_ifindex(map, ifindex);
 
+		if (j < old_map_fds && idx == map_replace[j].idx) {
+			err = bpf_map__reuse_fd(map, map_replace[j++].fd);
+			if (err) {
+				p_err("unable to set up map reuse: %d", err);
+				goto err_close_obj;
+			}
+
+			/* Next reuse wants to apply to the same map */
+			if (j < old_map_fds && map_replace[j].idx == idx) {
+				p_err("replacement for map idx %d specified more than once",
+				      idx);
+				goto err_close_obj;
+			}
+		}
+
+		idx++;
+	}
+	if (j < old_map_fds) {
+		p_err("map idx '%d' not used", map_replace[j].idx);
+		goto err_close_obj;
+	}
+
 	err = bpf_object__load(obj);
 	if (err) {
 		p_err("failed to load object file");
@@ -799,11 +912,18 @@ static int do_load(int argc, char **argv)
 		jsonw_null(json_wtr);
 
 	bpf_object__close(obj);
+	for (i = 0; i < old_map_fds; i++)
+		close(map_replace[i].fd);
+	free(map_replace);
 
 	return 0;
 
 err_close_obj:
 	bpf_object__close(obj);
+err_free_reuse_maps:
+	for (i = 0; i < old_map_fds; i++)
+		close(map_replace[i].fd);
+	free(map_replace);
 	return -1;
 }
 
@@ -819,9 +939,11 @@ static int do_help(int argc, char **argv)
 		"       %s %s dump xlated PROG [{ file FILE | opcodes | visual }]\n"
 		"       %s %s dump jited  PROG [{ file FILE | opcodes }]\n"
 		"       %s %s pin   PROG FILE\n"
-		"       %s %s load  OBJ  FILE [type TYPE] [dev NAME]\n"
+		"       %s %s load  OBJ  FILE [type TYPE] [dev NAME] \\\n"
+		"                         [map { idx IDX | name NAME } MAP]\n"
 		"       %s %s help\n"
 		"\n"
+		"       " HELP_SPEC_MAP "\n"
 		"       " HELP_SPEC_PROGRAM "\n"
 		"       TYPE := { socket | kprobe | kretprobe | classifier | action |\n"
 		"                 tracepoint | raw_tracepoint | xdp | perf_event | cgroup/skb |\n"