Re: [PATCH bpf-next 2/2] bpftool: support loading flow dissector

Hi Stanislav,

2018-11-07 11:35 UTC-0800 ~ Stanislav Fomichev sdf@google.com

This commit adds support for loading/attaching/detaching flow dissector program. The structure of the flow dissector program is assumed to be the same as in the selftests:

• flow_dissector section with the main entry point
• a bunch of tail call progs
• a jmp_table map that is populated with the tail call progs

When `bpftool load` is called with a flow_dissector prog (i.e. when the first section is flow_dissector of 'type flow_dissector' argument is passed), we load and pin all the programs and build the jump table.

The last argument of `bpftool attach` is made optional for this use case.

Example: bpftool prog load tools/testing/selftests/bpf/bpf_flow.o \ /sys/fs/bpf/flow type flow_dissector bpftool prog attach pinned /sys/fs/bpf/flow/flow_dissector/0 flow_dissector

Tested by using the above two lines to load the prog in the test_flow_dissector.sh selftest.

Signed-off-by: Stanislav Fomichev sdf@google.com

.../bpftool/Documentation/bpftool-prog.rst | 16 ++- tools/bpf/bpftool/common.c | 32 +++-- tools/bpf/bpftool/main.h | 1 + tools/bpf/bpftool/prog.c | 135 +++++++++++++++--- 4 files changed, 141 insertions(+), 43 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-prog.rst b/tools/bpf/bpftool/Documentation/bpftool-prog.rst index ac4e904b10fb..3caa9153435b 100644 --- a/tools/bpf/bpftool/Documentation/bpftool-prog.rst +++ b/tools/bpf/bpftool/Documentation/bpftool-prog.rst @@ -25,8 +25,8 @@ MAP COMMANDS | **bpftool** **prog dump jited** *PROG* [{**file** *FILE* | **opcodes**}] | **bpftool** **prog pin** *PROG* *FILE* | **bpftool** **prog load** *OBJ* *FILE* [**type** *TYPE*] [**map** {**idx** *IDX* | **name** *NAME*} *MAP*] [**dev** *NAME*] -| **bpftool** **prog attach** *PROG* *ATTACH_TYPE* *MAP* -| **bpftool** **prog detach** *PROG* *ATTACH_TYPE* *MAP* +| **bpftool** **prog attach** *PROG* *ATTACH_TYPE* [*MAP*] +| **bpftool** **prog detach** *PROG* *ATTACH_TYPE* [*MAP*] | **bpftool** **prog help** | | *MAP* := { **id** *MAP_ID* | **pinned** *FILE* } @@ -39,7 +39,9 @@ MAP COMMANDS | **cgroup/bind4** | **cgroup/bind6** | **cgroup/post_bind4** | **cgroup/post_bind6** | | **cgroup/connect4** | **cgroup/connect6** | **cgroup/sendmsg4** | **cgroup/sendmsg6** | } -| *ATTACH_TYPE* := { **msg_verdict** | **skb_verdict** | **skb_parse** } +| *ATTACH_TYPE* := { +| | **msg_verdict** | **skb_verdict** | **skb_parse** | **flow_dissector**

^ Nitpick: Could you please remove the above pipe?

+| } DESCRIPTION @@ -97,13 +99,13 @@ DESCRIPTION contain a dot character ('.'), which is reserved for future extensions of *bpffs*.

•    **bpftool prog attach** *PROG* *ATTACH_TYPE* *MAP*
  

•    **bpftool prog attach** *PROG* *ATTACH_TYPE* [*MAP*]
               Attach bpf program *PROG* (with type specified by *ATTACH_TYPE*)
  

•              to the map *MAP*.
  

•              to the optional map *MAP*.
  

•    **bpftool prog detach** *PROG* *ATTACH_TYPE* *MAP*
  

•    **bpftool prog detach** *PROG* *ATTACH_TYPE* [*MAP*]
               Detach bpf program *PROG* (with type specified by *ATTACH_TYPE*)
  

•              from the map *MAP*.
  

•              from the optional map *MAP*.
  

**bpftool prog help** Print short help message. diff --git a/tools/bpf/bpftool/common.c b/tools/bpf/bpftool/common.c index 25af85304ebe..963881142dfb 100644 --- a/tools/bpf/bpftool/common.c +++ b/tools/bpf/bpftool/common.c @@ -169,34 +169,24 @@ int open_obj_pinned_any(char *path, enum bpf_obj_type exp_type) return fd; } -int do_pin_fd(int fd, const char *name) +int mount_bpffs_for_pin(const char *name) { char err_str[ERR_MAX_LEN]; char *file; char *dir; int err = 0;

• err = bpf_obj_pin(fd, name);
• if (!err)

• goto out;
  

• file = malloc(strlen(name) + 1); strcpy(file, name); dir = dirname(file);

• if (errno != EPERM || is_bpffs(dir)) {

• p_err("can't pin the object (%s): %s", name, strerror(errno));
  

• if (is_bpffs(dir)) {

• /* nothing to do if already mounted */
  

  goto out_free; }

• /* Attempt to mount bpffs, then retry pinning. */ err = mnt_bpffs(dir, err_str, ERR_MAX_LEN);
• if (!err) {

• err = bpf_obj_pin(fd, name);
  

• if (err)
  

• 	p_err("can't pin the object (%s): %s", name,
  

• 	      strerror(errno));
  

• } else {

• if (err) { err_str[ERR_MAX_LEN - 1] = '\0'; p_err("can't mount BPF file system to pin the object (%s): %s", name, err_str);

@@ -204,10 +194,22 @@ int do_pin_fd(int fd, const char *name) out_free: free(file); -out: return err; } +int do_pin_fd(int fd, const char *name) +{

• int err = mount_bpffs_for_pin(name);
• if (err) {

• p_err("can't mount bpffs for pin %s: %s",
  

•       name, strerror(errno));
  

• return err;
  

• }
• return bpf_obj_pin(fd, name);

+}

int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(__u32)) { unsigned int id; diff --git a/tools/bpf/bpftool/main.h b/tools/bpf/bpftool/main.h index 28322ace2856..1383824c9baf 100644 --- a/tools/bpf/bpftool/main.h +++ b/tools/bpf/bpftool/main.h @@ -129,6 +129,7 @@ const char *get_fd_type_name(enum bpf_obj_type type); char *get_fdinfo(int fd, const char *key); int open_obj_pinned(char *path); int open_obj_pinned_any(char *path, enum bpf_obj_type exp_type); +int mount_bpffs_for_pin(const char *name); int do_pin_any(int argc, char **argv, int (*get_fd_by_id)(__u32)); int do_pin_fd(int fd, const char *name); diff --git a/tools/bpf/bpftool/prog.c b/tools/bpf/bpftool/prog.c index 5302ee282409..f3a07ec3a444 100644 --- a/tools/bpf/bpftool/prog.c +++ b/tools/bpf/bpftool/prog.c @@ -81,6 +81,7 @@ static const char * const attach_type_strings[] = { [BPF_SK_SKB_STREAM_PARSER] = "stream_parser", [BPF_SK_SKB_STREAM_VERDICT] = "stream_verdict", [BPF_SK_MSG_VERDICT] = "msg_verdict",

• [BPF_FLOW_DISSECTOR] = "flow_dissector", [__MAX_BPF_ATTACH_TYPE] = NULL,

}; @@ -724,9 +725,10 @@ int map_replace_compar(const void *p1, const void *p2) static int do_attach(int argc, char **argv) { enum bpf_attach_type attach_type;

• int err, mapfd, progfd;

• int err, progfd;
• int mapfd = 0;

• if (!REQ_ARGS(5)) {

• if (!REQ_ARGS(3)) { p_err("too few parameters for map attach"); return -EINVAL; }

@@ -741,10 +743,11 @@ static int do_attach(int argc, char **argv) return -EINVAL; } NEXT_ARG();

• mapfd = map_parse_fd(&argc, &argv);
• if (mapfd < 0)

• return mapfd;
  

• if (argc > 0) {

• mapfd = map_parse_fd(&argc, &argv);
  

• if (mapfd < 0)
  

• 	return mapfd;
  

• }

err = bpf_prog_attach(progfd, mapfd, attach_type, 0); if (err) { @@ -760,9 +763,10 @@ static int do_attach(int argc, char **argv) static int do_detach(int argc, char **argv) { enum bpf_attach_type attach_type;

• int err, mapfd, progfd;

• int err, progfd;
• int mapfd = 0;

• if (!REQ_ARGS(5)) {

• if (!REQ_ARGS(3)) { p_err("too few parameters for map detach"); return -EINVAL; }

@@ -777,10 +781,11 @@ static int do_detach(int argc, char **argv) return -EINVAL; } NEXT_ARG();

• mapfd = map_parse_fd(&argc, &argv);
• if (mapfd < 0)

• return mapfd;
  

• if (argc > 0) {

• mapfd = map_parse_fd(&argc, &argv);
  

• if (mapfd < 0)
  

• 	return mapfd;
  

• }

err = bpf_prog_detach2(progfd, mapfd, attach_type); if (err) { @@ -792,6 +797,56 @@ static int do_detach(int argc, char **argv) jsonw_null(json_wtr); return 0; }

+/* Flow dissector consists of a main program and a jump table for each

• • supported protocol. The assumption here is that the first prog is the main
• • one and the other progs are used in the tail calls. In this routine we
• • build the jump table for the non-main progs.
• */

+static int build_flow_dissector_jmp_table(struct bpf_object *obj,

• 			  struct bpf_program *prog,
  

• 			  const char *jmp_table_map)
  

+{

• struct bpf_map *jmp_table;
• struct bpf_program *pos;
• int i = 0;
• int prog_fd, jmp_table_fd, fd;
• prog_fd = bpf_program__fd(prog);
• if (prog_fd < 0) {

• p_err("failed to get fd of main prog");
  

• return prog_fd;
  

• }
• jmp_table = bpf_object__find_map_by_name(obj, jmp_table_map);
• if (jmp_table == NULL) {

• p_err("failed to find '%s' map", jmp_table_map);
  

• return -1;
  

• }
• jmp_table_fd = bpf_map__fd(jmp_table);
• if (jmp_table_fd < 0) {

• p_err("failed to get fd of jmp_table");
  

• return jmp_table_fd;
  

• }
• bpf_object__for_each_program(pos, obj) {

• fd = bpf_program__fd(pos);
  

• if (fd < 0) {
  

• 	p_err("failed to get fd of '%s'",
  

• 	      bpf_program__title(pos, false));
  

• 	return fd;
  

• }
  

• if (fd != prog_fd) {
  

• 	bpf_map_update_elem(jmp_table_fd, &i, &fd, BPF_ANY);
  

• 	++i;
  

• }
  

• }
• return 0;

+}

static int do_load(int argc, char **argv) { enum bpf_attach_type expected_attach_type; @@ -800,7 +855,7 @@ static int do_load(int argc, char **argv) }; struct map_replace *map_replace = NULL; unsigned int old_map_fds = 0;

• struct bpf_program *prog;

• struct bpf_program *prog, *pos; struct bpf_object *obj; struct bpf_map *map; const char *pinfile;

@@ -918,13 +973,19 @@ static int do_load(int argc, char **argv) goto err_free_reuse_maps; }

• prog = bpf_program__next(NULL, obj);

• if (attr.prog_type == BPF_PROG_TYPE_FLOW_DISSECTOR) {

• /* for the flow dissector type, the entry point is in the
  

•  * section flow_dissector; other progs are tail calls
  

•  */
  

• prog = bpf_object__find_program_by_title(obj, "flow_dissector");
  

Is the section always called like this? Or could we use instead the same assumption as above, i.e. the main program is the first one?

• } else {

• prog = bpf_program__next(NULL, obj);
  

• } if (!prog) { p_err("object file doesn't contain any bpf program"); goto err_close_obj; }

• bpf_program__set_ifindex(prog, ifindex); if (attr.prog_type == BPF_PROG_TYPE_UNSPEC) { const char *sec_name = bpf_program__title(prog, false);

@@ -936,8 +997,13 @@ static int do_load(int argc, char **argv) goto err_close_obj; } }

• bpf_program__set_type(prog, attr.prog_type);
• bpf_program__set_expected_attach_type(prog, expected_attach_type);

• bpf_object__for_each_program(pos, obj) {

• bpf_program__set_ifindex(pos, ifindex);
  

• bpf_program__set_type(pos, attr.prog_type);
  

• bpf_program__set_expected_attach_type(pos,
  

• 				      expected_attach_type);
  

• }

I believe it is possible to load program of several types or attach types from a same object file? If so, we would need to get individual prog types and attach types for each program with libbpf_prog_type_by_name().

qsort(map_replace, old_map_fds, sizeof(*map_replace), map_replace_compar); @@ -1001,8 +1067,34 @@ static int do_load(int argc, char **argv) goto err_close_obj; }

• if (do_pin_fd(bpf_program__fd(prog), pinfile))

• err = mount_bpffs_for_pin(pinfile);
• if (err) {

• p_err("failed to mount bpffs for pin '%s'", pinfile);
  

  goto err_close_obj;
• }
• if (attr.prog_type == BPF_PROG_TYPE_FLOW_DISSECTOR) {

• err = build_flow_dissector_jmp_table(obj, prog, "jmp_table");
  

• if (err) {
  

• 	p_err("failed to build flow dissector jump table");
  

• 	goto err_close_obj;
  

• }
  

• /* flow dissector consist of multiple programs,
  

•  * we want to pin them all
  

•  */
  

• err = bpf_object__pin(obj, pinfile);
  

• if (err) {
  

• 	p_err("failed to pin flow dissector object");
  

• 	goto err_close_obj;
  

• }
  

What happens for the programs previously loaded and pinned in one of the program fails? Do they remain loaded and pinned even if all programs were not successfully loaded? Or should we consider removing all links we added instead and go back to a "clean" state?

• } else {

• err = bpf_obj_pin(bpf_program__fd(prog), pinfile);
  

• if (err) {
  

• 	p_err("failed to pin program %s",
  

• 	      bpf_program__title(prog, false));
  

• 	goto err_close_obj;
  

• }
  

I don't have the same opinion as Jakub for pinning :). I was hoping we could also load additional programs (for tail calls) for non-flow_dissector programs. Could this be an occasion to update the code in that direction?

• }

if (json_output) jsonw_null(json_wtr); @@ -1037,8 +1129,8 @@ static int do_help(int argc, char **argv) " %s %s pin PROG FILE\n" " %s %s load OBJ FILE [type TYPE] [dev NAME] \\n" " [map { idx IDX | name NAME } MAP]\n"

• "       %s %s attach PROG ATTACH_TYPE MAP\n"
  

• "       %s %s detach PROG ATTACH_TYPE MAP\n"
  

• "       %s %s attach PROG ATTACH_TYPE [MAP]\n"
  

• "       %s %s detach PROG ATTACH_TYPE [MAP]\n"
  

  " %s %s help\n" "\n" " " HELP_SPEC_MAP "\n"

@@ -1050,7 +1142,8 @@ static int do_help(int argc, char **argv) " cgroup/bind4 | cgroup/bind6 | cgroup/post_bind4 |\n" " cgroup/post_bind6 | cgroup/connect4 | cgroup/connect6 |\n" " cgroup/sendmsg4 | cgroup/sendmsg6 }\n"

• "       ATTACH_TYPE := { msg_verdict | skb_verdict | skb_parse }\n"
  

• "       ATTACH_TYPE := { msg_verdict | skb_verdict | skb_parse |\n"
  

• "                        flow_dissector }\n"
  

  " " HELP_SPEC_OPTIONS "\n" "", bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],

Thanks a lot for the set! Quentin