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There is no support for creating maps of types array-of-map or
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hash-of-map in bpftool. This is because the kernel needs an inner_map_fd
to collect metadata on the inner maps to be supported by the new map,
but bpftool does not provide a way to pass this file descriptor.

Add a new optional "inner_map" keyword that can be used to pass a
reference to a map, retrieve a fd to that map, and pass it as the
inner_map_fd.

Add related documentation and bash completion. Note that we can
reference the inner map by its name, meaning we can have several times
the keyword "name" with different meanings (mandatory outer map name,
and possibly a name to use to find the inner_map_fd). The bash
completion will offer it just once, and will not suggest "name" on the
following command:

    # bpftool map create /sys/fs/bpf/my_outer_map type hash_of_maps \
        inner_map name my_inner_map [TAB]

Fixing that specific case seems too convoluted. Completion will work as
expected, however, if the outer map name comes first and the "inner_map
name ..." is passed second.

Signed-off-by: Quentin Monnet <quentin@isovalent.com>
Acked-by: Andrii Nakryiko <andriin@fb.com>
---
 .../bpf/bpftool/Documentation/bpftool-map.rst | 10 +++-
 tools/bpf/bpftool/bash-completion/bpftool     | 22 ++++++++-
 tools/bpf/bpftool/map.c                       | 48 +++++++++++++------
 3 files changed, 62 insertions(+), 18 deletions(-)
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@qmonnet @kernel-patches-bot
qmonnet authored and kernel-patches-bot committed Sep 9, 2020
1 parent ec3d400 commit 03c13ed
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Showing 3 changed files with 62 additions and 18 deletions.
10 changes: 8 additions & 2 deletions tools/bpf/bpftool/Documentation/bpftool-map.rst
View file
Original file line number Diff line number Diff line change
Expand Up @@ -23,7 +23,8 @@ MAP COMMANDS

| **bpftool** **map** { **show** | **list** } [*MAP*]
| **bpftool** **map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* \
| **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**dev** *NAME*]
| **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] \
| [**dev** *NAME*]
| **bpftool** **map dump** *MAP*
| **bpftool** **map update** *MAP* [**key** *DATA*] [**value** *VALUE*] [*UPDATE_FLAGS*]
| **bpftool** **map lookup** *MAP* [**key** *DATA*]
Expand Down Expand Up @@ -67,14 +68,19 @@ DESCRIPTION
maps. On such kernels bpftool will automatically emit this
information as well.

**bpftool map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**dev** *NAME*]
**bpftool map create** *FILE* **type** *TYPE* **key** *KEY_SIZE* **value** *VALUE_SIZE* **entries** *MAX_ENTRIES* **name** *NAME* [**flags** *FLAGS*] [**inner_map** *MAP*] [**dev** *NAME*]
Create a new map with given parameters and pin it to *bpffs*
as *FILE*.

*FLAGS* should be an integer which is the combination of
desired flags, e.g. 1024 for **BPF_F_MMAPABLE** (see bpf.h
UAPI header for existing flags).

To create maps of type array-of-maps or hash-of-maps, the
**inner_map** keyword must be used to pass an inner map. The
kernel needs it to collect metadata related to the inner maps
that the new map will work with.

Keyword **dev** expects a network interface name, and is used
to request hardware offload for the map.

Expand Down
22 changes: 21 additions & 1 deletion tools/bpf/bpftool/bash-completion/bpftool
View file
Original file line number Diff line number Diff line change
Expand Up @@ -709,16 +709,36 @@ _bpftool()
"$cur" ) )
return 0
;;
key|value|flags|name|entries)
key|value|flags|entries)
return 0
;;
inner_map)
COMPREPLY=( $( compgen -W "$MAP_TYPE" -- "$cur" ) )
return 0
;;
id)
_bpftool_get_map_ids
;;
name)
case $pprev in
inner_map)
_bpftool_get_map_names
;;
*)
return 0
;;
esac
;;
*)
_bpftool_once_attr 'type'
_bpftool_once_attr 'key'
_bpftool_once_attr 'value'
_bpftool_once_attr 'entries'
_bpftool_once_attr 'name'
_bpftool_once_attr 'flags'
if _bpftool_search_list 'array_of_maps' 'hash_of_maps'; then
_bpftool_once_attr 'inner_map'
fi
_bpftool_once_attr 'dev'
return 0
;;
Expand Down
48 changes: 33 additions & 15 deletions tools/bpf/bpftool/map.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1250,7 +1250,7 @@ static int do_create(int argc, char **argv)
{
struct bpf_create_map_attr attr = { NULL, };
const char *pinfile;
int err, fd;
int err = -1, fd;

if (!REQ_ARGS(7))
return -1;
Expand All @@ -1265,13 +1265,13 @@ static int do_create(int argc, char **argv)

if (attr.map_type) {
p_err("map type already specified");
return -1;
goto exit;
}

attr.map_type = map_type_from_str(*argv);
if ((int)attr.map_type < 0) {
p_err("unrecognized map type: %s", *argv);
return -1;
goto exit;
}
NEXT_ARG();
} else if (is_prefix(*argv, "name")) {
Expand All @@ -1280,61 +1280,79 @@ static int do_create(int argc, char **argv)
} else if (is_prefix(*argv, "key")) {
if (parse_u32_arg(&argc, &argv, &attr.key_size,
"key size"))
return -1;
goto exit;
} else if (is_prefix(*argv, "value")) {
if (parse_u32_arg(&argc, &argv, &attr.value_size,
"value size"))
return -1;
goto exit;
} else if (is_prefix(*argv, "entries")) {
if (parse_u32_arg(&argc, &argv, &attr.max_entries,
"max entries"))
return -1;
goto exit;
} else if (is_prefix(*argv, "flags")) {
if (parse_u32_arg(&argc, &argv, &attr.map_flags,
"flags"))
return -1;
goto exit;
} else if (is_prefix(*argv, "dev")) {
NEXT_ARG();

if (attr.map_ifindex) {
p_err("offload device already specified");
return -1;
goto exit;
}

attr.map_ifindex = if_nametoindex(*argv);
if (!attr.map_ifindex) {
p_err("unrecognized netdevice '%s': %s",
*argv, strerror(errno));
return -1;
goto exit;
}
NEXT_ARG();
} else if (is_prefix(*argv, "inner_map")) {
struct bpf_map_info info = {};
__u32 len = sizeof(info);
int inner_map_fd;

NEXT_ARG();
if (!REQ_ARGS(2))
usage();
inner_map_fd = map_parse_fd_and_info(&argc, &argv,
&info, &len);
if (inner_map_fd < 0)
return -1;
attr.inner_map_fd = inner_map_fd;
} else {
p_err("unknown arg %s", *argv);
return -1;
goto exit;
}
}

if (!attr.name) {
p_err("map name not specified");
return -1;
goto exit;
}

set_max_rlimit();

fd = bpf_create_map_xattr(&attr);
if (fd < 0) {
p_err("map create failed: %s", strerror(errno));
return -1;
goto exit;
}

err = do_pin_fd(fd, pinfile);
close(fd);
if (err)
return err;
goto exit;

if (json_output)
jsonw_null(json_wtr);
return 0;

exit:
if (attr.inner_map_fd > 0)
close(attr.inner_map_fd);

return err;
}

static int do_pop_dequeue(int argc, char **argv)
Expand Down Expand Up @@ -1420,7 +1438,7 @@ static int do_help(int argc, char **argv)
"Usage: %1$s %2$s { show | list } [MAP]\n"
" %1$s %2$s create FILE type TYPE key KEY_SIZE value VALUE_SIZE \\\n"
" entries MAX_ENTRIES name NAME [flags FLAGS] \\\n"
" [dev NAME]\n"
" [inner_map MAP] [dev NAME]\n"
" %1$s %2$s dump MAP\n"
" %1$s %2$s update MAP [key DATA] [value VALUE] [UPDATE_FLAGS]\n"
" %1$s %2$s lookup MAP [key DATA]\n"
Expand Down

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