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Subject[PATCH bpf-next v1 5/7] tools: bpftool: support loading map by fd from parent process
Date
From: Alban Crequy <alban@kinvolk.io>

Using a file descriptor passed by the parent process enables
applications to fork a bpftool command to inspect a map they know by
file descriptor even when they don't support bpffs or map ids.

Documentation and bash completion updated as well.

Signed-off-by: Alban Crequy <alban@kinvolk.io>
---
tools/bpf/bpftool/Documentation/bpftool-map.rst | 8 ++++++++
tools/bpf/bpftool/bash-completion/bpftool | 10 +++++-----
tools/bpf/bpftool/map.c | 13 +++++++++++++
3 files changed, 26 insertions(+), 5 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index dfd8352fa453..658fe2fb8ecf 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -265,6 +265,14 @@ would be lost as soon as bpftool exits).

anon_inode:bpf-map

+**# bpftool map exec pinned /sys/fs/bpf/foo fd 99 cmd -- bpftool map show fd 99**
+
+::
+
+ 10: hash name some_map flags 0x0
+ key 4B value 8B max_entries 2048 memlock 167936B
+
+
SEE ALSO
========
**bpf**\ (2),
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index 63cd53c4d3a7..9ec1833bda1e 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -253,7 +253,7 @@ _bpftool()
esac

local PROG_TYPE='id pinned tag'
- local MAP_TYPE='id pinned'
+ local MAP_TYPE='id pinned fd'
case $command in
show|list)
[[ $prev != "$command" ]] && return 0
@@ -343,7 +343,7 @@ _bpftool()
obj=${words[3]}

if [[ ${words[-4]} == "map" ]]; then
- COMPREPLY=( $( compgen -W "id pinned" -- "$cur" ) )
+ COMPREPLY=( $( compgen -W "id pinned fd" -- "$cur" ) )
return 0
fi
if [[ ${words[-3]} == "map" ]]; then
@@ -406,7 +406,7 @@ _bpftool()
esac
;;
map)
- local MAP_TYPE='id pinned'
+ local MAP_TYPE='id pinned fd'
case $command in
show|list|dump|peek|pop|dequeue)
case $prev in
@@ -462,7 +462,7 @@ _bpftool()
return 0
;;
innermap)
- COMPREPLY+=( $( compgen -W "id pinned" -- "$cur" ) )
+ COMPREPLY+=( $( compgen -W "id pinned fd" -- "$cur" ) )
return 0
;;
id)
@@ -525,7 +525,7 @@ _bpftool()
# map, depending on the type of the map to update.
case "$(_bpftool_map_guess_map_type)" in
array_of_maps|hash_of_maps)
- local MAP_TYPE='id pinned'
+ local MAP_TYPE='id pinned fd'
COMPREPLY+=( $( compgen -W "$MAP_TYPE" \
-- "$cur" ) )
return 0
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 768497364cee..9befcabc299d 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -125,6 +125,19 @@ int map_parse_fd(int *argc, char ***argv)
NEXT_ARGP();

return open_obj_pinned_any(path, BPF_OBJ_MAP);
+ } else if (is_prefix(**argv, "fd")) {
+ char *endptr;
+
+ NEXT_ARGP();
+
+ fd = strtoul(**argv, &endptr, 0);
+ if (*endptr) {
+ p_err("can't parse %s as fd", **argv);
+ return -1;
+ }
+ NEXT_ARGP();
+
+ return dup(fd);
}

p_err("expected 'id' or 'pinned', got: '%s'?", **argv);
--
2.20.1
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