[PATCH bpf-next 4/6] bpftool: add peek command

[Stanislav Fomichev <sdf@google.com>]

This is intended to be used with queues and stacks and be more
user-friendly than 'lookup' without key/value.

Example:
bpftool map create /sys/fs/bpf/q type queue value 4 entries 10 name q
bpftool map update pinned /sys/fs/bpf/q value 0 1 2 3
bpftool map peek pinned /sys/fs/bpf/q
value: 00 01 02 03

Signed-off-by: Stanislav Fomichev <sdf@google.com>
---
 tools/bpf/bpftool/Documentation/bpftool-map.rst | 4 ++++
 tools/bpf/bpftool/bash-completion/bpftool       | 5 +++--
 tools/bpf/bpftool/map.c                         | 4 +++-
 3 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/tools/bpf/bpftool/Documentation/bpftool-map.rst b/tools/bpf/bpftool/Documentation/bpftool-map.rst
index f34cace771bd..b79da683da88 100644
--- a/tools/bpf/bpftool/Documentation/bpftool-map.rst
+++ b/tools/bpf/bpftool/Documentation/bpftool-map.rst
@@ -31,6 +31,7 @@ MAP COMMANDS
 |	**bpftool** **map delete**     *MAP*  **key** *DATA*
 |	**bpftool** **map pin**        *MAP*  *FILE*
 |	**bpftool** **map event_pipe** *MAP* [**cpu** *N* **index** *M*]
+|	**bpftool** **map peek**       *MAP*
 |	**bpftool** **map help**
 |
 |	*MAP* := { **id** *MAP_ID* | **pinned** *FILE* }
@@ -107,6 +108,9 @@ DESCRIPTION
 		  replace any existing ring.  Any other application will stop
 		  receiving events if it installed its rings earlier.
 
+	**bpftool map peek**  *MAP*
+		  Peek next **value** in the queue or stack.
+
 	**bpftool map help**
 		  Print short help message.
 
diff --git a/tools/bpf/bpftool/bash-completion/bpftool b/tools/bpf/bpftool/bash-completion/bpftool
index e4e4fab1b8c7..fe4880d9bd8d 100644
--- a/tools/bpf/bpftool/bash-completion/bpftool
+++ b/tools/bpf/bpftool/bash-completion/bpftool
@@ -382,7 +382,7 @@ _bpftool()
         map)
             local MAP_TYPE='id pinned'
             case $command in
-                show|list|dump)
+                show|list|dump|peek)
                     case $prev in
                         $command)
                             COMPREPLY=( $( compgen -W "$MAP_TYPE" -- "$cur" ) )
@@ -546,7 +546,8 @@ _bpftool()
                 *)
                     [[ $prev == $object ]] && \
                         COMPREPLY=( $( compgen -W 'delete dump getnext help \
-                            lookup pin event_pipe show list update create' -- \
+                            lookup pin event_pipe show list update create \
+                            peek' -- \
                             "$cur" ) )
                     ;;
             esac
diff --git a/tools/bpf/bpftool/map.c b/tools/bpf/bpftool/map.c
index 3f599399913b..d7344fcd2089 100644
--- a/tools/bpf/bpftool/map.c
+++ b/tools/bpf/bpftool/map.c
@@ -1168,6 +1168,7 @@ static int do_help(int argc, char **argv)
 		"       %s %s delete     MAP  key DATA\n"
 		"       %s %s pin        MAP  FILE\n"
 		"       %s %s event_pipe MAP [cpu N index M]\n"
+		"       %s %s peek       MAP\n"
 		"       %s %s help\n"
 		"\n"
 		"       " HELP_SPEC_MAP "\n"
@@ -1185,7 +1186,7 @@ static int do_help(int argc, char **argv)
 		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
 		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
 		bin_name, argv[-2], bin_name, argv[-2], bin_name, argv[-2],
-		bin_name, argv[-2]);
+		bin_name, argv[-2], bin_name, argv[-2]);
 
 	return 0;
 }
@@ -1202,6 +1203,7 @@ static const struct cmd cmds[] = {
 	{ "pin",	do_pin },
 	{ "event_pipe",	do_event_pipe },
 	{ "create",	do_create },
+	{ "peek",	do_lookup },
 	{ 0 }
 };
 
-- 
2.20.1.97.g81188d93c3-goog