netdev - [PATCH iproute2] devlink: Fix dumps where interface map is used

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Date:   Thu, 27 Apr 2023 08:25:21 +0300
From:   Ido Schimmel <idosch@...dia.com>
To:     netdev@...r.kernel.org
Cc:     stephen@...workplumber.org, dsahern@...il.com, jiri@...dia.com,
        Ido Schimmel <idosch@...dia.com>
Subject: [PATCH iproute2] devlink: Fix dumps where interface map is used

The devlink utility stores an interface map that can be used to map an
interface name to a devlink port and vice versa. The map is populated by
issuing a devlink port dump via 'DEVLINK_CMD_PORT_GET' command.

Cited commits started to populate the map only when it is actually
needed. One such case is when a dump (e.g., shared buffer dump) only
returns devlink port handles. When pretty printing is required, the
utility will consult the map to translate the devlink port handles to
the corresponding interface names.

The above is problematic as it means that the port dump response(s) will
be queued to the same receive buffer as the response(s) of the dump that
triggered the port dump, resulting in a failed dump [1].

Fix by using a different netlink socket for the population of the
interface map.

[1]
$ devlink sb tc bind show
kernel answers: Device or resource busy
Failed to create index map
//0:
  sb 0 tc 4 type egress pool 4 threshold 9
kernel answers: Device or resource busy
[...]
$ echo $?
1

Fixes: 5cddbb274eab ("devlink: load port-ifname map on demand")
Fixes: 63d84b1fc98d ("devlink: load ifname map on demand from ifname_map_rev_lookup() as well")
Signed-off-by: Ido Schimmel <idosch@...dia.com>
---
 devlink/devlink.c | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/devlink/devlink.c b/devlink/devlink.c
index 795f8318c0c4..019ffc23e766 100644
--- a/devlink/devlink.c
+++ b/devlink/devlink.c
@@ -931,6 +931,7 @@ static void ifname_map_init(struct dl *dl)

 static int ifname_map_load(struct dl *dl, const char *ifname)
 {
+	struct mnlu_gen_socket nlg_map;
 	struct nlmsghdr *nlh;
 	int err;

@@ -943,15 +944,20 @@ static int ifname_map_load(struct dl *dl, const char *ifname)
 		 */
 	}

-	nlh = mnlu_gen_socket_cmd_prepare(&dl->nlg, DEVLINK_CMD_PORT_GET,
+	err = mnlu_gen_socket_open(&nlg_map, DEVLINK_GENL_NAME,
+				   DEVLINK_GENL_VERSION);
+	if (err)
+		return err;
+
+	nlh = mnlu_gen_socket_cmd_prepare(&nlg_map, DEVLINK_CMD_PORT_GET,
 			       NLM_F_REQUEST | NLM_F_ACK | NLM_F_DUMP);

-	err = mnlu_gen_socket_sndrcv(&dl->nlg, nlh, ifname_map_cb, dl);
-	if (err) {
+	err = mnlu_gen_socket_sndrcv(&nlg_map, nlh, ifname_map_cb, dl);
+	if (err)
 		ifname_map_fini(dl);
-		return err;
-	}
-	return 0;
+
+	mnlu_gen_socket_close(&nlg_map);
+	return err;
 }

 static int ifname_map_check_load(struct dl *dl, const char *ifname)
-- 
2.40.0