[PATCH iproute2-next v2] devlink: support kernel-side snapshot id allocation

[Jakub Kicinski]

Make ID argument optional and read the snapshot info
that kernel sends us.

  $ devlink region new netdevsim/netdevsim1/dummy
  netdevsim/netdevsim1/dummy: snapshot 0
  $ devlink -jp region new netdevsim/netdevsim1/dummy
  {
      "regions": {
          "netdevsim/netdevsim1/dummy": {
              "snapshot": [ 1 ]
          }
      }
  }
  $ devlink region show netdevsim/netdevsim1/dummy
  netdevsim/netdevsim1/dummy: size 32768 snapshot [0 1]

In case the operation fails only the error is printed:

  $ devlink region new netdevsim/netdevsim1/dummy
  Error: devlink: failure injected after ID notification was sent.
  devlink answers: Input/output error
  $

v2:
 - make sure we don't print anything on failure.

Signed-off-by: Jakub Kicinski <k...@kernel.org>
---
 devlink/devlink.c | 66 ++++++++++++++++++++++++++++++++++++++++++++---
 1 file changed, 63 insertions(+), 3 deletions(-)

diff --git a/devlink/devlink.c b/devlink/devlink.c
index bd48a73bc0e4..73a1f02a5339 100644
--- a/devlink/devlink.c
+++ b/devlink/devlink.c
@@ -6476,20 +6476,80 @@ static int cmd_region_read(struct dl *dl)
        return err;
 }
 
+static int cmd_region_snapshot_new_response_print(struct dl *dl,
+                                                 const struct nlmsghdr *nlh)
+{
+       struct nlattr *tb[DEVLINK_ATTR_MAX + 1] = {};
+
+       if (dl->opts.present & DL_OPT_REGION_SNAPSHOT_ID)
+               return 0;
+
+       if (!nlh->nlmsg_len) {
+               pr_err("no response from the kernel\n");
+               return -EINVAL;
+       }
+
+       mnl_attr_parse(nlh, sizeof(struct genlmsghdr), attr_cb, tb);
+       if (!tb[DEVLINK_ATTR_BUS_NAME] || !tb[DEVLINK_ATTR_DEV_NAME] ||
+           !tb[DEVLINK_ATTR_REGION_NAME] ||
+           !tb[DEVLINK_ATTR_REGION_SNAPSHOT_ID]) {
+               pr_err("kernel response does not contain expected 
attributes\n");
+               return -EINVAL;
+       }
+
+       pr_out_section_start(dl, "regions");
+       pr_out_region(dl, tb);
+       pr_out_section_end(dl);
+
+       return 0;
+}
+
+static int cmd_region_snapshot_new_cb(const struct nlmsghdr *nlh, void *data)
+{
+       struct genlmsghdr *genl = mnl_nlmsg_get_payload(nlh);
+       struct nlmsghdr *nlh_copy = data;
+
+       if (genl->cmd != DEVLINK_CMD_REGION_NEW)
+               return MNL_CB_OK;
+
+       /* Make sure we only receive one message from the kernel */
+       if (nlh_copy->nlmsg_len)
+               return MNL_CB_ERROR;
+
+       if (nlh->nlmsg_len > MNL_SOCKET_BUFFER_SIZE)
+               return MNL_CB_ERROR;
+
+       memcpy(data, nlh, nlh->nlmsg_len);
+
+       return MNL_CB_OK;
+}
+
 static int cmd_region_snapshot_new(struct dl *dl)
 {
+       unsigned char *msg_copy;
        struct nlmsghdr *nlh;
        int err;
 
        nlh = mnlg_msg_prepare(dl->nlg, DEVLINK_CMD_REGION_NEW,
                               NLM_F_REQUEST | NLM_F_ACK);
 
-       err = dl_argv_parse_put(nlh, dl, DL_OPT_HANDLE_REGION |
-                               DL_OPT_REGION_SNAPSHOT_ID, 0);
+       err = dl_argv_parse_put(nlh, dl, DL_OPT_HANDLE_REGION,
+                               DL_OPT_REGION_SNAPSHOT_ID);
        if (err)
                return err;
 
-       return _mnlg_socket_sndrcv(dl->nlg, nlh, NULL, NULL);
+       msg_copy = calloc(MNL_SOCKET_BUFFER_SIZE, 1);
+
+       err = _mnlg_socket_sndrcv(dl->nlg, nlh, cmd_region_snapshot_new_cb,
+                                 msg_copy);
+       if (err)
+               goto out;
+
+       err = cmd_region_snapshot_new_response_print(dl, (void *)msg_copy);
+out:
+       free(msg_copy);
+
+       return err;
 }
 
 static void cmd_region_help(void)
-- 
2.25.4