On Wed, 2020-09-30 at 17:05 -0700, Jakub Kicinski wrote:
> Right now CTRL_CMD_GETPOLICY can only dump the family-wide
> policy. Support dumping policy of a specific op.
So, hmm.
Yeah, I guess this is fine, but you could end up having to do a lot of
dumps, and with e.g. ethtool you'd end up with a lot of duplicate data
too, since it's structured as
common_policy = { ... }
cmd1_policy = {
[CMD1_COMMON] = NLA_NESTED_POLICY(common_policy),
...
};
cmd2_policy = {
[CMD2_COMMON] = NLA_NESTED_POLICY(common_policy),
...
};
etc.
So you end up dumping per command (and in practice, since they can be
different, you now *have to* unless you know out-of-band that there are
no per-command policies).
Even if I don't have a good idea now on how to avoid the duplication, it
might be nicer to have a (flag) attribute here for "CTRL_ATTR_ALL_OPS"?
johannes
> Signed-off-by: Jakub Kicinski <k...@kernel.org>
> ---
> include/uapi/linux/genetlink.h | 1 +
> net/netlink/genetlink.c | 23 +++++++++++++++++++++--
> 2 files changed, 22 insertions(+), 2 deletions(-)
>
> diff --git a/include/uapi/linux/genetlink.h b/include/uapi/linux/genetlink.h
> index 9c0636ec2286..7dbe2d5d7d46 100644
> --- a/include/uapi/linux/genetlink.h
> +++ b/include/uapi/linux/genetlink.h
> @@ -64,6 +64,7 @@ enum {
> CTRL_ATTR_OPS,
> CTRL_ATTR_MCAST_GROUPS,
> CTRL_ATTR_POLICY,
> + CTRL_ATTR_OP,
> __CTRL_ATTR_MAX,
> };
>
> diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
> index f2833e9165c7..12e9f323af35 100644
> --- a/net/netlink/genetlink.c
> +++ b/net/netlink/genetlink.c
> @@ -1113,12 +1113,14 @@ static int genl_ctrl_event(int event, const struct
> genl_family *family,
> struct ctrl_dump_policy_ctx {
> unsigned long state;
> unsigned int fam_id;
> + u8 cmd;
> };
>
> static const struct nla_policy ctrl_policy_policy[] = {
> [CTRL_ATTR_FAMILY_ID] = { .type = NLA_U16 },
> [CTRL_ATTR_FAMILY_NAME] = { .type = NLA_NUL_STRING,
> .len = GENL_NAMSIZ - 1 },
> + [CTRL_ATTR_OP] = { .type = NLA_U8 },
> };
>
> static int ctrl_dumppolicy_start(struct netlink_callback *cb)
> @@ -1127,6 +1129,8 @@ static int ctrl_dumppolicy_start(struct
> netlink_callback *cb)
> struct ctrl_dump_policy_ctx *ctx = (void *)cb->args;
> struct nlattr **tb = info->attrs;
> const struct genl_family *rt;
> + struct genl_ops op;
> + int err;
>
> if (!tb[CTRL_ATTR_FAMILY_ID] && !tb[CTRL_ATTR_FAMILY_NAME])
> return -EINVAL;
> @@ -1145,10 +1149,23 @@ static int ctrl_dumppolicy_start(struct
> netlink_callback *cb)
> if (!rt)
> return -ENOENT;
>
> - if (!rt->policy)
> + if (tb[CTRL_ATTR_OP]) {
> + ctx->cmd = nla_get_u8(tb[CTRL_ATTR_OP]);
> +
> + err = genl_get_cmd(ctx->cmd, rt, &op);
> + if (err) {
> + NL_SET_BAD_ATTR(cb->extack, tb[CTRL_ATTR_OP]);
> + return err;
> + }
> + } else {
> + op.policy = rt->policy;
> + op.maxattr = rt->maxattr;
> + }
> +
> + if (!op.policy)
> return -ENODATA;
>
> - return netlink_policy_dump_start(rt->policy, rt->maxattr, &ctx->state);
> + return netlink_policy_dump_start(op.policy, op.maxattr, &ctx->state);
> }
>
> static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
> @@ -1167,6 +1184,8 @@ static int ctrl_dumppolicy(struct sk_buff *skb, struct
> netlink_callback *cb)
>
> if (nla_put_u16(skb, CTRL_ATTR_FAMILY_ID, ctx->fam_id))
> goto nla_put_failure;
> + if (ctx->cmd && nla_put_u8(skb, CTRL_ATTR_OP, ctx->cmd))
> + goto nla_put_failure;
>
> nest = nla_nest_start(skb, CTRL_ATTR_POLICY);
> if (!nest)
