[RFC net-next 9/9] genetlink: allow dumping command-specific policy

[Jakub Kicinski]

Right now CTRL_CMD_GETPOLICY can only dump the family-wide
policy. Support dumping policy of a specific op.

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)
-- 
2.26.2