[PATCH 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.

v1:
 - don't echo op in the output in a naive way, this should
   make it cleaner to extend the output format for dumping
   policies for all the commands at once in the future.

Signed-off-by: Jakub Kicinski <k...@kernel.org>
---
 include/uapi/linux/genetlink.h |  1 +
 net/netlink/genetlink.c        | 18 ++++++++++++++++--
 2 files changed, 17 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 81f0b960e9f8..bc5a6fd60abc 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1119,6 +1119,7 @@ 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 +1128,8 @@ static int ctrl_dumppolicy_start(struct netlink_callback 
*cb)
        struct ctrl_dump_policy_ctx *ctx = (void *)cb->ctx;
        struct nlattr **tb = info->attrs;
        const struct genl_family *rt;
+       struct genl_ops op;
+       int err;
 
        BUILD_BUG_ON(sizeof(*ctx) > sizeof(cb->ctx));
 
@@ -1147,10 +1150,21 @@ static int ctrl_dumppolicy_start(struct 
netlink_callback *cb)
        if (!rt)
                return -ENOENT;
 
-       if (!rt->policy)
+       if (tb[CTRL_ATTR_OP]) {
+               err = genl_get_cmd(nla_get_u8(tb[CTRL_ATTR_OP]), 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)
-- 
2.26.2