genetlink: introduce split op representation

We currently have two forms of operations - small ops and "full" ops
(or just ops). The former does not have pointers for some of the less
commonly used features (namely dump start/done and policy).

The "full" ops, however, still don't contain all the necessary
information. In particular the policy is per command ID, while
do and dump often accept different attributes. It's also not
possible to define different pre_doit and post_doit callbacks
for different commands within the family.

At the same time a lot of commands do not support dumping and
therefore all the dump-related information is wasted space.

Create a new command representation which can hold info about
a do implementation or a dump implementation, but not both at
the same time.

Use this new representation on the command execution path
(genl_family_rcv_msg) as we either run a do or a dump and
don't have to create a "full" op there.

Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Reviewed-by: Jacob Keller <jacob.e.keller@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 64 insertions, 15 deletions

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 0a7a856e9ce0..c66299740c05 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -189,6 +189,51 @@ static int genl_get_cmd(u32 cmd, const struct genl_family *family,
 	return genl_get_cmd_small(cmd, family, op);
 }
 
+static void
+genl_cmd_full_to_split(struct genl_split_ops *op,
+		       const struct genl_family *family,
+		       const struct genl_ops *full, u8 flags)
+{
+	if (flags & GENL_CMD_CAP_DUMP) {
+		op->start	= full->start;
+		op->dumpit	= full->dumpit;
+		op->done	= full->done;
+	} else {
+		op->pre_doit	= family->pre_doit;
+		op->doit	= full->doit;
+		op->post_doit	= family->post_doit;
+	}
+
+	op->policy		= full->policy;
+	op->maxattr		= full->maxattr;
+
+	op->cmd			= full->cmd;
+	op->internal_flags	= full->internal_flags;
+	op->flags		= full->flags;
+	op->validate		= full->validate;
+
+	/* Make sure flags include the GENL_CMD_CAP_DO / GENL_CMD_CAP_DUMP */
+	op->flags		|= flags;
+}
+
+static int
+genl_get_cmd_split(u32 cmd, u8 flags, const struct genl_family *family,
+		   struct genl_split_ops *op)
+{
+	struct genl_ops full;
+	int err;
+
+	err = genl_get_cmd(cmd, family, &full);
+	if (err) {
+		memset(op, 0, sizeof(*op));
+		return err;
+	}
+
+	genl_cmd_full_to_split(op, family, &full, flags);
+
+	return 0;
+}
+
 static void genl_get_cmd_by_index(unsigned int i,
 				  const struct genl_family *family,
 				  struct genl_ops *op)
@@ -544,7 +589,7 @@ static struct nlattr **
 genl_family_rcv_msg_attrs_parse(const struct genl_family *family,
 				struct nlmsghdr *nlh,
 				struct netlink_ext_ack *extack,
-				const struct genl_ops *ops,
+				const struct genl_split_ops *ops,
 				int hdrlen,
 				enum genl_validate_flags no_strict_flag)
 {
@@ -580,18 +625,19 @@ struct genl_start_context {
 	const struct genl_family *family;
 	struct nlmsghdr *nlh;
 	struct netlink_ext_ack *extack;
-	const struct genl_ops *ops;
+	const struct genl_split_ops *ops;
 	int hdrlen;
 };
 
 static int genl_start(struct netlink_callback *cb)
 {
 	struct genl_start_context *ctx = cb->data;
-	const struct genl_ops *ops = ctx->ops;
+	const struct genl_split_ops *ops;
 	struct genl_dumpit_info *info;
 	struct nlattr **attrs = NULL;
 	int rc = 0;
 
+	ops = ctx->ops;
 	if (ops->validate & GENL_DONT_VALIDATE_DUMP)
 		goto no_attrs;
 
@@ -633,7 +679,7 @@ no_attrs:
 
 static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 {
-	const struct genl_ops *ops = &genl_dumpit_info(cb)->op;
+	const struct genl_split_ops *ops = &genl_dumpit_info(cb)->op;
 	int rc;
 
 	genl_lock();
@@ -645,7 +691,7 @@ static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
 static int genl_lock_done(struct netlink_callback *cb)
 {
 	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
-	const struct genl_ops *ops = &info->op;
+	const struct genl_split_ops *ops = &info->op;
 	int rc = 0;
 
 	if (ops->done) {
@@ -661,7 +707,7 @@ static int genl_lock_done(struct netlink_callback *cb)
 static int genl_parallel_done(struct netlink_callback *cb)
 {
 	const struct genl_dumpit_info *info = genl_dumpit_info(cb);
-	const struct genl_ops *ops = &info->op;
+	const struct genl_split_ops *ops = &info->op;
 	int rc = 0;
 
 	if (ops->done)
@@ -675,7 +721,7 @@ static int genl_family_rcv_msg_dumpit(const struct genl_family *family,
 				      struct sk_buff *skb,
 				      struct nlmsghdr *nlh,
 				      struct netlink_ext_ack *extack,
-				      const struct genl_ops *ops,
+				      const struct genl_split_ops *ops,
 				      int hdrlen, struct net *net)
 {
 	struct genl_start_context ctx;
@@ -721,7 +767,7 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 				    struct sk_buff *skb,
 				    struct nlmsghdr *nlh,
 				    struct netlink_ext_ack *extack,
-				    const struct genl_ops *ops,
+				    const struct genl_split_ops *ops,
 				    int hdrlen, struct net *net)
 {
 	struct nlattr **attrbuf;
@@ -747,16 +793,16 @@ static int genl_family_rcv_msg_doit(const struct genl_family *family,
 	genl_info_net_set(&info, net);
 	memset(&info.user_ptr, 0, sizeof(info.user_ptr));
 
-	if (family->pre_doit) {
-		err = family->pre_doit(ops, skb, &info);
+	if (ops->pre_doit) {
+		err = ops->pre_doit(ops, skb, &info);
 		if (err)
 			goto out;
 	}
 
 	err = ops->doit(skb, &info);
 
-	if (family->post_doit)
-		family->post_doit(ops, skb, &info);
+	if (ops->post_doit)
+		ops->post_doit(ops, skb, &info);
 
 out:
 	genl_family_rcv_msg_attrs_free(attrbuf);
@@ -801,8 +847,9 @@ static int genl_family_rcv_msg(const struct genl_family *family,
 {
 	struct net *net = sock_net(skb->sk);
 	struct genlmsghdr *hdr = nlmsg_data(nlh);
-	struct genl_ops op;
+	struct genl_split_ops op;
 	int hdrlen;
+	u8 flags;
 
 	/* this family doesn't exist in this netns */
 	if (!family->netnsok && !net_eq(net, &init_net))
@@ -815,7 +862,9 @@ static int genl_family_rcv_msg(const struct genl_family *family,
 	if (genl_header_check(family, nlh, hdr, extack))
 		return -EINVAL;
 
-	if (genl_get_cmd(hdr->cmd, family, &op))
+	flags = (nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP ?
+		GENL_CMD_CAP_DUMP : GENL_CMD_CAP_DO;
+	if (genl_get_cmd_split(hdr->cmd, flags, family, &op))
 		return -EOPNOTSUPP;
 
 	if ((op.flags & GENL_ADMIN_PERM) &&
@@ -826,7 +875,7 @@ static int genl_family_rcv_msg(const struct genl_family *family,
 	    !netlink_ns_capable(skb, net->user_ns, CAP_NET_ADMIN))
 		return -EPERM;
 
-	if ((nlh->nlmsg_flags & NLM_F_DUMP) == NLM_F_DUMP)
+	if (flags & GENL_CMD_CAP_DUMP)
 		return genl_family_rcv_msg_dumpit(family, skb, nlh, extack,
 						  &op, hdrlen, net);
 	else