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Date: Sat, 3 Oct 2020 10:44:43 +0200
From: Johannes Berg <johannes@...solutions.net>
To: netdev@...r.kernel.org
Cc: Jakub Kicinski <kuba@...nel.org>, David Ahern <dsahern@...il.com>,
Johannes Berg <johannes.berg@...el.com>
Subject: [PATCH v3 2/5] netlink: rework policy dump to support multiple policies
From: Johannes Berg <johannes.berg@...el.com>
Rework the policy dump code a bit to support adding multiple
policies to a single dump, in order to e.g. support per-op
policies in generic netlink.
v2:
- move kernel-doc to implementation [Jakub]
- squash the first patch to not flip-flop on the prototype
[Jakub]
- merge netlink_policy_dump_get_policy_idx() with the old
get_policy_idx() we already had
- rebase without Jakub's patch to have per-op dump
Signed-off-by: Johannes Berg <johannes.berg@...el.com>
---
include/net/netlink.h | 9 ++--
net/netlink/genetlink.c | 3 +-
net/netlink/policy.c | 102 ++++++++++++++++++++++++++++++++--------
3 files changed, 90 insertions(+), 24 deletions(-)
diff --git a/include/net/netlink.h b/include/net/netlink.h
index 00258590f2cb..5a5ff97cc596 100644
--- a/include/net/netlink.h
+++ b/include/net/netlink.h
@@ -1937,9 +1937,12 @@ void nla_get_range_signed(const struct nla_policy *pt,
struct netlink_policy_dump_state;
-int netlink_policy_dump_start(const struct nla_policy *policy,
- unsigned int maxtype,
- struct netlink_policy_dump_state **state);
+int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
+ const struct nla_policy *policy,
+ unsigned int maxtype);
+int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
+ const struct nla_policy *policy,
+ unsigned int maxtype);
bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state);
int netlink_policy_dump_write(struct sk_buff *skb,
struct netlink_policy_dump_state *state);
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 7ddc574931f4..89646b97300c 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -1150,7 +1150,8 @@ static int ctrl_dumppolicy_start(struct netlink_callback *cb)
if (!rt->policy)
return -ENODATA;
- return netlink_policy_dump_start(rt->policy, rt->maxattr, &ctx->state);
+ return netlink_policy_dump_add_policy(&ctx->state, rt->policy,
+ rt->maxattr);
}
static int ctrl_dumppolicy(struct sk_buff *skb, struct netlink_callback *cb)
diff --git a/net/netlink/policy.c b/net/netlink/policy.c
index 753b265acec5..cf23c0151721 100644
--- a/net/netlink/policy.c
+++ b/net/netlink/policy.c
@@ -63,44 +63,85 @@ static int add_policy(struct netlink_policy_dump_state **statep,
return 0;
}
-static unsigned int get_policy_idx(struct netlink_policy_dump_state *state,
- const struct nla_policy *policy,
- unsigned int maxtype)
+/**
+ * netlink_policy_dump_get_policy_idx - retrieve policy index
+ * @state: the policy dump state
+ * @policy: the policy to find
+ * @maxtype: the policy's maxattr
+ *
+ * Returns: the index of the given policy in the dump state
+ *
+ * Call this to find a policy index when you've added multiple and e.g.
+ * need to tell userspace which command has which policy (by index).
+ *
+ * Note: this will WARN and return 0 if the policy isn't found, which
+ * means it wasn't added in the first place, which would be an
+ * internal consistency bug.
+ */
+int netlink_policy_dump_get_policy_idx(struct netlink_policy_dump_state *state,
+ const struct nla_policy *policy,
+ unsigned int maxtype)
{
unsigned int i;
+ if (WARN_ON(!policy || !maxtype))
+ return 0;
+
for (i = 0; i < state->n_alloc; i++) {
if (state->policies[i].policy == policy &&
state->policies[i].maxtype == maxtype)
return i;
}
- WARN_ON_ONCE(1);
- return -1;
+ WARN_ON(1);
+ return 0;
}
-int netlink_policy_dump_start(const struct nla_policy *policy,
- unsigned int maxtype,
- struct netlink_policy_dump_state **statep)
+static struct netlink_policy_dump_state *alloc_state(void)
{
struct netlink_policy_dump_state *state;
+
+ state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
+ GFP_KERNEL);
+ if (!state)
+ return ERR_PTR(-ENOMEM);
+ state->n_alloc = INITIAL_POLICIES_ALLOC;
+
+ return state;
+}
+
+/**
+ * netlink_policy_dump_add_policy - add a policy to the dump
+ * @pstate: state to add to, may be reallocated, must be %NULL the first time
+ * @policy: the new policy to add to the dump
+ * @maxtype: the new policy's max attr type
+ *
+ * Returns: 0 on success, a negative error code otherwise.
+ *
+ * Call this to allocate a policy dump state, and to add policies to it. This
+ * should be called from the dump start() callback.
+ *
+ * Note: on failures, any previously allocated state is freed.
+ */
+int netlink_policy_dump_add_policy(struct netlink_policy_dump_state **pstate,
+ const struct nla_policy *policy,
+ unsigned int maxtype)
+{
+ struct netlink_policy_dump_state *state = *pstate;
unsigned int policy_idx;
int err;
- if (*statep)
- return 0;
+ if (!state) {
+ state = alloc_state();
+ if (IS_ERR(state))
+ return PTR_ERR(state);
+ }
/*
* walk the policies and nested ones first, and build
* a linear list of them.
*/
- state = kzalloc(struct_size(state, policies, INITIAL_POLICIES_ALLOC),
- GFP_KERNEL);
- if (!state)
- return -ENOMEM;
- state->n_alloc = INITIAL_POLICIES_ALLOC;
-
err = add_policy(&state, policy, maxtype);
if (err)
return err;
@@ -131,8 +172,7 @@ int netlink_policy_dump_start(const struct nla_policy *policy,
}
}
- *statep = state;
-
+ *pstate = state;
return 0;
}
@@ -143,11 +183,26 @@ netlink_policy_dump_finished(struct netlink_policy_dump_state *state)
!state->policies[state->policy_idx].policy;
}
+/**
+ * netlink_policy_dump_loop - dumping loop indicator
+ * @state: the policy dump state
+ *
+ * Returns: %true if the dump continues, %false otherwise
+ *
+ * Note: this frees the dump state when finishing
+ */
bool netlink_policy_dump_loop(struct netlink_policy_dump_state *state)
{
return !netlink_policy_dump_finished(state);
}
+/**
+ * netlink_policy_dump_write - write current policy dump attributes
+ * @skb: the message skb to write to
+ * @state: the policy dump state
+ *
+ * Returns: 0 on success, an error code otherwise
+ */
int netlink_policy_dump_write(struct sk_buff *skb,
struct netlink_policy_dump_state *state)
{
@@ -185,8 +240,9 @@ int netlink_policy_dump_write(struct sk_buff *skb,
type = NL_ATTR_TYPE_NESTED_ARRAY;
if (pt->nested_policy && pt->len &&
(nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_IDX,
- get_policy_idx(state, pt->nested_policy,
- pt->len)) ||
+ netlink_policy_dump_get_policy_idx(state,
+ pt->nested_policy,
+ pt->len)) ||
nla_put_u32(skb, NL_POLICY_TYPE_ATTR_POLICY_MAXTYPE,
pt->len)))
goto nla_put_failure;
@@ -309,6 +365,12 @@ int netlink_policy_dump_write(struct sk_buff *skb,
return -ENOBUFS;
}
+/**
+ * netlink_policy_dump_free - free policy dump state
+ * @state: the policy dump state to free
+ *
+ * Call this from the done() method to ensure dump state is freed.
+ */
void netlink_policy_dump_free(struct netlink_policy_dump_state *state)
{
kfree(state);
--
2.26.2
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