[PATCH 4.4 01/27] netlink: add a start callback for starting a netlink dump

Greg Kroah-Hartman
2017-12-04T16:43:48Z

From: Tom Herbert <tom@herbertland.com>

commit fc9e50f5a5a4e1fa9ba2756f745a13e693cf6a06 upstream.

The start callback allows the caller to set up a context for the
dump callbacks. Presumably, the context can then be destroyed in
the done callback.

Signed-off-by: Tom Herbert <tom@herbertland.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
include/linux/netlink.h | 2 ++
include/net/genetlink.h | 2 ++
net/netlink/af_netlink.c | 4 ++++
net/netlink/genetlink.c | 16 ++++++++++++++++
4 files changed, 24 insertions(+)

--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -131,6 +131,7 @@ netlink_skb_clone(struct sk_buff *skb, g
struct netlink_callback {
struct sk_buff *skb;
const struct nlmsghdr *nlh;
+ int (*start)(struct netlink_callback *);
int (*dump)(struct sk_buff * skb,
struct netlink_callback *cb);
int (*done)(struct netlink_callback *cb);
@@ -153,6 +154,7 @@ struct nlmsghdr *
__nlmsg_put(struct sk_buff *skb, u32 portid, u32 seq, int type, int len, int flags);

struct netlink_dump_control {
+ int (*start)(struct netlink_callback *);
int (*dump)(struct sk_buff *skb, struct netlink_callback *);
int (*done)(struct netlink_callback *);
void *data;
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -114,6 +114,7 @@ static inline void genl_info_net_set(str
* @flags: flags
* @policy: attribute validation policy
* @doit: standard command callback
+ * @start: start callback for dumps
* @dumpit: callback for dumpers
* @done: completion callback for dumps
* @ops_list: operations list
@@ -122,6 +123,7 @@ struct genl_ops {
const struct nla_policy *policy;
int (*doit)(struct sk_buff *skb,
struct genl_info *info);
+ int (*start)(struct netlink_callback *cb);
int (*dumpit)(struct sk_buff *skb,
struct netlink_callback *cb);
int (*done)(struct netlink_callback *cb);
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2203,6 +2203,7 @@ int __netlink_dump_start(struct sock *ss

cb = &nlk->cb;
memset(cb, 0, sizeof(*cb));
+ cb->start = control->start;
cb->dump = control->dump;
cb->done = control->done;
cb->nlh = nlh;
@@ -2216,6 +2217,9 @@ int __netlink_dump_start(struct sock *ss

mutex_unlock(nlk->cb_mutex);

+ if (cb->start)
+ cb->start(cb);
+
ret = netlink_dump(sk);
sock_put(sk);

--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -513,6 +513,20 @@ void *genlmsg_put(struct sk_buff *skb, u
}
EXPORT_SYMBOL(genlmsg_put);

+static int genl_lock_start(struct netlink_callback *cb)
+{
+ /* our ops are always const - netlink API doesn't propagate that */
+ const struct genl_ops *ops = cb->data;
+ int rc = 0;
+
+ if (ops->start) {
+ genl_lock();
+ rc = ops->start(cb);
+ genl_unlock();
+ }
+ return rc;
+}
+
static int genl_lock_dumpit(struct sk_buff *skb, struct netlink_callback *cb)
{
/* our ops are always const - netlink API doesn't propagate that */
@@ -577,6 +591,7 @@ static int genl_family_rcv_msg(struct ge
.module = family->module,
/* we have const, but the netlink API doesn't */
.data = (void *)ops,
+ .start = genl_lock_start,
.dump = genl_lock_dumpit,
.done = genl_lock_done,
};
@@ -588,6 +603,7 @@ static int genl_family_rcv_msg(struct ge
} else {
struct netlink_dump_control c = {
.module = family->module,
+ .start = ops->start,
.dump = ops->dumpit,
.done = ops->done,
};