netlink: add a start callback for starting a netlink dump

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>

diff --git a/include/linux/netlink.h b/include/linux/netlink.h
index 639e9b8..0b41959 100644 (file)
--- a/include/linux/netlink.h
+++ b/include/linux/netlink.h
@@ -131,6 +131,7 @@ netlink_skb_clone(struct sk_buff *skb, gfp_t gfp_mask)
 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;

diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 1b6b6dc..43c0e77 100644 (file)
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -114,6 +114,7 @@ static inline void genl_info_net_set(struct genl_info *info, struct net *net)
  * @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);

diff --git a/net/netlink/af_netlink.c b/net/netlink/af_netlink.c
index 59651af..81dc1bb 100644 (file)
--- a/net/netlink/af_netlink.c
+++ b/net/netlink/af_netlink.c
@@ -2915,6 +2915,7 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 
        cb = &nlk->cb;
        memset(cb, 0, sizeof(*cb));
+       cb->start = control->start;
        cb->dump = control->dump;
        cb->done = control->done;
        cb->nlh = nlh;
@@ -2927,6 +2928,9 @@ int __netlink_dump_start(struct sock *ssk, struct sk_buff *skb,
 
        mutex_unlock(nlk->cb_mutex);
 
+       if (cb->start)
+               cb->start(cb);
+
        ret = netlink_dump(sk);
        sock_put(sk);
 

diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index bc0e504..8e63662 100644 (file)
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -513,6 +513,20 @@ void *genlmsg_put(struct sk_buff *skb, u32 portid, u32 seq,
 }
 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 genl_family *family,
                                .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 genl_family *family,
                } else {
                        struct netlink_dump_control c = {
                                .module = family->module,
+                               .start = ops->start,
                                .dump = ops->dumpit,
                                .done = ops->done,
                        };