[GENL]: Provide more information to userspace about registered genl families

Additionaly exports the following information when providing
the list of registered generic netlink families:
  - protocol version
  - header size
  - maximum number of attributes
  - list of available operations including
      - id
      - flags
      - avaiability of policy and doit/dumpit function

libnl HEAD provides a utility to read this new information:

	0x0010 nlctrl version 1
	    hdrsize 0 maxattr 6
	      op GETFAMILY (0x03) [POLICY,DOIT,DUMPIT]
	0x0011 NLBL_MGMT version 1
	    hdrsize 0 maxattr 0
	      op unknown (0x02) [DOIT]
	      op unknown (0x03) [DOIT]
	      ....

Signed-off-by: Thomas Graf <tgraf@suug.ch>
Signed-off-by: David S. Miller <davem@davemloft.net>

3 files changed, 58 insertions, 2 deletions

diff --git a/include/linux/genetlink.h b/include/linux/genetlink.h
index 84f12a41dc01..9049dc65ae51 100644
--- a/include/linux/genetlink.h
+++ b/include/linux/genetlink.h
@@ -16,6 +16,8 @@ struct genlmsghdr {
 
 #define GENL_HDRLEN     NLMSG_ALIGN(sizeof(struct genlmsghdr))
 
+#define GENL_ADMIN_PERM         0x01
+
 /*
  * List of reserved static generic netlink identifiers:
  */
@@ -43,9 +45,25 @@ enum {
         CTRL_ATTR_UNSPEC,
         CTRL_ATTR_FAMILY_ID,
         CTRL_ATTR_FAMILY_NAME,
+        CTRL_ATTR_VERSION,
+        CTRL_ATTR_HDRSIZE,
+        CTRL_ATTR_MAXATTR,
+        CTRL_ATTR_OPS,
         __CTRL_ATTR_MAX,
 };
 
 #define CTRL_ATTR_MAX (__CTRL_ATTR_MAX - 1)
 
+enum {
+        CTRL_ATTR_OP_UNSPEC,
+        CTRL_ATTR_OP_ID,
+        CTRL_ATTR_OP_FLAGS,
+        CTRL_ATTR_OP_POLICY,
+        CTRL_ATTR_OP_DOIT,
+        CTRL_ATTR_OP_DUMPIT,
+        __CTRL_ATTR_OP_MAX,
+};
+
+#define CTRL_ATTR_OP_MAX (__CTRL_ATTR_OP_MAX - 1)
+
 #endif  /* __LINUX_GENERIC_NETLINK_H */
diff --git a/include/net/genetlink.h b/include/net/genetlink.h
index 97d6d3aba9d2..4a38d85e4e25 100644
--- a/include/net/genetlink.h
+++ b/include/net/genetlink.h
@@ -27,8 +27,6 @@ struct genl_family
         struct list_head        family_list;    /* private */
 };
 
-#define GENL_ADMIN_PERM         0x01
-
 /**
  * struct genl_info - receiving information
  * @snd_seq: sending sequence number
diff --git a/net/netlink/genetlink.c b/net/netlink/genetlink.c
index 3ac942cdb677..49bc2db7982b 100644
--- a/net/netlink/genetlink.c
+++ b/net/netlink/genetlink.c
@@ -387,7 +387,10 @@ static void genl_rcv(struct sock *sk, int len)
 static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
                           u32 flags, struct sk_buff *skb, u8 cmd)
 {
+        struct nlattr *nla_ops;
+        struct genl_ops *ops;
         void *hdr;
+        int idx = 1;
 
         hdr = genlmsg_put(skb, pid, seq, GENL_ID_CTRL, 0, flags, cmd,
                           family->version);
@@ -396,6 +399,37 @@ static int ctrl_fill_info(struct genl_family *family, u32 pid, u32 seq,
 
         NLA_PUT_STRING(skb, CTRL_ATTR_FAMILY_NAME, family->name);
         NLA_PUT_U16(skb, CTRL_ATTR_FAMILY_ID, family->id);
+        NLA_PUT_U32(skb, CTRL_ATTR_VERSION, family->version);
+        NLA_PUT_U32(skb, CTRL_ATTR_HDRSIZE, family->hdrsize);
+        NLA_PUT_U32(skb, CTRL_ATTR_MAXATTR, family->maxattr);
+
+        nla_ops = nla_nest_start(skb, CTRL_ATTR_OPS);
+        if (nla_ops == NULL)
+                goto nla_put_failure;
+
+        list_for_each_entry(ops, &family->ops_list, ops_list) {
+                struct nlattr *nest;
+
+                nest = nla_nest_start(skb, idx++);
+                if (nest == NULL)
+                        goto nla_put_failure;
+
+                NLA_PUT_U32(skb, CTRL_ATTR_OP_ID, ops->cmd);
+                NLA_PUT_U32(skb, CTRL_ATTR_OP_FLAGS, ops->flags);
+
+                if (ops->policy)
+                        NLA_PUT_FLAG(skb, CTRL_ATTR_OP_POLICY);
+
+                if (ops->doit)
+                        NLA_PUT_FLAG(skb, CTRL_ATTR_OP_DOIT);
+
+                if (ops->dumpit)
+                        NLA_PUT_FLAG(skb, CTRL_ATTR_OP_DUMPIT);
+
+                nla_nest_end(skb, nest);
+        }
+
+        nla_nest_end(skb, nla_ops);
 
         return genlmsg_end(skb, hdr);
 
@@ -411,6 +445,9 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
         int chains_to_skip = cb->args[0];
         int fams_to_skip = cb->args[1];
 
+        if (chains_to_skip != 0)
+                genl_lock();
+
         for (i = 0; i < GENL_FAM_TAB_SIZE; i++) {
                 if (i < chains_to_skip)
                         continue;
@@ -428,6 +465,9 @@ static int ctrl_dumpfamily(struct sk_buff *skb, struct netlink_callback *cb)
         }
 
 errout:
+        if (chains_to_skip != 0)
+                genl_unlock();
+
         cb->args[0] = i;
         cb->args[1] = n;