netlink: make nla_nest_start() add NLA_F_NESTED flag

Even if the NLA_F_NESTED flag was introduced more than 11 years ago, most
netlink based interfaces (including recently added ones) are still not
setting it in kernel generated messages. Without the flag, message parsers
not aware of attribute semantics (e.g. wireshark dissector or libmnl's
mnl_nlmsg_fprintf()) cannot recognize nested attributes and won't display
the structure of their contents.

Unfortunately we cannot just add the flag everywhere as there may be
userspace applications which check nlattr::nla_type directly rather than
through a helper masking out the flags. Therefore the patch renames
nla_nest_start() to nla_nest_start_noflag() and introduces nla_nest_start()
as a wrapper adding NLA_F_NESTED. The calls which add NLA_F_NESTED manually
are rewritten to use nla_nest_start().

Except for changes in include/net/netlink.h, the patch was generated using
this semantic patch:

@@ expression E1, E2; @@
-nla_nest_start(E1, E2)
+nla_nest_start_noflag(E1, E2)

@@ expression E1, E2; @@
-nla_nest_start_noflag(E1, E2 | NLA_F_NESTED)
+nla_nest_start(E1, E2)

Signed-off-by: Michal Kubecek <mkubecek@suse.cz>
Acked-by: Jiri Pirko <jiri@mellanox.com>
Acked-by: David Ahern <dsahern@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 2 insertions, 2 deletions

diff --git a/net/l2tp/l2tp_netlink.c b/net/l2tp/l2tp_netlink.c
index 77595fcc9f75..c31b50cc48d9 100644
--- a/net/l2tp/l2tp_netlink.c
+++ b/net/l2tp/l2tp_netlink.c
@@ -345,7 +345,7 @@ static int l2tp_nl_tunnel_send(struct sk_buff *skb, u32 portid, u32 seq, int fla
 	    nla_put_u16(skb, L2TP_ATTR_ENCAP_TYPE, tunnel->encap))
 		goto nla_put_failure;
 
-	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
 	if (nest == NULL)
 		goto nla_put_failure;
 
@@ -742,7 +742,7 @@ static int l2tp_nl_session_send(struct sk_buff *skb, u32 portid, u32 seq, int fl
 			   session->reorder_timeout, L2TP_ATTR_PAD)))
 		goto nla_put_failure;
 
-	nest = nla_nest_start(skb, L2TP_ATTR_STATS);
+	nest = nla_nest_start_noflag(skb, L2TP_ATTR_STATS);
 	if (nest == NULL)
 		goto nla_put_failure;