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, 4 insertions, 3 deletions

diff --git a/net/openvswitch/datapath.c b/net/openvswitch/datapath.c
index a64d3eb1f9a9..356677c3a0c2 100644
--- a/net/openvswitch/datapath.c
+++ b/net/openvswitch/datapath.c
@@ -463,7 +463,8 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
                           nla_data(upcall_info->userdata));
 
         if (upcall_info->egress_tun_info) {
-                nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_EGRESS_TUN_KEY);
+                nla = nla_nest_start_noflag(user_skb,
+                                            OVS_PACKET_ATTR_EGRESS_TUN_KEY);
                 if (!nla) {
                         err = -EMSGSIZE;
                         goto out;
@@ -475,7 +476,7 @@ static int queue_userspace_packet(struct datapath *dp, struct sk_buff *skb,
         }
 
         if (upcall_info->actions_len) {
-                nla = nla_nest_start(user_skb, OVS_PACKET_ATTR_ACTIONS);
+                nla = nla_nest_start_noflag(user_skb, OVS_PACKET_ATTR_ACTIONS);
                 if (!nla) {
                         err = -EMSGSIZE;
                         goto out;
@@ -776,7 +777,7 @@ static int ovs_flow_cmd_fill_actions(const struct sw_flow *flow,
          * This can only fail for dump operations because the skb is always
          * properly sized for single flows.
          */
-        start = nla_nest_start(skb, OVS_FLOW_ATTR_ACTIONS);
+        start = nla_nest_start_noflag(skb, OVS_FLOW_ATTR_ACTIONS);
         if (start) {
                 const struct sw_flow_actions *sf_acts;