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, 3 insertions, 3 deletions

diff --git a/net/ipv4/ipmr.c b/net/ipv4/ipmr.c
index a8eb97777c0a..1322573b8228 100644
--- a/net/ipv4/ipmr.c
+++ b/net/ipv4/ipmr.c
@@ -2783,7 +2783,7 @@ static bool ipmr_fill_vif(struct mr_table *mrt, u32 vifid, struct sk_buff *skb)
 		return true;
 
 	vif = &mrt->vif_table[vifid];
-	vif_nest = nla_nest_start(skb, IPMRA_VIF);
+	vif_nest = nla_nest_start_noflag(skb, IPMRA_VIF);
 	if (!vif_nest)
 		return false;
 	if (nla_put_u32(skb, IPMRA_VIFA_IFINDEX, vif->dev->ifindex) ||
@@ -2867,7 +2867,7 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
 		memset(hdr, 0, sizeof(*hdr));
 		hdr->ifi_family = RTNL_FAMILY_IPMR;
 
-		af = nla_nest_start(skb, IFLA_AF_SPEC);
+		af = nla_nest_start_noflag(skb, IFLA_AF_SPEC);
 		if (!af) {
 			nlmsg_cancel(skb, nlh);
 			goto out;
@@ -2878,7 +2878,7 @@ static int ipmr_rtm_dumplink(struct sk_buff *skb, struct netlink_callback *cb)
 			goto out;
 		}
 
-		vifs = nla_nest_start(skb, IPMRA_TABLE_VIFS);
+		vifs = nla_nest_start_noflag(skb, IPMRA_TABLE_VIFS);
 		if (!vifs) {
 			nla_nest_end(skb, af);
 			nlmsg_end(skb, nlh);