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>

3 files changed, 3 insertions, 3 deletions

diff --git a/net/ipv6/addrconf.c b/net/ipv6/addrconf.c
index 340a0f06f974..01f081aa718c 100644
--- a/net/ipv6/addrconf.c
+++ b/net/ipv6/addrconf.c
@@ -5752,7 +5752,7 @@ static int inet6_fill_ifinfo(struct sk_buff *skb, struct inet6_dev *idev,
             nla_put_u8(skb, IFLA_OPERSTATE,
                        netif_running(dev) ? dev->operstate : IF_OPER_DOWN))
                 goto nla_put_failure;
-        protoinfo = nla_nest_start(skb, IFLA_PROTINFO);
+        protoinfo = nla_nest_start_noflag(skb, IFLA_PROTINFO);
         if (!protoinfo)
                 goto nla_put_failure;
 
diff --git a/net/ipv6/route.c b/net/ipv6/route.c
index 9c0127a44f9f..e2b47f47de92 100644
--- a/net/ipv6/route.c
+++ b/net/ipv6/route.c
@@ -4777,7 +4777,7 @@ static int rt6_fill_node(struct net *net, struct sk_buff *skb,
                 struct fib6_info *sibling, *next_sibling;
                 struct nlattr *mp;
 
-                mp = nla_nest_start(skb, RTA_MULTIPATH);
+                mp = nla_nest_start_noflag(skb, RTA_MULTIPATH);
                 if (!mp)
                         goto nla_put_failure;
 
diff --git a/net/ipv6/seg6_local.c b/net/ipv6/seg6_local.c
index 60325dbfe88b..67005ac71341 100644
--- a/net/ipv6/seg6_local.c
+++ b/net/ipv6/seg6_local.c
@@ -853,7 +853,7 @@ static int put_nla_bpf(struct sk_buff *skb, struct seg6_local_lwt *slwt)
         if (!slwt->bpf.prog)
                 return 0;
 
-        nest = nla_nest_start(skb, SEG6_LOCAL_BPF);
+        nest = nla_nest_start_noflag(skb, SEG6_LOCAL_BPF);
         if (!nest)
                 return -EMSGSIZE;