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>

4 files changed, 6 insertions, 6 deletions

diff --git a/net/ipv4/fib_semantics.c b/net/ipv4/fib_semantics.c
index 4336f1ec8ab0..71c2165a2ce3 100644
--- a/net/ipv4/fib_semantics.c
+++ b/net/ipv4/fib_semantics.c
@@ -1550,7 +1550,7 @@ static int fib_add_multipath(struct sk_buff *skb, struct fib_info *fi)
 {
         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/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);
diff --git a/net/ipv4/ipmr_base.c b/net/ipv4/ipmr_base.c
index 3e614cc824f7..278834d4babc 100644
--- a/net/ipv4/ipmr_base.c
+++ b/net/ipv4/ipmr_base.c
@@ -228,7 +228,7 @@ int mr_fill_mroute(struct mr_table *mrt, struct sk_buff *skb,
         if (c->mfc_flags & MFC_OFFLOAD)
                 rtm->rtm_flags |= RTNH_F_OFFLOAD;
 
-        mp_attr = nla_nest_start(skb, RTA_MULTIPATH);
+        mp_attr = nla_nest_start_noflag(skb, RTA_MULTIPATH);
         if (!mp_attr)
                 return -EMSGSIZE;
 
diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 4ccec4c705f7..9a08bfb0672c 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -658,7 +658,7 @@ static int tcp_metrics_fill_info(struct sk_buff *msg,
         {
                 int n = 0;
 
-                nest = nla_nest_start(msg, TCP_METRICS_ATTR_VALS);
+                nest = nla_nest_start_noflag(msg, TCP_METRICS_ATTR_VALS);
                 if (!nest)
                         goto nla_put_failure;
                 for (i = 0; i < TCP_METRIC_MAX_KERNEL + 1; i++) {