[PATCH iproute2] Show 'external' link mode in output

[Phil Dibowitz <phil@ipom.com>]

Recently `external` support was added to the tunnel drivers, but there is no way
to introspect this from userspace. This adds support for that.

Now `ip -details link` shows it:

```
7: tunl60@NONE: <NOARP> mtu 1452 qdisc noop state DOWN mode DEFAULT group
default qlen 1
    link/tunnel6 :: brd :: promiscuity 0
    ip6tnl external any remote :: local :: encaplimit 0 hoplimit 0 tclass 0x00 flowlabel 0x00000 (flowinfo 0x00000000) addrgenmode eui64 numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
```

Signed-off-by: Phil Dibowitz <phil@ipom.com>
---
 ip/link_ip6tnl.c | 3 +++
 ip/link_iptnl.c  | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/ip/link_ip6tnl.c b/ip/link_ip6tnl.c
index 43287ab..5d0efc8 100644
--- a/ip/link_ip6tnl.c
+++ b/ip/link_ip6tnl.c
@@ -345,6 +345,9 @@ static void ip6tunnel_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb
 	if (!tb)
 		return;
 
+        if (tb[IFLA_IPTUN_COLLECT_METADATA])
+                print_bool(PRINT_ANY, "external", "external ", true);
+
 	if (tb[IFLA_IPTUN_FLAGS])
 		flags = rta_getattr_u32(tb[IFLA_IPTUN_FLAGS]);
 
diff --git a/ip/link_iptnl.c b/ip/link_iptnl.c
index 4940b8b..e345b5c 100644
--- a/ip/link_iptnl.c
+++ b/ip/link_iptnl.c
@@ -393,6 +393,9 @@ static void iptunnel_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[
 	if (!tb)
 		return;
 
+        if (tb[IFLA_IPTUN_COLLECT_METADATA])
+                print_bool(PRINT_ANY, "external", "external ", true);
+
 	if (tb[IFLA_IPTUN_REMOTE]) {
 		unsigned int addr = rta_getattr_u32(tb[IFLA_IPTUN_REMOTE]);
 
-- 
2.9.5