[PATCH v3 iproute2 net-next] gre6: add collect metadata support

[William Tu <u9012063@gmail.com>]

The patch adds 'external' option to support collect metadata
gre6 tunnel.  The 'external' keyword is already used to set the
device into collect metadata mode such as vxlan, geneve, ipip,
etc.  This patch extends support for ipv6 gre and gretap.
Examples of L3 and L2 gre device:
bash:~# ip link add dev ip6gre123 type ip6gre external
bash:~# ip link add dev ip6gretap123 type ip6gretap external

Signed-off-by: William Tu <u9012063@gmail.com>
Cc: Daniel Borkmann <daniel@iogearbox.net>
---
change in v3:
  - explain a little more on man page about 'external'
change in v2:
  - remove "noexternal" in man page
---
 ip/link_gre6.c        | 55 ++++++++++++++++++++++++++++++++-------------------
 man/man8/ip-link.8.in |  7 +++++++
 2 files changed, 42 insertions(+), 20 deletions(-)

diff --git a/ip/link_gre6.c b/ip/link_gre6.c
index 0a82eaecf2cd..2cb46ca116d0 100644
--- a/ip/link_gre6.c
+++ b/ip/link_gre6.c
@@ -105,6 +105,7 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u16 encapflags = TUNNEL_ENCAP_FLAG_CSUM6;
 	__u16 encapsport = 0;
 	__u16 encapdport = 0;
+	__u8 metadata = 0;
 	int len;
 	__u32 fwmark = 0;
 	__u32 erspan_idx = 0;
@@ -178,6 +179,9 @@ get_failed:
 		if (greinfo[IFLA_GRE_ENCAP_SPORT])
 			encapsport = rta_getattr_u16(greinfo[IFLA_GRE_ENCAP_SPORT]);
 
+		if (greinfo[IFLA_GRE_COLLECT_METADATA])
+			metadata = 1;
+
 		if (greinfo[IFLA_GRE_ENCAP_DPORT])
 			encapdport = rta_getattr_u16(greinfo[IFLA_GRE_ENCAP_DPORT]);
 
@@ -355,6 +359,8 @@ get_failed:
 			encapflags |= TUNNEL_ENCAP_FLAG_REMCSUM;
 		} else if (strcmp(*argv, "noencap-remcsum") == 0) {
 			encapflags &= ~TUNNEL_ENCAP_FLAG_REMCSUM;
+		} else if (strcmp(*argv, "external") == 0) {
+			metadata = 1;
 		} else if (strcmp(*argv, "fwmark") == 0) {
 			NEXT_ARG();
 			if (strcmp(*argv, "inherit") == 0) {
@@ -388,26 +394,30 @@ get_failed:
 		argc--; argv++;
 	}
 
-	addattr32(n, 1024, IFLA_GRE_IKEY, ikey);
-	addattr32(n, 1024, IFLA_GRE_OKEY, okey);
-	addattr_l(n, 1024, IFLA_GRE_IFLAGS, &iflags, 2);
-	addattr_l(n, 1024, IFLA_GRE_OFLAGS, &oflags, 2);
-	addattr_l(n, 1024, IFLA_GRE_LOCAL, &laddr, sizeof(laddr));
-	addattr_l(n, 1024, IFLA_GRE_REMOTE, &raddr, sizeof(raddr));
-	if (link)
-		addattr32(n, 1024, IFLA_GRE_LINK, link);
-	addattr_l(n, 1024, IFLA_GRE_TTL, &hop_limit, 1);
-	addattr_l(n, 1024, IFLA_GRE_ENCAP_LIMIT, &encap_limit, 1);
-	addattr_l(n, 1024, IFLA_GRE_FLOWINFO, &flowinfo, 4);
-	addattr32(n, 1024, IFLA_GRE_FLAGS, flags);
-	addattr32(n, 1024, IFLA_GRE_FWMARK, fwmark);
-	if (erspan_idx != 0)
-		addattr32(n, 1024, IFLA_GRE_ERSPAN_INDEX, erspan_idx);
-
-	addattr16(n, 1024, IFLA_GRE_ENCAP_TYPE, encaptype);
-	addattr16(n, 1024, IFLA_GRE_ENCAP_FLAGS, encapflags);
-	addattr16(n, 1024, IFLA_GRE_ENCAP_SPORT, htons(encapsport));
-	addattr16(n, 1024, IFLA_GRE_ENCAP_DPORT, htons(encapdport));
+	if (!metadata) {
+		addattr32(n, 1024, IFLA_GRE_IKEY, ikey);
+		addattr32(n, 1024, IFLA_GRE_OKEY, okey);
+		addattr_l(n, 1024, IFLA_GRE_IFLAGS, &iflags, 2);
+		addattr_l(n, 1024, IFLA_GRE_OFLAGS, &oflags, 2);
+		addattr_l(n, 1024, IFLA_GRE_LOCAL, &laddr, sizeof(laddr));
+		addattr_l(n, 1024, IFLA_GRE_REMOTE, &raddr, sizeof(raddr));
+		if (link)
+			addattr32(n, 1024, IFLA_GRE_LINK, link);
+		addattr_l(n, 1024, IFLA_GRE_TTL, &hop_limit, 1);
+		addattr_l(n, 1024, IFLA_GRE_ENCAP_LIMIT, &encap_limit, 1);
+		addattr_l(n, 1024, IFLA_GRE_FLOWINFO, &flowinfo, 4);
+		addattr32(n, 1024, IFLA_GRE_FLAGS, flags);
+		addattr32(n, 1024, IFLA_GRE_FWMARK, fwmark);
+		if (erspan_idx != 0)
+			addattr32(n, 1024, IFLA_GRE_ERSPAN_INDEX, erspan_idx);
+
+		addattr16(n, 1024, IFLA_GRE_ENCAP_TYPE, encaptype);
+		addattr16(n, 1024, IFLA_GRE_ENCAP_FLAGS, encapflags);
+		addattr16(n, 1024, IFLA_GRE_ENCAP_SPORT, htons(encapsport));
+		addattr16(n, 1024, IFLA_GRE_ENCAP_DPORT, htons(encapdport));
+	} else {
+		addattr_l(n, 1024, IFLA_GRE_COLLECT_METADATA, NULL, 0);
+	}
 
 	return 0;
 }
@@ -426,6 +436,11 @@ static void gre_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 	if (!tb)
 		return;
 
+	if (tb[IFLA_GRE_COLLECT_METADATA]) {
+		print_bool(PRINT_ANY, "collect_metadata", "external", true);
+		return;
+	}
+
 	if (tb[IFLA_GRE_FLAGS])
 		flags = rta_getattr_u32(tb[IFLA_GRE_FLAGS]);
 
diff --git a/man/man8/ip-link.8.in b/man/man8/ip-link.8.in
index 0db2582e19f7..4d954b31d438 100644
--- a/man/man8/ip-link.8.in
+++ b/man/man8/ip-link.8.in
@@ -768,6 +768,8 @@ the following additional arguments are supported:
 .BI "dscp inherit"
 ] [
 .BI dev " PHYS_DEV "
+] [
+.RB external
 ]
 
 .in +8
@@ -846,6 +848,11 @@ or
 .IR 00 ".." ff
 when tunneling non-IP packets. The default value is 00.
 
+.sp
+.RB external
+- make this tunnel externally controlled (or not, which is the default).
+This is also known as collect_metadata mode for tunnels.
+
 .in -8
 
 .TP
-- 
2.7.4