[PATCH iproute2 net-next] gre: add support for ERSPAN tunnel

[William Tu <u9012063@gmail.com>]

The patch adds ERSPAN type II tunnel support.  The implementation
is based on the draft at https://tools.ietf.org/html/draft-foschiano-erspan-01
One of the purposes is for Linux box to be able to receive ERSPAN
monitoring traffic sent from the Cisco switch, by creating a ERSPAN
tunnel device.  In addition, the patch also adds ERSPAN TX, so traffic
can also be encapsulated into ERSPAN and sent out.

The implementation reuses the key as ERSPAN session ID, and
field 'erspan' as ERSPAN Index fields:
./ip link add dev ers11 type erspan seq key 100 erspan 123 \
		local 172.16.1.200 remote 172.16.1.100

Signed-off-by: William Tu <u9012063@gmail.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Alexey Kuznetsov <kuznet@ms2.inr.ac.ru>
---
 include/linux/if_tunnel.h |  1 +
 ip/link_gre.c             | 26 +++++++++++++++++++++++++-
 2 files changed, 26 insertions(+), 1 deletion(-)

diff --git a/include/linux/if_tunnel.h b/include/linux/if_tunnel.h
index 7375335a0773..21834cac4c0d 100644
--- a/include/linux/if_tunnel.h
+++ b/include/linux/if_tunnel.h
@@ -134,6 +134,7 @@ enum {
 	IFLA_GRE_COLLECT_METADATA,
 	IFLA_GRE_IGNORE_DF,
 	IFLA_GRE_FWMARK,
+	IFLA_GRE_ERSPAN_INDEX,
 	__IFLA_GRE_MAX,
 };
 
diff --git a/ip/link_gre.c b/ip/link_gre.c
index c2ec5f26902f..c28fac1eb5de 100644
--- a/ip/link_gre.c
+++ b/ip/link_gre.c
@@ -26,7 +26,7 @@
 static void print_usage(FILE *f)
 {
 	fprintf(f,
-		"Usage: ... { gre | gretap } [ remote ADDR ]\n"
+		"Usage: ... { gre | gretap | erspan } [ remote ADDR ]\n"
 		"                            [ local ADDR ]\n"
 		"                            [ [i|o]seq ]\n"
 		"                            [ [i|o]key KEY ]\n"
@@ -44,6 +44,7 @@ static void print_usage(FILE *f)
 		"                            [ [no]encap-csum6 ]\n"
 		"                            [ [no]encap-remcsum ]\n"
 		"                            [ fwmark MARK ]\n"
+		"                            [ erspan IDX ]\n"
 		"\n"
 		"Where: ADDR := { IP_ADDRESS | any }\n"
 		"       TOS  := { NUMBER | inherit }\n"
@@ -96,6 +97,7 @@ static int gre_parse_opt(struct link_util *lu, int argc, char **argv,
 	__u8 metadata = 0;
 	__u8 ignore_df = 0;
 	__u32 fwmark = 0;
+	__u32 erspan_idx = 0;
 
 	if (!(n->nlmsg_flags & NLM_F_CREATE)) {
 		if (rtnl_talk(&rth, &req.n, &req.n, sizeof(req)) < 0) {
@@ -172,6 +174,9 @@ get_failed:
 
 		if (greinfo[IFLA_GRE_FWMARK])
 			fwmark = rta_getattr_u32(greinfo[IFLA_GRE_FWMARK]);
+
+		if (greinfo[IFLA_GRE_ERSPAN_INDEX])
+			erspan_idx = rta_getattr_u32(greinfo[IFLA_GRE_ERSPAN_INDEX]);
 	}
 
 	while (argc > 0) {
@@ -328,6 +333,10 @@ get_failed:
 			NEXT_ARG();
 			if (get_u32(&fwmark, *argv, 0))
 				invarg("invalid fwmark\n", *argv);
+		} else if (strcmp(*argv, "erspan") == 0) {
+			NEXT_ARG();
+			if (get_u32(&erspan_idx, *argv, 0))
+				invarg("invalid erspan index\n", *argv);
 		} else
 			usage();
 		argc--; argv++;
@@ -359,6 +368,7 @@ get_failed:
 		addattr_l(n, 1024, IFLA_GRE_TTL, &ttl, 1);
 		addattr_l(n, 1024, IFLA_GRE_TOS, &tos, 1);
 		addattr32(n, 1024, IFLA_GRE_FWMARK, fwmark);
+		addattr32(n, 1024, IFLA_GRE_ERSPAN_INDEX, htonl(erspan_idx));
 	} else {
 		addattr_l(n, 1024, IFLA_GRE_COLLECT_METADATA, NULL, 0);
 	}
@@ -473,6 +483,12 @@ static void gre_print_opt(struct link_util *lu, FILE *f, struct rtattr *tb[])
 	if (tb[IFLA_GRE_IGNORE_DF] && rta_getattr_u8(tb[IFLA_GRE_IGNORE_DF]))
 		fputs("ignore-df ", f);
 
+	if (tb[IFLA_GRE_ERSPAN_INDEX]) {
+		__u32 erspan_idx = rta_getattr_u32(tb[IFLA_GRE_ERSPAN_INDEX]);
+
+		fprintf(f, "erspan_index %u", erspan_idx);
+	}
+
 	if (tb[IFLA_GRE_ENCAP_TYPE] &&
 	    rta_getattr_u16(tb[IFLA_GRE_ENCAP_TYPE]) != TUNNEL_ENCAP_NONE) {
 		__u16 type = rta_getattr_u16(tb[IFLA_GRE_ENCAP_TYPE]);
@@ -538,3 +554,11 @@ struct link_util gretap_link_util = {
 	.print_opt = gre_print_opt,
 	.print_help = gre_print_help,
 };
+
+struct link_util erspan_link_util = {
+	.id = "erspan",
+	.maxattr = IFLA_GRE_MAX,
+	.parse_opt = gre_parse_opt,
+	.print_opt = gre_print_opt,
+	.print_help = gre_print_help,
+};
-- 
2.7.4