[iproute2-next v2] seg6: add support for vrftable attribute in SRv6 End.DT4/DT6 behaviors

[Paolo Lungaroni <paolo.lungaroni@cnit.it>]

We introduce the "vrftable" attribute for supporting the SRv6 End.DT4 and
End.DT6 behaviors in iproute2.
The "vrftable" attribute indicates the routing table associated with
the VRF device used by SRv6 End.DT4/DT6 for routing IPv4/IPv6 packets.

The SRv6 End.DT4/DT6 is used to implement IPv4/IPv6 L3 VPNs based on Segment
Routing over IPv6 networks in multi-tenants environments.
It decapsulates the received packets and it performs the IPv4/IPv6 routing
lookup in the routing table of the tenant.

The SRv6 End.DT4/DT6 leverages a VRF device in order to force the routing
lookup into the associated routing table using the "vrftable" attribute.

Some examples:
 $ ip -6 route add 2001:db8::1 encap seg6local action End.DT4 vrftable 100 dev eth0
 $ ip -6 route add 2001:db8::2 encap seg6local action End.DT6 vrftable 200 dev eth0

Standard Output:
 $ ip -6 route show 2001:db8::1
 2001:db8::1  encap seg6local action End.DT4 vrftable 100 dev eth0 metric 1024 pref medium

JSON Output:
$ ip -6 -j -p route show 2001:db8::2
[ {
        "dst": "2001:db8::2",
        "encap": "seg6local",
        "action": "End.DT6",
        "vrftable": 200,
        "dev": "eth0",
        "metric": 1024,
        "flags": [ ],
        "pref": "medium"
} ]

v2:
 - no changes made: resubmit after pulling out this patch from the kernel
   patchset.

v1:
 - mixing this patch with the kernel patchset confused patckwork.

Signed-off-by: Paolo Lungaroni <paolo.lungaroni@cnit.it>
Signed-off-by: Andrea Mayer <andrea.mayer@uniroma2.it>
---
 include/uapi/linux/seg6_local.h |  1 +
 ip/iproute_lwtunnel.c           | 19 ++++++++++++++++---
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/include/uapi/linux/seg6_local.h b/include/uapi/linux/seg6_local.h
index 5312de80..bb5c8ddf 100644
--- a/include/uapi/linux/seg6_local.h
+++ b/include/uapi/linux/seg6_local.h
@@ -26,6 +26,7 @@ enum {
 	SEG6_LOCAL_IIF,
 	SEG6_LOCAL_OIF,
 	SEG6_LOCAL_BPF,
+	SEG6_LOCAL_VRFTABLE,
 	__SEG6_LOCAL_MAX,
 };
 #define SEG6_LOCAL_MAX (__SEG6_LOCAL_MAX - 1)
diff --git a/ip/iproute_lwtunnel.c b/ip/iproute_lwtunnel.c
index 9b4f0885..1ab95cd2 100644
--- a/ip/iproute_lwtunnel.c
+++ b/ip/iproute_lwtunnel.c
@@ -294,6 +294,11 @@ static void print_encap_seg6local(FILE *fp, struct rtattr *encap)
 			     rtnl_rttable_n2a(rta_getattr_u32(tb[SEG6_LOCAL_TABLE]),
 			     b1, sizeof(b1)));
 
+	if (tb[SEG6_LOCAL_VRFTABLE])
+		print_string(PRINT_ANY, "vrftable", "vrftable %s ",
+			     rtnl_rttable_n2a(rta_getattr_u32(tb[SEG6_LOCAL_VRFTABLE]),
+			     b1, sizeof(b1)));
+
 	if (tb[SEG6_LOCAL_NH4]) {
 		print_string(PRINT_ANY, "nh4",
 			     "nh4 %s ", rt_addr_n2a_rta(AF_INET, tb[SEG6_LOCAL_NH4]));
@@ -860,9 +865,10 @@ static int lwt_parse_bpf(struct rtattr *rta, size_t len,
 static int parse_encap_seg6local(struct rtattr *rta, size_t len, int *argcp,
 				 char ***argvp)
 {
-	int segs_ok = 0, hmac_ok = 0, table_ok = 0, nh4_ok = 0, nh6_ok = 0;
-	int iif_ok = 0, oif_ok = 0, action_ok = 0, srh_ok = 0, bpf_ok = 0;
-	__u32 action = 0, table, iif, oif;
+	int segs_ok = 0, hmac_ok = 0, table_ok = 0, vrftable_ok = 0;
+	int nh4_ok = 0, nh6_ok = 0, iif_ok = 0, oif_ok = 0;
+	__u32 action = 0, table, vrftable, iif, oif;
+	int action_ok = 0, srh_ok = 0, bpf_ok = 0;
 	struct ipv6_sr_hdr *srh;
 	char **argv = *argvp;
 	int argc = *argcp;
@@ -887,6 +893,13 @@ static int parse_encap_seg6local(struct rtattr *rta, size_t len, int *argcp,
 				duparg2("table", *argv);
 			rtnl_rttable_a2n(&table, *argv);
 			ret = rta_addattr32(rta, len, SEG6_LOCAL_TABLE, table);
+		} else if (strcmp(*argv, "vrftable") == 0) {
+			NEXT_ARG();
+			if (vrftable_ok++)
+				duparg2("vrftable", *argv);
+			rtnl_rttable_a2n(&vrftable, *argv);
+			ret = rta_addattr32(rta, len, SEG6_LOCAL_VRFTABLE,
+					    vrftable);
 		} else if (strcmp(*argv, "nh4") == 0) {
 			NEXT_ARG();
 			if (nh4_ok++)
-- 
2.20.1