isisd: Unpack Node MSD Sub-TLV with SRv6 MSDs

The Router Capabilities TLV unpack function already unpacks the Node MSD
Sub-TLV.

This commit extends Router Capabilities TLV unpack function to extract
SRv6 MSDs from the Node MSD Sub-TLV (RFC 9352 section #4).

Signed-off-by: Carmine Scarpitta <carmine.scarpitta@uniroma2.it>

diff --git a/isisd/isis_tlvs.c b/isisd/isis_tlvs.c
index 53ba0f853a83a717f3246366f6da574a2d037b93..dd4a72d2c4d8664ef712f81fc8c529d61e50956a 100644 (file)
--- a/isisd/isis_tlvs.c
+++ b/isisd/isis_tlvs.c
@@ -4464,6 +4464,7 @@ static int unpack_tlv_router_cap(enum isis_tlv_context context,
        uint8_t length;
        uint8_t subtlv_len;
        uint8_t size;
+       int num_msd;
 
        sbuf_push(log, indent, "Unpacking Router Capability TLV...\n");
        if (tlv_len < ISIS_ROUTER_CAP_SIZE) {
@@ -4632,19 +4633,66 @@ static int unpack_tlv_router_cap(enum isis_tlv_context context,
 
                        break;
                case ISIS_SUBTLV_NODE_MSD:
+                       sbuf_push(log, indent,
+                                 "Unpacking Node MSD sub-TLV...\n");
+
                        /* Check that MSD is correctly formated */
-                       if (length < MSD_TLV_SIZE) {
+                       if (length % 2) {
+                               sbuf_push(
+                                       log, indent,
+                                       "WARNING: Unexpected MSD sub-TLV length\n");
                                stream_forward_getp(s, length);
                                break;
                        }
-                       msd_type = stream_getc(s);
-                       rcap->msd = stream_getc(s);
-                       /* Only BMI-MSD type has been defined in RFC 8491 */
-                       if (msd_type != MSD_TYPE_BASE_MPLS_IMPOSITION)
-                               rcap->msd = 0;
-                       /* Only one MSD is standardized. Skip others */
-                       if (length > MSD_TLV_SIZE)
-                               stream_forward_getp(s, length - MSD_TLV_SIZE);
+
+                       /* Get the number of MSDs carried in the value field of
+                        * the Node MSD sub-TLV. The value field consists of one
+                        * or more pairs of a 1-octet MSD-Type and 1-octet
+                        * MSD-Value */
+                       num_msd = length / 2;
+
+                       /* Unpack MSDs */
+                       for (int i = 0; i < num_msd; i++) {
+                               msd_type = stream_getc(s);
+
+                               switch (msd_type) {
+                               case MSD_TYPE_BASE_MPLS_IMPOSITION:
+                                       /* BMI-MSD type as per RFC 8491 */
+                                       rcap->msd = stream_getc(s);
+                                       break;
+                               case ISIS_SUBTLV_SRV6_MAX_SL_MSD:
+                                       /* SRv6 Maximum Segments Left MSD Type
+                                        * as per RFC 9352 section #4.1 */
+                                       rcap->srv6_msd.max_seg_left_msd =
+                                               stream_getc(s);
+                                       break;
+                               case ISIS_SUBTLV_SRV6_MAX_END_POP_MSD:
+                                       /* SRv6 Maximum End Pop MSD Type as per
+                                        * RFC 9352 section #4.2 */
+                                       rcap->srv6_msd.max_end_pop_msd =
+                                               stream_getc(s);
+                                       break;
+                               case ISIS_SUBTLV_SRV6_MAX_H_ENCAPS_MSD:
+                                       /* SRv6 Maximum H.Encaps MSD Type as per
+                                        * RFC 9352 section #4.3 */
+                                       rcap->srv6_msd.max_h_encaps_msd =
+                                               stream_getc(s);
+                                       break;
+                               case ISIS_SUBTLV_SRV6_MAX_END_D_MSD:
+                                       /* SRv6 Maximum End D MSD Type as per
+                                        * RFC 9352 section #4.4 */
+                                       rcap->srv6_msd.max_end_d_msd =
+                                               stream_getc(s);
+                                       break;
+                               default:
+                                       /* Unknown MSD, let's skip it */
+                                       sbuf_push(
+                                               log, indent,
+                                               "WARNING: Skipping unknown MSD Type %hhu (1 byte)\n",
+                                               msd_type);
+                                       stream_forward_getp(s, 1);
+                               }
+                       }
                        break;
 #ifndef FABRICD
                case ISIS_SUBTLV_FAD: