From 0a5d2935ffa1cd48d48e71b9a0bd77faeec24c9e Mon Sep 17 00:00:00 2001
From: Hannes Gredler <hannes@rtbrick.com>
Date: Tue, 24 May 2022 11:19:28 +0000
Subject: [PATCH] add support for serializing small-metrics IPv4 REACH TLVs 128
 and 130

---
 code/lspgen/src/lspgen_config.c | 19 +++++++++++++++++--
 code/lspgen/src/lspgen_isis.h   |  3 +++
 code/lspgen/src/lspgen_lsdb.h   |  3 ++-
 code/lspgen/src/lspgen_packet.c | 21 +++++++++++++++++++++
 4 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/code/lspgen/src/lspgen_config.c b/code/lspgen/src/lspgen_config.c
index 58c18ac0..1f897375 100644
--- a/code/lspgen/src/lspgen_config.c
+++ b/code/lspgen/src/lspgen_config.c
@@ -486,6 +486,10 @@ lspgen_read_common_prefix_config(lsdb_attr_t *attr, json_t *obj)
     if (value && json_is_boolean(value)) {
         attr->key.prefix.s_flag = json_boolean_value(value);
     }
+    value = json_object_get(obj, "small_metrics");
+    if (value && json_is_boolean(value)) {
+        attr->key.prefix.small_metrics = json_boolean_value(value);
+    }
 }
 
 void
@@ -500,7 +504,18 @@ lspgen_read_ipv4_prefix_config(lsdb_node_t *node, json_t *obj)
 
         lspgen_read_common_prefix_config(&attr_template, obj);
 
-        attr_template.key.attr_type = ISIS_TLV_EXTD_IPV4_REACH;
+	/*
+	 * TLV type depends on small-metrics and external flag.
+	 */
+	if (attr_template.key.prefix.small_metrics) {
+	    if (attr_template.key.prefix.ext_flag) {
+		attr_template.key.attr_type = ISIS_TLV_EXT_IPV4_REACH;
+	    } else {
+		attr_template.key.attr_type = ISIS_TLV_INT_IPV4_REACH;
+	    }
+	} else {
+	    attr_template.key.attr_type = ISIS_TLV_EXTD_IPV4_REACH;
+	}
         lsdb_add_node_attr(node, &attr_template);
     }
 }
@@ -789,4 +804,4 @@ lspgen_read_config(lsdb_ctx_t *ctx)
     }
 
     json_decref(root_obj);
-}
\ No newline at end of file
+}
diff --git a/code/lspgen/src/lspgen_isis.h b/code/lspgen/src/lspgen_isis.h
index af34f020..1b6ac04b 100644
--- a/code/lspgen/src/lspgen_isis.h
+++ b/code/lspgen/src/lspgen_isis.h
@@ -23,9 +23,12 @@ enum {
 #define TLV_OVERHEAD               2
 
 #define ISIS_TLV_AREA              1
+#define ISIS_TLV_IS_REACH          2
 #define ISIS_TLV_AUTH             10
 #define ISIS_TLV_EXTD_IS_REACH    22
+#define ISIS_TLV_INT_IPV4_REACH  128
 #define ISIS_TLV_PROTOCOLS       129
+#define ISIS_TLV_EXT_IPV4_REACH  130
 #define ISIS_TLV_IPV4_ADDR       132
 #define ISIS_TLV_EXTD_IPV4_REACH 135
 #define ISIS_TLV_HOSTNAME        137
diff --git a/code/lspgen/src/lspgen_lsdb.h b/code/lspgen/src/lspgen_lsdb.h
index 3d1575f7..27c74a78 100644
--- a/code/lspgen/src/lspgen_lsdb.h
+++ b/code/lspgen/src/lspgen_lsdb.h
@@ -216,7 +216,8 @@ typedef struct lsdb_attr_prefix_ {
     s_flag:1, /* domain wide flooding */
     adv_range:1, /* Advertise range (binding TLV) */
     adv_sid:1, /* Advertise SID */
-    adv_tag:1; /* Advertise Tag */
+    adv_tag:1, /* Advertise Tag */
+    small_metrics:1; /* old-style 6-bit metrics */
 
     uint8_t sid_algo;
     uint32_t metric;
diff --git a/code/lspgen/src/lspgen_packet.c b/code/lspgen/src/lspgen_packet.c
index ce3e8967..aa8c802a 100644
--- a/code/lspgen/src/lspgen_packet.c
+++ b/code/lspgen/src/lspgen_packet.c
@@ -329,6 +329,7 @@ lspgen_serialize_prefix_subtlv(lsdb_attr_t *attr, io_buffer_t *buf,
 void
 lspgen_serialize_attr(lsdb_attr_t *attr, io_buffer_t *buf)
 {
+    uint32_t metric, mask;
     uint8_t attr_len, flags;
     bool subtlv_present;
 
@@ -358,6 +359,26 @@ lspgen_serialize_attr(lsdb_attr_t *attr, io_buffer_t *buf)
             attr_len = strnlen(attr->key.hostname, sizeof(attr->key.hostname));
             push_data(buf, (uint8_t *)attr->key.hostname, attr_len);
             break;
+        case ISIS_TLV_INT_IPV4_REACH: /* fall through */
+        case ISIS_TLV_EXT_IPV4_REACH:
+	    metric = attr->key.prefix.metric;
+	    if (metric > 63) {
+		metric = 63; /* limit metric to 6 bits */
+	    }
+	    flags = metric;
+            if (attr->key.prefix.updown_flag) {
+                flags |= 0x80;
+            }
+            push_be_uint(buf, 1, flags); /* default metric */
+            push_be_uint(buf, 1, 0x80); /* delay metric */
+            push_be_uint(buf, 1, 0x80); /* expense metric */
+            push_be_uint(buf, 1, 0x80); /* error metric */
+            push_data(buf, (uint8_t*)&attr->key.prefix.ipv4_prefix.address, 4);
+	    mask = 0xffffffff;
+	    /* convert prefix length to mask */
+	    mask &= ~((1 << ((32 - attr->key.prefix.ipv4_prefix.len)))-1);
+	    push_be_uint(buf, 4, mask);
+	    break;
         case ISIS_TLV_EXTD_IPV4_REACH:
             push_be_uint(buf, 4, attr->key.prefix.metric); /* Metric */
             flags = attr->key.prefix.ipv4_prefix.len & 0x3f;