From 114be2af28e5c124bd479a487f89244ba99c272d Mon Sep 17 00:00:00 2001
From: Ondrej Zajicek <santiago@crfreenet.org>
Date: Tue, 5 Mar 2024 16:38:24 +0100
Subject: [PATCH] Filter: Add route attribute gw_mpls_stack

Add route attribute gw_mpls_stack to make MPLS stack of route nexthop
accessible from filters. Its type is T_CLIST, which is really not correct
(as it is a list, while T_CLIST is a set). Therefore, we keep this
attribute *undocumented* and it will be *changed* without further notice.

Based on a patch from Trisha Biswas <tbiswas@fastly.com>, thanks!
---
 filter/config.Y |  3 ++-
 filter/data.h   |  1 +
 filter/f-inst.c | 56 +++++++++++++++++++++++++++++++++++++++++++++++++
 lib/ip.h        |  1 +
 nest/rt-show.c  |  2 +-
 5 files changed, 61 insertions(+), 2 deletions(-)

diff --git a/filter/config.Y b/filter/config.Y
index 79786faa..09d4fd89 100644
--- a/filter/config.Y
+++ b/filter/config.Y
@@ -362,7 +362,7 @@ CF_KEYWORDS(FUNCTION, PRINT, PRINTN, UNSET, RETURN,
 	IF, THEN, ELSE, CASE,
 	FOR, DO,
 	TRUE, FALSE, RT, RO, UNKNOWN, GENERIC,
-	FROM, GW, NET, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS, ONLINK,
+	FROM, GW, NET, PROTO, SOURCE, SCOPE, DEST, IFNAME, IFINDEX, WEIGHT, GW_MPLS, GW_MPLS_STACK, ONLINK,
 	PREFERENCE,
 	ROA_CHECK,
 	DEFINED,
@@ -879,6 +879,7 @@ static_attr:
  | WEIGHT  { $$ = f_new_static_attr(T_INT,        SA_WEIGHT,	0); }
  | PREFERENCE { $$ = f_new_static_attr(T_INT,	  SA_PREF,	0); }
  | GW_MPLS { $$ = f_new_static_attr(T_INT,        SA_GW_MPLS,	0); }
+ | GW_MPLS_STACK { $$ = f_new_static_attr(T_CLIST, SA_GW_MPLS_STACK,	0); }
  | ONLINK  { $$ = f_new_static_attr(T_BOOL,       SA_ONLINK,	0); }
  ;
 
diff --git a/filter/data.h b/filter/data.h
index 21a78bf6..df8d6a8f 100644
--- a/filter/data.h
+++ b/filter/data.h
@@ -120,6 +120,7 @@ enum f_sa_code {
   SA_WEIGHT,
   SA_PREF,
   SA_GW_MPLS,
+  SA_GW_MPLS_STACK,
   SA_ONLINK,
 } PACKED;
 
diff --git a/filter/f-inst.c b/filter/f-inst.c
index a3f441fc..6593a381 100644
--- a/filter/f-inst.c
+++ b/filter/f-inst.c
@@ -692,6 +692,16 @@
       case SA_WEIGHT:	RESULT(sa.f_type, i, rta->nh.weight + 1); break;
       case SA_PREF:	RESULT(sa.f_type, i, rta->pref); break;
       case SA_GW_MPLS:	RESULT(sa.f_type, i, rta->nh.labels ? rta->nh.label[0] : MPLS_NULL); break;
+      case SA_GW_MPLS_STACK:
+        {
+	  uint len = rta->nh.labels * sizeof(u32);
+	  struct adata *list = falloc(sizeof(struct adata) + len);
+	  list->length = len;
+	  memcpy(list->data, rta->nh.label, len);
+	  RESULT(sa.f_type, ad, list);
+	  break;
+	}
+
       case SA_ONLINK:	RESULT(sa.f_type, i, rta->nh.flags & RNF_ONLINK ? 1 : 0); break;
 
       default:
@@ -779,6 +789,36 @@
 	  }
 	  else
 	    rta->nh.labels = 0;
+
+	  rta->nh.labels_orig = rta->hostentry ? rta->nh.labels : 0;
+	}
+	break;
+
+      case SA_GW_MPLS_STACK:
+	{
+	  int len = int_set_get_size(v1.val.ad);
+	  u32 *l = int_set_get_data(v1.val.ad);
+
+	  if (len > MPLS_MAX_LABEL_STACK)
+	    runtime("Too many MPLS labels in stack (%d)", len);
+
+	  int i;
+	  for (i = 0; i < len; i++)
+	  {
+	    u32 label = l[i];
+
+	    if (label >= 0x100000)
+	      runtime("Invalid MPLS label (%u)", label);
+
+	    /* Ignore rest of label stack if implicit-NULL label (3) is set */
+	    if (label == MPLS_NULL)
+	      break;
+
+	    rta->nh.label[i] = label;
+	  }
+
+	  rta->nh.labels = i;
+	  rta->nh.labels_orig = rta->hostentry ? i : 0;
 	}
 	break;
 
@@ -1262,6 +1302,14 @@
     RESULT(T_CLIST, ad, [[ int_set_add(fpool, v1.val.ad, v2.val.i) ]]);
   }
 
+  /* Hack for gw_mpls_list */
+  INST(FI_CLIST_ADD_INT, 2, 1) {
+    ARG(1, T_CLIST);
+    ARG(2, T_INT);
+    METHOD_CONSTRUCTOR("add");
+    RESULT(T_CLIST, ad, [[ int_set_add(fpool, v1.val.ad, v2.val.i) ]]);
+  }
+
   INST(FI_CLIST_ADD_IP, 2, 1) {
     ARG(1, T_CLIST);
     ARG(2, T_IP);
@@ -1344,6 +1392,14 @@
     RESULT(T_CLIST, ad, [[ int_set_del(fpool, v1.val.ad, v2.val.i) ]]);
   }
 
+  /* Hack for gw_mpls_list */
+  INST(FI_CLIST_DELETE_INT, 2, 1) {
+    ARG(1, T_CLIST);
+    ARG(2, T_INT);
+    METHOD_CONSTRUCTOR("delete");
+    RESULT(T_CLIST, ad, [[ int_set_del(fpool, v1.val.ad, v2.val.i) ]]);
+  }
+
   INST(FI_CLIST_DELETE_IP, 2, 1) {
     ARG(1, T_CLIST);
     ARG(2, T_IP);
diff --git a/lib/ip.h b/lib/ip.h
index 8dd925ed..0a25d5bc 100644
--- a/lib/ip.h
+++ b/lib/ip.h
@@ -392,6 +392,7 @@ static inline ip6_addr ip6_ntoh(ip6_addr a)
 #define MPLS_MAX_LABEL 0x100000
 
 #define MPLS_MAX_LABEL_STACK 8
+#define MPLS_MAX_LABEL_STRING MPLS_MAX_LABEL_STACK*12 + 5
 typedef struct mpls_label_stack {
   uint len;
   u32 stack[MPLS_MAX_LABEL_STACK];
diff --git a/nest/rt-show.c b/nest/rt-show.c
index 265d5c44..fb71fba8 100644
--- a/nest/rt-show.c
+++ b/nest/rt-show.c
@@ -72,7 +72,7 @@ rt_show_rte(struct cli *c, byte *ia, rte *e, struct rt_show_data *d, int primary
   if (a->dest == RTD_UNICAST)
     for (nh = &(a->nh); nh; nh = nh->next)
     {
-      char mpls[MPLS_MAX_LABEL_STACK*12 + 5], *lsp = mpls;
+      char mpls[MPLS_MAX_LABEL_STRING], *lsp = mpls;
       char *onlink = (nh->flags & RNF_ONLINK) ? " onlink" : "";
       char weight[16] = "";