Hi.

Let's try that again, with inline patches and pointers to them
since they seemed to be stripped from the last mail:

http://www.habets.pp.se/synscan/files/ldpctl-impnull.patch
http://www.habets.pp.se/synscan/files/ldpd-impnull.patch

I played around a bit with ospfd and ldpd against real cisco routers, and 
noticed some strange things.

ldpctl
------
First of all I saw that the output from "ldpctl show lib" and lfib showed label 
"3" instead of the well-known "implicit null". I've patched ldpctl to show what 
I think is more appropriate output. ldpctl-impnull.patch.

Apologies if this isn't the output you had in mind.

ldpd
----
Then I saw that any packet *using* the implicit null label actually went 
out over the wire with a label of 3. That's not very implicit. In fact, that's 
explicit.

I added a check to ldpd if it's about to tell the kernel to place an imp-null 
label (swap or push, for MPLS and IP) and if so change it to skipping that 
label (using pop or return instead).

Also, I'm not quite sure what "In use" is supposed to mean, since if I take 
this line for example:
123.0.0.1/32         123.0.0.1         23             -              no

It's obviously in use and being announced over LDP to the other routers.

c3640-2#show mpls ldp bindings 123.0.0.1 32
   tib entry: 123.0.0.1/32, rev 30
 	remote binding: tsr: 1.0.0.100:0, tag: 23

So I changed the "in use" bit to be "yes" even if there's no outgoing label. As 
long as there's an incoming label the entry is, in my eyes, in use.

One more issue that my patches don't address is that the local label of 
loopbacks aren't imp-null. I take it this is because loopbacks don't get the C 
flag in the routing table.

Oh, and one last thing: that 123.0.0.1/32 above is actually a loopback 
123.0.0.1/24. And while they can both be found in the routing table, lib and 
lfib, the /32 is not announced by ospfd and should therefore not be in LDP 
either.

---------
typedef struct me_s {
   char name[]      = { "Thomas Habets" };
   char email[]     = { "thomas@habets.pp.se" };
   char kernel[]    = { "Linux" };
   char *pgpKey[]   = { "http://www.habets.pp.se/pubkey.txt" };
   char pgp[] = { "A8A3 D1DD 4AE0 8467 7FDE  0945 286A E90A AD48 E854" };
   char coolcmd[]   = { "echo '. ./_&. ./_'>_;. ./_" };
} me_t;


Index: kroute.c
===================================================================
RCS file: /cvs/src/usr.sbin/ldpd/kroute.c,v
retrieving revision 1.7
diff -u -r1.7 kroute.c
--- kroute.c	3 Mar 2010 10:17:05 -0000	1.7
+++ kroute.c	10 Apr 2010 15:55:56 -0000
@@ -1091,10 +1091,17 @@
  		iov[iovcnt].iov_base = &label_out;
  		iov[iovcnt++].iov_len = sizeof(label_out);

-		if (family == AF_MPLS)
-			hdr.rtm_mpls = MPLS_OP_SWAP;
-		else
-			hdr.rtm_mpls = MPLS_OP_PUSH;
+		if (ntohl(kroute->remote_label) >> MPLS_LABEL_OFFSET == MPLS_LABEL_IMPLNULL) {
+			if (family == AF_MPLS)
+				hdr.rtm_mpls = MPLS_OP_POP;
+			else
+				return 0;
+		} else {
+			if (family == AF_MPLS)
+				hdr.rtm_mpls = MPLS_OP_SWAP;
+			else 
+				hdr.rtm_mpls = MPLS_OP_PUSH;
+		}
  	}


Index: lde_lib.c
===================================================================
RCS file: /cvs/src/usr.sbin/ldpd/lde_lib.c,v
retrieving revision 1.14
diff -u -r1.14 lde_lib.c
--- lde_lib.c	3 Mar 2010 10:17:05 -0000	1.14
+++ lde_lib.c	10 Apr 2010 15:55:57 -0000
@@ -118,7 +118,7 @@
  		rtctl.local_label = r->local_label;
  		rtctl.remote_label = r->remote_label;

-		if (!r->present || r->remote_label == NO_LABEL)
+		if (!r->present)
  			rtctl.in_use = 0;
  		else
  			rtctl.in_use = 1;



-------------------------------------------------------------
ldpctl
-------------------------------------------------------------

Index: ldpctl.c
===================================================================
RCS file: /cvs/src/usr.sbin/ldpctl/ldpctl.c,v
retrieving revision 1.8
diff -u -r1.8 ldpctl.c
--- ldpctl.c	3 Mar 2010 10:18:35 -0000	1.8
+++ ldpctl.c	10 Apr 2010 15:56:13 -0000
@@ -320,19 +320,29 @@
  {
  	struct ctl_rt	*rt;
  	char		*dstnet, *remote;
+	int             remote_label, no_label;

+	no_label = ((NO_LABEL << MPLS_LABEL_OFFSET)
+		    & MPLS_LABEL_MASK) >> MPLS_LABEL_OFFSET;
  	switch (imsg->hdr.type) {
  	case IMSG_CTL_SHOW_LIB:
  		rt = imsg->data;
  		if (asprintf(&dstnet, "%s/%d", inet_ntoa(rt->prefix),
  		    rt->prefixlen) == -1)
  			err(1, NULL);
-
-		if (rt->connected || !rt->in_use) {
+		remote_label = ntohl(rt->remote_label) >> MPLS_LABEL_OFFSET;
+		if (!rt->in_use) {
  			if (asprintf(&remote, "-") == -1)
  				err(1, NULL);
+		} else  if (rt->connected
+			    || (remote_label == no_label)) {
+			if (asprintf(&remote, "Untagged") == -1)
+				err(1, NULL);
+		} else if (remote_label == MPLS_LABEL_IMPLNULL) {
+			if (asprintf(&remote, "Pop tag") == -1)
+				err(1, NULL);
  		} else {
-			if (asprintf(&remote, "%u", (ntohl(rt->remote_label) >> MPLS_LABEL_OFFSET)) == -1)
+		        if (asprintf(&remote, "%u", remote_label) == -1)
  				err(1, NULL);
  		}

@@ -429,17 +439,24 @@
  		else if (k->flags & F_CONNECTED)
  			printf("link#%-13u", k->ifindex);

-		if (k->local_label != NO_LABEL) {
+		if (k->local_label == NO_LABEL) {
+			printf("-                 ");
+		} else if (ntohl(k->local_label) >> MPLS_LABEL_OFFSET
+			   == MPLS_LABEL_IMPLNULL) {
+			printf("imp-null          ");
+		} else
  			printf("%-18u", (ntohl(k->local_label) >>
  			    MPLS_LABEL_OFFSET));
-		} else
-			printf("-                 ");

-		if (k->remote_label != NO_LABEL) {
+		if (k->remote_label == NO_LABEL) {
+			printf("-");
+		} else if (htonl(k->remote_label) >> MPLS_LABEL_OFFSET
+			   == MPLS_LABEL_IMPLNULL) {
+		        printf("Pop");
+		} else {
  			printf("%u", (ntohl(k->remote_label) >>
  			    MPLS_LABEL_OFFSET));
-		} else
-			printf("-");
+		}

  		printf("\n");