Map the TTL when building the initial MPLS stack from the encapsulated

packet. For IP and IPv6 the corresponding mapttl sysctl needs to be set.
This is needed to make traceroute work over MPLS.
OK michele@

2 files changed, 53 insertions, 4 deletions

diff --git a/sys/netmpls/mpls.h b/sys/netmpls/mpls.h
index 316d0f7ed86..64122e8679d 100644
--- a/sys/netmpls/mpls.h
+++ b/sys/netmpls/mpls.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: mpls.h,v 1.24 2010/06/09 11:40:36 claudio Exp $	*/
+/*	$OpenBSD: mpls.h,v 1.25 2010/09/08 08:00:56 claudio Exp $	*/
 
 /*
  * Copyright (C) 1999, 2000 and 2001 AYAME Project, WIDE Project.
@@ -168,6 +168,9 @@ extern int mpls_raw_usrreq(struct socket *, int, struct mbuf *,
 extern struct ifqueue	mplsintrq;	/* MPLS input queue */
 extern int		mplsqmaxlen;	/* MPLS input queue length */
 extern int		mpls_defttl;
+extern int		mpls_mapttl_ip;
+extern int		mpls_mapttl_ip6;
+
 
 void	mpls_init(void);
 void	mplsintr(void);
diff --git a/sys/netmpls/mpls_output.c b/sys/netmpls/mpls_output.c
index f2025764dfe..aa756b69835 100644
--- a/sys/netmpls/mpls_output.c
+++ b/sys/netmpls/mpls_output.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: mpls_output.c,v 1.11 2010/07/07 14:50:02 claudio Exp $ */
+/* $OpenBSD: mpls_output.c,v 1.12 2010/09/08 08:00:56 claudio Exp $ */
 
 /*
  * Copyright (c) 2008 Claudio Jeker <claudio@openbsd.org>
@@ -33,13 +33,18 @@
 #include <netinet/ip.h>
 #endif
 
+#ifdef INET6
+#include <netinet/ip6.h>
+#endif
+
 extern int	mpls_inkloop;
 
 #ifdef MPLS_DEBUG
 #define MPLS_LABEL_GET(l)	((ntohl((l) & MPLS_LABEL_MASK)) >> MPLS_LABEL_OFFSET)
 #endif
 
-void	mpls_do_cksum(struct mbuf *);
+void		mpls_do_cksum(struct mbuf *);
+u_int8_t	mpls_getttl(struct mbuf *, sa_family_t);
 
 int
 mpls_output(struct ifnet *ifp0, struct mbuf *m, struct sockaddr *dst,
@@ -52,6 +57,7 @@ mpls_output(struct ifnet *ifp0, struct mbuf *m, struct sockaddr *dst,
 	struct rtentry		*rt = rt0;
 	struct rt_mpls		*rt_mpls;
 	int			 i, error;
+	u_int8_t		 ttl;
 
 	if (rt0 == NULL || (dst->sa_family != AF_INET &&
 	    dst->sa_family != AF_INET6 && dst->sa_family != AF_MPLS)) {
@@ -72,6 +78,8 @@ mpls_output(struct ifnet *ifp0, struct mbuf *m, struct sockaddr *dst,
 	smpls->smpls_family = AF_MPLS;
 	smpls->smpls_len = sizeof(*smpls);
 
+	ttl = mpls_getttl(m, dst->sa_family);
+
 	for (i = 0; i < mpls_inkloop; i++) {
 		rt_mpls = (struct rt_mpls *)rt->rt_llinfo;
 		if (rt_mpls == NULL || (rt->rt_flags & RTF_MPLS) == 0) {
@@ -134,7 +142,7 @@ mpls_output(struct ifnet *ifp0, struct mbuf *m, struct sockaddr *dst,
 
 	/* write back TTL */
 	shim->shim_label &= ~MPLS_TTL_MASK;
-	shim->shim_label |= htonl(mpls_defttl);
+	shim->shim_label |= htonl(ttl);
 
 #ifdef MPLS_DEBUG
 	printf("MPLS: sending on %s outshim %x outlabel %d\n",
@@ -181,3 +189,41 @@ mpls_do_cksum(struct mbuf *m)
 	}
 #endif
 }
+
+u_int8_t
+mpls_getttl(struct mbuf *m, sa_family_t af)
+{
+	struct shim_hdr *shim;
+	struct ip *ip;
+	struct ip6_hdr *ip6hdr;
+	u_int8_t ttl = mpls_defttl;
+
+	/* If the AF is MPLS then inherit the TTL from the present label. */
+	if (af == AF_MPLS) {
+		shim = mtod(m, struct shim_hdr *);
+		ttl = ntohl(shim->shim_label & MPLS_TTL_MASK);
+		return (ttl);
+	}
+	/* Else extract TTL from the encapsualted packet. */
+	switch (*mtod(m, u_char *) >> 4) {
+	case IPVERSION:
+		if (!mpls_mapttl_ip)
+			break;
+		if (m->m_len < sizeof(*ip))
+			break;			/* impossible */
+		ip = mtod(m, struct ip *);
+		ttl = ip->ip_ttl;
+		break;
+	case IPV6_VERSION >> 4:
+		if (!mpls_mapttl_ip6)
+			break;
+		if (m->m_len < sizeof(struct ip6_hdr))
+			break;			/* impossible */
+		ip6hdr = mtod(m, struct ip6_hdr *);
+		ttl = ip6hdr->ip6_hlim;
+		break;
+	default:
+		break;
+	}
+	return (ttl);
+}