It is sometimes desirable to present an MPLS transport network as a single hop to traffic transiting it because it prevents confusion when diagnosing failures. An example of where confusion can be generated is when addresses used in the provider network overlap with addresses in the overlay network and the addresses get exposed through ICMP errors generated as packets transit the provider network.
In addition, RFC 3443 defines two methods of deriving TTL for an outgoing packet: Uniform Model where the TTL is propagated to/from the MPLS header and both Pipe Models and Short Pipe Models (with and without PHP) where the TTL is not propagated to/from the MPLS header. Changes in v2: - add references to RFC 3443 as suggested by David Ahern - fix setting of skb->protocol as noticed by David Ahern - implement per-route/per-LWT configurability as suggested by Eric Biederman - split into two patches for ease of review Robert Shearman (2): mpls: allow TTL propagation to IP packets to be configured mpls: allow TTL propagation from IP packets to be configured Documentation/networking/mpls-sysctl.txt | 19 ++++++ include/net/mpls_iptunnel.h | 2 + include/net/netns/mpls.h | 3 + include/uapi/linux/mpls_iptunnel.h | 2 + include/uapi/linux/rtnetlink.h | 1 + net/mpls/af_mpls.c | 99 ++++++++++++++++++++++++++------ net/mpls/internal.h | 7 +++ net/mpls/mpls_iptunnel.c | 64 ++++++++++++++++----- 8 files changed, 168 insertions(+), 29 deletions(-) -- 2.1.4
