[PATCH v6 0/1] Introduce MPLS over GRE

[PATCH v6 0/1] Introduce MPLS over GRE

[Amine Kherbouche]

This patch introduces the MPLS over GRE encapsulation (RFC 4023).

Various applications of MPLS make use of label stacks with multiple
entries.  In some cases, it is possible to replace the top label of
the stack with an IP-based encapsulation, thereby, it is possible for
two LSRs that are adjacent on an LSP to be separated by an IP network,
even if that IP network does not provide MPLS.

On 09/29/2017 06:11 AM, Tom Herbert wrote:
> I don't see why MPLS/GRE needs to be a special case in gre_rcv. Can't
> we just follow the normal processing patch which calls the proto ops
> handler for the protocol in the GRE header? Also, if protocol specific
> code is added to rcv function that most likely means that we need to
> update the related offloads also (grant it that MPLS doesn't support
> GRO but it looks like it supports GSO). Additionally, we'd need to
> consider if flow dissector needs a similar special case (I will point
> out that my recently posted patches there eliminated TEB as the one
> special case in GRE dissection).

Regarding Tom's comment, the RX path of MPLSoGRE packet should follow
the normal processing path. That will prevent it to be a special case to
maintain separately. TX path is also shared, knowing that gre type is load
from skb->protocol which already is set by mpls stack.

Changes in v6:
  - remove mpls_forward() function exportation patch.
  - remove mpls_gre_rcv() and let the skb follow ipgre rx path and the mpls
    proto handler will be called.

Changes in v5:
  - Reword first commit title.

Changes in v4:
  - Bring back mpls_forward() function exportation patch.
  - Move back mpls_gre_rcv() to gre module file and wrap it under
    ifdef.

Changes in v3:
  - remove mpls_forward() function exportation patch.
  - wrap efficiently mpls iptunnel add/del functions and dependent
    function/structure.
  - move mpls_gre_rcv to af_mpls.c file and export it.
  - remove unnecessary functions.
 
Changes in v2:
  - wrap ip tunnel functions under ifdef in mpls file.
  - fix indentation.
  - check return code.

An example of configuration:


         node1                LER1                       LER2                node2
        +-----+             +------+                   +------+             +-----+
        |     |             |      |                   |      |             |     |
        |     |             |      |p3  GRE tunnel   p4|      |             |     |
        |     |p1         p2|      +-------------------+      |p5         p6|     |
        |     +-------------+      +-------------------+      +------------+|     |
        |     |10.100.0.0/24|      |                   |      |10.200.0.0/24|     |
        |     |fd00:100::/64|      |  10.125.0.0/24    |      |fd00:200::/64|     |
        |     |             |      |  fd00:125::/64    |      |             |     |
        |     |             |      |                   |      |             |     |
        |     |             |      |                   |      |             |     |
        |     |             |      |                   |      |             |     |
        |     |             |      |                   |      |             |     |
        +-----+             +------+                   +------+             +-----+


		###	node1	###

ip link set p1 up
ip addr add 10.100.0.1/24 dev p1

		###	LER1	###

ip link set p2 up
ip addr add 10.100.0.2/24 dev p2

ip link set p3 up
ip addr add 10.125.0.1/24 dev p3

ip link add gre1 type gre ttl 64 local 10.125.0.1 remote 10.125.0.2 dev p3
ip link set dev gre1 up

modprobe mpls_router
sysctl -w net.mpls.conf.p2.input=1
sysctl -w net.mpls.conf.p3.input=1
sysctl -w net.mpls.conf.gre1.input=1
sysctl -w net.mpls.platform_labels=1000

ip -M route add 111 as 222 dev gre1
ip -M route add 555 as 666 via inet 10.100.0.1 dev p2

		###	LER2	###

ip link set p5 up
ip addr add 10.200.0.2/24 dev p5

ip link set p4 up
ip addr add 10.125.0.2/24 dev p4

ip link add gre1 type gre ttl 64 local 10.125.0.2 remote 10.125.0.1 dev p4
ip link set dev gre1 up

modprobe mpls_router
sysctl -w net.mpls.conf.p4.input=1
sysctl -w net.mpls.conf.p5.input=1
sysctl -w net.mpls.conf.gre1.input=1
sysctl -w net.mpls.platform_labels=1000

ip -M route add 444 as 555 dev gre1
ip -M route add 222 as 333 via inet 10.200.0.1 dev p5

		###	node2	###

ip link set p6 up
ip addr add 10.200.0.1/24 dev p6


Now using this scapy to forge and send packets from the port p1 of node1:

p = Ether(src='de:ed:01:0c:41:09', dst='de:ed:01:2f:3b:ba')
p /= MPLS(s=1, ttl=64, label=111)/Raw(load='\xde')
sendp(p, iface="p1", count=20, inter=0.1)

Amine Kherbouche (1):
  ip_tunnel: add mpls over gre support

 include/uapi/linux/if_tunnel.h |  1 +
 net/mpls/af_mpls.c             | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

-- 
2.1.4

[PATCH v6 1/1] ip_tunnel: add mpls over gre support

[Amine Kherbouche]

This commit introduces the MPLSoGRE support (RFC 4023), using ip tunnel
API by simply adding ipgre_tunnel_encap_(add|del)_mpls_ops() and the new
tunnel type TUNNEL_ENCAP_MPLS.

Signed-off-by: Amine Kherbouche <amine.kherbouche@6wind.com>
---
 include/uapi/linux/if_tunnel.h |  1 +
 net/mpls/af_mpls.c             | 36 ++++++++++++++++++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/include/uapi/linux/if_tunnel.h b/include/uapi/linux/if_tunnel.h
index 2e52088..a2f48c0 100644
--- a/include/uapi/linux/if_tunnel.h
+++ b/include/uapi/linux/if_tunnel.h
@@ -84,6 +84,7 @@ enum tunnel_encap_types {
 	TUNNEL_ENCAP_NONE,
 	TUNNEL_ENCAP_FOU,
 	TUNNEL_ENCAP_GUE,
+	TUNNEL_ENCAP_MPLS,
 };
 
 #define TUNNEL_ENCAP_FLAG_CSUM		(1<<0)
diff --git a/net/mpls/af_mpls.c b/net/mpls/af_mpls.c
index c5b9ce4..9745e8f 100644
--- a/net/mpls/af_mpls.c
+++ b/net/mpls/af_mpls.c
@@ -16,6 +16,7 @@
 #include <net/arp.h>
 #include <net/ip_fib.h>
 #include <net/netevent.h>
+#include <net/ip_tunnels.h>
 #include <net/netns/generic.h>
 #if IS_ENABLED(CONFIG_IPV6)
 #include <net/ipv6.h>
@@ -39,6 +40,36 @@ static int one = 1;
 static int label_limit = (1 << 20) - 1;
 static int ttl_max = 255;
 
+#if IS_ENABLED(CONFIG_NET_IP_TUNNEL)
+size_t ipgre_mpls_encap_hlen(struct ip_tunnel_encap *e)
+{
+	return sizeof(struct mpls_shim_hdr);
+}
+
+static const struct ip_tunnel_encap_ops mpls_iptun_ops = {
+	.encap_hlen	= ipgre_mpls_encap_hlen,
+};
+
+static int ipgre_tunnel_encap_add_mpls_ops(void)
+{
+	return ip_tunnel_encap_add_ops(&mpls_iptun_ops, TUNNEL_ENCAP_MPLS);
+}
+
+static void ipgre_tunnel_encap_del_mpls_ops(void)
+{
+	ip_tunnel_encap_del_ops(&mpls_iptun_ops, TUNNEL_ENCAP_MPLS);
+}
+#else
+static int ipgre_tunnel_encap_add_mpls_ops(void)
+{
+	return 0;
+}
+
+static void ipgre_tunnel_encap_del_mpls_ops(void)
+{
+}
+#endif
+
 static void rtmsg_lfib(int event, u32 label, struct mpls_route *rt,
 		       struct nlmsghdr *nlh, struct net *net, u32 portid,
 		       unsigned int nlm_flags);
@@ -2485,6 +2516,10 @@ static int __init mpls_init(void)
 		      0);
 	rtnl_register(PF_MPLS, RTM_GETNETCONF, mpls_netconf_get_devconf,
 		      mpls_netconf_dump_devconf, 0);
+	err = ipgre_tunnel_encap_add_mpls_ops();
+	if (err)
+		pr_err("Can't add mpls over gre tunnel ops\n");
+
 	err = 0;
 out:
 	return err;
@@ -2502,6 +2537,7 @@ static void __exit mpls_exit(void)
 	dev_remove_pack(&mpls_packet_type);
 	unregister_netdevice_notifier(&mpls_dev_notifier);
 	unregister_pernet_subsys(&mpls_net_ops);
+	ipgre_tunnel_encap_del_mpls_ops();
 }
 module_exit(mpls_exit);
 
-- 
2.1.4

Re: [PATCH v6 1/1] ip_tunnel: add mpls over gre support

[David Miller]

From: Amine Kherbouche <amine.kherbouche@6wind.com>
Date: Wed,  4 Oct 2017 19:35:57 +0200

> This commit introduces the MPLSoGRE support (RFC 4023), using ip tunnel
> API by simply adding ipgre_tunnel_encap_(add|del)_mpls_ops() and the new
> tunnel type TUNNEL_ENCAP_MPLS.
> 
> Signed-off-by: Amine Kherbouche <amine.kherbouche@6wind.com>

Applied, thanks.