In the context of internet scale routing a requirement that always comes
up is the need to partition the available routing tables into disjoint
routing planes. A specific use case is the multi-tenancy problem where
each tenant has their own unique routing tables and in the very least
need different default gateways.
This patch allows the ability to create virtual router domains (aka VRFs
(VRF-lite to be specific) in the linux packet forwarding stack. The main
observation is that through the use of rules and socket binding to interfaces,
all the facilities that we need are already present in the infrastructure. What
is missing is a handle that identifies a routing domain and can be used to
gather applicable rules/tables and uniqify neighbor selection. The scheme used
needs to preserves the notions of ECMP, and general routing principles.
This driver is a cross between functionality that the IPVLAN driver
and the Team drivers provide where a device is created and packets
into/out of the routing domain are shuttled through this device. The
device is then used as a handle to identify the applicable rules. The
VRF device is thus the layer3 equivalent of a vlan device.
The very important point to note is that this is only a Layer3 concept
so L2 tools (e.g., LLDP) do not need to be run in each VRF, processes can
run in unaware mode or select a VRF to be talking through. Also the
behavioral model is a generalized application of the familiar VRF-Lite
model with some performance paths that need optimization. (Specifically
the output route selector that Roopa, Robert, Thomas and EricB are
currently discussing on the MPLS thread)
High Level points
=================
1. Simple overlay driver (minimal changes to current stack)
* uses the existing fib tables and fib rules infrastructure
2. Modelled closely after the ipvlan driver
3. Uses current API and infrastructure.
* Applications can use SO_BINDTODEVICE or cmsg device indentifiers
to pick VRF (ping, traceroute just work)
* Standard IP Rules work, and since they are aggregated against the
device, scale is manageable
4. Completely orthogonal to Namespaces and only provides separation in
the routing plane (and ARP)
N2
N1 (all configs here) +---------------+
+--------------+ | |
|swp1 :10.0.1.1+----------------------+swp1 :10.0.1.2 |
| | | |
|swp2 :10.0.2.1+----------------------+swp2 :10.0.2.2 |
| | +---------------+
| VRF 1 |
| table 5 |
| |
+---------------+
| |
| VRF 2 | N3
| table 6 | +---------------+
| | | |
|swp3 :10.0.2.1+----------------------+swp1 :10.0.2.2 |
| | | |
|swp4 :10.0.3.1+----------------------+swp2 :10.0.3.2 |
+--------------+ +---------------+
Given the topology above, the setup needed to get the basic VRF
functions working would be
Create the VRF devices and associate with a table
ip link add vrf1 type vrf table 5
ip link add vrf2 type vrf table 6
Install the lookup rules that map table to VRF domain
ip rule add pref 200 oif vrf1 lookup 5
ip rule add pref 200 iif vrf1 lookup 5
ip rule add pref 200 oif vrf2 lookup 6
ip rule add pref 200 iif vrf2 lookup 6
ip link set vrf1 up
ip link set vrf2 up
Enslave the routing member interfaces
ip link set swp1 master vrf1
ip link set swp2 master vrf1
ip link set swp3 master vrf2
ip link set swp4 master vrf2
Connected routes are automatically moved from main table to the VRF
table.
ping using VRF0 is simply
ping -I vrf0 10.0.1.2
Or using the task context and a command such as the example chvrf in
patch 15 unmodified applications are run in a VRF context using:
chvrf -v 1 ping 10.0.1.2
Design Highlights
=================
If a device is enslaved to a VRF device (ie., associated with a VRF)
then:
1. Rx path
The master device index is used as the iif for all lookups.
2. Tx path
Similarly, for Tx the VRF device oif is used in the flow to direct
lookups to the table associated with the VRF via its rule. From there
the FLOWI_FLAG_VRFSRC flag is used to indicate that the oif should
not be used for FIB table lookups.
3. Connected and local routes
On link up for a device, connected and local routes are added to the
table associated with the VRF device, rather than the local and main
tables.
4. Socket lookups
Socket lookups use the VRF device for comparison with sk_bound_dev_if.
If a socket is not bound to a device a socket match can happen based
on destination address, port and protocol in which case a VRF global
or agnostic process handles the connection (ie., this allows 1 listener
socket to handle connections across VRFs). The child socket becomes
bound to the VRF (sk_bound_dev_if is set to the VRF device).
5. Neighbor entries
Neighbor entries are not impacted by the VRF device. Entries are
associated with a particular interface; the VRF association is indirect
via the interface-to-VRF device enslavement.
Version 3
- addressed comments from first 2 RFCs with the exception of the name
Nicolas: We will do the name conversion once we agree on what the
correct name should be (vrf, mrf or something else)
- packets flow through the VRF device in both directions allowing the
following:
- tcpdump -i vrf<n>
- tc rules on vrf device
- netfilter rules on vrf device
Ingo/Andy: I added you two as a start point for the proposed task related
changes. Not sure who should be the reviewer; please let me know
if someone else is more appropriate. Thanks.
TO-DO
=====
1. IPv6
2. listen filter to restrict VRF connections
- i.e., bind to VRF's a, b, c only or NOT VRFs e, f, g
Bug-Fixes and ideas from Hannes, Roopa Prabhu, Jon Toppins, Jamal
Patches can also be pulled from:
https://github.com/dsahern/linux.git, vrf-dev-rfc3 branch
https://github.com/dsahern/iproute2, vrf-dev-rfc3 branch
David Ahern (15):
net: Refactor rtable allocation and initialization
net: export a few FIB functions
net: Introduce VRF related flags and helpers
net: Use VRF device index for lookups on RX
net: Use VRF device index for lookups on TX
net: Tx via VRF device
net: Add inet_addr lookup by table
net: Fix up inet_addr_type checks
net: Add routes to the table associated with the device
net: Use passed in table for nexthop lookups
net: Use VRF device index for socket lookups
net: Add ipv4 route helper to set next hop
net: Introduce VRF device driver - v2
net: Add sk_bind_dev_if to task_struct
net: Add chvrf command
net: FIB debugging tracepoints
drivers/net/Kconfig | 7 +
drivers/net/Makefile | 1 +
drivers/net/vrf.c | 596
+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/linux/netdevice.h | 21 +++
include/linux/sched.h | 3 +
include/net/flow.h | 1 +
include/net/route.h | 13 ++
include/net/vrf.h | 83 +++++++++++
include/uapi/linux/if_link.h | 9 ++
include/uapi/linux/prctl.h | 4 +
kernel/fork.c | 2 +
kernel/sys.c | 35 +++++
net/ipv4/af_inet.c | 14 +-
net/ipv4/arp.c | 15 +-
net/ipv4/fib_frontend.c | 68 +++++++--
net/ipv4/fib_semantics.c | 44 ++++--
net/ipv4/fib_trie.c | 8 +-
net/ipv4/icmp.c | 9 +-
net/ipv4/route.c | 149 +++++++++++--------
net/ipv4/syncookies.c | 5 +-
net/ipv4/tcp_input.c | 6 +-
net/ipv4/tcp_ipv4.c | 11 +-
net/ipv6/af_inet6.c | 1 +
net/ipv6/route.c | 2 +-
tools/net/Makefile | 6 +-
tools/net/chvrf.c | 225 ++++++++++++++++++++++++++++
26 files changed, 1230 insertions(+), 108 deletions(-)
create mode 100644 drivers/net/vrf.c
create mode 100644 include/net/vrf.h
create mode 100644 tools/net/chvrf.c
--
2.3.2 (Apple Git-55)
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