[0/4] Introduce IF proxy library

  What is this useful for
=======================

Usually, when an ethernet port is assigned to DPDK it vanishes from the
system and user looses ability to control it via normal configuration
utilities (e.g. those from iproute2 package).  Moreover by default DPDK
application is not aware of the network configuration of the system.

To address both of these issues application needs to:
- add some command line interface (or other mechanism) allowing for
  control of the port and its configuration
- query the status of network configuration and monitor its changes

The purpose of this library is to help with both of these tasks (as long
as they remain in domain of configuration available to the system).  In
other words, if DPDK application has some special needs, that cannot be
addressed by the normal system configuration utilities, then they need
to be solved by the application itself.

The connection between DPDK and system is based on the existence of
ports that are visible to both DPDK and system (like Tap, KNI and
possibly some other drivers).  These ports serve as an interface
proxies.

Let's visualize the action of the library by the following example:

              Linux             |            DPDK
==============================================================
                                |
                                |   +-------+       +-------+
                                |   | Port1 |       | Port2 |
"ip link set dev tap1 mtu 1600" |   +-------+       +-------+
                          |     |       ^              ^ ^
                          |  +------+   | mtu_change   | |
                          `->| Tap1 |---' callback     | |
                             +------+                  | |
"ip addr add 198.51.100.14 \    |                      | |
                  dev tap2"     |                      | |
                          |  +------+                  | |
                          +->| Tap2 |------------------' |
                          |  +------+  addr_add callback |
"ip route add 198.0.2.0/24 \    |  |                     |
                  dev tap2"     |  | route_add callback  |
                                |  `---------------------'

So we have two ports Port1 and Port2 that are not visible to the system.
We create two proxy interfaces (here based on Tap driver) and bind the
ports to their proxies.  When user issues a command changing MTU for
Tap1 interface the library notes this and calls "mtu_change" callback
for the Port1.  Similarly when user adds an IPv4 address to the Tap2
interface "addr_add" callback is called for the Port2 and the same
happens for configuration of routing rule pointing to Tap2.  Apart from
callbacks this library can notify about changes via adding events to
notification queues.  See below for more inforamtion about that and
a complete list of available callbacks.

Please note that nothing has been mentioned about forwarding of the
packets between system and DPDK.  Since the proxies are normal DPDK
ports you can receive/send to them via usual RX/TX burst API.  However
since the library is not aware of the structure of packet processing
used by the application it cannot automatically forward the packets - it
is responsibility of the application to include proxy ports into its
packet processing engine.

As mentioned above the intention of the library is to:
- provide information about network configuration that would allow
  application to decide what to do with the packets received on DPDK
  ports,
- allow for control of the ports via standard configuration utilities

Although the library only helps you to identify proxy for given port
(and vice versa) and calls appropriate callbacks it does open some
interesting possibilities.  For example you can use the proxy ports to
forward packets for protocols that you do not wish to handle in DPDK
application to the system protocol stack and just listen to the
configuration changes - so that way you can "offload" handling of those
protocols to the system.

How to use it
=============

Usage of this library is rather simple.  You have to:
1. Create proxy (if you don't have port suitable for being proxy or you
  have one but do not wish to use it as a proxy).
2. Bind port to proxy.
3. Register callbacks and/or event queues.
4. Start listening to the network configuration.

The only mandatory requirement for DPDK port to be able to act as
a proxy is that it is visible in the system - this is checked during
port to proxy binding by calling rte_eth_dev_info_get() on proxy port
and inspecting 'if_index' field (it has to be non-zero).
One can create such port in the application by calling:

  proxy_id = rte_ifpx_create(RTE_IFPX_DEFAULT);

Upon success this returns id of DPDK proxy port created
(RTE_MAX_ETHPORTS on failure).  The argument selects type of proxy port
to create (currently Tap/KNI only).  This function actually is just
a wrapper around:

  uint16_t rte_ifpx_create_by_devarg(const char *devarg);

creating valid 'devarg' string for the chosen type of proxy.  If you have
other driver capable of acting as a proxy you can call
rte_ifpx_create_by_devarg() directly passing appropriate argument.

Once you have id of both port and proxy you can bind the two via:

  rte_ifpx_port_bind(port_id, proxy_id);

This creates logical binding - as mentioned above there is no automatic
packet forwarding.  With this binding whenever user changes the state of
proxy interface in the system (link up/down, change mac/mtu, add/remove
IPv4/IPv6) you get appropriate notification for the bound port.

So far we've mentioned several times that the library calls callbacks.
They are grouped in 'struct rte_ifpx_callbacks' and user provides them
to the library via:

  rte_ifpx_callbacks_register(&cbs);

It is worth mentioning that the context (lcore/thread) in which these
callbacks are called is implementation defined.  It might differ between
different platforms, so the application needs to assume that some kind
of inter lcore/thread synchronization/communication is required.

Apart from notification via callbacks this library also supports
notifying about the changes via adding events to the configured
notification queues.  The queues are registered via:

  int rte_ifpx_queue_add(struct rte_ring *r);

and the actual logic used is: if there is callback registered then it is
called, if it returns non-zero then event is considered completed,
otherwise event is added to each configured notification queue.
That way application can update data structures that are safe to be
modified by single writer from within callback or do the common
preprocessing steps (if any needed) in callback and data that is
replicated can be updated during handling of queued events.

Once we have bindings in place and notification configured, the only
essential part that remains is to get the current network configuration
and start listening to its changes.  This is accomplished via a call to:

  rte_ifpx_listen();

And basically this is all one needs to understand how to use this
library.  Other less essential parts include:
- ability to query what events are available for given platform
- getting mapping between proxy and port
- unbinding the ports from proxy
- destroying proxy port
- closing the listening service
- getting basic information about proxy


Currently available features and implementation
===============================================

The library's API is system independent but it obviously needs some
system dependent parts.  We provide exemplary Linux implementation (based
on netlink sockets).  Very similar implementation is possible for
FreeBSD (with the usage of PF_ROUTE sockets).  Windows implementation
would need to differ much (probably IP Helper library would be of some help).

Here is the list of currently implemented callbacks:

struct rte_ifpx_callbacks {
  int (*mac_change)(const struct rte_ifpx_mac_change *event);
  int (*mtu_change)(const struct rte_ifpx_mtu_change *event);
  int (*link_change)(const struct rte_ifpx_link_change *event);
  int (*addr_add)(const struct rte_ifpx_addr_change *event);
  int (*addr_del)(const struct rte_ifpx_addr_change *event);
  int (*addr6_add)(const struct rte_ifpx_addr6_change *event);
  int (*addr6_del)(const struct rte_ifpx_addr6_change *event);
  int (*route_add)(const struct rte_ifpx_route_change *event);
  int (*route_del)(const struct rte_ifpx_route_change *event);
  int (*route6_add)(const struct rte_ifpx_route6_change *event);
  int (*route6_del)(const struct rte_ifpx_route6_change *event);
  int (*neigh_add)(const struct rte_ifpx_neigh_change *event);
  int (*neigh_del)(const struct rte_ifpx_neigh_change *event);
  int (*neigh6_add)(const struct rte_ifpx_neigh6_change *event);
  int (*neigh6_del)(const struct rte_ifpx_neigh6_change *event);
  int (*cfg_done)(void);
};

They are all rather self-descriptive with the exception of the last one.
When the user calls rte_ifpx_listen() the library first queries the
system for its current configuration.  That might require several
request/reply exchanges between DPDK and system and once it is finished
this callback is called to let application know that all info has been
gathered.

It is worth to mention also that while typical case would be a 1-to-1
mapping between port and proxy, the 1-to-many mapping is also supported.
In that case port related callbacks will be called for each port bound
to given proxy interface - in that case it is application responsibility
to define semantic of such mapping (e.g. all changes apply to all ports,
or link changes apply to all but other are accepted in "round robin"
fashion, or ...).

As mentioned above Linux implementation is based on netlink socket.
This socket is registered as file descriptor in EAL interrupts
(similarly to how EAL alarms are implemented).

What has changed since the RFC
==============================

- Platform dependent parts has been separated into a ifpx_platform
  structure with callbacks for initialization, getting information about
  the interface, listening to the changes and closing of the library.
  That should allow easier reimplementation.

- Notification scheme has been changed - instead of having just
  callbacks now event queueing is also available (or a mix of those
  two).

- Filtering of events only related to the proxy ports - previously all
  network configuration changes were reported.  But DPDK application
  needs not to know all configuration - only just portion related to the
  proxy ports.  If a packet comes that does not match rules then it can
  be forwarded via proxy to the system to decide what to do with it.  If
  that is not desired and such packets should be dropped then null port
  can be created with proxy and e.g. default route installed on it.

- Removed previous example which was just printing notification.
  Instead added a simplified (stripped vectorization and other
  performance improvements) version of l3fwd that should serve as an
  example of using this library in real applications.

With regards
Andrzej Ostruszka

Andrzej Ostruszka (4):
  lib: introduce IF Proxy library
  if_proxy: add library documentation
  if_proxy: add simple functionality test
  if_proxy: add example application

 MAINTAINERS                                   |    6 +
 app/test/Makefile                             |    5 +
 app/test/meson.build                          |    4 +
 app/test/test_if_proxy.c                      |  706 +++++++++++
 config/common_base                            |    5 +
 config/common_linux                           |    1 +
 doc/guides/prog_guide/if_proxy_lib.rst        |  142 +++
 doc/guides/prog_guide/index.rst               |    1 +
 examples/Makefile                             |    1 +
 examples/l3fwd-ifpx/Makefile                  |   60 +
 examples/l3fwd-ifpx/l3fwd.c                   | 1123 +++++++++++++++++
 examples/l3fwd-ifpx/l3fwd.h                   |   98 ++
 examples/l3fwd-ifpx/main.c                    |  729 +++++++++++
 examples/l3fwd-ifpx/meson.build               |   11 +
 examples/meson.build                          |    2 +-
 lib/Makefile                                  |    2 +
 .../common/include/rte_eal_interrupts.h       |    2 +
 lib/librte_eal/linux/eal/eal_interrupts.c     |   14 +-
 lib/librte_if_proxy/Makefile                  |   29 +
 lib/librte_if_proxy/if_proxy_common.c         |  494 ++++++++
 lib/librte_if_proxy/if_proxy_priv.h           |   97 ++
 lib/librte_if_proxy/linux/Makefile            |    4 +
 lib/librte_if_proxy/linux/if_proxy.c          |  552 ++++++++
 lib/librte_if_proxy/meson.build               |   19 +
 lib/librte_if_proxy/rte_if_proxy.h            |  561 ++++++++
 lib/librte_if_proxy/rte_if_proxy_version.map  |   19 +
 lib/meson.build                               |    2 +-
 27 files changed, 4683 insertions(+), 6 deletions(-)
 create mode 100644 app/test/test_if_proxy.c
 create mode 100644 doc/guides/prog_guide/if_proxy_lib.rst
 create mode 100644 examples/l3fwd-ifpx/Makefile
 create mode 100644 examples/l3fwd-ifpx/l3fwd.c
 create mode 100644 examples/l3fwd-ifpx/l3fwd.h
 create mode 100644 examples/l3fwd-ifpx/main.c
 create mode 100644 examples/l3fwd-ifpx/meson.build
 create mode 100644 lib/librte_if_proxy/Makefile
 create mode 100644 lib/librte_if_proxy/if_proxy_common.c
 create mode 100644 lib/librte_if_proxy/if_proxy_priv.h
 create mode 100644 lib/librte_if_proxy/linux/Makefile
 create mode 100644 lib/librte_if_proxy/linux/if_proxy.c
 create mode 100644 lib/librte_if_proxy/meson.build
 create mode 100644 lib/librte_if_proxy/rte_if_proxy.h
 create mode 100644 lib/librte_if_proxy/rte_if_proxy_version.map
  

My apologies - I have forgotten to run checkpatch on the series.
I will correct these in version 2 - in the mean time please skip these
minor faults and comment on the rest.

With regards
Andrzej Ostruszka
  

On Fri, 6 Mar 2020 17:41:00 +0100
Andrzej Ostruszka <aostruszka@marvell.com> wrote:

> What is this useful for
> =======================
> 
> Usually, when an ethernet port is assigned to DPDK it vanishes from the
> system and user looses ability to control it via normal configuration
> utilities (e.g. those from iproute2 package).  Moreover by default DPDK
> application is not aware of the network configuration of the system.
> 
> To address both of these issues application needs to:
> - add some command line interface (or other mechanism) allowing for
>   control of the port and its configuration
> - query the status of network configuration and monitor its changes
> 
> The purpose of this library is to help with both of these tasks (as long
> as they remain in domain of configuration available to the system).  In
> other words, if DPDK application has some special needs, that cannot be
> addressed by the normal system configuration utilities, then they need
> to be solved by the application itself.
> 
> The connection between DPDK and system is based on the existence of
> ports that are visible to both DPDK and system (like Tap, KNI and
> possibly some other drivers).  These ports serve as an interface
> proxies.
> 
> Let's visualize the action of the library by the following example:
> 
>               Linux             |            DPDK
> ==============================================================
>                                 |
>                                 |   +-------+       +-------+
>                                 |   | Port1 |       | Port2 |
> "ip link set dev tap1 mtu 1600" |   +-------+       +-------+
>                           |     |       ^              ^ ^
>                           |  +------+   | mtu_change   | |
>                           `->| Tap1 |---' callback     | |
>                              +------+                  | |
> "ip addr add 198.51.100.14 \    |                      | |
>                   dev tap2"     |                      | |
>                           |  +------+                  | |
>                           +->| Tap2 |------------------' |
>                           |  +------+  addr_add callback |
> "ip route add 198.0.2.0/24 \    |  |                     |
>                   dev tap2"     |  | route_add callback  |
>                                 |  `---------------------'

Has anyone investigated solving this in the kernel rather than
creating the added overhead of more Linux devices?

What I am thinking of is a netlink to userspace interface.
The kernel already has File-System-in-Userspace (FUSE) to allow
for filesystems. What about having a NUSE (Netlink in userspace)?

Then DPDK could have a daemon that is a provider to NUSE.
This solution would also benefit other non-DPDK projects like VPP
and allow DPDK to integrate with devlink etc.
  

On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Fri, 6 Mar 2020 17:41:00 +0100
> Andrzej Ostruszka <aostruszka@marvell.com> wrote:
>
> > What is this useful for
> > =======================
> >
> > Usually, when an ethernet port is assigned to DPDK it vanishes from the
> > system and user looses ability to control it via normal configuration
> > utilities (e.g. those from iproute2 package).  Moreover by default DPDK
> > application is not aware of the network configuration of the system.
> >
> > To address both of these issues application needs to:
> > - add some command line interface (or other mechanism) allowing for
> >   control of the port and its configuration
> > - query the status of network configuration and monitor its changes
> >
> > The purpose of this library is to help with both of these tasks (as long
> > as they remain in domain of configuration available to the system).  In
> > other words, if DPDK application has some special needs, that cannot be
> > addressed by the normal system configuration utilities, then they need
> > to be solved by the application itself.
> >
> > The connection between DPDK and system is based on the existence of
> > ports that are visible to both DPDK and system (like Tap, KNI and
> > possibly some other drivers).  These ports serve as an interface
> > proxies.
> >
> > Let's visualize the action of the library by the following example:
> >
> >               Linux             |            DPDK
> > ==============================================================
> >                                 |
> >                                 |   +-------+       +-------+
> >                                 |   | Port1 |       | Port2 |
> > "ip link set dev tap1 mtu 1600" |   +-------+       +-------+
> >                           |     |       ^              ^ ^
> >                           |  +------+   | mtu_change   | |
> >                           `->| Tap1 |---' callback     | |
> >                              +------+                  | |
> > "ip addr add 198.51.100.14 \    |                      | |
> >                   dev tap2"     |                      | |
> >                           |  +------+                  | |
> >                           +->| Tap2 |------------------' |
> >                           |  +------+  addr_add callback |
> > "ip route add 198.0.2.0/24 \    |  |                     |
> >                   dev tap2"     |  | route_add callback  |
> >                                 |  `---------------------'
>
> Has anyone investigated solving this in the kernel rather than
> creating the added overhead of more Linux devices?
>
> What I am thinking of is a netlink to userspace interface.
> The kernel already has File-System-in-Userspace (FUSE) to allow
> for filesystems. What about having a NUSE (Netlink in userspace)?

IMO, there is no issue with the Linux Netlink _userspace_ interface.
The goal of IF proxy to abstract the OS differences so that it can
work with Linux, FreeBSD, and Windows(if needed).


>
> Then DPDK could have a daemon that is a provider to NUSE.
> This solution would also benefit other non-DPDK projects like VPP
> and allow DPDK to integrate with devlink etc.
  

On Thu, 16 Apr 2020 22:19:05 +0530
Jerin Jacob <jerinjacobk@gmail.com> wrote:

> On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
> <stephen@networkplumber.org> wrote:
> >
> > On Fri, 6 Mar 2020 17:41:00 +0100
> > Andrzej Ostruszka <aostruszka@marvell.com> wrote:
> >  
> > > What is this useful for
> > > =======================
> > >
> > > Usually, when an ethernet port is assigned to DPDK it vanishes from the
> > > system and user looses ability to control it via normal configuration
> > > utilities (e.g. those from iproute2 package).  Moreover by default DPDK
> > > application is not aware of the network configuration of the system.
> > >
> > > To address both of these issues application needs to:
> > > - add some command line interface (or other mechanism) allowing for
> > >   control of the port and its configuration
> > > - query the status of network configuration and monitor its changes
> > >
> > > The purpose of this library is to help with both of these tasks (as long
> > > as they remain in domain of configuration available to the system).  In
> > > other words, if DPDK application has some special needs, that cannot be
> > > addressed by the normal system configuration utilities, then they need
> > > to be solved by the application itself.
> > >
> > > The connection between DPDK and system is based on the existence of
> > > ports that are visible to both DPDK and system (like Tap, KNI and
> > > possibly some other drivers).  These ports serve as an interface
> > > proxies.
> > >
> > > Let's visualize the action of the library by the following example:
> > >
> > >               Linux             |            DPDK
> > > ==============================================================
> > >                                 |
> > >                                 |   +-------+       +-------+
> > >                                 |   | Port1 |       | Port2 |
> > > "ip link set dev tap1 mtu 1600" |   +-------+       +-------+
> > >                           |     |       ^              ^ ^
> > >                           |  +------+   | mtu_change   | |
> > >                           `->| Tap1 |---' callback     | |
> > >                              +------+                  | |
> > > "ip addr add 198.51.100.14 \    |                      | |
> > >                   dev tap2"     |                      | |
> > >                           |  +------+                  | |
> > >                           +->| Tap2 |------------------' |
> > >                           |  +------+  addr_add callback |
> > > "ip route add 198.0.2.0/24 \    |  |                     |
> > >                   dev tap2"     |  | route_add callback  |
> > >                                 |  `---------------------'  
> >
> > Has anyone investigated solving this in the kernel rather than
> > creating the added overhead of more Linux devices?
> >
> > What I am thinking of is a netlink to userspace interface.
> > The kernel already has File-System-in-Userspace (FUSE) to allow
> > for filesystems. What about having a NUSE (Netlink in userspace)?  
> 
> IMO, there is no issue with the Linux Netlink _userspace_ interface.
> The goal of IF proxy to abstract the OS differences so that it can
> work with Linux, FreeBSD, and Windows(if needed).
> 
> 
> >
> > Then DPDK could have a daemon that is a provider to NUSE.
> > This solution would also benefit other non-DPDK projects like VPP
> > and allow DPDK to integrate with devlink etc.  

With the wider use of tap devices like this, it may be a problem
for other usages of TAP. If nothing else, having to figure out which
tap is which would be error prone.

Also, TAP on Windows is only available as an out-of-tree driver
from OpenVPN. And the TAP on Windows is quite, limited, deprecated,
poorly supported and buggy. There is no standard TAP like interface
in Windows.

TAP on BSD is different than Linux and has different control functions.
Don't remember what the interface notification mechanism is on BSD,
it is not netlink.

So is IF proxy even going to work on these other OS?
  

On 4/16/20 6:49 PM, Jerin Jacob wrote:
> On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
> <stephen@networkplumber.org> wrote:
[...]
>> Has anyone investigated solving this in the kernel rather than
>> creating the added overhead of more Linux devices?
>>
>> What I am thinking of is a netlink to userspace interface.
>> The kernel already has File-System-in-Userspace (FUSE) to allow
>> for filesystems. What about having a NUSE (Netlink in userspace)?
> 
> IMO, there is no issue with the Linux Netlink _userspace_ interface.
> The goal of IF proxy to abstract the OS differences so that it can
> work with Linux, FreeBSD, and Windows(if needed).

My understanding of Stephen's question is a bit different - Stephen
please correct me if I'm wrong.  By the comparison with FUSE he was
thinking about providing a "kernel proxy" to userspace-based
port/interface, which could be used not only by DPDK but by other too.

The answer from me is: no I have not.  For two reasons:
- that would be Linux only
- if we would create such proxy, we would probably end up with tap like
driver in the end

With regards
Andrzej Ostruszka
  

On Thu, 16 Apr 2020 17:12:07 +0000
"Andrzej Ostruszka [C]" <aostruszka@marvell.com> wrote:

> On 4/16/20 6:49 PM, Jerin Jacob wrote:
> > On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
> > <stephen@networkplumber.org> wrote:  
> [...]
> >> Has anyone investigated solving this in the kernel rather than
> >> creating the added overhead of more Linux devices?
> >>
> >> What I am thinking of is a netlink to userspace interface.
> >> The kernel already has File-System-in-Userspace (FUSE) to allow
> >> for filesystems. What about having a NUSE (Netlink in userspace)?  
> > 
> > IMO, there is no issue with the Linux Netlink _userspace_ interface.
> > The goal of IF proxy to abstract the OS differences so that it can
> > work with Linux, FreeBSD, and Windows(if needed).  
> 
> My understanding of Stephen's question is a bit different - Stephen
> please correct me if I'm wrong.  By the comparison with FUSE he was
> thinking about providing a "kernel proxy" to userspace-based
> port/interface, which could be used not only by DPDK but by other too.
> 
> The answer from me is: no I have not.  For two reasons:
> - that would be Linux only
> - if we would create such proxy, we would probably end up with tap like
> driver in the end
> 
> With regards
> Andrzej Ostruszka

The point is think of the problem beyond just DPDK.
  

On 4/16/20 7:04 PM, Stephen Hemminger wrote:
> On Thu, 16 Apr 2020 22:19:05 +0530
> Jerin Jacob <jerinjacobk@gmail.com> wrote:
> 
>> On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
>> <stephen@networkplumber.org> wrote:
[...]
>>> Has anyone investigated solving this in the kernel rather than
>>> creating the added overhead of more Linux devices?
>>>
>>> What I am thinking of is a netlink to userspace interface.
>>> The kernel already has File-System-in-Userspace (FUSE) to allow
>>> for filesystems. What about having a NUSE (Netlink in userspace)?  
>>
>> IMO, there is no issue with the Linux Netlink _userspace_ interface.
>> The goal of IF proxy to abstract the OS differences so that it can
>> work with Linux, FreeBSD, and Windows(if needed).
>>
>>
>>>
>>> Then DPDK could have a daemon that is a provider to NUSE.
>>> This solution would also benefit other non-DPDK projects like VPP
>>> and allow DPDK to integrate with devlink etc.  
> 
> With the wider use of tap devices like this, it may be a problem
> for other usages of TAP. If nothing else, having to figure out which
> tap is which would be error prone.

Stephen, the library does not require TAP - only some DPDK port that is
visible to the system (has non-zero if_index).  As to the confusion - if
we use TAP then it has optional 'iface=...' argument, so we can name
those proxy interfaces as 'iface=proxy0' or something like that.  This
is under control of application (just call ...create_by_devarg() with
proper argument).

> Also, TAP on Windows is only available as an out-of-tree driver
> from OpenVPN. And the TAP on Windows is quite, limited, deprecated,
> poorly supported and buggy. There is no standard TAP like interface
> in Windows.
> 
> TAP on BSD is different than Linux and has different control functions.
> Don't remember what the interface notification mechanism is on BSD,
> it is not netlink.
> 
> So is IF proxy even going to work on these other OS?

No.  At the moment only Linux is supported.  I don't know much about
Windows, it would need some TAP-like driver and implementation would
probably make use of "IP Helper" library (some extra thread doing
polling?).  As for FreeBSD I'm convinced that very similar
implementation is possible by using PF_ROUTE sockets.

What the library does to help with other platforms is that it defines
following structure:

/* Every implementation should provide definition of this structure:
 * - init : called during library initialization (NULL when not needed)
 * - events : this should return bitmask of supported events (can be
 *     NULL if all defined events are supported by the implementation)
 * - listen : this function should start service listening to the
 *     network configuration events/changes,
 * - close : this function should close the service started by listen()
 * - get_info : this function should query system for current
 *     configuration of interface with index 'if_index'.  After
 *     successful initialization of listening service this function is
 *     called with 0 as an argument.  In that case configuration of all
 *     ports should be obtained - and when this procedure completes a
 *     RTE_IFPX_CFG_DONE event should be signaled via
 *     ifpx_notify_event().
 */
extern
struct ifpx_platform_callbacks {
	void (*init)(void);
	uint64_t (*events)(void);
	int (*listen)(void);
	int (*close)(void);
	void (*get_info)(int if_index);
} ifpx_platform;

With regards
Andrzej Ostruszka
  

On Thu, Apr 16, 2020 at 10:34 PM Stephen Hemminger
<stephen@networkplumber.org> wrote:
>
> On Thu, 16 Apr 2020 22:19:05 +0530
> Jerin Jacob <jerinjacobk@gmail.com> wrote:
>
> > On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
> > <stephen@networkplumber.org> wrote:
> > >
> > > On Fri, 6 Mar 2020 17:41:00 +0100
> > > Andrzej Ostruszka <aostruszka@marvell.com> wrote:
> > >
> > > > What is this useful for
> > > > =======================
> > > >
> > > > Usually, when an ethernet port is assigned to DPDK it vanishes from the
> > > > system and user looses ability to control it via normal configuration
> > > > utilities (e.g. those from iproute2 package).  Moreover by default DPDK
> > > > application is not aware of the network configuration of the system.
> > > >
> > > > To address both of these issues application needs to:
> > > > - add some command line interface (or other mechanism) allowing for
> > > >   control of the port and its configuration
> > > > - query the status of network configuration and monitor its changes
> > > >
> > > > The purpose of this library is to help with both of these tasks (as long
> > > > as they remain in domain of configuration available to the system).  In
> > > > other words, if DPDK application has some special needs, that cannot be
> > > > addressed by the normal system configuration utilities, then they need
> > > > to be solved by the application itself.
> > > >
> > > > The connection between DPDK and system is based on the existence of
> > > > ports that are visible to both DPDK and system (like Tap, KNI and
> > > > possibly some other drivers).  These ports serve as an interface
> > > > proxies.
> > > >
> > > > Let's visualize the action of the library by the following example:
> > > >
> > > >               Linux             |            DPDK
> > > > ==============================================================
> > > >                                 |
> > > >                                 |   +-------+       +-------+
> > > >                                 |   | Port1 |       | Port2 |
> > > > "ip link set dev tap1 mtu 1600" |   +-------+       +-------+
> > > >                           |     |       ^              ^ ^
> > > >                           |  +------+   | mtu_change   | |
> > > >                           `->| Tap1 |---' callback     | |
> > > >                              +------+                  | |
> > > > "ip addr add 198.51.100.14 \    |                      | |
> > > >                   dev tap2"     |                      | |
> > > >                           |  +------+                  | |
> > > >                           +->| Tap2 |------------------' |
> > > >                           |  +------+  addr_add callback |
> > > > "ip route add 198.0.2.0/24 \    |  |                     |
> > > >                   dev tap2"     |  | route_add callback  |
> > > >                                 |  `---------------------'
> > >
> > > Has anyone investigated solving this in the kernel rather than
> > > creating the added overhead of more Linux devices?
> > >
> > > What I am thinking of is a netlink to userspace interface.
> > > The kernel already has File-System-in-Userspace (FUSE) to allow
> > > for filesystems. What about having a NUSE (Netlink in userspace)?
> >
> > IMO, there is no issue with the Linux Netlink _userspace_ interface.
> > The goal of IF proxy to abstract the OS differences so that it can
> > work with Linux, FreeBSD, and Windows(if needed).
> >
> >
> > >
> > > Then DPDK could have a daemon that is a provider to NUSE.
> > > This solution would also benefit other non-DPDK projects like VPP
> > > and allow DPDK to integrate with devlink etc.
>
> With the wider use of tap devices like this, it may be a problem
> for other usages of TAP. If nothing else, having to figure out which
> tap is which would be error prone.
>
> Also, TAP on Windows is only available as an out-of-tree driver
> from OpenVPN. And the TAP on Windows is quite, limited, deprecated,
> poorly supported and buggy. There is no standard TAP like interface
> in Windows.
>
> TAP on BSD is different than Linux and has different control functions.
> Don't remember what the interface notification mechanism is on BSD,
> it is not netlink.
>
> So is IF proxy even going to work on these other OS?

I dont know about Windows. BSD has a control interface.
The library gives abstraction and public API definitions and driver interface.
 It is up to the implementer to implement driver API for a specific
EAL environment.
That would help us to not, directly calling  Linux specific interface
in the DPDK application.




>
>
>