[dpdk-dev] [PATCH 0/4] Introduce IF proxy library

[Jerin Jacob]

On Thu, Apr 16, 2020 at 10:34 PM Stephen Hemminger
<stephen at networkplumber.org> wrote:
>
> On Thu, 16 Apr 2020 22:19:05 +0530
> Jerin Jacob <jerinjacobk at gmail.com> wrote:
>
> > On Thu, Apr 16, 2020 at 9:41 PM Stephen Hemminger
> > <stephen at networkplumber.org> wrote:
> > >
> > > On Fri, 6 Mar 2020 17:41:00 +0100
> > > Andrzej Ostruszka <aostruszka at 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.




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