netdev - Re: [PATCH] net-icmp: make icmp{,v6} (ping) sockets available to all by default

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Date:   Sat, 9 May 2020 19:24:01 -0600
From:   David Ahern <dsahern@...il.com>
To:     Maciej Żenczykowski <zenczykowski@...il.com>
Cc:     Ido Schimmel <idosch@...sch.org>,
        "David S . Miller" <davem@...emloft.net>,
        Linux Network Development Mailing List 
        <netdev@...r.kernel.org>
Subject: Re: [PATCH] net-icmp: make icmp{,v6} (ping) sockets available to all
 by default

On 5/9/20 3:35 PM, Maciej Żenczykowski wrote:
> Do we have some sort of beginner's introduction to Linux VRF somewhere?
> What they are? How to use them?

Ido's response gave introductory commands which can also be found here:
    https://www.kernel.org/doc/Documentation/networking/vrf.txt

This should answer most questions about more advanced topics:
    http://schd.ws/hosted_files/ossna2017/fe/vrf-tutorial-oss.pdf

Lately, I am putting blogs on https://people.kernel.org/dsahern for
recurring questions.

> 
> Currently the concept simply doesn't fit into my mental model of networking...

network namespaces = device level separation and up
VRF = Layer 3 and up separation

> 
> We've actually talked about maybe possibly using VRF's in Android (for
> our multi network support)...
> but no-one on our team has the faintest idea about how they work...
> (and there's rumours that they don't work with ipv6 link local)
> 

Rumors are ugly. If in doubt, ask. LLA with VRF is a primary requirement
from the beginning.

With 5.3 and up, you can have IPv4 routes with IPv6 LLA gateways with
and without VRFs.