netdev - Re: [PATCH v2 net-next] Introduce a sysctl that modifies the value of PROT

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Date:   Thu, 12 Jan 2017 06:39:57 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Krister Johansen <kjlx@...pleofstupid.com>
Cc:     Stephen Hemminger <stephen@...workplumber.org>,
        "David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org
Subject: Re: [PATCH v2 net-next] Introduce a sysctl that modifies the value
 of PROT_SOCK.

On Wed, 2017-01-11 at 22:52 -0800, Krister Johansen wrote:
> Add net.ipv4.ip_unprotected_port_start, which is a per namespace sysctl
> that denotes the first unprotected inet port in the namespace.  To
> disable all protected ports set this to zero.  It also checks for
> overlap with the local port range.  The protected and local range may
> not overlap.
> 
> The use case for this change is to allow containerized processes to bind
> to priviliged ports, but prevent them from ever being allowed to modify
> their container's network configuration.  The latter is accomplished by
> ensuring that the network namespace is not a child of the user
> namespace.  This modification was needed to allow the container manager
> to disable a namespace's priviliged port restrictions without exposing
> control of the network namespace to processes in the user namespace.
> 
> Signed-off-by: Krister Johansen <kjlx@...pleofstupid.com>
> ---
>  include/net/ip.h               | 10 +++++++++
>  include/net/netns/ipv4.h       |  1 +
>  net/ipv4/af_inet.c             |  5 ++++-
>  net/ipv4/sysctl_net_ipv4.c     | 50 +++++++++++++++++++++++++++++++++++++++++-
>  net/ipv6/af_inet6.c            |  3 ++-
>  net/netfilter/ipvs/ip_vs_ctl.c |  7 +++---
>  net/sctp/socket.c              | 10 +++++----
>  security/selinux/hooks.c       |  3 ++-

Adding a new sysctl without documentation is generally not accepted.

Please take a look at Documentation/networking/ip-sysctl.txt

BTW, sticking to 'unprivileged' ports might be better than 'unprotected'
which is vague.