Re: [PATCH 05/15] connection tracking helper for SLP

From: Pablo Neira Ayuso
Date: Tue May 07 2013 - 22:03:43 EST


On Tue, May 07, 2013 at 04:18:13PM +0200, Jiri Slaby wrote:
> From: Jiri Bohac <jbohac@xxxxxxx>
>
> A simple connection tracking helper for SLP. Marks replies to a
> SLP broadcast query as ESTABLISHED to allow them to pass through the
> firewall.
>
> Signed-off-by: Jiri Bohac <jbohac@xxxxxxx>
> Signed-off-by: Jiri Slaby <jslaby@xxxxxxx>
> Cc: netfilter-devel@xxxxxxxxxxxxxxx
> Cc: netfilter@xxxxxxxxxxxxxxx
> Cc: coreteam@xxxxxxxxxxxxx
> Cc: netdev@xxxxxxxxxxxxxxx
> Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
> Cc: Patrick McHardy <kaber@xxxxxxxxx>
> Cc: Pablo Neira Ayuso <pablo@xxxxxxxxxxxxx>
> ---
> net/netfilter/Kconfig | 15 +++++
> net/netfilter/Makefile | 1 +
> net/netfilter/nf_conntrack_slp.c | 131 +++++++++++++++++++++++++++++++++++++++
> 3 files changed, 147 insertions(+)
> create mode 100644 net/netfilter/nf_conntrack_slp.c
>
> diff --git a/net/netfilter/Kconfig b/net/netfilter/Kconfig
> index 56d22ca..ec61b30 100644
> --- a/net/netfilter/Kconfig
> +++ b/net/netfilter/Kconfig
> @@ -320,6 +320,21 @@ config NF_CONNTRACK_TFTP
>
> To compile it as a module, choose M here. If unsure, say N.
>
> +config NF_CONNTRACK_SLP
> + tristate "SLP protocol support"
> + depends on NF_CONNTRACK
> + depends on NETFILTER_ADVANCED
> + help
> + SLP queries are sometimes sent as broadcast messages from an
> + unprivileged port and responded to with unicast messages to the
> + same port. This make them hard to firewall properly because connection
> + tracking doesn't deal with broadcasts. This helper tracks locally
> + originating broadcast SLP queries and the corresponding
> + responses. It relies on correct IP address configuration, specifically
> + netmask and broadcast address.

We have the user-space helper infrastructure in the conntrack-tools,
this helper has to go there.
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