Subject: Re: [patch 08/12] net namespace : find namespace by addr

From: Herbert Poetzl <[email-masked]>
Date: Sat, 20 Jan 2007 05:56:13 +0100

On Fri, Jan 19, 2007 at 04:47:22PM +0100, [email-masked] wrote:
> From: Daniel Lezcano <[email-masked]>
> 
> Switch to the the l3 namespace using the destination address.
> 
> Signed-off-by: Daniel Lezcano <[email-masked]>
> 
> ---
>  include/linux/net_namespace.h |    7 +++++++
>  net/core/net_namespace.c      |   35 +++++++++++++++++++++++++++++++++++
>  net/ipv4/ip_input.c           |   16 +++++++++++++++-
>  3 files changed, 57 insertions(+), 1 deletion(-)
> 
> Index: 2.6.20-rc4-mm1/net/ipv4/ip_input.c
> ===================================================================
> --- 2.6.20-rc4-mm1.orig/net/ipv4/ip_input.c
> +++ 2.6.20-rc4-mm1/net/ipv4/ip_input.c
> @@ -374,6 +374,9 @@
>  {
>  	struct iphdr *iph;
>  	u32 len;
> +	int err;
> +	struct net_namespace *net_ns = current_net_ns;
> +	struct net_namespace *dst_net_ns = NULL;
>  
>  	/* When the interface is in promisc. mode, drop all the crap
>  	 * that it receives, do not try to analyse it.
> @@ -393,6 +396,9 @@
>  
>  	iph = skb->nh.iph;
>  
> +	dst_net_ns = net_ns_find_from_dest_addr(iph->daddr);
> +	if (dst_net_ns && !net_ns_match(net_ns, dst_net_ns))
> +		push_net_ns(dst_net_ns);
>  	/*
>  	 *	RFC1122: 3.1.2.2 MUST silently discard any IP frame that fails the checksum.
>  	 *
> @@ -431,10 +437,18 @@
>  	/* Remove any debris in the socket control block */
>  	memset(IPCB(skb), 0, sizeof(struct inet_skb_parm));
>  
> -	return NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
> +	err =  NF_HOOK(PF_INET, NF_IP_PRE_ROUTING, skb, dev, NULL,
>  		       ip_rcv_finish);
>  
> +	if (dst_net_ns && !net_ns_match(net_ns, dst_net_ns))
> +		pop_net_ns(net_ns);
> +
> +	return err;
> +
>  inhdr_error:
> +	if (dst_net_ns && !net_ns_match(net_ns, dst_net_ns))
> +		pop_net_ns(net_ns);
> +
>  	IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
>  drop:
>          kfree_skb(skb);
> Index: 2.6.20-rc4-mm1/include/linux/net_namespace.h
> ===================================================================
> --- 2.6.20-rc4-mm1.orig/include/linux/net_namespace.h
> +++ 2.6.20-rc4-mm1/include/linux/net_namespace.h
> @@ -99,6 +99,8 @@
>  extern __be32 net_ns_select_source_address(const struct net_device *dev,
>  					   u32 dst, int scope);
>  
> +extern struct net_namespace *net_ns_find_from_dest_addr(u32 daddr);
> +
>  #define SELECT_SRC_ADDR net_ns_select_source_address
>  
>  #else /* CONFIG_NET_NS */
> @@ -167,6 +169,11 @@
>  	return 0;
>  }
>  
> +static inline struct net_namespace *net_ns_find_from_dest_addr(u32 daddr)
> +{
> +	return NULL;
> +}
> +
>  #define SELECT_SRC_ADDR inet_select_addr
>  
>  #endif /* !CONFIG_NET_NS */
> Index: 2.6.20-rc4-mm1/net/core/net_namespace.c
> ===================================================================
> --- 2.6.20-rc4-mm1.orig/net/core/net_namespace.c
> +++ 2.6.20-rc4-mm1/net/core/net_namespace.c
> @@ -385,4 +385,39 @@
>  out:
>  	return addr;
>  }
> +
> +/*
> + * This function finds the network namespace destination deduced from
> + * the destination address. The network namespace is retrieved from
> + * the ifaddr owned by a network namespace

this basically disallows to 'share' IPs between
namespaces, as it is permitted in Linux-VServer
right now, or am I misinterpreting this?

TIA,
Herbert

> + * @daddr  : destination
> + * Returns : the network namespace destination or NULL if not found
> + */
> +struct net_namespace *net_ns_find_from_dest_addr(u32 daddr)
> +{
> +	struct net_namespace *net_ns = NULL;
> +	struct net_device *dev;
> +	struct in_device *in_dev;
> +
> +	if (LOOPBACK(daddr))
> +		return current_net_ns;
> +
> +	read_lock(&dev_base_lock);
> +	rcu_read_lock();
> +	for (dev = dev_base; dev; dev = dev->next) {
> +		if ((in_dev = __in_dev_get_rcu(dev)) == NULL)
> +			continue;
> +		for_ifa(in_dev) {
> +			if (ifa->ifa_local == daddr) {
> +				net_ns = ifa->ifa_net_ns;
> +				goto out_unlock_both;
> +			}
> +		} endfor_ifa(in_dev);
> +	}
> +out_unlock_both:
> +	read_unlock(&dev_base_lock);
> +	rcu_read_unlock();
> +
> +	return net_ns;
> +}
>  #endif /* CONFIG_NET_NS */
> 
> -- 
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