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Date: Thu, 23 Jun 2011 15:29:29 -0700
From: Stephen Hemminger <shemminger@...ux-foundation.org>
To: Nick Carter <ncarter100@...il.com>
Cc: netdev@...r.kernel.org, davem@...emloft.net
Subject: Re: [PATCH] bridge: Forward EAPOL Kconfig option BRIDGE_PAE_FORWARD
On Thu, 23 Jun 2011 22:39:52 +0100
Nick Carter <ncarter100@...il.com> wrote:
> Signed-off-by: Nick Carter <ncarter100@...il.com>
>
> This Kconfig option is used to enable a bridge to forward 802.1x
> (EAPOL) Port Access Entity (PAE) frames. One use of this would be to
> enable 802.1x authentication between a PAE supplicant running inside a
> virtual machine, with the EAPOL frames bridged out to an external PAE
> authenticator.
>
> If BRIDGE_PAE_FORWARD is not set the behaviour of bridge.ko is unchanged.
>
> If BRIDGE_PAE_FORWARD is set then by default the only new behaviour is
> that unicast EAPOL frames attempting to traverse the bridge will be
> dropped. This makes the bridge standards compliant by preventing
> crosstalk (IEEE Std 802.1X-2001 C.3.3).
>
> Writing a 1 to the new sysfs attribute ../bridge/pae_forward will
> enable the forwarding of EAPOL frames, both unicast and link local
> multicast (01-80-C2-00-00-03).
>
> diff --git a/net/bridge/Kconfig b/net/bridge/Kconfig
> index 6dee7bf..c47a49e 100644
> --- a/net/bridge/Kconfig
> +++ b/net/bridge/Kconfig
> @@ -46,3 +46,22 @@ config BRIDGE_IGMP_SNOOPING
> Say N to exclude this support and reduce the binary size.
>
> If unsure, say Y.
> +
> +config BRIDGE_PAE_FORWARD
> + bool "PAE Forwarding"
> + depends on BRIDGE
> + default n
> + ---help---
> + If you say Y here, then the Ethernet bridge will be able to forward
> + 802.1x (EAPOL) Port Access Entity (PAE) frames. One use of this would
> + be to enable 802.1x authentication between a PAE supplicant running
> + inside a virtual machine, with the EAPOL frames bridged out to an
> + external PAE authenticator.
> +
> + On a running kernel with this support, enable PAE forwarding by
> + writing a '1' to the bridge devices pae_forward attribute.
> + e.g. echo 1 > /sys/devices/virtual/net/br73/bridge/pae_forward
> +
> + Say N to exclude this support.
> +
> + If unsure, say N.
> diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
> index d9d1e2b..b493474 100644
> --- a/net/bridge/br_if.c
> +++ b/net/bridge/br_if.c
> @@ -214,6 +214,9 @@ static struct net_device *new_bridge_dev(struct
> net *net, const char *name)
> br->topology_change = 0;
> br->topology_change_detected = 0;
> br->ageing_time = 300 * HZ;
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> + br->pae_forward = BR_PAE_DEFAULT;
> +#endif
>
> br_netfilter_rtable_init(br);
>
> diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
> index 90e985b..183c40f 100644
> --- a/net/bridge/br_input.c
> +++ b/net/bridge/br_input.c
> @@ -43,6 +43,24 @@ static int br_pass_frame_up(struct sk_buff *skb)
> netif_receive_skb);
> }
>
> +static inline bool br_pae_forward(struct net_bridge *br, __be16 proto)
> +{
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> + return br->pae_forward == BR_PAE_FORWARD && proto == htons(ETH_P_PAE);
> +#else
> + return false;
> +#endif
> +}
> +
> +static inline bool br_pae_drop(struct net_bridge *br, __be16 proto)
> +{
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> + return br->pae_forward == BR_PAE_DEFAULT && proto == htons(ETH_P_PAE);
> +#else
> + return false;
> +#endif
> +}
> +
> /* note: already called with rcu_read_lock */
> int br_handle_frame_finish(struct sk_buff *skb)
> {
> @@ -98,6 +116,10 @@ int br_handle_frame_finish(struct sk_buff *skb)
> }
>
> if (skb) {
> + /* Prevent Crosstalk (IEEE Std 802.1X-2001 C.3.3) */
> + if (unlikely(br_pae_drop(br, skb->protocol)))
> + goto drop;
> +
> if (dst)
> br_forward(dst->dst, skb, skb2);
> else
> @@ -166,6 +188,10 @@ struct sk_buff *br_handle_frame(struct sk_buff *skb)
> if (p->br->stp_enabled == BR_NO_STP && dest[5] == 0)
> goto forward;
>
> + /* Check if PAE frame should be forwarded */
> + if (br_pae_forward(p->br, skb->protocol))
> + goto forward;
> +
> if (NF_HOOK(NFPROTO_BRIDGE, NF_BR_LOCAL_IN, skb, skb->dev,
> NULL, br_handle_local_finish))
> return NULL; /* frame consumed by filter */
> diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
> index 4e1b620..a523032 100644
> --- a/net/bridge/br_private.h
> +++ b/net/bridge/br_private.h
> @@ -244,6 +244,13 @@ struct net_bridge
> struct timer_list multicast_query_timer;
> #endif
>
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> + enum {
> + BR_PAE_DEFAULT, /* 802.1x frames consumed by bridge */
> + BR_PAE_FORWARD, /* 802.1x frames forwarded by bridge */
> + } pae_forward;
> +#endif
> +
> struct timer_list hello_timer;
> struct timer_list tcn_timer;
> struct timer_list topology_change_timer;
> diff --git a/net/bridge/br_sysfs_br.c b/net/bridge/br_sysfs_br.c
> index 5c1e555..c5ffd97 100644
> --- a/net/bridge/br_sysfs_br.c
> +++ b/net/bridge/br_sysfs_br.c
> @@ -679,6 +679,33 @@ static DEVICE_ATTR(nf_call_arptables, S_IRUGO | S_IWUSR,
> show_nf_call_arptables, store_nf_call_arptables);
> #endif
>
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> +static ssize_t show_pae_forward(struct device *d, struct
> device_attribute *attr,
> + char *buf)
> +{
> + struct net_bridge *br = to_bridge(d);
> + return sprintf(buf, "%d\n", br->pae_forward);
> +}
> +
> +static int set_pae_forward(struct net_bridge *br, unsigned long val)
> +{
> + if (val > BR_PAE_FORWARD)
> + return -EINVAL;
> +
> + br->pae_forward = val;
> + return 0;
> +}
> +
> +static ssize_t store_pae_forward(struct device *d,
> + struct device_attribute *attr, const char *buf,
> + size_t len)
> +{
> + return store_bridge_parm(d, buf, len, set_pae_forward);
> +}
> +static DEVICE_ATTR(pae_forward, S_IRUGO | S_IWUSR, show_pae_forward,
> + store_pae_forward);
> +#endif
> +
> static struct attribute *bridge_attrs[] = {
> &dev_attr_forward_delay.attr,
> &dev_attr_hello_time.attr,
> @@ -717,6 +744,9 @@ static struct attribute *bridge_attrs[] = {
> &dev_attr_nf_call_ip6tables.attr,
> &dev_attr_nf_call_arptables.attr,
> #endif
> +#ifdef CONFIG_BRIDGE_PAE_FORWARD
> + &dev_attr_pae_forward.attr,
> +#endif
> NULL
> };
Don't make it a config option, users and distros won't get it right.
The bridge already makes special case for multicast, why not add
some smarts and always do it.
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