Commit 9eb8eff0 authored by Vladimir Oltean's avatar Vladimir Oltean Committed by Jakub Kicinski
Browse files

net: bridge: allow enslaving some DSA master network devices 



Commit 8db0a2ee ("net: bridge: reject DSA-enabled master netdevices
as bridge members") added a special check in br_if.c in order to check
for a DSA master network device with a tagging protocol configured. This
was done because back then, such devices, once enslaved in a bridge
would become inoperative and would not pass DSA tagged traffic anymore
due to br_handle_frame returning RX_HANDLER_CONSUMED.

But right now we have valid use cases which do require bridging of DSA
masters. One such example is when the DSA master ports are DSA switch
ports themselves (in a disjoint tree setup). This should be completely
equivalent, functionally speaking, from having multiple DSA switches
hanging off of the ports of a switchdev driver. So we should allow the
enslaving of DSA tagged master network devices.

Instead of the regular br_handle_frame(), install a new function
br_handle_frame_dummy() on these DSA masters, which returns
RX_HANDLER_PASS in order to call into the DSA specific tagging protocol
handlers, and lift the restriction from br_add_if.

Suggested-by: default avatarNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Suggested-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: default avatarVladimir Oltean <vladimir.oltean@nxp.com>
Acked-by: default avatarNikolay Aleksandrov <nikolay@cumulusnetworks.com>
Reviewed-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Tested-by: default avatarFlorian Fainelli <f.fainelli@gmail.com>
Signed-off-by: default avatarJakub Kicinski <kuba@kernel.org>
parent 90d9834e

include/net/dsa.h

+1 −1
Original line number Diff line number Diff line
@@ -651,7 +651,7 @@ struct dsa_switch_driver { 
struct net_device *dsa_dev_to_net_device(struct device *dev);



/* Keep inline for faster access in hot path */

static inline bool netdev_uses_dsa(struct net_device *dev)

static inline bool netdev_uses_dsa(const struct net_device *dev)

{

#if IS_ENABLED(CONFIG_NET_DSA)

	return dev->dsa_ptr && dev->dsa_ptr->rcv;

net/bridge/br_if.c

+23 −9
Original line number Diff line number Diff line
@@ -563,18 +563,32 @@ int br_add_if(struct net_bridge *br, struct net_device *dev, 
	unsigned br_hr, dev_hr;

	bool changed_addr;



	/* Don't allow bridging non-ethernet like devices, or DSA-enabled

	 * master network devices since the bridge layer rx_handler prevents

	 * the DSA fake ethertype handler to be invoked, so we do not strip off

	 * the DSA switch tag protocol header and the bridge layer just return

	 * RX_HANDLER_CONSUMED, stopping RX processing for these frames.

	 */

	/* Don't allow bridging non-ethernet like devices. */

	if ((dev->flags & IFF_LOOPBACK) ||

	    dev->type != ARPHRD_ETHER || dev->addr_len != ETH_ALEN ||

	    !is_valid_ether_addr(dev->dev_addr) ||

	    netdev_uses_dsa(dev))

	    !is_valid_ether_addr(dev->dev_addr))

		return -EINVAL;



	/* Also don't allow bridging of net devices that are DSA masters, since

	 * the bridge layer rx_handler prevents the DSA fake ethertype handler

	 * to be invoked, so we don't get the chance to strip off and parse the

	 * DSA switch tag protocol header (the bridge layer just returns

	 * RX_HANDLER_CONSUMED, stopping RX processing for these frames).

	 * The only case where that would not be an issue is when bridging can

	 * already be offloaded, such as when the DSA master is itself a DSA

	 * or plain switchdev port, and is bridged only with other ports from

	 * the same hardware device.

	 */

	if (netdev_uses_dsa(dev)) {

		list_for_each_entry(p, &br->port_list, list) {

			if (!netdev_port_same_parent_id(dev, p->dev)) {

				NL_SET_ERR_MSG(extack,

					       "Cannot do software bridging with a DSA master");

				return -EINVAL;

			}

		}

	}



	/* No bridging of bridges */

	if (dev->netdev_ops->ndo_start_xmit == br_dev_xmit) {

		NL_SET_ERR_MSG(extack,
@@ -618,7 +632,7 @@ int br_add_if(struct net_bridge *br, struct net_device *dev, 
	if (err)

		goto err3;



	err = netdev_rx_handler_register(dev, br_handle_frame, p);

	err = netdev_rx_handler_register(dev, br_get_rx_handler(dev), p);

	if (err)

		goto err4;

net/bridge/br_input.c

+22 −1
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#endif

#include <linux/neighbour.h>

#include <net/arp.h>

#include <net/dsa.h>

#include <linux/export.h>

#include <linux/rculist.h>

#include "br_private.h"
@@ -257,7 +258,7 @@ frame_finish: 
 * Return NULL if skb is handled

 * note: already called with rcu_read_lock

 */

rx_handler_result_t br_handle_frame(struct sk_buff **pskb)

static rx_handler_result_t br_handle_frame(struct sk_buff **pskb)

{

	struct net_bridge_port *p;

	struct sk_buff *skb = *pskb;
@@ -359,3 +360,23 @@ drop: 
	}

	return RX_HANDLER_CONSUMED;

}



/* This function has no purpose other than to appease the br_port_get_rcu/rtnl

 * helpers which identify bridged ports according to the rx_handler installed

 * on them (so there _needs_ to be a bridge rx_handler even if we don't need it

 * to do anything useful). This bridge won't support traffic to/from the stack,

 * but only hardware bridging. So return RX_HANDLER_PASS so we don't steal

 * frames from the ETH_P_XDSA packet_type handler.

 */

static rx_handler_result_t br_handle_frame_dummy(struct sk_buff **pskb)

{

	return RX_HANDLER_PASS;

}



rx_handler_func_t *br_get_rx_handler(const struct net_device *dev)

{

	if (netdev_uses_dsa(dev))

		return br_handle_frame_dummy;



	return br_handle_frame;

}

net/bridge/br_private.h

+3 −3
Original line number Diff line number Diff line
@@ -702,16 +702,16 @@ int nbp_backup_change(struct net_bridge_port *p, struct net_device *backup_dev); 


/* br_input.c */

int br_handle_frame_finish(struct net *net, struct sock *sk, struct sk_buff *skb);

rx_handler_result_t br_handle_frame(struct sk_buff **pskb);

rx_handler_func_t *br_get_rx_handler(const struct net_device *dev);



static inline bool br_rx_handler_check_rcu(const struct net_device *dev)

{

	return rcu_dereference(dev->rx_handler) == br_handle_frame;

	return rcu_dereference(dev->rx_handler) == br_get_rx_handler(dev);

}



static inline bool br_rx_handler_check_rtnl(const struct net_device *dev)

{

	return rcu_dereference_rtnl(dev->rx_handler) == br_handle_frame;

	return rcu_dereference_rtnl(dev->rx_handler) == br_get_rx_handler(dev);

}



static inline struct net_bridge_port *br_port_get_check_rcu(const struct net_device *dev)

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