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Message-Id: <20200430202542.11797-2-olteanv@gmail.com>
Date: Thu, 30 Apr 2020 23:25:39 +0300
From: Vladimir Oltean <olteanv@...il.com>
To: andrew@...n.ch, f.fainelli@...il.com, vivien.didelot@...il.com,
davem@...emloft.net
Cc: jiri@...nulli.us, idosch@...sch.org, kuba@...nel.org,
netdev@...r.kernel.org, leoyang.li@....com,
nikolay@...ulusnetworks.com, roopa@...ulusnetworks.com
Subject: [PATCH v2 net-next 1/4] net: bridge: allow enslaving some DSA master network devices
From: Vladimir Oltean <vladimir.oltean@....com>
Commit 8db0a2ee2c63 ("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: Nikolay Aleksandrov <nikolay@...ulusnetworks.com>
Suggested-by: Florian Fainelli <f.fainelli@...il.com>
Signed-off-by: Vladimir Oltean <vladimir.oltean@....com>
---
Changes in v2:
* Removed the hotpath netdev_uses_dsa check and installed a dummy
rx_handler for such net devices.
* Improved the check of which DSA master net devices are able to be
bridged and which aren't.
* At this stage, the patch is different enough from where I took it from
(aka https://github.com/ffainelli/linux/commit/75618cea75ada8d9eef7936c002b5ec3dd3e4eac)
that I just added my authorship to it).
include/net/dsa.h | 2 +-
net/bridge/br_if.c | 32 +++++++++++++++++++++++---------
net/bridge/br_input.c | 23 ++++++++++++++++++++++-
net/bridge/br_private.h | 6 +++---
4 files changed, 49 insertions(+), 14 deletions(-)
diff --git a/include/net/dsa.h b/include/net/dsa.h
index fb3f9222f2a1..3c0ae84156c8 100644
--- a/include/net/dsa.h
+++ b/include/net/dsa.h
@@ -650,7 +650,7 @@ 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;
diff --git a/net/bridge/br_if.c b/net/bridge/br_if.c
index ca685c0cdf95..a0e9a7937412 100644
--- a/net/bridge/br_if.c
+++ b/net/bridge/br_if.c
@@ -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;
diff --git a/net/bridge/br_input.c b/net/bridge/br_input.c
index d5c34f36f0f4..59a318b9f646 100644
--- a/net/bridge/br_input.c
+++ b/net/bridge/br_input.c
@@ -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 @@ static int nf_hook_bridge_pre(struct sk_buff *skb, struct sk_buff **pskb)
* 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 @@ rx_handler_result_t br_handle_frame(struct sk_buff **pskb)
}
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;
+}
diff --git a/net/bridge/br_private.h b/net/bridge/br_private.h
index c35647cb138a..0defc2ff365f 100644
--- a/net/bridge/br_private.h
+++ b/net/bridge/br_private.h
@@ -705,16 +705,16 @@ 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)
--
2.17.1
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