switchdev: add offload_fwd_mark generator helper

skb->offload_fwd_mark and dev->offload_fwd_mark are 32-bit and should be
unique for device and may even be unique for a sub-set of ports within
device, so add switchdev helper function to generate unique marks based on
port's switch ID and group_ifindex.  group_ifindex would typically be the
container dev's ifindex, such as the bridge's ifindex.

The generator uses a global hash table to store offload_fwd_marks hashed by
{switch ID, group_ifindex} key.

Signed-off-by: Scott Feldman <sfeldma@gmail.com>
Acked-by: Jiri Pirko <jiri@resnulli.us>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 103 insertions, 0 deletions

diff --git a/net/switchdev/switchdev.c b/net/switchdev/switchdev.c
index 4e5bba50ccff..33bafa2e703e 100644
--- a/net/switchdev/switchdev.c
+++ b/net/switchdev/switchdev.c
@@ -1039,3 +1039,106 @@ void switchdev_fib_ipv4_abort(struct fib_info *fi)
         fi->fib_net->ipv4.fib_offload_disabled = true;
 }
 EXPORT_SYMBOL_GPL(switchdev_fib_ipv4_abort);
+
+static bool switchdev_port_same_parent_id(struct net_device *a,
+                                          struct net_device *b)
+{
+        struct switchdev_attr a_attr = {
+                .id = SWITCHDEV_ATTR_PORT_PARENT_ID,
+                .flags = SWITCHDEV_F_NO_RECURSE,
+        };
+        struct switchdev_attr b_attr = {
+                .id = SWITCHDEV_ATTR_PORT_PARENT_ID,
+                .flags = SWITCHDEV_F_NO_RECURSE,
+        };
+
+        if (switchdev_port_attr_get(a, &a_attr) ||
+            switchdev_port_attr_get(b, &b_attr))
+                return false;
+
+        return netdev_phys_item_id_same(&a_attr.u.ppid, &b_attr.u.ppid);
+}
+
+static u32 switchdev_port_fwd_mark_get(struct net_device *dev,
+                                       struct net_device *group_dev)
+{
+        struct net_device *lower_dev;
+        struct list_head *iter;
+
+        netdev_for_each_lower_dev(group_dev, lower_dev, iter) {
+                if (lower_dev == dev)
+                        continue;
+                if (switchdev_port_same_parent_id(dev, lower_dev))
+                        return lower_dev->offload_fwd_mark;
+                return switchdev_port_fwd_mark_get(dev, lower_dev);
+        }
+
+        return dev->ifindex;
+}
+
+static void switchdev_port_fwd_mark_reset(struct net_device *group_dev,
+                                          u32 old_mark, u32 *reset_mark)
+{
+        struct net_device *lower_dev;
+        struct list_head *iter;
+
+        netdev_for_each_lower_dev(group_dev, lower_dev, iter) {
+                if (lower_dev->offload_fwd_mark == old_mark) {
+                        if (!*reset_mark)
+                                *reset_mark = lower_dev->ifindex;
+                        lower_dev->offload_fwd_mark = *reset_mark;
+                }
+                switchdev_port_fwd_mark_reset(lower_dev, old_mark, reset_mark);
+        }
+}
+
+/**
+ *      switchdev_port_fwd_mark_set - Set port offload forwarding mark
+ *
+ *      @dev: port device
+ *      @group_dev: containing device
+ *      @joining: true if dev is joining group; false if leaving group
+ *
+ *      An ungrouped port's offload mark is just its ifindex.  A grouped
+ *      port's (member of a bridge, for example) offload mark is the ifindex
+ *      of one of the ports in the group with the same parent (switch) ID.
+ *      Ports on the same device in the same group will have the same mark.
+ *
+ *      Example:
+ *
+ *              br0             ifindex=9
+ *                sw1p1         ifindex=2       mark=2
+ *                sw1p2         ifindex=3       mark=2
+ *                sw2p1         ifindex=4       mark=5
+ *                sw2p2         ifindex=5       mark=5
+ *
+ *      If sw2p2 leaves the bridge, we'll have:
+ *
+ *              br0             ifindex=9
+ *                sw1p1         ifindex=2       mark=2
+ *                sw1p2         ifindex=3       mark=2
+ *                sw2p1         ifindex=4       mark=4
+ *              sw2p2           ifindex=5       mark=5
+ */
+void switchdev_port_fwd_mark_set(struct net_device *dev,
+                                 struct net_device *group_dev,
+                                 bool joining)
+{
+        u32 mark = dev->ifindex;
+        u32 reset_mark = 0;
+
+        if (group_dev && joining) {
+                mark = switchdev_port_fwd_mark_get(dev, group_dev);
+        } else if (group_dev && !joining) {
+                if (dev->offload_fwd_mark == mark)
+                        /* Ohoh, this port was the mark reference port,
+                         * but it's leaving the group, so reset the
+                         * mark for the remaining ports in the group.
+                         */
+                        switchdev_port_fwd_mark_reset(group_dev, mark,
+                                                      &reset_mark);
+        }
+
+        dev->offload_fwd_mark = mark;
+}
+EXPORT_SYMBOL_GPL(switchdev_port_fwd_mark_set);