171 lines
4.9 KiB
Diff
171 lines
4.9 KiB
Diff
From: Pablo Neira Ayuso <pablo@netfilter.org>
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Date: Sun, 10 Jan 2021 15:53:58 +0100
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Subject: [PATCH] net: resolve forwarding path from virtual netdevice and
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HW destination address
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This patch adds dev_fill_forward_path() which resolves the path to reach
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the real netdevice from the IP forwarding side. This function takes as
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input the netdevice and the destination hardware address and it walks
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down the devices calling .ndo_fill_forward_path() for each device until
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the real device is found.
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For instance, assuming the following topology:
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IP forwarding
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/ \
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br0 eth0
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/ \
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eth1 eth2
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.
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.
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.
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ethX
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ab:cd:ef:ab:cd:ef
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where eth1 and eth2 are bridge ports and eth0 provides WAN connectivity.
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ethX is the interface in another box which is connected to the eth1
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bridge port.
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For packets going through IP forwarding to br0 whose destination MAC
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address is ab:cd:ef:ab:cd:ef, dev_fill_forward_path() provides the
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following path:
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br0 -> eth1
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.ndo_fill_forward_path for br0 looks up at the FDB for the bridge port
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from the destination MAC address to get the bridge port eth1.
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This information allows to create a fast path that bypasses the classic
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bridge and IP forwarding paths, so packets go directly from the bridge
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port eth1 to eth0 (wan interface) and vice versa.
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fast path
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.------------------------.
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/ \
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| IP forwarding |
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| / \ \/
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| br0 eth0
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. / \
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-> eth1 eth2
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.
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.
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.
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ethX
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ab:cd:ef:ab:cd:ef
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Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>
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---
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--- a/include/linux/netdevice.h
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+++ b/include/linux/netdevice.h
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@@ -833,6 +833,27 @@ typedef u16 (*select_queue_fallback_t)(s
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struct sk_buff *skb,
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struct net_device *sb_dev);
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+enum net_device_path_type {
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+ DEV_PATH_ETHERNET = 0,
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+};
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+
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+struct net_device_path {
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+ enum net_device_path_type type;
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+ const struct net_device *dev;
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+};
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+
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+#define NET_DEVICE_PATH_STACK_MAX 5
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+
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+struct net_device_path_stack {
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+ int num_paths;
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+ struct net_device_path path[NET_DEVICE_PATH_STACK_MAX];
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+};
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+
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+struct net_device_path_ctx {
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+ const struct net_device *dev;
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+ const u8 *daddr;
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+};
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+
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enum tc_setup_type {
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TC_SETUP_QDISC_MQPRIO,
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TC_SETUP_CLSU32,
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@@ -1279,6 +1300,8 @@ struct netdev_net_notifier {
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* struct net_device *(*ndo_get_peer_dev)(struct net_device *dev);
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* If a device is paired with a peer device, return the peer instance.
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* The caller must be under RCU read context.
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+ * int (*ndo_fill_forward_path)(struct net_device_path_ctx *ctx, struct net_device_path *path);
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+ * Get the forwarding path to reach the real device from the HW destination address
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*/
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struct net_device_ops {
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int (*ndo_init)(struct net_device *dev);
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@@ -1487,6 +1510,8 @@ struct net_device_ops {
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int (*ndo_tunnel_ctl)(struct net_device *dev,
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struct ip_tunnel_parm *p, int cmd);
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struct net_device * (*ndo_get_peer_dev)(struct net_device *dev);
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+ int (*ndo_fill_forward_path)(struct net_device_path_ctx *ctx,
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+ struct net_device_path *path);
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};
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/**
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@@ -2798,6 +2823,8 @@ void dev_remove_offload(struct packet_of
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int dev_get_iflink(const struct net_device *dev);
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int dev_fill_metadata_dst(struct net_device *dev, struct sk_buff *skb);
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+int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
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+ struct net_device_path_stack *stack);
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struct net_device *__dev_get_by_flags(struct net *net, unsigned short flags,
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unsigned short mask);
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struct net_device *dev_get_by_name(struct net *net, const char *name);
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--- a/net/core/dev.c
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+++ b/net/core/dev.c
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@@ -846,6 +846,52 @@ int dev_fill_metadata_dst(struct net_dev
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}
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EXPORT_SYMBOL_GPL(dev_fill_metadata_dst);
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+static struct net_device_path *dev_fwd_path(struct net_device_path_stack *stack)
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+{
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+ int k = stack->num_paths++;
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+
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+ if (WARN_ON_ONCE(k >= NET_DEVICE_PATH_STACK_MAX))
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+ return NULL;
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+
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+ return &stack->path[k];
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+}
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+
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+int dev_fill_forward_path(const struct net_device *dev, const u8 *daddr,
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+ struct net_device_path_stack *stack)
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+{
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+ const struct net_device *last_dev;
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+ struct net_device_path_ctx ctx = {
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+ .dev = dev,
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+ .daddr = daddr,
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+ };
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+ struct net_device_path *path;
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+ int ret = 0;
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+
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+ stack->num_paths = 0;
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+ while (ctx.dev && ctx.dev->netdev_ops->ndo_fill_forward_path) {
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+ last_dev = ctx.dev;
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+ path = dev_fwd_path(stack);
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+ if (!path)
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+ return -1;
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+
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+ memset(path, 0, sizeof(struct net_device_path));
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+ ret = ctx.dev->netdev_ops->ndo_fill_forward_path(&ctx, path);
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+ if (ret < 0)
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+ return -1;
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+
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+ if (WARN_ON_ONCE(last_dev == ctx.dev))
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+ return -1;
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+ }
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+ path = dev_fwd_path(stack);
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+ if (!path)
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+ return -1;
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+ path->type = DEV_PATH_ETHERNET;
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+ path->dev = ctx.dev;
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+
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+ return ret;
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+}
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+EXPORT_SYMBOL_GPL(dev_fill_forward_path);
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+
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/**
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* __dev_get_by_name - find a device by its name
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* @net: the applicable net namespace
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