xdp: add bpf_redirect helper function

This adds support for a bpf_redirect helper function to the XDP
infrastructure. For now this only supports redirecting to the egress
path of a port.

In order to support drivers handling a xdp_buff natively this patches
uses a new ndo operation ndo_xdp_xmit() that takes pushes a xdp_buff
to the specified device.

If the program specifies either (a) an unknown device or (b) a device
that does not support the operation a BPF warning is thrown and the
XDP_ABORTED error code is returned.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/include/linux/filter.h b/include/linux/filter.h
index bfef1e5..64cae7a 100644 (file)
--- a/include/linux/filter.h
+++ b/include/linux/filter.h
@@ -711,7 +711,11 @@ bool bpf_helper_changes_pkt_data(void *func);
 
 struct bpf_prog *bpf_patch_insn_single(struct bpf_prog *prog, u32 off,
                                       const struct bpf_insn *patch, u32 len);
+
+int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp);
+
 void bpf_warn_invalid_xdp_action(u32 act);
+void bpf_warn_invalid_xdp_redirect(u32 ifindex);
 
 #ifdef CONFIG_BPF_JIT
 extern int bpf_jit_enable;

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 779b235..77f5376 100644 (file)
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -66,6 +66,7 @@ struct mpls_dev;
 /* UDP Tunnel offloads */
 struct udp_tunnel_info;
 struct bpf_prog;
+struct xdp_buff;
 
 void netdev_set_default_ethtool_ops(struct net_device *dev,
                                    const struct ethtool_ops *ops);
@@ -1138,6 +1139,9 @@ struct xfrmdev_ops {
  * int (*ndo_xdp)(struct net_device *dev, struct netdev_xdp *xdp);
  *     This function is used to set or query state related to XDP on the
  *     netdevice. See definition of enum xdp_netdev_command for details.
+ * int (*ndo_xdp_xmit)(struct net_device *dev, struct xdp_buff *xdp);
+ *     This function is used to submit a XDP packet for transmit on a
+ *     netdevice.
  *
  */
 struct net_device_ops {
@@ -1323,6 +1327,8 @@ struct net_device_ops {
                                                       int needed_headroom);
        int                     (*ndo_xdp)(struct net_device *dev,
                                           struct netdev_xdp *xdp);
+       int                     (*ndo_xdp_xmit)(struct net_device *dev,
+                                               struct xdp_buff *xdp);
 };
 
 /**

diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index e99e3e6..4dbb7a3 100644 (file)
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -717,6 +717,7 @@ enum xdp_action {
        XDP_DROP,
        XDP_PASS,
        XDP_TX,
+       XDP_REDIRECT,
 };
 
 /* user accessible metadata for XDP packet hook

diff --git a/net/core/filter.c b/net/core/filter.c
index c7f7370..d606a66 100644 (file)
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -2412,6 +2412,51 @@ static const struct bpf_func_proto bpf_xdp_adjust_head_proto = {
        .arg2_type      = ARG_ANYTHING,
 };
 
+static int __bpf_tx_xdp(struct net_device *dev, struct xdp_buff *xdp)
+{
+       if (dev->netdev_ops->ndo_xdp_xmit) {
+               dev->netdev_ops->ndo_xdp_xmit(dev, xdp);
+               return 0;
+       }
+       bpf_warn_invalid_xdp_redirect(dev->ifindex);
+       return -EOPNOTSUPP;
+}
+
+int xdp_do_redirect(struct net_device *dev, struct xdp_buff *xdp)
+{
+       struct redirect_info *ri = this_cpu_ptr(&redirect_info);
+
+       dev = dev_get_by_index_rcu(dev_net(dev), ri->ifindex);
+       ri->ifindex = 0;
+       if (unlikely(!dev)) {
+               bpf_warn_invalid_xdp_redirect(ri->ifindex);
+               return -EINVAL;
+       }
+
+       return __bpf_tx_xdp(dev, xdp);
+}
+EXPORT_SYMBOL_GPL(xdp_do_redirect);
+
+BPF_CALL_2(bpf_xdp_redirect, u32, ifindex, u64, flags)
+{
+       struct redirect_info *ri = this_cpu_ptr(&redirect_info);
+
+       if (unlikely(flags))
+               return XDP_ABORTED;
+
+       ri->ifindex = ifindex;
+       ri->flags = flags;
+       return XDP_REDIRECT;
+}
+
+static const struct bpf_func_proto bpf_xdp_redirect_proto = {
+       .func           = bpf_xdp_redirect,
+       .gpl_only       = false,
+       .ret_type       = RET_INTEGER,
+       .arg1_type      = ARG_ANYTHING,
+       .arg2_type      = ARG_ANYTHING,
+};
+
 bool bpf_helper_changes_pkt_data(void *func)
 {
        if (func == bpf_skb_vlan_push ||
@@ -3011,6 +3056,8 @@ xdp_func_proto(enum bpf_func_id func_id)
                return &bpf_get_smp_processor_id_proto;
        case BPF_FUNC_xdp_adjust_head:
                return &bpf_xdp_adjust_head_proto;
+       case BPF_FUNC_redirect:
+               return &bpf_xdp_redirect_proto;
        default:
                return bpf_base_func_proto(func_id);
        }
@@ -3310,6 +3357,11 @@ void bpf_warn_invalid_xdp_action(u32 act)
 }
 EXPORT_SYMBOL_GPL(bpf_warn_invalid_xdp_action);
 
+void bpf_warn_invalid_xdp_redirect(u32 ifindex)
+{
+       WARN_ONCE(1, "Illegal XDP redirect to unsupported device ifindex(%i)\n", ifindex);
+}
+
 static bool __is_valid_sock_ops_access(int off, int size)
 {
        if (off < 0 || off >= sizeof(struct bpf_sock_ops))