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Commit 814abfab authored by John Fastabend's avatar John Fastabend Committed by David S. Miller
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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: default avatarJohn Fastabend <john.fastabend@gmail.com>
Acked-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent d4455169

include/linux/filter.h

+4 −0
Original line number Diff line number Diff line
@@ -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;

include/linux/netdevice.h

+6 −0
Original line number Diff line number Diff line
@@ -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);

};



/**

include/uapi/linux/bpf.h

+1 −0
Original line number Diff line number Diff line
@@ -717,6 +717,7 @@ enum xdp_action { 
	XDP_DROP,

	XDP_PASS,

	XDP_TX,

	XDP_REDIRECT,

};



/* user accessible metadata for XDP packet hook

net/core/filter.c

+52 −0
Original line number Diff line number Diff line
@@ -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))