rtnl: add option for setting link xdp prog

Sets the bpf program represented by fd as an early filter in the rx path
of the netdev. The fd must have been created as BPF_PROG_TYPE_XDP.
Providing a negative value as fd clears the program. Getting the fd back
via rtnl is not possible, therefore reading of this value merely
provides a bool whether the program is valid on the link or not.

Signed-off-by: Brenden Blanco <bblanco@plumgrid.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/uapi/linux/if_link.h

@@ -156,6 +156,7 @@ enum {
 	IFLA_GSO_MAX_SEGS,
 	IFLA_GSO_MAX_SIZE,
 	IFLA_PAD,
+	IFLA_XDP,
 	__IFLA_MAX
 };
 
@@ -843,4 +844,15 @@ enum {
 };
 #define LINK_XSTATS_TYPE_MAX (__LINK_XSTATS_TYPE_MAX - 1)
 
+/* XDP section */
+
+enum {
+	IFLA_XDP_UNSPEC,
+	IFLA_XDP_FD,
+	IFLA_XDP_ATTACHED,
+	__IFLA_XDP_MAX,
+};
+
+#define IFLA_XDP_MAX (__IFLA_XDP_MAX - 1)
+
 #endif /* _UAPI_LINUX_IF_LINK_H */

net/core/rtnetlink.c

@@ -891,6 +891,16 @@ static size_t rtnl_port_size(const struct net_device *dev,
 		return port_self_size;
 }
 
+static size_t rtnl_xdp_size(const struct net_device *dev)
+{
+	size_t xdp_size = nla_total_size(1);	/* XDP_ATTACHED */
+
+	if (!dev->netdev_ops->ndo_xdp)
+		return 0;
+	else
+		return xdp_size;
+}
+
 static noinline size_t if_nlmsg_size(const struct net_device *dev,
 				     u32 ext_filter_mask)
 {
@@ -927,6 +937,7 @@ static noinline size_t if_nlmsg_size(const struct net_device *dev,
 	       + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_PORT_ID */
 	       + nla_total_size(MAX_PHYS_ITEM_ID_LEN) /* IFLA_PHYS_SWITCH_ID */
 	       + nla_total_size(IFNAMSIZ) /* IFLA_PHYS_PORT_NAME */
+	       + rtnl_xdp_size(dev) /* IFLA_XDP */
 	       + nla_total_size(1); /* IFLA_PROTO_DOWN */
 
 }
@@ -1211,6 +1222,33 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
 	return 0;
 }
 
+static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
+{
+	struct netdev_xdp xdp_op = {};
+	struct nlattr *xdp;
+	int err;
+
+	if (!dev->netdev_ops->ndo_xdp)
+		return 0;
+	xdp = nla_nest_start(skb, IFLA_XDP);
+	if (!xdp)
+		return -EMSGSIZE;
+	xdp_op.command = XDP_QUERY_PROG;
+	err = dev->netdev_ops->ndo_xdp(dev, &xdp_op);
+	if (err)
+		goto err_cancel;
+	err = nla_put_u8(skb, IFLA_XDP_ATTACHED, xdp_op.prog_attached);
+	if (err)
+		goto err_cancel;
+
+	nla_nest_end(skb, xdp);
+	return 0;
+
+err_cancel:
+	nla_nest_cancel(skb, xdp);
+	return err;
+}
+
 static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 			    int type, u32 pid, u32 seq, u32 change,
 			    unsigned int flags, u32 ext_filter_mask)
@@ -1307,6 +1345,9 @@ static int rtnl_fill_ifinfo(struct sk_buff *skb, struct net_device *dev,
 	if (rtnl_port_fill(skb, dev, ext_filter_mask))
 		goto nla_put_failure;
 
+	if (rtnl_xdp_fill(skb, dev))
+		goto nla_put_failure;
+
 	if (dev->rtnl_link_ops || rtnl_have_link_slave_info(dev)) {
 		if (rtnl_link_fill(skb, dev) < 0)
 			goto nla_put_failure;
@@ -1392,6 +1433,7 @@ static const struct nla_policy ifla_policy[IFLA_MAX+1] = {
 	[IFLA_PHYS_SWITCH_ID]	= { .type = NLA_BINARY, .len = MAX_PHYS_ITEM_ID_LEN },
 	[IFLA_LINK_NETNSID]	= { .type = NLA_S32 },
 	[IFLA_PROTO_DOWN]	= { .type = NLA_U8 },
+	[IFLA_XDP]		= { .type = NLA_NESTED },
 };
 
 static const struct nla_policy ifla_info_policy[IFLA_INFO_MAX+1] = {
@@ -1429,6 +1471,11 @@ static const struct nla_policy ifla_port_policy[IFLA_PORT_MAX+1] = {
 	[IFLA_PORT_RESPONSE]	= { .type = NLA_U16, },
 };
 
+static const struct nla_policy ifla_xdp_policy[IFLA_XDP_MAX + 1] = {
+	[IFLA_XDP_FD]		= { .type = NLA_S32 },
+	[IFLA_XDP_ATTACHED]	= { .type = NLA_U8 },
+};
+
 static const struct rtnl_link_ops *linkinfo_to_kind_ops(const struct nlattr *nla)
 {
 	const struct rtnl_link_ops *ops = NULL;
@@ -2054,6 +2101,23 @@ static int do_setlink(const struct sk_buff *skb,
 		status |= DO_SETLINK_NOTIFY;
 	}
 
+	if (tb[IFLA_XDP]) {
+		struct nlattr *xdp[IFLA_XDP_MAX + 1];
+
+		err = nla_parse_nested(xdp, IFLA_XDP_MAX, tb[IFLA_XDP],
+				       ifla_xdp_policy);
+		if (err < 0)
+			goto errout;
+
+		if (xdp[IFLA_XDP_FD]) {
+			err = dev_change_xdp_fd(dev,
+						nla_get_s32(xdp[IFLA_XDP_FD]));
+			if (err)
+				goto errout;
+			status |= DO_SETLINK_NOTIFY;
+		}
+	}
+
 errout:
 	if (status & DO_SETLINK_MODIFIED) {
 		if (status & DO_SETLINK_NOTIFY)