This provides a generic non-optimized XDP implementation when the
device driver does not provide an optimized one.
It is arguable that perhaps I should have required something like
this as part of the initial XDP feature merge.
I believe this is critical for two reasons:
1) Accessibility. More people can play with XDP with less
dependencies. Yes I know we have XDP support in virtio_net, but
that just creates another depedency for learning how to use this
facility.
I wrote this to make life easier for the XDP newbies.
2) As a model for what the expected semantics are. If there is a pure
generic core implementation, it serves as a semantic example for
driver folks adding XDP support.
This is just a rough draft and is untested.
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
---
v2:
- Add some "fall through" comments in switch statements based
upon feedback from Andrew Lunn
- Use RCU for generic xdp_prog, thanks to Johannes Berg.
diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index cc07c3b..f8ff49c 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -1892,6 +1892,7 @@ struct net_device {
struct lock_class_key *qdisc_tx_busylock;
struct lock_class_key *qdisc_running_key;
bool proto_down;
+ struct bpf_prog __rcu *xdp_prog;
};
#define to_net_dev(d) container_of(d, struct net_device, dev)
diff --git a/net/core/dev.c b/net/core/dev.c
index 7efb417..ad6de2d 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -95,6 +95,7 @@
#include <linux/notifier.h>
#include <linux/skbuff.h>
#include <linux/bpf.h>
+#include <linux/bpf_trace.h>
#include <net/net_namespace.h>
#include <net/sock.h>
#include <net/busy_poll.h>
@@ -4247,6 +4248,83 @@ static int __netif_receive_skb(struct sk_buff *skb)
return ret;
}
+static struct static_key generic_xdp_needed __read_mostly;
+
+static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)
+{
+ struct bpf_prog *new = xdp->prog;
+ int ret = 0;
+
+ switch (xdp->command) {
+ case XDP_SETUP_PROG: {
+ struct bpf_prog *old = rtnl_dereference(dev->xdp_prog);
+
+ rcu_assign_pointer(dev->xdp_prog, new);
+ if (old)
+ bpf_prog_put(old);
+
+ if (old && !new)
+ static_key_slow_dec(&generic_xdp_needed);
+ else if (new && !old)
+ static_key_slow_inc(&generic_xdp_needed);
+ break;
+ }
+
+ case XDP_QUERY_PROG:
+ xdp->prog_attached = !!rcu_access_pointer(dev->xdp_prog);
+ break;
+
+ default:
+ ret = -EINVAL;
+ break;
+ }
+
+ return ret;
+}
+
+static u32 netif_receive_generic_xdp(struct sk_buff *skb,
+ struct bpf_prog *xdp_prog)
+{
+ struct xdp_buff xdp;
+ u32 act = XDP_DROP;
+ void *orig_data;
+ int hlen, off;
+
+ if (skb_linearize(skb))
+ goto do_drop;
+
+ hlen = skb_headlen(skb);
+ xdp.data = skb->data;
+ xdp.data_end = xdp.data + hlen;
+ xdp.data_hard_start = xdp.data - skb_headroom(skb);
+ orig_data = xdp.data;
+
+ act = bpf_prog_run_xdp(xdp_prog, &xdp);
+
+ off = xdp.data - orig_data;
+ if (off)
+ __skb_push(skb, off);
+
+ switch (act) {
+ case XDP_PASS:
+ case XDP_TX:
+ break;
+
+ default:
+ bpf_warn_invalid_xdp_action(act);
+ /* fall through */
+ case XDP_ABORTED:
+ trace_xdp_exception(skb->dev, xdp_prog, act);
+ /* fall through */
+ case XDP_DROP:
+ do_drop:
+ kfree_skb(skb);
+ break;
+ }
+
+ return act;
+}
+
static int netif_receive_skb_internal(struct sk_buff *skb)
{
int ret;
@@ -4258,6 +4336,21 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
rcu_read_lock();
+ if (static_key_false(&generic_xdp_needed)) {
+ struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog);
+
+ if (xdp_prog) {
+ u32 act = netif_receive_generic_xdp(skb, xdp_prog);
+
+ if (act != XDP_PASS) {
+ rcu_read_unlock();
+ if (act == XDP_TX)
+ dev_queue_xmit(skb);
+ return NET_RX_DROP;
+ }
+ }
+ }
+
#ifdef CONFIG_RPS
if (static_key_false(&rps_needed)) {
struct rps_dev_flow voidflow, *rflow = &voidflow;
@@ -6718,6 +6811,7 @@ EXPORT_SYMBOL(dev_change_proto_down);
*/
int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags)
{
+ int (*xdp_op)(struct net_device *dev, struct netdev_xdp *xdp);
const struct net_device_ops *ops = dev->netdev_ops;
struct bpf_prog *prog = NULL;
struct netdev_xdp xdp;
@@ -6725,14 +6819,16 @@ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags)
ASSERT_RTNL();
- if (!ops->ndo_xdp)
- return -EOPNOTSUPP;
+ xdp_op = ops->ndo_xdp;
+ if (!xdp_op)
+ xdp_op = generic_xdp_install;
+
if (fd >= 0) {
if (flags & XDP_FLAGS_UPDATE_IF_NOEXIST) {
memset(&xdp, 0, sizeof(xdp));
xdp.command = XDP_QUERY_PROG;
- err = ops->ndo_xdp(dev, &xdp);
+ err = xdp_op(dev, &xdp);
if (err < 0)
return err;
if (xdp.prog_attached)
@@ -6748,7 +6844,7 @@ int dev_change_xdp_fd(struct net_device *dev, int fd, u32 flags)
xdp.command = XDP_SETUP_PROG;
xdp.prog = prog;
- err = ops->ndo_xdp(dev, &xdp);
+ err = xdp_op(dev, &xdp);
if (err < 0 && prog)
bpf_prog_put(prog);
@@ -7789,6 +7885,7 @@ EXPORT_SYMBOL(alloc_netdev_mqs);
void free_netdev(struct net_device *dev)
{
struct napi_struct *p, *n;
+ struct bpf_prog *prog;
might_sleep();
netif_free_tx_queues(dev);
@@ -7807,6 +7904,12 @@ void free_netdev(struct net_device *dev)
free_percpu(dev->pcpu_refcnt);
dev->pcpu_refcnt = NULL;
+ prog = rcu_dereference(dev->xdp_prog);
+ if (prog) {
+ bpf_prog_put(prog);
+ static_key_slow_dec(&generic_xdp_needed);
+ }
+
/* Compatibility with error handling in drivers */
if (dev->reg_state == NETREG_UNINITIALIZED) {
netdev_freemem(dev);
diff --git a/net/core/rtnetlink.c b/net/core/rtnetlink.c
index b2bd4c9..c73c7b7 100644
--- a/net/core/rtnetlink.c
+++ b/net/core/rtnetlink.c
@@ -896,15 +896,12 @@ 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)
+static size_t rtnl_xdp_size(void)
{
size_t xdp_size = nla_total_size(0) + /* nest IFLA_XDP */
nla_total_size(1); /* XDP_ATTACHED */
- if (!dev->netdev_ops->ndo_xdp)
- return 0;
- else
- return xdp_size;
+ return xdp_size;
}
static noinline size_t if_nlmsg_size(const struct net_device *dev,
@@ -943,7 +940,7 @@ 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 */
+ + rtnl_xdp_size() /* IFLA_XDP */
+ nla_total_size(4) /* IFLA_EVENT */
+ nla_total_size(1); /* IFLA_PROTO_DOWN */
@@ -1252,20 +1249,25 @@ static int rtnl_fill_link_ifmap(struct sk_buff *skb, struct net_device *dev)
static int rtnl_xdp_fill(struct sk_buff *skb, struct net_device *dev)
{
- struct netdev_xdp xdp_op = {};
struct nlattr *xdp;
int err;
+ u8 val;
- 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 (dev->netdev_ops->ndo_xdp) {
+ struct netdev_xdp xdp_op = {};
+
+ xdp_op.command = XDP_QUERY_PROG;
+ err = dev->netdev_ops->ndo_xdp(dev, &xdp_op);
+ if (err)
+ goto err_cancel;
+ val = xdp_op.prog_attached;
+ } else {
+ val = rcu_access_pointer(dev->xdp_prog) ? 1 : 0;
+ }
+ err = nla_put_u8(skb, IFLA_XDP_ATTACHED, val);
if (err)
goto err_cancel;
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