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net: xdp: support xdp generic on virtual devices

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XDP generic allows users to test XDP programs and/or run them with
degraded performance on devices that do not yet support XDP. For
testing I typically test eBPF programs using a set of veth devices.
This allows testing topologies that would otherwise be difficult to
setup especially in the early stages of development.

This patch adds a xdp generic hook to the netif_rx_internal()
function which is called from dev_forward_skb(). With this addition
attaching XDP programs to veth devices works as expected! Also I
noticed multiple drivers using netif_rx(). These devices will also
benefit and generic XDP will work for them as well.

Signed-off-by: John Fastabend <john.fastabend@gmail.com>
Tested-by: Andy Gospodarek <andy@greyhouse.net>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
John Fastabend 2017-07-17 09:26:45 -07:00 committed by David S. Miller
parent 90382dca61
commit d445516966
1 changed files with 113 additions and 95 deletions
repo.diff.show_diff_stats Download patch file Download diff file Expand all files Collapse all files

208
net/core/dev.c
View file

@ -3865,6 +3865,107 @@ static int enqueue_to_backlog(struct sk_buff *skb, int cpu,
return NET_RX_DROP; return NET_RX_DROP;
} }
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;
u32 mac_len;
/* Reinjected packets coming from act_mirred or similar should
* not get XDP generic processing.
*/
if (skb_cloned(skb))
return XDP_PASS;
if (skb_linearize(skb))
goto do_drop;
/* The XDP program wants to see the packet starting at the MAC
* header.
*/
mac_len = skb->data - skb_mac_header(skb);
hlen = skb_headlen(skb) + mac_len;
xdp.data = skb->data - mac_len;
xdp.data_end = xdp.data + hlen;
xdp.data_hard_start = skb->data - skb_headroom(skb);
orig_data = xdp.data;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
off = xdp.data - orig_data;
if (off > 0)
__skb_pull(skb, off);
else if (off < 0)
__skb_push(skb, -off);
switch (act) {
case XDP_TX:
__skb_push(skb, mac_len);
/* fall through */
case XDP_PASS:
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;
}
/* When doing generic XDP we have to bypass the qdisc layer and the
* network taps in order to match in-driver-XDP behavior.
*/
static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
{
struct net_device *dev = skb->dev;
struct netdev_queue *txq;
bool free_skb = true;
int cpu, rc;
txq = netdev_pick_tx(dev, skb, NULL);
cpu = smp_processor_id();
HARD_TX_LOCK(dev, txq, cpu);
if (!netif_xmit_stopped(txq)) {
rc = netdev_start_xmit(skb, dev, txq, 0);
if (dev_xmit_complete(rc))
free_skb = false;
}
HARD_TX_UNLOCK(dev, txq);
if (free_skb) {
trace_xdp_exception(dev, xdp_prog, XDP_TX);
kfree_skb(skb);
}
}
static struct static_key generic_xdp_needed __read_mostly;
static int do_xdp_generic(struct sk_buff *skb)
{
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) {
if (act == XDP_TX)
generic_xdp_tx(skb, xdp_prog);
return XDP_DROP;
}
}
return XDP_PASS;
}
static int netif_rx_internal(struct sk_buff *skb) static int netif_rx_internal(struct sk_buff *skb)
{ {
int ret; int ret;
@ -3872,6 +3973,14 @@ static int netif_rx_internal(struct sk_buff *skb)
net_timestamp_check(netdev_tstamp_prequeue, skb); net_timestamp_check(netdev_tstamp_prequeue, skb);
trace_netif_rx(skb); trace_netif_rx(skb);
if (static_key_false(&generic_xdp_needed)) {
int ret = do_xdp_generic(skb);
if (ret != XDP_PASS)
return NET_RX_DROP;
}
#ifdef CONFIG_RPS #ifdef CONFIG_RPS
if (static_key_false(&rps_needed)) { if (static_key_false(&rps_needed)) {
struct rps_dev_flow voidflow, *rflow = &voidflow; struct rps_dev_flow voidflow, *rflow = &voidflow;
@ -4338,8 +4447,6 @@ static int __netif_receive_skb(struct sk_buff *skb)
return ret; return ret;
} }
static struct static_key generic_xdp_needed __read_mostly;
static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp) static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)
{ {
struct bpf_prog *old = rtnl_dereference(dev->xdp_prog); struct bpf_prog *old = rtnl_dereference(dev->xdp_prog);
@ -4373,89 +4480,6 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_xdp *xdp)
return ret; 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;
u32 mac_len;
/* Reinjected packets coming from act_mirred or similar should
* not get XDP generic processing.
*/
if (skb_cloned(skb))
return XDP_PASS;
if (skb_linearize(skb))
goto do_drop;
/* The XDP program wants to see the packet starting at the MAC
* header.
*/
mac_len = skb->data - skb_mac_header(skb);
hlen = skb_headlen(skb) + mac_len;
xdp.data = skb->data - mac_len;
xdp.data_end = xdp.data + hlen;
xdp.data_hard_start = skb->data - skb_headroom(skb);
orig_data = xdp.data;
act = bpf_prog_run_xdp(xdp_prog, &xdp);
off = xdp.data - orig_data;
if (off > 0)
__skb_pull(skb, off);
else if (off < 0)
__skb_push(skb, -off);
switch (act) {
case XDP_TX:
__skb_push(skb, mac_len);
/* fall through */
case XDP_PASS:
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;
}
/* When doing generic XDP we have to bypass the qdisc layer and the
* network taps in order to match in-driver-XDP behavior.
*/
static void generic_xdp_tx(struct sk_buff *skb, struct bpf_prog *xdp_prog)
{
struct net_device *dev = skb->dev;
struct netdev_queue *txq;
bool free_skb = true;
int cpu, rc;
txq = netdev_pick_tx(dev, skb, NULL);
cpu = smp_processor_id();
HARD_TX_LOCK(dev, txq, cpu);
if (!netif_xmit_stopped(txq)) {
rc = netdev_start_xmit(skb, dev, txq, 0);
if (dev_xmit_complete(rc))
free_skb = false;
}
HARD_TX_UNLOCK(dev, txq);
if (free_skb) {
trace_xdp_exception(dev, xdp_prog, XDP_TX);
kfree_skb(skb);
}
}
static int netif_receive_skb_internal(struct sk_buff *skb) static int netif_receive_skb_internal(struct sk_buff *skb)
{ {
int ret; int ret;
@ -4468,17 +4492,11 @@ static int netif_receive_skb_internal(struct sk_buff *skb)
rcu_read_lock(); rcu_read_lock();
if (static_key_false(&generic_xdp_needed)) { if (static_key_false(&generic_xdp_needed)) {
struct bpf_prog *xdp_prog = rcu_dereference(skb->dev->xdp_prog); int ret = do_xdp_generic(skb);
if (xdp_prog) { if (ret != XDP_PASS) {
u32 act = netif_receive_generic_xdp(skb, xdp_prog); rcu_read_unlock();
return NET_RX_DROP;
if (act != XDP_PASS) {
rcu_read_unlock();
if (act == XDP_TX)
generic_xdp_tx(skb, xdp_prog);
return NET_RX_DROP;
}
} }
} }