[PATCH RFC bpf-next 43/52] net, xdp: build XDP generic metadata on Generic (skb) XDP path

Alexander Lobakin
2022-06-28T19:53:31Z

Now that the core has the routine to make XDP generic metadata from
the skb fields and &net_device stores meta_thresh, provide XDP
generic metadata to BPF programs running on Generic/skb XDP path.
skb fields are being updated from the metadata after BPF program
exits (if it's still there).

Signed-off-by: Alexander Lobakin <alexandr.lobakin@intel.com>
---
net/bpf/dev.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++----
1 file changed, 47 insertions(+), 4 deletions(-)

diff --git a/net/bpf/dev.c b/net/bpf/dev.c
index 350ebdc783a0..f4187b357a0c 100644
--- a/net/bpf/dev.c
+++ b/net/bpf/dev.c
@@ -1,7 +1,20 @@
// SPDX-License-Identifier: GPL-2.0-only

+#include <net/xdp_meta.h>
#include <trace/events/xdp.h>

+enum {
+ GENERIC_XDP_META_GEN,
+
+ /* Must be last */
+ GENERIC_XDP_META_NONE,
+ __GENERIC_XDP_META_NUM,
+};
+
+static const char * const generic_xdp_meta_types[__GENERIC_XDP_META_NUM] = {
+ [GENERIC_XDP_META_GEN] = "struct xdp_meta_generic",
+};
+
DEFINE_STATIC_KEY_FALSE(generic_xdp_needed_key);

static struct netdev_rx_queue *netif_get_rxqueue(struct sk_buff *skb)
@@ -27,17 +40,33 @@ static struct netdev_rx_queue *netif_get_rxqueue(struct sk_buff *skb)
return rxqueue;
}

+static void generic_xdp_handle_meta(struct xdp_buff *xdp, struct sk_buff *skb,
+ const struct xdp_attachment_info *info)
+{
+ if (xdp->data_end - xdp->data < READ_ONCE(info->meta_thresh))
+ return;
+
+ switch (READ_ONCE(info->drv_cookie)) {
+ case GENERIC_XDP_META_GEN:
+ xdp_build_meta_generic_from_skb(skb);
+ xdp->data_meta = skb_metadata_end(skb) - skb_metadata_len(skb);
+ break;
+ default:
+ break;
+ }
+}
+
u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
struct bpf_prog *xdp_prog)
{
void *orig_data, *orig_data_end, *hard_start;
struct net_device *dev = skb->dev;
struct netdev_rx_queue *rxqueue;
+ u32 metalen, orig_metalen, act;
bool orig_bcast, orig_host;
u32 mac_len, frame_sz;
__be16 orig_eth_type;
struct ethhdr *eth;
- u32 metalen, act;
int off;

/* The XDP program wants to see the packet starting at the MAC
@@ -62,6 +91,9 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
orig_bcast = is_multicast_ether_addr_64bits(eth->h_dest);
orig_eth_type = eth->h_proto;

+ generic_xdp_handle_meta(xdp, skb, &dev->xdp_info);
+ orig_metalen = xdp->data - xdp->data_meta;
+
act = bpf_prog_run_xdp(xdp_prog, xdp);

/* check if bpf_xdp_adjust_head was used */
@@ -105,11 +137,15 @@ u32 bpf_prog_run_generic_xdp(struct sk_buff *skb, struct xdp_buff *xdp,
case XDP_REDIRECT:
case XDP_TX:
__skb_push(skb, mac_len);
- break;
+ fallthrough;
case XDP_PASS:
metalen = xdp->data - xdp->data_meta;
- if (metalen)
+ if (metalen != orig_metalen)
skb_metadata_set(skb, metalen);
+ if (metalen)
+ xdp_populate_skb_meta_generic(skb);
+ else if (orig_metalen)
+ skb_metadata_nocomp_clear(skb);
break;
}

@@ -244,10 +280,15 @@ static void dev_disable_gro_hw(struct net_device *dev)
static int generic_xdp_install(struct net_device *dev, struct netdev_bpf *xdp)
{
bool old = !!rtnl_dereference(dev->xdp_info.prog_rcu);
- int ret = 0;
+ int ret;

switch (xdp->command) {
case XDP_SETUP_PROG:
+ ret = xdp_meta_match_id(generic_xdp_meta_types, xdp->btf_id);
+ if (ret < 0)
+ return ret;
+
+ WRITE_ONCE(dev->xdp_info.drv_cookie, ret);
xdp_attachment_setup_rcu(&dev->xdp_info, xdp);

if (old && !xdp->prog) {
@@ -257,6 +298,8 @@ static int generic_xdp_install(struct net_device *dev, struct netdev_bpf *xdp)
dev_disable_lro(dev);
dev_disable_gro_hw(dev);
}
+
+ ret = 0;
break;

default:
--
2.36.1