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bpf, xdp: Maintain info on attached XDP BPF programs in net_device
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Instead of delegating to drivers, maintain information about which BPF
programs are attached in which XDP modes (generic/skb, driver, or hardware)
locally in net_device. This effectively obsoletes XDP_QUERY_PROG command.

Such re-organization simplifies existing code already. But it also allows to
further add bpf_link-based XDP attachments without drivers having to know
about any of this at all, which seems like a good setup.
XDP_SETUP_PROG/XDP_SETUP_PROG_HW are just low-level commands to driver to
install/uninstall active BPF program. All the higher-level concerns about
prog/link interaction will be contained within generic driver-agnostic logic.

All the XDP_QUERY_PROG calls to driver in dev_xdp_uninstall() were removed.
It's not clear for me why dev_xdp_uninstall() were passing previous prog_flags
when resetting installed programs. That seems unnecessary, plus most drivers
don't populate prog_flags anyways. Having XDP_SETUP_PROG vs XDP_SETUP_PROG_HW
should be enough of an indicator of what is required of driver to correctly
reset active BPF program. dev_xdp_uninstall() is also generalized as an
iteration over all three supported mode.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-3-andriin@fb.com
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Andrii Nakryiko authored and Alexei Starovoitov committed Jul 26, 2020
1 parent 6cc7d1e commit 7f0a838
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Showing 3 changed files with 105 additions and 75 deletions.
17 changes: 15 additions & 2 deletions include/linux/netdevice.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -889,6 +889,17 @@ struct netlink_ext_ack;
struct xdp_umem;
struct xdp_dev_bulk_queue;

enum bpf_xdp_mode {
XDP_MODE_SKB = 0,
XDP_MODE_DRV = 1,
XDP_MODE_HW = 2,
__MAX_XDP_MODE
};

struct bpf_xdp_entity {
struct bpf_prog *prog;
};

struct netdev_bpf {
enum bpf_netdev_command command;
union {
Expand Down Expand Up @@ -2142,6 +2153,9 @@ struct net_device {
#endif
const struct udp_tunnel_nic_info *udp_tunnel_nic_info;
struct udp_tunnel_nic *udp_tunnel_nic;

/* protected by rtnl_lock */
struct bpf_xdp_entity xdp_state[__MAX_XDP_MODE];
};
#define to_net_dev(d) container_of(d, struct net_device, dev)

Expand Down Expand Up @@ -3817,8 +3831,7 @@ struct sk_buff *dev_hard_start_xmit(struct sk_buff *skb, struct net_device *dev,
typedef int (*bpf_op_t)(struct net_device *dev, struct netdev_bpf *bpf);
int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
int fd, int expected_fd, u32 flags);
u32 __dev_xdp_query(struct net_device *dev, bpf_op_t xdp_op,
enum bpf_netdev_command cmd);
u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode);
int xdp_umem_query(struct net_device *dev, u16 queue_id);

int __dev_forward_skb(struct net_device *dev, struct sk_buff *skb);
Expand Down
158 changes: 88 additions & 70 deletions net/core/dev.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -8716,84 +8716,103 @@ int dev_change_proto_down_generic(struct net_device *dev, bool proto_down)
}
EXPORT_SYMBOL(dev_change_proto_down_generic);

u32 __dev_xdp_query(struct net_device *dev, bpf_op_t bpf_op,
enum bpf_netdev_command cmd)
static enum bpf_xdp_mode dev_xdp_mode(u32 flags)
{
struct netdev_bpf xdp;
if (flags & XDP_FLAGS_HW_MODE)
return XDP_MODE_HW;
if (flags & XDP_FLAGS_DRV_MODE)
return XDP_MODE_DRV;
return XDP_MODE_SKB;
}

if (!bpf_op)
return 0;
static bpf_op_t dev_xdp_bpf_op(struct net_device *dev, enum bpf_xdp_mode mode)
{
switch (mode) {
case XDP_MODE_SKB:
return generic_xdp_install;
case XDP_MODE_DRV:
case XDP_MODE_HW:
return dev->netdev_ops->ndo_bpf;
default:
return NULL;
};
}

memset(&xdp, 0, sizeof(xdp));
xdp.command = cmd;
static struct bpf_prog *dev_xdp_prog(struct net_device *dev,
enum bpf_xdp_mode mode)
{
return dev->xdp_state[mode].prog;
}

u32 dev_xdp_prog_id(struct net_device *dev, enum bpf_xdp_mode mode)
{
struct bpf_prog *prog = dev_xdp_prog(dev, mode);

/* Query must always succeed. */
WARN_ON(bpf_op(dev, &xdp) < 0 && cmd == XDP_QUERY_PROG);
return prog ? prog->aux->id : 0;
}

return xdp.prog_id;
static void dev_xdp_set_prog(struct net_device *dev, enum bpf_xdp_mode mode,
struct bpf_prog *prog)
{
dev->xdp_state[mode].prog = prog;
}

static int dev_xdp_install(struct net_device *dev, bpf_op_t bpf_op,
struct netlink_ext_ack *extack, u32 flags,
struct bpf_prog *prog)
static int dev_xdp_install(struct net_device *dev, enum bpf_xdp_mode mode,
bpf_op_t bpf_op, struct netlink_ext_ack *extack,
u32 flags, struct bpf_prog *prog)
{
bool non_hw = !(flags & XDP_FLAGS_HW_MODE);
struct bpf_prog *prev_prog = NULL;
struct netdev_bpf xdp;
int err;

if (non_hw) {
prev_prog = bpf_prog_by_id(__dev_xdp_query(dev, bpf_op,
XDP_QUERY_PROG));
if (IS_ERR(prev_prog))
prev_prog = NULL;
}

memset(&xdp, 0, sizeof(xdp));
if (flags & XDP_FLAGS_HW_MODE)
xdp.command = XDP_SETUP_PROG_HW;
else
xdp.command = XDP_SETUP_PROG;
xdp.command = mode == XDP_MODE_HW ? XDP_SETUP_PROG_HW : XDP_SETUP_PROG;
xdp.extack = extack;
xdp.flags = flags;
xdp.prog = prog;

/* Drivers assume refcnt is already incremented (i.e, prog pointer is
* "moved" into driver), so they don't increment it on their own, but
* they do decrement refcnt when program is detached or replaced.
* Given net_device also owns link/prog, we need to bump refcnt here
* to prevent drivers from underflowing it.
*/
if (prog)
bpf_prog_inc(prog);
err = bpf_op(dev, &xdp);
if (!err && non_hw)
bpf_prog_change_xdp(prev_prog, prog);
if (err) {
if (prog)
bpf_prog_put(prog);
return err;
}

if (prev_prog)
bpf_prog_put(prev_prog);
if (mode != XDP_MODE_HW)
bpf_prog_change_xdp(dev_xdp_prog(dev, mode), prog);

return err;
return 0;
}

static void dev_xdp_uninstall(struct net_device *dev)
{
struct netdev_bpf xdp;
bpf_op_t ndo_bpf;
struct bpf_prog *prog;
enum bpf_xdp_mode mode;
bpf_op_t bpf_op;

/* Remove generic XDP */
WARN_ON(dev_xdp_install(dev, generic_xdp_install, NULL, 0, NULL));
ASSERT_RTNL();

/* Remove from the driver */
ndo_bpf = dev->netdev_ops->ndo_bpf;
if (!ndo_bpf)
return;
for (mode = XDP_MODE_SKB; mode < __MAX_XDP_MODE; mode++) {
prog = dev_xdp_prog(dev, mode);
if (!prog)
continue;

memset(&xdp, 0, sizeof(xdp));
xdp.command = XDP_QUERY_PROG;
WARN_ON(ndo_bpf(dev, &xdp));
if (xdp.prog_id)
WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags,
NULL));
bpf_op = dev_xdp_bpf_op(dev, mode);
if (!bpf_op)
continue;

/* Remove HW offload */
memset(&xdp, 0, sizeof(xdp));
xdp.command = XDP_QUERY_PROG_HW;
if (!ndo_bpf(dev, &xdp) && xdp.prog_id)
WARN_ON(dev_xdp_install(dev, ndo_bpf, NULL, xdp.prog_flags,
NULL));
WARN_ON(dev_xdp_install(dev, mode, bpf_op, NULL, 0, NULL));

bpf_prog_put(prog);
dev_xdp_set_prog(dev, mode, NULL);
}
}

/**
Expand All @@ -8810,29 +8829,22 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
int fd, int expected_fd, u32 flags)
{
const struct net_device_ops *ops = dev->netdev_ops;
enum bpf_netdev_command query;
enum bpf_xdp_mode mode = dev_xdp_mode(flags);
bool offload = mode == XDP_MODE_HW;
u32 prog_id, expected_id = 0;
bpf_op_t bpf_op, bpf_chk;
struct bpf_prog *prog;
bool offload;
bpf_op_t bpf_op;
int err;

ASSERT_RTNL();

offload = flags & XDP_FLAGS_HW_MODE;
query = offload ? XDP_QUERY_PROG_HW : XDP_QUERY_PROG;

bpf_op = bpf_chk = ops->ndo_bpf;
if (!bpf_op && (flags & (XDP_FLAGS_DRV_MODE | XDP_FLAGS_HW_MODE))) {
bpf_op = dev_xdp_bpf_op(dev, mode);
if (!bpf_op) {
NL_SET_ERR_MSG(extack, "underlying driver does not support XDP in native mode");
return -EOPNOTSUPP;
}
if (!bpf_op || (flags & XDP_FLAGS_SKB_MODE))
bpf_op = generic_xdp_install;
if (bpf_op == bpf_chk)
bpf_chk = generic_xdp_install;

prog_id = __dev_xdp_query(dev, bpf_op, query);
prog_id = dev_xdp_prog_id(dev, mode);
if (flags & XDP_FLAGS_REPLACE) {
if (expected_fd >= 0) {
prog = bpf_prog_get_type_dev(expected_fd,
Expand All @@ -8850,8 +8862,11 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
}
}
if (fd >= 0) {
if (!offload && __dev_xdp_query(dev, bpf_chk, XDP_QUERY_PROG)) {
NL_SET_ERR_MSG(extack, "native and generic XDP can't be active at the same time");
enum bpf_xdp_mode other_mode = mode == XDP_MODE_SKB
? XDP_MODE_DRV : XDP_MODE_SKB;

if (!offload && dev_xdp_prog_id(dev, other_mode)) {
NL_SET_ERR_MSG(extack, "Native and generic XDP can't be active at the same time");
return -EEXIST;
}

Expand All @@ -8866,7 +8881,7 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
return PTR_ERR(prog);

if (!offload && bpf_prog_is_dev_bound(prog->aux)) {
NL_SET_ERR_MSG(extack, "using device-bound program without HW_MODE flag is not supported");
NL_SET_ERR_MSG(extack, "Using device-bound program without HW_MODE flag is not supported");
bpf_prog_put(prog);
return -EINVAL;
}
Expand Down Expand Up @@ -8895,11 +8910,14 @@ int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
prog = NULL;
}

err = dev_xdp_install(dev, bpf_op, extack, flags, prog);
if (err < 0 && prog)
err = dev_xdp_install(dev, mode, bpf_op, extack, flags, prog);
if (err < 0 && prog) {
bpf_prog_put(prog);
return err;
}
dev_xdp_set_prog(dev, mode, prog);

return err;
return 0;
}

/**
Expand Down
5 changes: 2 additions & 3 deletions net/core/rtnetlink.c
View file
Original file line number Diff line number Diff line change
Expand Up @@ -1416,13 +1416,12 @@ static u32 rtnl_xdp_prog_skb(struct net_device *dev)

static u32 rtnl_xdp_prog_drv(struct net_device *dev)
{
return __dev_xdp_query(dev, dev->netdev_ops->ndo_bpf, XDP_QUERY_PROG);
return dev_xdp_prog_id(dev, XDP_MODE_DRV);
}

static u32 rtnl_xdp_prog_hw(struct net_device *dev)
{
return __dev_xdp_query(dev, dev->netdev_ops->ndo_bpf,
XDP_QUERY_PROG_HW);
return dev_xdp_prog_id(dev, XDP_MODE_HW);
}

static int rtnl_xdp_report_one(struct sk_buff *skb, struct net_device *dev,
Expand Down

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