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bpf, xdp: Extract common XDP program attachment logic
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Further refactor XDP attachment code. dev_change_xdp_fd() is split into two
parts: getting bpf_progs from FDs and attachment logic, working with
bpf_progs. This makes attachment  logic a bit more straightforward and
prepares code for bpf_xdp_link inclusion, which will share the common logic.

Signed-off-by: Andrii Nakryiko <[email protected]>
Signed-off-by: Alexei Starovoitov <[email protected]>
Link: https://lore.kernel.org/bpf/[email protected]
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@anakryiko
anakryiko authored and Alexei Starovoitov committed Jul 26, 2020
1 parent 7f0a838 commit d4baa93
Showing 1 changed file with 91 additions and 74 deletions.
165 changes: 91 additions & 74 deletions net/core/dev.c
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Original file line number Diff line number Diff line change
Expand Up @@ -8815,111 +8815,128 @@ static void dev_xdp_uninstall(struct net_device *dev)
}
}

/**
* dev_change_xdp_fd - set or clear a bpf program for a device rx path
* @dev: device
* @extack: netlink extended ack
* @fd: new program fd or negative value to clear
* @expected_fd: old program fd that userspace expects to replace or clear
* @flags: xdp-related flags
*
* Set or clear a bpf program for a device
*/
int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
int fd, int expected_fd, u32 flags)
static int dev_xdp_attach(struct net_device *dev, struct netlink_ext_ack *extack,
struct bpf_prog *new_prog, struct bpf_prog *old_prog,
u32 flags)
{
const struct net_device_ops *ops = dev->netdev_ops;
enum bpf_xdp_mode mode = dev_xdp_mode(flags);
bool offload = mode == XDP_MODE_HW;
u32 prog_id, expected_id = 0;
struct bpf_prog *prog;
struct bpf_prog *cur_prog;
enum bpf_xdp_mode mode;
bpf_op_t bpf_op;
int err;

ASSERT_RTNL();

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;
/* just one XDP mode bit should be set, zero defaults to SKB mode */
if (hweight32(flags & XDP_FLAGS_MODES) > 1) {
NL_SET_ERR_MSG(extack, "Only one XDP mode flag can be set");
return -EINVAL;
}
/* old_prog != NULL implies XDP_FLAGS_REPLACE is set */
if (old_prog && !(flags & XDP_FLAGS_REPLACE)) {
NL_SET_ERR_MSG(extack, "XDP_FLAGS_REPLACE is not specified");
return -EINVAL;
}

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,
BPF_PROG_TYPE_XDP,
bpf_op == ops->ndo_bpf);
if (IS_ERR(prog))
return PTR_ERR(prog);
expected_id = prog->aux->id;
bpf_prog_put(prog);
}

if (prog_id != expected_id) {
NL_SET_ERR_MSG(extack, "Active program does not match expected");
return -EEXIST;
}
mode = dev_xdp_mode(flags);
cur_prog = dev_xdp_prog(dev, mode);
if ((flags & XDP_FLAGS_REPLACE) && cur_prog != old_prog) {
NL_SET_ERR_MSG(extack, "Active program does not match expected");
return -EEXIST;
}
if (fd >= 0) {
if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && cur_prog) {
NL_SET_ERR_MSG(extack, "XDP program already attached");
return -EBUSY;
}

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

if ((flags & XDP_FLAGS_UPDATE_IF_NOEXIST) && prog_id) {
NL_SET_ERR_MSG(extack, "XDP program already attached");
return -EBUSY;
}

prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
bpf_op == ops->ndo_bpf);
if (IS_ERR(prog))
return PTR_ERR(prog);

if (!offload && bpf_prog_is_dev_bound(prog->aux)) {
if (!offload && bpf_prog_is_dev_bound(new_prog->aux)) {
NL_SET_ERR_MSG(extack, "Using device-bound program without HW_MODE flag is not supported");
bpf_prog_put(prog);
return -EINVAL;
}

if (prog->expected_attach_type == BPF_XDP_DEVMAP) {
if (new_prog->expected_attach_type == BPF_XDP_DEVMAP) {
NL_SET_ERR_MSG(extack, "BPF_XDP_DEVMAP programs can not be attached to a device");
bpf_prog_put(prog);
return -EINVAL;
}

if (prog->expected_attach_type == BPF_XDP_CPUMAP) {
NL_SET_ERR_MSG(extack,
"BPF_XDP_CPUMAP programs can not be attached to a device");
bpf_prog_put(prog);
if (new_prog->expected_attach_type == BPF_XDP_CPUMAP) {
NL_SET_ERR_MSG(extack, "BPF_XDP_CPUMAP programs can not be attached to a device");
return -EINVAL;
}
}

/* prog->aux->id may be 0 for orphaned device-bound progs */
if (prog->aux->id && prog->aux->id == prog_id) {
bpf_prog_put(prog);
return 0;
/* don't call drivers if the effective program didn't change */
if (new_prog != cur_prog) {
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;
}
} else {
if (!prog_id)
return 0;
prog = NULL;
}

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

dev_xdp_set_prog(dev, mode, new_prog);
if (cur_prog)
bpf_prog_put(cur_prog);

return 0;
}

/**
* dev_change_xdp_fd - set or clear a bpf program for a device rx path
* @dev: device
* @extack: netlink extended ack
* @fd: new program fd or negative value to clear
* @expected_fd: old program fd that userspace expects to replace or clear
* @flags: xdp-related flags
*
* Set or clear a bpf program for a device
*/
int dev_change_xdp_fd(struct net_device *dev, struct netlink_ext_ack *extack,
int fd, int expected_fd, u32 flags)
{
enum bpf_xdp_mode mode = dev_xdp_mode(flags);
struct bpf_prog *new_prog = NULL, *old_prog = NULL;
int err;

ASSERT_RTNL();

if (fd >= 0) {
new_prog = bpf_prog_get_type_dev(fd, BPF_PROG_TYPE_XDP,
mode != XDP_MODE_SKB);
if (IS_ERR(new_prog))
return PTR_ERR(new_prog);
}

if (expected_fd >= 0) {
old_prog = bpf_prog_get_type_dev(expected_fd, BPF_PROG_TYPE_XDP,
mode != XDP_MODE_SKB);
if (IS_ERR(old_prog)) {
err = PTR_ERR(old_prog);
old_prog = NULL;
goto err_out;
}
}

err = dev_xdp_attach(dev, extack, new_prog, old_prog, flags);

err_out:
if (err && new_prog)
bpf_prog_put(new_prog);
if (old_prog)
bpf_prog_put(old_prog);
return err;
}

/**
* dev_new_index - allocate an ifindex
* @net: the applicable net namespace
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