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bpf, xdp: Implement LINK_UPDATE for BPF XDP link

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Add support for LINK_UPDATE command for BPF XDP link to enable reliable
replacement of underlying BPF program.

Signed-off-by: Andrii Nakryiko <andriin@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Link: https://lore.kernel.org/bpf/20200722064603.3350758-6-andriin@fb.com
This commit is contained in:
Andrii Nakryiko 2020-07-21 23:45:58 -07:00 • committed by Alexei Starovoitov
parent aa8d3a716b
commit 026a4c28e1
1 changed files with 43 additions and 0 deletions
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43
net/core/dev.c
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@ -8996,9 +8996,52 @@ static void bpf_xdp_link_dealloc(struct bpf_link *link)
kfree(xdp_link); kfree(xdp_link);
} }
static int bpf_xdp_link_update(struct bpf_link *link, struct bpf_prog *new_prog,
struct bpf_prog *old_prog)
{
struct bpf_xdp_link *xdp_link = container_of(link, struct bpf_xdp_link, link);
enum bpf_xdp_mode mode;
bpf_op_t bpf_op;
int err = 0;
rtnl_lock();
/* link might have been auto-released already, so fail */
if (!xdp_link->dev) {
err = -ENOLINK;
goto out_unlock;
}
if (old_prog && link->prog != old_prog) {
err = -EPERM;
goto out_unlock;
}
old_prog = link->prog;
if (old_prog == new_prog) {
/* no-op, don't disturb drivers */
bpf_prog_put(new_prog);
goto out_unlock;
}
mode = dev_xdp_mode(xdp_link->flags);
bpf_op = dev_xdp_bpf_op(xdp_link->dev, mode);
err = dev_xdp_install(xdp_link->dev, mode, bpf_op, NULL,
xdp_link->flags, new_prog);
if (err)
goto out_unlock;
old_prog = xchg(&link->prog, new_prog);
bpf_prog_put(old_prog);
out_unlock:
rtnl_unlock();
return err;
}
static const struct bpf_link_ops bpf_xdp_link_lops = { static const struct bpf_link_ops bpf_xdp_link_lops = {
.release = bpf_xdp_link_release, .release = bpf_xdp_link_release,
.dealloc = bpf_xdp_link_dealloc, .dealloc = bpf_xdp_link_dealloc,
.update_prog = bpf_xdp_link_update,
}; };
int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog) int bpf_xdp_link_attach(const union bpf_attr *attr, struct bpf_prog *prog)