By improving the BPF_LINK_UPDATE command of bpf(), it should allow you
to conveniently switch between different struct_ops on a single
bpf_link. This would enable smoother transitions from one struct_ops
to another.
The struct_ops maps passing along with BPF_LINK_UPDATE should have the
BPF_F_LINK flag.
Signed-off-by: Kui-Feng Lee <kuifeng@xxxxxxxx>
---
include/linux/bpf.h | 2 ++
include/uapi/linux/bpf.h | 8 +++++--
kernel/bpf/bpf_struct_ops.c | 38 ++++++++++++++++++++++++++++++++++
kernel/bpf/syscall.c | 20 ++++++++++++++++++
net/bpf/bpf_dummy_struct_ops.c | 6 ++++++
net/ipv4/bpf_tcp_ca.c | 6 ++++++
tools/include/uapi/linux/bpf.h | 8 +++++--
7 files changed, 84 insertions(+), 4 deletions(-)
diff --git a/include/linux/bpf.h b/include/linux/bpf.h
index 455b14bf8f28..56e6ab7559ef 100644
--- a/include/linux/bpf.h
+++ b/include/linux/bpf.h
@@ -1474,6 +1474,7 @@ struct bpf_link_ops {
void (*show_fdinfo)(const struct bpf_link *link, struct seq_file *seq);
int (*fill_link_info)(const struct bpf_link *link,
struct bpf_link_info *info);
+ int (*update_map)(struct bpf_link *link, struct bpf_map *new_map);
};
struct bpf_tramp_link {
@@ -1516,6 +1517,7 @@ struct bpf_struct_ops {
void *kdata, const void *udata);
int (*reg)(void *kdata);
void (*unreg)(void *kdata);
+ int (*update)(void *kdata, void *old_kdata);
int (*validate)(void *kdata);
const struct btf_type *type;
const struct btf_type *value_type;
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 42f40ee083bf..24e1dec4ad97 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1555,8 +1555,12 @@ union bpf_attr {
struct { /* struct used by BPF_LINK_UPDATE command */
__u32 link_fd; /* link fd */
- /* new program fd to update link with */
- __u32 new_prog_fd;
+ union {
+ /* new program fd to update link with */
+ __u32 new_prog_fd;
+ /* new struct_ops map fd to update link with */
+ __u32 new_map_fd;
+ };
__u32 flags; /* extra flags */
/* expected link's program fd; is specified only if
* BPF_F_REPLACE flag is set in flags */
diff --git a/kernel/bpf/bpf_struct_ops.c b/kernel/bpf/bpf_struct_ops.c
index 8ce6c7581ca3..5a9e10b92423 100644
--- a/kernel/bpf/bpf_struct_ops.c
+++ b/kernel/bpf/bpf_struct_ops.c
@@ -807,10 +807,48 @@ static int bpf_struct_ops_map_link_fill_link_info(const struct bpf_link *link,
return 0;
}
+static int bpf_struct_ops_map_link_update(struct bpf_link *link, struct bpf_map *new_map)
+{
+ struct bpf_struct_ops_map *st_map, *old_st_map;
+ struct bpf_struct_ops_link *st_link;
+ struct bpf_map *old_map;
+ int err = 0;
+
+ st_link = container_of(link, struct bpf_struct_ops_link, link);
+ st_map = container_of(new_map, struct bpf_struct_ops_map, map);
+
+ if (!bpf_struct_ops_valid_to_reg(new_map))
+ return -EINVAL;
+
+ mutex_lock(&update_mutex);
+
+ old_map = rcu_dereference_protected(st_link->map, lockdep_is_held(&update_mutex));
+ old_st_map = container_of(old_map, struct bpf_struct_ops_map, map);
+ /* The new and old struct_ops must be the same type. */
+ if (st_map->st_ops != old_st_map->st_ops) {
+ err = -EINVAL;
+ goto err_out;
+ }
+
+ err = st_map->st_ops->update(st_map->kvalue.data, old_st_map->kvalue.data);
+ if (err)
+ goto err_out;
+
+ bpf_map_inc(new_map);
+ rcu_assign_pointer(st_link->map, new_map);
+ bpf_map_put(old_map);
+
+err_out:
+ mutex_unlock(&update_mutex);
+
+ return err;
+}
+
static const struct bpf_link_ops bpf_struct_ops_map_lops = {
.dealloc = bpf_struct_ops_map_link_dealloc,
.show_fdinfo = bpf_struct_ops_map_link_show_fdinfo,
.fill_link_info = bpf_struct_ops_map_link_fill_link_info,
+ .update_map = bpf_struct_ops_map_link_update,
};
int bpf_struct_ops_link_create(union bpf_attr *attr)
diff --git a/kernel/bpf/syscall.c b/kernel/bpf/syscall.c
index 5a45e3bf34e2..6fa10d108278 100644
--- a/kernel/bpf/syscall.c
+++ b/kernel/bpf/syscall.c
@@ -4676,6 +4676,21 @@ static int link_create(union bpf_attr *attr, bpfptr_t uattr)
return ret;
}
+static int link_update_map(struct bpf_link *link, union bpf_attr *attr)
+{
+ struct bpf_map *new_map;
+ int ret = 0;
+
+ new_map = bpf_map_get(attr->link_update.new_map_fd);
+ if (IS_ERR(new_map))
+ return -EINVAL;
