On 4/5/24 8:19 AM, John Fastabend wrote:
Yonghong Song wrote:
Add bpf_link support for sk_msg and sk_skb programs. We have an
internal request to support bpf_link for sk_msg programs so user
space can have a uniform handling with bpf_link based libbpf
APIs. Using bpf_link based libbpf API also has a benefit which
makes system robust by decoupling prog life cycle and
attachment life cycle.
Signed-off-by: Yonghong Song <yonghong.song@xxxxxxxxx>
---
include/linux/bpf.h | 6 +
include/linux/skmsg.h | 4 +
include/uapi/linux/bpf.h | 5 +
kernel/bpf/syscall.c | 4 +
net/core/sock_map.c | 268 ++++++++++++++++++++++++++++++++-
tools/include/uapi/linux/bpf.h | 5 +
6 files changed, 284 insertions(+), 8 deletions(-)
LGTM one question below.
+/* Handle the following two cases:
+ * case 1: link != NULL, prog != NULL, old != NULL
+ * case 2: link != NULL, prog != NULL, old == NULL
+ */
+static int sock_map_link_update_prog(struct bpf_link *link,
+ struct bpf_prog *prog,
+ struct bpf_prog *old)
+{
+ const struct sockmap_link *sockmap_link = container_of(link, struct sockmap_link, link);
+ struct bpf_prog **pprog;
+ struct bpf_link **plink;
+ int ret = 0;
+
+ mutex_lock(&sockmap_mutex);
+
+ /* If old prog is not NULL, ensure old prog is the same as link->prog. */
+ if (old && link->prog != old) {
+ ret = -EINVAL;
+ goto out;
+ }
+ /* Ensure link->prog has the same type/attach_type as the new prog. */
+ if (link->prog->type != prog->type ||
+ link->prog->expected_attach_type != prog->expected_attach_type) {
+ ret = -EINVAL;
+ goto out;
+ }
+
+ ret = sock_map_prog_lookup(sockmap_link->map, &pprog,
+ sockmap_link->attach_type);
+ if (ret)
+ goto out;
+
+ /* Ensure the same link between the one in map and the passed-in. */
+ ret = sock_map_link_lookup(sockmap_link->map, &plink, link, false,
+ sockmap_link->attach_type);
+ if (ret)
+ goto out;
+
+ if (old) {
+ ret = psock_replace_prog(pprog, prog, old);
+ goto out;
+ }
+
+ psock_set_prog(pprog, prog);
+
+out:
+ if (!ret) {
+ bpf_prog_inc(prog);
+ old = xchg(&link->prog, prog);
+ bpf_prog_put(old);
Need to check old? I don't think we can clal bpf_prog_put on null?
if (old)
bpf_prog_put(old)
The 'old' here represents the *old* link->prog program and
link->prog should not be NULL at this point.
If sock_map_link_update_prog() is called here, that means,
the kernel already holds a reference for the bpf link.
See kernel/bpf/syscall.c, link_update().
So the bpf_link is valid and not in released stage, and
link->prog should not be NULL.
+ }
+ mutex_unlock(&sockmap_mutex);
+ return ret;
+}
+
