The helper function bpf_sock_ops_cb_flags_set() can be used to both
set and clear the sock_ops callback flags. However, its current
behavior is not consistent. BPF program may clear a flag if more than
one were set, or replace a flag with another one, but cannot clear all
flags.
This patch also updates the documentation to clarify the ability to
clear flags of this helper function.
Signed-off-by: Hoang Tran <hoang.tran@xxxxxxxxxxxx>
---
include/uapi/linux/bpf.h | 9 ++++++++-
net/core/filter.c | 3 +--
2 files changed, 9 insertions(+), 3 deletions(-)
diff --git a/include/uapi/linux/bpf.h b/include/uapi/linux/bpf.h
index 929c8e537a14..f9ee093fe8d3 100644
--- a/include/uapi/linux/bpf.h
+++ b/include/uapi/linux/bpf.h
@@ -1694,12 +1694,19 @@ union bpf_attr {
* error if an eBPF program tries to set a callback that is not
* supported in the current kernel.
*
- * The supported callback values that *argval* can combine are:
+ * *argval* is a flag array which can combine these flags:
*
* * **BPF_SOCK_OPS_RTO_CB_FLAG** (retransmission time out)
* * **BPF_SOCK_OPS_RETRANS_CB_FLAG** (retransmission)
* * **BPF_SOCK_OPS_STATE_CB_FLAG** (TCP state change)
*
+ * Therefore, this function can be used to clear a callback flag by
+ * setting the appropriate bit to zero. e.g. to disable the RTO
+ * callback:
+ *
+ * **bpf_sock_ops_cb_flags_set(bpf_sock,**
+ * **bpf_sock->bpf_sock_ops_cb_flags & ~BPF_SOCK_OPS_RTO_CB_FLAG)**
+ *
* Here are some examples of where one could call such eBPF
* program:
*
diff --git a/net/core/filter.c b/net/core/filter.c
index fc92ebc4e200..0c4cdfbb2fc7 100644
--- a/net/core/filter.c
+++ b/net/core/filter.c
@@ -4355,8 +4355,7 @@ BPF_CALL_2(bpf_sock_ops_cb_flags_set, struct bpf_sock_ops_kern *, bpf_sock,
if (!IS_ENABLED(CONFIG_INET) || !sk_fullsock(sk))
return -EINVAL;
- if (val)
- tcp_sk(sk)->bpf_sock_ops_cb_flags = val;
+ tcp_sk(sk)->bpf_sock_ops_cb_flags = val;
return argval & (~BPF_SOCK_OPS_ALL_CB_FLAGS);
}
--
2.17.1
