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bpf: allow clearing all sock_ops callback flags

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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@uclouvain.be>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
This commit is contained in:
Viet Hoang Tran 2019-04-15 09:54:55 +00:00 • committed by Alexei Starovoitov
parent 809041e765
commit 725721a650
2 changed files with 9 additions and 3 deletions
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9
include/uapi/linux/bpf.h
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@ -1737,12 +1737,19 @@ 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:
*