Commit 725721a6 authored by Viet Hoang Tran's avatar Viet Hoang Tran Committed by Alexei Starovoitov
Browse files

bpf: allow clearing all sock_ops callback flags 



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: default avatarHoang Tran <hoang.tran@uclouvain.be>
Acked-by: default avatarMartin KaFai Lau <kafai@fb.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 809041e7

include/uapi/linux/bpf.h

+8 −1
Original line number Diff line number Diff line
@@ -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:

 *

net/core/filter.c

+1 −2
Original line number Diff line number Diff line
@@ -4437,7 +4437,6 @@ 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;



	return argval & (~BPF_SOCK_OPS_ALL_CB_FLAGS);

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