Commit 9f0265e9 authored by Jörn-Thorben Hinz's avatar Jörn-Thorben Hinz Committed by Alexei Starovoitov
Browse files

bpf: Require only one of cong_avoid() and cong_control() from a TCP CC 



Remove the check for required and optional functions in a struct
tcp_congestion_ops from bpf_tcp_ca.c. Rely on
tcp_register_congestion_control() to reject a BPF CC that does not
implement all required functions, as it will do for a non-BPF CC.

When a CC implements tcp_congestion_ops.cong_control(), the alternate
cong_avoid() is not in use in the TCP stack. Previously, a BPF CC was
still forced to implement cong_avoid() as a no-op since it was
non-optional in bpf_tcp_ca.c.

Signed-off-by: default avatarJörn-Thorben Hinz <jthinz@mailbox.tu-berlin.de>
Reviewed-by: default avatarMartin KaFai Lau <kafai@fb.com>
Link: https://lore.kernel.org/r/20220622191227.898118-3-jthinz@mailbox.tu-berlin.de


Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
parent 41c95dd6

kernel/bpf/bpf_struct_ops.c

+3 −4
Original line number Diff line number Diff line
@@ -503,10 +503,9 @@ static int bpf_struct_ops_map_update_elem(struct bpf_map *map, void *key, 
		goto unlock;

	}



	/* Error during st_ops->reg().  It is very unlikely since

	 * the above init_member() should have caught it earlier

	 * before reg().  The only possibility is if there was a race

	 * in registering the struct_ops (under the same name) to

	/* Error during st_ops->reg(). Can happen if this struct_ops needs to be

	 * verified as a whole, after all init_member() calls. Can also happen if

	 * there was a race in registering the struct_ops (under the same name) to

	 * a sub-system through different struct_ops's maps.

	 */

	set_memory_nx((long)st_map->image, 1);

net/ipv4/bpf_tcp_ca.c

+0 −33
Original line number Diff line number Diff line
@@ -14,18 +14,6 @@ 
/* "extern" is to avoid sparse warning.  It is only used in bpf_struct_ops.c. */

extern struct bpf_struct_ops bpf_tcp_congestion_ops;



static u32 optional_ops[] = {

	offsetof(struct tcp_congestion_ops, init),

	offsetof(struct tcp_congestion_ops, release),

	offsetof(struct tcp_congestion_ops, set_state),

	offsetof(struct tcp_congestion_ops, cwnd_event),

	offsetof(struct tcp_congestion_ops, in_ack_event),

	offsetof(struct tcp_congestion_ops, pkts_acked),

	offsetof(struct tcp_congestion_ops, min_tso_segs),

	offsetof(struct tcp_congestion_ops, sndbuf_expand),

	offsetof(struct tcp_congestion_ops, cong_control),

};



static u32 unsupported_ops[] = {

	offsetof(struct tcp_congestion_ops, get_info),

};
@@ -51,18 +39,6 @@ static int bpf_tcp_ca_init(struct btf *btf) 
	return 0;

}



static bool is_optional(u32 member_offset)

{

	unsigned int i;



	for (i = 0; i < ARRAY_SIZE(optional_ops); i++) {

		if (member_offset == optional_ops[i])

			return true;

	}



	return false;

}



static bool is_unsupported(u32 member_offset)

{

	unsigned int i;
@@ -246,7 +222,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t, 
{

	const struct tcp_congestion_ops *utcp_ca;

	struct tcp_congestion_ops *tcp_ca;

	int prog_fd;

	u32 moff;



	utcp_ca = (const struct tcp_congestion_ops *)udata;
@@ -268,14 +243,6 @@ static int bpf_tcp_ca_init_member(const struct btf_type *t, 
		return 1;

	}



	if (!btf_type_resolve_func_ptr(btf_vmlinux, member->type, NULL))

		return 0;



	/* Ensure bpf_prog is provided for compulsory func ptr */

	prog_fd = (int)(*(unsigned long *)(udata + moff));

	if (!prog_fd && !is_optional(moff) && !is_unsupported(moff))

		return -EINVAL;



	return 0;

}