netdev - [PATCH bpf-next 2/2] bpf: Require only one of cong_avoid() and cong

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Message-ID: <20220608174843.1936060-3-jthinz@mailbox.tu-berlin.de>
Date:   Wed, 8 Jun 2022 19:48:43 +0200
From:   Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>
To:     <bpf@...r.kernel.org>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>, <netdev@...r.kernel.org>,
        Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>
Subject: [PATCH bpf-next 2/2] bpf: Require only one of cong_avoid() and cong_control() from a TCP CC

When a CC implements tcp_congestion_ops.cong_control(), the alternate
cong_avoid() is not in use in the TCP stack. Do not force a BPF CC to
implement cong_avoid() as a no-op by always requiring it.

An incomplete BPF CC implementing neither cong_avoid() nor
cong_control() will still get rejected by
tcp_register_congestion_control().

Signed-off-by: Jörn-Thorben Hinz <jthinz@...lbox.tu-berlin.de>
---
 net/ipv4/bpf_tcp_ca.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 1f5c53ede4e5..37290d0bf134 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -17,6 +17,7 @@ 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, cong_avoid),
 	offsetof(struct tcp_congestion_ops, set_state),
 	offsetof(struct tcp_congestion_ops, cwnd_event),
 	offsetof(struct tcp_congestion_ops, in_ack_event),
-- 
2.30.2