bpf: Add BPF_FUNC_tcp_send_ack helper

Add a helper to send out a tcp-ack.  It will be used in the later
bpf_dctcp implementation that requires to send out an ack
when the CE state changed.

Signed-off-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Yonghong Song <yhs@fb.com>
Link: https://lore.kernel.org/bpf/20200109004551.3900448-1-kafai@fb.com

1 files changed, 23 insertions, 1 deletions

diff --git a/net/ipv4/bpf_tcp_ca.c b/net/ipv4/bpf_tcp_ca.c
index 9c7745b958d7..574972bc7299 100644
--- a/net/ipv4/bpf_tcp_ca.c
+++ b/net/ipv4/bpf_tcp_ca.c
@@ -143,11 +143,33 @@ static int bpf_tcp_ca_btf_struct_access(struct bpf_verifier_log *log,
 	return NOT_INIT;
 }
 
+BPF_CALL_2(bpf_tcp_send_ack, struct tcp_sock *, tp, u32, rcv_nxt)
+{
+	/* bpf_tcp_ca prog cannot have NULL tp */
+	__tcp_send_ack((struct sock *)tp, rcv_nxt);
+	return 0;
+}
+
+static const struct bpf_func_proto bpf_tcp_send_ack_proto = {
+	.func		= bpf_tcp_send_ack,
+	.gpl_only	= false,
+	/* In case we want to report error later */
+	.ret_type	= RET_INTEGER,
+	.arg1_type	= ARG_PTR_TO_BTF_ID,
+	.arg2_type	= ARG_ANYTHING,
+	.btf_id		= &tcp_sock_id,
+};
+
 static const struct bpf_func_proto *
 bpf_tcp_ca_get_func_proto(enum bpf_func_id func_id,
 			  const struct bpf_prog *prog)
 {
-	return bpf_base_func_proto(func_id);
+	switch (func_id) {
+	case BPF_FUNC_tcp_send_ack:
+		return &bpf_tcp_send_ack_proto;
+	default:
+		return bpf_base_func_proto(func_id);
+	}
 }
 
 static const struct bpf_verifier_ops bpf_tcp_ca_verifier_ops = {