1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2021 Facebook */
 3#include "bpf_tracing_net.h"
 4
 5char _license[] SEC("license") = "GPL";
 6
 7__s32 page_size = 0;
 8
 9const char cc_reno[TCP_CA_NAME_MAX] = "reno";
10const char cc_cubic[TCP_CA_NAME_MAX] = "cubic";
11
12SEC("cgroup/setsockopt")
13int sockopt_qos_to_cc(struct bpf_sockopt *ctx)
14{
15	void *optval_end = ctx->optval_end;
16	int *optval = ctx->optval;
17	char buf[TCP_CA_NAME_MAX];
18
19	if (ctx->level != SOL_IPV6 || ctx->optname != IPV6_TCLASS)
20		goto out;
21
22	if (optval + 1 > optval_end)
23		return 0; /* EPERM, bounds check */
24
25	if (bpf_getsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
26		return 0;
27
28	if (bpf_strncmp(buf, sizeof(buf), cc_cubic))
29		return 0;
30
31	if (*optval == 0x2d) {
32		if (bpf_setsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, (void *)&cc_reno,
33				sizeof(cc_reno)))
34			return 0;
35	}
36	return 1;
37
38out:
39	/* optval larger than PAGE_SIZE use kernel's buffer. */
40	if (ctx->optlen > page_size)
41		ctx->optlen = 0;
42	return 1;
43}