1 // SPDX-License-Identifier: GPL-2.0
2 /* Copyright (c) 2021 Facebook */
3 #include <string.h>
4 #include <linux/tcp.h>
5 #include <netinet/in.h>
6 #include <linux/bpf.h>
7 #include <bpf/bpf_helpers.h>
8 #include "bpf_tcp_helpers.h"
9 
10 char _license[] SEC("license") = "GPL";
11 
12 SEC("cgroup/setsockopt")
sockopt_qos_to_cc(struct bpf_sockopt * ctx)13 int 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 	char cc_reno[TCP_CA_NAME_MAX] = "reno";
19 	char cc_cubic[TCP_CA_NAME_MAX] = "cubic";
20 
21 	if (ctx->level != SOL_IPV6 || ctx->optname != IPV6_TCLASS)
22 		return 1;
23 
24 	if (optval + 1 > optval_end)
25 		return 0; /* EPERM, bounds check */
26 
27 	if (bpf_getsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
28 		return 0;
29 
30 	if (!tcp_cc_eq(buf, cc_cubic))
31 		return 0;
32 
33 	if (*optval == 0x2d) {
34 		if (bpf_setsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &cc_reno,
35 				sizeof(cc_reno)))
36 			return 0;
37 	}
38 	return 1;
39 }
40