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 __u32 page_size = 0;
13 
14 SEC("cgroup/setsockopt")
15 int sockopt_qos_to_cc(struct bpf_sockopt *ctx)
16 {
17 	void *optval_end = ctx->optval_end;
18 	int *optval = ctx->optval;
19 	char buf[TCP_CA_NAME_MAX];
20 	char cc_reno[TCP_CA_NAME_MAX] = "reno";
21 	char cc_cubic[TCP_CA_NAME_MAX] = "cubic";
22 
23 	if (ctx->level != SOL_IPV6 || ctx->optname != IPV6_TCLASS)
24 		goto out;
25 
26 	if (optval + 1 > optval_end)
27 		return 0; /* EPERM, bounds check */
28 
29 	if (bpf_getsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &buf, sizeof(buf)))
30 		return 0;
31 
32 	if (!tcp_cc_eq(buf, cc_cubic))
33 		return 0;
34 
35 	if (*optval == 0x2d) {
36 		if (bpf_setsockopt(ctx->sk, SOL_TCP, TCP_CONGESTION, &cc_reno,
37 				sizeof(cc_reno)))
38 			return 0;
39 	}
40 	return 1;
41 
42 out:
43 	/* optval larger than PAGE_SIZE use kernel's buffer. */
44 	if (ctx->optlen > page_size)
45 		ctx->optlen = 0;
46 	return 1;
47 }
48