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