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")
sockopt_qos_to_cc(struct bpf_sockopt * ctx)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