1// SPDX-License-Identifier: GPL-2.0
2/* Copyright (c) 2021 Facebook */
3#include "bpf_iter.h"
4#include "bpf_tracing_net.h"
5#include <bpf/bpf_helpers.h>
6#include <bpf/bpf_endian.h>
7
8#define bpf_tcp_sk(skc)	({				\
9	struct sock_common *_skc = skc;			\
10	sk = NULL;					\
11	tp = NULL;					\
12	if (_skc) {					\
13		tp = bpf_skc_to_tcp_sock(_skc);		\
14		sk = (struct sock *)tp;			\
15	}						\
16	tp;						\
17})
18
19unsigned short reuse_listen_hport = 0;
20unsigned short listen_hport = 0;
21char cubic_cc[TCP_CA_NAME_MAX] = "bpf_cubic";
22char dctcp_cc[TCP_CA_NAME_MAX] = "bpf_dctcp";
23bool random_retry = false;
24
25static bool tcp_cc_eq(const char *a, const char *b)
26{
27	int i;
28
29	for (i = 0; i < TCP_CA_NAME_MAX; i++) {
30		if (a[i] != b[i])
31			return false;
32		if (!a[i])
33			break;
34	}
35
36	return true;
37}
38
39SEC("iter/tcp")
40int change_tcp_cc(struct bpf_iter__tcp *ctx)
41{
42	char cur_cc[TCP_CA_NAME_MAX];
43	struct tcp_sock *tp;
44	struct sock *sk;
45
46	if (!bpf_tcp_sk(ctx->sk_common))
47		return 0;
48
49	if (sk->sk_family != AF_INET6 ||
50	    (sk->sk_state != TCP_LISTEN &&
51	     sk->sk_state != TCP_ESTABLISHED) ||
52	    (sk->sk_num != reuse_listen_hport &&
53	     sk->sk_num != listen_hport &&
54	     bpf_ntohs(sk->sk_dport) != listen_hport))
55		return 0;
56
57	if (bpf_getsockopt(tp, SOL_TCP, TCP_CONGESTION,
58			   cur_cc, sizeof(cur_cc)))
59		return 0;
60
61	if (!tcp_cc_eq(cur_cc, cubic_cc))
62		return 0;
63
64	if (random_retry && bpf_get_prandom_u32() % 4 == 1)
65		return 1;
66
67	bpf_setsockopt(tp, SOL_TCP, TCP_CONGESTION, dctcp_cc, sizeof(dctcp_cc));
68	return 0;
69}
70
71char _license[] SEC("license") = "GPL";
72