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
19 unsigned short reuse_listen_hport = 0;
20 unsigned short listen_hport = 0;
21 char cubic_cc[TCP_CA_NAME_MAX] = "bpf_cubic";
22 char dctcp_cc[TCP_CA_NAME_MAX] = "bpf_dctcp";
23 bool random_retry = false;
24
tcp_cc_eq(const char * a,const char * b)25 static 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
39 SEC("iter/tcp")
change_tcp_cc(struct bpf_iter__tcp * ctx)40 int 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
71 char _license[] SEC("license") = "GPL";
72