bpf_iter_setsockopt.c

 1// SPDX-License-Identifier: GPL-2.0
 2/* Copyright (c) 2021 Facebook */
 3#include <vmlinux.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;
21const char cubic_cc[] = "bpf_cubic";
22char dctcp_cc[TCP_CA_NAME_MAX] = "bpf_dctcp";
23bool random_retry = false;
24
25
26SEC("iter/tcp")
27int change_tcp_cc(struct bpf_iter__tcp *ctx)
28{
29	char cur_cc[TCP_CA_NAME_MAX];
30	struct tcp_sock *tp;
31	struct sock *sk;
32
33	if (!bpf_tcp_sk(ctx->sk_common))
34		return 0;
35
36	if (sk->sk_family != AF_INET6 ||
37	    (sk->sk_state != TCP_LISTEN &&
38	     sk->sk_state != TCP_ESTABLISHED) ||
39	    (sk->sk_num != reuse_listen_hport &&
40	     sk->sk_num != listen_hport &&
41	     bpf_ntohs(sk->sk_dport) != listen_hport))
42		return 0;
43
44	if (bpf_getsockopt(tp, SOL_TCP, TCP_CONGESTION,
45			   cur_cc, sizeof(cur_cc)))
46		return 0;
47
48	if (bpf_strncmp(cur_cc, TCP_CA_NAME_MAX, cubic_cc))
49		return 0;
50
51	if (random_retry && bpf_get_prandom_u32() % 4 == 1)
52		return 1;
53
54	bpf_setsockopt(tp, SOL_TCP, TCP_CONGESTION, dctcp_cc, sizeof(dctcp_cc));
55	return 0;
56}
57
58char _license[] SEC("license") = "GPL";