1/* Copyright (c) 2017 Facebook
 2 *
 3 * This program is free software; you can redistribute it and/or
 4 * modify it under the terms of version 2 of the GNU General Public
 5 * License as published by the Free Software Foundation.
 6 *
 7 * BPF program to set base_rtt to 80us when host is running TCP-NV and
 8 * both hosts are in the same datacenter (as determined by IPv6 prefix).
 9 *
10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
11 */
12
13#include <uapi/linux/bpf.h>
14#include <uapi/linux/tcp.h>
15#include <uapi/linux/if_ether.h>
16#include <uapi/linux/if_packet.h>
17#include <uapi/linux/ip.h>
18#include <linux/socket.h>
19#include <bpf/bpf_helpers.h>
20#include <bpf/bpf_endian.h>
21
22#define DEBUG 1
23
 
 
 
 
 
 
 
24SEC("sockops")
25int bpf_basertt(struct bpf_sock_ops *skops)
26{
27	char cong[20];
28	char nv[] = "nv";
29	int rv = 0, n;
30	int op;
31
32	op = (int) skops->op;
33
34#ifdef DEBUG
35	bpf_printk("BPF command: %d\n", op);
36#endif
37
38	/* Check if both hosts are in the same datacenter. For this
39	 * example they are if the 1st 5.5 bytes in the IPv6 address
40	 * are the same.
41	 */
42	if (skops->family == AF_INET6 &&
43	    skops->local_ip6[0] == skops->remote_ip6[0] &&
44	    (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
45	    (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
46		switch (op) {
47		case BPF_SOCK_OPS_BASE_RTT:
48			n = bpf_getsockopt(skops, SOL_TCP, TCP_CONGESTION,
49					   cong, sizeof(cong));
50			if (!n && !__builtin_memcmp(cong, nv, sizeof(nv))) {
51				/* Set base_rtt to 80us */
52				rv = 80;
53			} else if (n) {
54				rv = n;
55			} else {
56				rv = -1;
57			}
58			break;
59		default:
60			rv = -1;
61		}
62	} else {
63		rv = -1;
64	}
65#ifdef DEBUG
66	bpf_printk("Returning %d\n", rv);
67#endif
68	skops->reply = rv;
69	return 1;
70}
71char _license[] SEC("license") = "GPL";

 1/* Copyright (c) 2017 Facebook
 2 *
 3 * This program is free software; you can redistribute it and/or
 4 * modify it under the terms of version 2 of the GNU General Public
 5 * License as published by the Free Software Foundation.
 6 *
 7 * BPF program to set base_rtt to 80us when host is running TCP-NV and
 8 * both hosts are in the same datacenter (as determined by IPv6 prefix).
 9 *
10 * Use load_sock_ops to load this BPF program.
11 */
12
13#include <uapi/linux/bpf.h>
14#include <uapi/linux/tcp.h>
15#include <uapi/linux/if_ether.h>
16#include <uapi/linux/if_packet.h>
17#include <uapi/linux/ip.h>
18#include <linux/socket.h>
19#include "bpf_helpers.h"
20#include "bpf_endian.h"
21
22#define DEBUG 1
23
24#define bpf_printk(fmt, ...)					\
25({								\
26	       char ____fmt[] = fmt;				\
27	       bpf_trace_printk(____fmt, sizeof(____fmt),	\
28				##__VA_ARGS__);			\
29})
30
31SEC("sockops")
32int bpf_basertt(struct bpf_sock_ops *skops)
33{
34	char cong[20];
35	char nv[] = "nv";
36	int rv = 0, n;
37	int op;
38
39	op = (int) skops->op;
40
41#ifdef DEBUG
42	bpf_printk("BPF command: %d\n", op);
43#endif
44
45	/* Check if both hosts are in the same datacenter. For this
46	 * example they are if the 1st 5.5 bytes in the IPv6 address
47	 * are the same.
48	 */
49	if (skops->family == AF_INET6 &&
50	    skops->local_ip6[0] == skops->remote_ip6[0] &&
51	    (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
52	    (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
53		switch (op) {
54		case BPF_SOCK_OPS_BASE_RTT:
55			n = bpf_getsockopt(skops, SOL_TCP, TCP_CONGESTION,
56					   cong, sizeof(cong));
57			if (!n && !__builtin_memcmp(cong, nv, sizeof(nv)+1)) {
58				/* Set base_rtt to 80us */
59				rv = 80;
60			} else if (n) {
61				rv = n;
62			} else {
63				rv = -1;
64			}
65			break;
66		default:
67			rv = -1;
68		}
69	} else {
70		rv = -1;
71	}
72#ifdef DEBUG
73	bpf_printk("Returning %d\n", rv);
74#endif
75	skops->reply = rv;
76	return 1;
77}
78char _license[] SEC("license") = "GPL";