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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 | * | |
ea9b6362 | 10 | * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program. |
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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> | |
7cf245a3 THJ |
19 | #include <bpf/bpf_helpers.h> |
20 | #include <bpf/bpf_endian.h> | |
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21 | |
22 | #define DEBUG 1 | |
23 | ||
c890063e LB |
24 | SEC("sockops") |
25 | int 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)+1)) { | |
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 | } | |
71 | char _license[] SEC("license") = "GPL"; |