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 | |
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))) { |
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" ; |
72 | |