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 SYN and SYN-ACK RTOs to 10ms when using IPv6 addresses |
8 | * and the first 5.5 bytes of the IPv6 addresses are the same (in this example |
9 | * that means both hosts are in the same datacenter). |
10 | * |
11 | * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program. |
12 | */ |
13 | |
14 | #include <uapi/linux/bpf.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_synrto(struct bpf_sock_ops *skops) |
26 | { |
27 | int rv = -1; |
28 | int op; |
29 | |
30 | /* For testing purposes, only execute rest of BPF program |
31 | * if neither port numberis 55601 |
32 | */ |
33 | if (bpf_ntohl(skops->remote_port) != 55601 && |
34 | skops->local_port != 55601) { |
35 | skops->reply = -1; |
36 | return 1; |
37 | } |
38 | |
39 | op = (int) skops->op; |
40 | |
41 | #ifdef DEBUG |
42 | bpf_printk("BPF command: %d\n" , op); |
43 | #endif |
44 | |
45 | /* Check for TIMEOUT_INIT operation and IPv6 addresses */ |
46 | if (op == BPF_SOCK_OPS_TIMEOUT_INIT && |
47 | skops->family == AF_INET6) { |
48 | |
49 | /* If the first 5.5 bytes of the IPv6 address are the same |
50 | * then both hosts are in the same datacenter |
51 | * so use an RTO of 10ms |
52 | */ |
53 | if (skops->local_ip6[0] == skops->remote_ip6[0] && |
54 | (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) == |
55 | (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) |
56 | rv = 10; |
57 | } |
58 | #ifdef DEBUG |
59 | bpf_printk("Returning %d\n" , rv); |
60 | #endif |
61 | skops->reply = rv; |
62 | return 1; |
63 | } |
64 | char _license[] SEC("license" ) = "GPL" ; |
65 | |