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 congestion control to dctcp when both hosts are |
8 | * in the same datacenter (as deteremined 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_cong(struct bpf_sock_ops *skops) |
26 | { |
27 | char cong[] = "dctcp" ; |
28 | int rv = 0; |
29 | int op; |
30 | |
31 | /* For testing purposes, only execute rest of BPF program |
32 | * if neither port numberis 55601 |
33 | */ |
34 | if (bpf_ntohl(skops->remote_port) != 55601 && |
35 | skops->local_port != 55601) { |
36 | skops->reply = -1; |
37 | return 1; |
38 | } |
39 | |
40 | op = (int) skops->op; |
41 | |
42 | #ifdef DEBUG |
43 | bpf_printk("BPF command: %d\n" , op); |
44 | #endif |
45 | |
46 | /* Check if both hosts are in the same datacenter. For this |
47 | * example they are if the 1st 5.5 bytes in the IPv6 address |
48 | * are the same. |
49 | */ |
50 | if (skops->family == AF_INET6 && |
51 | skops->local_ip6[0] == skops->remote_ip6[0] && |
52 | (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) == |
53 | (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) { |
54 | switch (op) { |
55 | case BPF_SOCK_OPS_NEEDS_ECN: |
56 | rv = 1; |
57 | break; |
58 | case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB: |
59 | rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, |
60 | cong, sizeof(cong)); |
61 | break; |
62 | case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB: |
63 | rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION, |
64 | cong, sizeof(cong)); |
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 | } |
78 | char _license[] SEC("license" ) = "GPL" ; |
79 | |