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1/* Copyright (c) 2017 Facebook2 *3 * This program is free software; you can redistribute it and/or4 * modify it under the terms of version 2 of the GNU General Public5 * License as published by the Free Software Foundation.6 *7 * BPF program to set congestion control to dctcp when both hosts are8 * 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 123 24SEC("sockops")25int 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 program32 * if neither port numberis 5560133 */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 DEBUG43 bpf_printk("BPF command: %d\n", op);44#endif45 46 /* Check if both hosts are in the same datacenter. For this47 * example they are if the 1st 5.5 bytes in the IPv6 address48 * 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 DEBUG73 bpf_printk("Returning %d\n", rv);74#endif75 skops->reply = rv;76 return 1;77}78char _license[] SEC("license") = "GPL";79