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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 initial congestion window and initial receive8 * window to 40 packets and send and receive buffers to 1.5MB. This9 * would usually be done after doing appropriate checks that indicate10 * the hosts are far enough away (i.e. large RTT).11 *12 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.13 */14 15#include <uapi/linux/bpf.h>16#include <uapi/linux/if_ether.h>17#include <uapi/linux/if_packet.h>18#include <uapi/linux/ip.h>19#include <linux/socket.h>20#include <bpf/bpf_helpers.h>21#include <bpf/bpf_endian.h>22 23#define DEBUG 124 25SEC("sockops")26int bpf_iw(struct bpf_sock_ops *skops)27{28 int bufsize = 1500000;29 int rwnd_init = 40;30 int iw = 40;31 int rv = 0;32 int op;33 34 /* For testing purposes, only execute rest of BPF program35 * if neither port numberis 5560136 */37 if (bpf_ntohl(skops->remote_port) != 55601 &&38 skops->local_port != 55601) {39 skops->reply = -1;40 return 1;41 }42 43 op = (int) skops->op;44 45#ifdef DEBUG46 bpf_printk("BPF command: %d\n", op);47#endif48 49 /* Usually there would be a check to insure the hosts are far50 * from each other so it makes sense to increase buffer sizes51 */52 switch (op) {53 case BPF_SOCK_OPS_RWND_INIT:54 rv = rwnd_init;55 break;56 case BPF_SOCK_OPS_TCP_CONNECT_CB:57 /* Set sndbuf and rcvbuf of active connections */58 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,59 sizeof(bufsize));60 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,61 &bufsize, sizeof(bufsize));62 break;63 case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:64 rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,65 sizeof(iw));66 break;67 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:68 /* Set sndbuf and rcvbuf of passive connections */69 rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,70 sizeof(bufsize));71 rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,72 &bufsize, sizeof(bufsize));73 break;74 default:75 rv = -1;76 }77#ifdef DEBUG78 bpf_printk("Returning %d\n", rv);79#endif80 skops->reply = rv;81 return 1;82}83char _license[] SEC("license") = "GPL";84