/* Copyright (c) 2017 Facebook
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of version 2 of the GNU General Public
* License as published by the Free Software Foundation.
*
* BPF program to set initial congestion window and initial receive
* window to 40 packets and send and receive buffers to 1.5MB. This
* would usually be done after doing appropriate checks that indicate
* the hosts are far enough away (i.e. large RTT).
*
* Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
*/
#include <uapi/linux/bpf.h>
#include <uapi/linux/if_ether.h>
#include <uapi/linux/if_packet.h>
#include <uapi/linux/ip.h>
#include <linux/socket.h>
#include <bpf/bpf_helpers.h>
#include <bpf/bpf_endian.h>
#define DEBUG 1
SEC("sockops")
int bpf_iw(struct bpf_sock_ops *skops)
{
int bufsize = 1500000;
int rwnd_init = 40;
int iw = 40;
int rv = 0;
int op;
/* For testing purposes, only execute rest of BPF program
* if neither port numberis 55601
*/
if (bpf_ntohl(skops->remote_port) != 55601 &&
skops->local_port != 55601) {
skops->reply = -1;
return 1;
}
op = (int) skops->op;
#ifdef DEBUG
bpf_printk("BPF command: %d\n", op);
#endif
/* Usually there would be a check to insure the hosts are far
* from each other so it makes sense to increase buffer sizes
*/
switch (op) {
case BPF_SOCK_OPS_RWND_INIT:
rv = rwnd_init;
break;
case BPF_SOCK_OPS_TCP_CONNECT_CB:
/* Set sndbuf and rcvbuf of active connections */
rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
sizeof(bufsize));
rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
&bufsize, sizeof(bufsize));
break;
case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
rv = bpf_setsockopt(skops, SOL_TCP, TCP_BPF_IW, &iw,
sizeof(iw));
break;
case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
/* Set sndbuf and rcvbuf of passive connections */
rv = bpf_setsockopt(skops, SOL_SOCKET, SO_SNDBUF, &bufsize,
sizeof(bufsize));
rv += bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,
&bufsize, sizeof(bufsize));
break;
default:
rv = -1;
}
#ifdef DEBUG
bpf_printk("Returning %d\n", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";
