72 lines
1.8 KiB
C
72 lines
1.8 KiB
C
/* 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 receive window to 40 packets when using IPv6
|
|
* and the first 5.5 bytes of the IPv6 addresses are not the same (in this
|
|
* example that means both hosts are not the same datacenter).
|
|
*
|
|
* Use load_sock_ops 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_helpers.h"
|
|
#include "bpf_endian.h"
|
|
|
|
#define DEBUG 1
|
|
|
|
#define bpf_printk(fmt, ...) \
|
|
({ \
|
|
char ____fmt[] = fmt; \
|
|
bpf_trace_printk(____fmt, sizeof(____fmt), \
|
|
##__VA_ARGS__); \
|
|
})
|
|
|
|
SEC("sockops")
|
|
int bpf_rwnd(struct bpf_sock_ops *skops)
|
|
{
|
|
int rv = -1;
|
|
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
|
|
|
|
/* Check for RWND_INIT operation and IPv6 addresses */
|
|
if (op == BPF_SOCK_OPS_RWND_INIT &&
|
|
skops->family == AF_INET6) {
|
|
|
|
/* If the first 5.5 bytes of the IPv6 address are not the same
|
|
* then both hosts are not in the same datacenter
|
|
* so use a larger initial advertized window (40 packets)
|
|
*/
|
|
if (skops->local_ip6[0] != skops->remote_ip6[0] ||
|
|
(bpf_ntohl(skops->local_ip6[1]) & 0xfffff000) !=
|
|
(bpf_ntohl(skops->remote_ip6[1]) & 0xfffff000))
|
|
rv = 40;
|
|
}
|
|
#ifdef DEBUG
|
|
bpf_printk("Returning %d\n", rv);
|
|
#endif
|
|
skops->reply = rv;
|
|
return 1;
|
|
}
|
|
char _license[] SEC("license") = "GPL";
|