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samples/bpf/tcp_clamp_kern.c
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/* 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.
*
* Sample BPF program to set send and receive buffers to 150KB, sndcwnd clamp
* to 100 packets and SYN and SYN_ACK RTOs to 10ms when both hosts are within
* the same datacenter. For his example, we assume they are within the same
* datacenter when the first 5.5 bytes of their IPv6 addresses are the same.
*
* 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_clamp(struct bpf_sock_ops *skops)
{
int bufsize = 150000;
int to_init = 10;
int clamp = 100;
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)
return -1;
op = (int) skops->op;
#ifdef DEBUG
bpf_printk("BPF command: %d
", op);
#endif
/* Check that both hosts are within same datacenter. For this example
* it is the case when the first 5.5 bytes of their IPv6 addresses are
* the same.
*/
if (skops->family == AF_INET6 &&
skops->local_ip6[0] == skops->remote_ip6[0] &&
(bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
(bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
switch (op) {
case BPF_SOCK_OPS_TIMEOUT_INIT:
rv = to_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 = rv*100 + 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_SNDCWND_CLAMP,
&clamp, sizeof(clamp));
break;
case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
/* Set sndbuf and rcvbuf of passive connections */
rv = bpf_setsockopt(skops, SOL_TCP,
TCP_BPF_SNDCWND_CLAMP,
&clamp, sizeof(clamp));
rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET,
SO_SNDBUF, &bufsize,
sizeof(bufsize));
rv = rv*100 + bpf_setsockopt(skops, SOL_SOCKET,
SO_RCVBUF, &bufsize,
sizeof(bufsize));
break;
default:
rv = -1;
}
} else {
rv = -1;
}
#ifdef DEBUG
bpf_printk("Returning %d
", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";
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