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Commit d9925368 authored by Lawrence Brakmo's avatar Lawrence Brakmo Committed by David S. Miller
Browse files

bpf: Sample BPF program to set buffer sizes 



This patch contains a BPF program to set 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).

Signed-off-by: default avatarLawrence Brakmo <brakmo@fb.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 9872a4bd

samples/bpf/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -115,6 +115,7 @@ always += test_map_in_map_kern.o 
always += cookie_uid_helper_example.o

always += tcp_synrto_kern.o

always += tcp_rwnd_kern.o

always += tcp_bufs_kern.o



HOSTCFLAGS += -I$(objtree)/usr/include

HOSTCFLAGS += -I$(srctree)/tools/lib/

samples/bpf/tcp_bufs_kern.c

0 → 100644
+86 −0
Original line number Diff line number Diff line 
/* 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 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 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_bufs(struct bpf_sock_ops *skops)

{

	int bufsize = 1500000;

	int rwnd_init = 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)

		return -1;



	op = (int) skops->op;



#ifdef DEBUG

	bpf_printk("Returning %d\n", rv);

#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 = rv*100 + bpf_setsockopt(skops, SOL_SOCKET, SO_RCVBUF,

					     &bufsize, sizeof(bufsize));

		break;

	case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:

		/* Nothing to do */

		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 = rv*100 + 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";