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bpf: Sample bpf program to set initial window 

The sample bpf program, tcp_rwnd_kern.c, sets the initial
advertized window to 40 packets in an environment where
distinct IPv6 prefixes indicate that both hosts are not
in the same data center.

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lawrence Brakmo 2017-06-30 20:02:45 -07:00 committed by David S. Miller
parent 13d3b1ebe2
commit c400296bf6
2 changed files with 70 additions and 0 deletions
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1
samples/bpf/Makefile
View File

@ -114,6 +114,7 @@ always += xdp_tx_iptunnel_kern.o
always += test_map_in_map_kern.o
always += cookie_uid_helper_example.o
always += tcp_synrto_kern.o
always += tcp_rwnd_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/

69
samples/bpf/tcp_rwnd_kern.c Normal file
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@ -0,0 +1,69 @@
/* 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)
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";