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bpf: Sample bpf program to set SYN/SYN-ACK RTOs

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The sample BPF program, tcp_synrto_kern.c, sets the SYN and SYN-ACK
RTOs to 10ms when both hosts are within the same datacenter (i.e.
small RTTs) in an environment where common IPv6 prefixes indicate
both hosts are 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 20:02:43 -07:00 committed by David S. Miller
parent 8550f328f4
commit 61bc4d8daa
2 changed files with 70 additions and 0 deletions
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1
samples/bpf/Makefile
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@ -113,6 +113,7 @@ always += lwt_len_hist_kern.o
always += xdp_tx_iptunnel_kern.o
always += test_map_in_map_kern.o
always += cookie_uid_helper_example.o
always += tcp_synrto_kern.o
HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/

69
samples/bpf/tcp_synrto_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 SYN and SYN-ACK RTOs to 10ms when using IPv6 addresses
* and the first 5.5 bytes of the IPv6 addresses are the same (in this example
* that means both hosts are in 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_synrto(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 TIMEOUT_INIT operation and IPv6 addresses */
if (op == BPF_SOCK_OPS_TIMEOUT_INIT &&
skops->family == AF_INET6) {
/* If the first 5.5 bytes of the IPv6 address are the same
* then both hosts are in the same datacenter
* so use an RTO of 10ms
*/
if (skops->local_ip6[0] == skops->remote_ip6[0] &&
(bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
(bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000))
rv = 10;
}
#ifdef DEBUG
bpf_printk("Returning %d\n", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";