Skip to content

Commit

Permalink
bpf: Sample bpf program to set sndcwnd clamp
Browse files Browse the repository at this point in the history
Sample BPF program, tcp_clamp_kern.c, to demostrate the use
of setting the sndcwnd clamp. This program assumes that if the
first 5.5 bytes of the host's IPv6 addresses are the same, then
the hosts are in the same datacenter and sets sndcwnd clamp to
100 packets, SYN and SYN-ACK RTOs to 10ms and send/receive buffer
sizes to 150KB.

Signed-off-by: Lawrence Brakmo <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
  • Loading branch information
Lawrence Brakmo authored and davem330 committed Jul 1, 2017
1 parent 13bf964 commit 6c4a01b
Show file tree
Hide file tree
Showing 2 changed files with 103 additions and 0 deletions.
1 change: 1 addition & 0 deletions samples/bpf/Makefile
Original file line number Diff line number Diff line change
Expand Up @@ -118,6 +118,7 @@ always += tcp_rwnd_kern.o
always += tcp_bufs_kern.o
always += tcp_cong_kern.o
always += tcp_iw_kern.o
always += tcp_clamp_kern.o

HOSTCFLAGS += -I$(objtree)/usr/include
HOSTCFLAGS += -I$(srctree)/tools/lib/
Expand Down
102 changes: 102 additions & 0 deletions samples/bpf/tcp_clamp_kern.c
Original file line number Diff line number Diff line change
@@ -0,0 +1,102 @@
/* 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\n", 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\n", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";

0 comments on commit 6c4a01b

Please sign in to comment.