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bpf: sample BPF_SOCKET_OPS_BASE_RTT program 

Sample socket_ops BPF program to test the BPF helper function
bpf_getsocketops and the new socket_ops op BPF_SOCKET_OPS_BASE_RTT.

The program provides a base RTT of 80us when the calling flow is
within a DC (as determined by the IPV6 prefix) and the congestion
algorithm is "nv".

Signed-off-by: Lawrence Brakmo <brakmo@fb.com>
Acked-by: Daniel Borkmann <daniel@iogearbox.net>
Acked_by: Alexei Starovoitov <ast@fb.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
Lawrence Brakmo 2017-10-20 11:05:42 -07:00 committed by David S. Miller
parent 85cce21578
commit c890063e44
2 changed files with 79 additions and 0 deletions
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1
samples/bpf/Makefile
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@ -129,6 +129,7 @@ always += tcp_bufs_kern.o
always += tcp_cong_kern.o
always += tcp_iw_kern.o
always += tcp_clamp_kern.o
always += tcp_basertt_kern.o
always += xdp_redirect_kern.o
always += xdp_redirect_map_kern.o
always += xdp_redirect_cpu_kern.o

78
samples/bpf/tcp_basertt_kern.c Normal file
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@ -0,0 +1,78 @@
/* 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 base_rtt to 80us when host is running TCP-NV and
* both hosts are in the same datacenter (as determined by IPv6 prefix).
*
* Use load_sock_ops to load this BPF program.
*/
#include <uapi/linux/bpf.h>
#include <uapi/linux/tcp.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_basertt(struct bpf_sock_ops *skops)
{
char cong[20];
char nv[] = "nv";
int rv = 0, n;
int op;
op = (int) skops->op;
#ifdef DEBUG
bpf_printk("BPF command: %d\n", op);
#endif
/* Check if both hosts are in the same datacenter. For this
* example they are if the 1st 5.5 bytes in the IPv6 address
* 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_BASE_RTT:
n = bpf_getsockopt(skops, SOL_TCP, TCP_CONGESTION,
cong, sizeof(cong));
if (!n && !__builtin_memcmp(cong, nv, sizeof(nv)+1)) {
/* Set base_rtt to 80us */
rv = 80;
} else if (n) {
rv = n;
} else {
rv = -1;
}
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";