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samples/bpf/tcp_cong_kern.c
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/* 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 congestion control to dctcp when both hosts are
* in the same datacenter (as deteremined 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_cong(struct bpf_sock_ops *skops)
{
char cong[] = "dctcp";
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
", 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_NEEDS_ECN:
rv = 1;
break;
case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
cong, sizeof(cong));
break;
case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
cong, sizeof(cong));
break;
default:
rv = -1;
}
} else {
rv = -1;
}
#ifdef DEBUG
bpf_printk("Returning %d
", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";
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