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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 base_rtt to 80u s when host is running TCP - NV and
* both hosts are in the same datacenter ( as determined by IPv6 prefix ) .
*
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* Use " bpftool cgroup attach $cg sock_ops $prog " to load this BPF program .
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*/
# 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>
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# include <bpf/bpf_helpers.h>
# include <bpf/bpf_endian.h>
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# define DEBUG 1
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 1 st 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 ) ) ;
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if ( ! n & & ! __builtin_memcmp ( cong , nv , sizeof ( nv ) ) ) {
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/* 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 " ;