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// SPDX-License-Identifier: GPL-2.0
/*
* Copyright (c) 2018 Facebook
*
* BPF program to automatically reflect TOS option from received syn packet
*
* Use "bpftool cgroup attach $cg sock_ops $prog" 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 <uapi/linux/ipv6.h>
#include <uapi/linux/in.h>
#include <linux/socket.h>
#include "bpf_helpers.h"
#include "bpf_endian.h"
#define DEBUG 1
SEC("sockops")
int bpf_basertt(struct bpf_sock_ops *skops)
{
char header[sizeof(struct ipv6hdr)];
struct ipv6hdr *hdr6;
struct iphdr *hdr;
int hdr_size = 0;
int save_syn = 1;
int tos = 0;
int rv = 0;
int op;
op = (int) skops->op;
#ifdef DEBUG
bpf_printk("BPF command: %d\n", op);
#endif
switch (op) {
case BPF_SOCK_OPS_TCP_LISTEN_CB:
rv = bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,
&save_syn, sizeof(save_syn));
break;
case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
if (skops->family == AF_INET)
hdr_size = sizeof(struct iphdr);
else
hdr_size = sizeof(struct ipv6hdr);
rv = bpf_getsockopt(skops, SOL_TCP, TCP_SAVED_SYN,
header, hdr_size);
if (!rv) {
if (skops->family == AF_INET) {
hdr = (struct iphdr *) header;
tos = hdr->tos;
if (tos != 0)
bpf_setsockopt(skops, SOL_IP, IP_TOS,
&tos, sizeof(tos));
} else {
hdr6 = (struct ipv6hdr *) header;
tos = ((hdr6->priority) << 4 |
(hdr6->flow_lbl[0]) >> 4);
if (tos)
bpf_setsockopt(skops, SOL_IPV6,
IPV6_TCLASS,
&tos, sizeof(tos));
}
rv = 0;
}
break;
default:
rv = -1;
}
#ifdef DEBUG
bpf_printk("Returning %d\n", rv);
#endif
skops->reply = rv;
return 1;
}
char _license[] SEC("license") = "GPL";
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