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1// SPDX-License-Identifier: GPL-2.02/*3 * Copyright (c) 2018 Facebook4 *5 * BPF program to automatically reflect TOS option from received syn packet6 *7 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.8 */9 10#include <uapi/linux/bpf.h>11#include <uapi/linux/tcp.h>12#include <uapi/linux/if_ether.h>13#include <uapi/linux/if_packet.h>14#include <uapi/linux/ip.h>15#include <uapi/linux/ipv6.h>16#include <uapi/linux/in.h>17#include <linux/socket.h>18#include <bpf/bpf_helpers.h>19#include <bpf/bpf_endian.h>20 21#define DEBUG 122 23SEC("sockops")24int bpf_basertt(struct bpf_sock_ops *skops)25{26 char header[sizeof(struct ipv6hdr)];27 struct ipv6hdr *hdr6;28 struct iphdr *hdr;29 int hdr_size = 0;30 int save_syn = 1;31 int tos = 0;32 int rv = 0;33 int op;34 35 op = (int) skops->op;36 37#ifdef DEBUG38 bpf_printk("BPF command: %d\n", op);39#endif40 switch (op) {41 case BPF_SOCK_OPS_TCP_LISTEN_CB:42 rv = bpf_setsockopt(skops, SOL_TCP, TCP_SAVE_SYN,43 &save_syn, sizeof(save_syn));44 break;45 case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:46 if (skops->family == AF_INET)47 hdr_size = sizeof(struct iphdr);48 else49 hdr_size = sizeof(struct ipv6hdr);50 rv = bpf_getsockopt(skops, SOL_TCP, TCP_SAVED_SYN,51 header, hdr_size);52 if (!rv) {53 if (skops->family == AF_INET) {54 hdr = (struct iphdr *) header;55 tos = hdr->tos;56 if (tos != 0)57 bpf_setsockopt(skops, SOL_IP, IP_TOS,58 &tos, sizeof(tos));59 } else {60 hdr6 = (struct ipv6hdr *) header;61 tos = ((hdr6->priority) << 4 |62 (hdr6->flow_lbl[0]) >> 4);63 if (tos)64 bpf_setsockopt(skops, SOL_IPV6,65 IPV6_TCLASS,66 &tos, sizeof(tos));67 }68 rv = 0;69 }70 break;71 default:72 rv = -1;73 }74#ifdef DEBUG75 bpf_printk("Returning %d\n", rv);76#endif77 skops->reply = rv;78 return 1;79}80char _license[] SEC("license") = "GPL";81