bpf.c

   1 // SPDX-License-Identifier: GPL-2.0-or-later
   2 /*
   3  * Copyright (C) 2022 Felix Fietkau <nbd@nbd.name>
   4  */
   5 #define _GNU_SOURCE
   6 #include <sys/types.h>
   7 #include <sys/socket.h>
   8 #include <sys/resource.h>
   9 #include <netinet/if_ether.h>
  10 #include <netlink/msg.h>
  11 #include <netlink/attr.h>
  12 #include <netlink/socket.h>
  13 #include <linux/rtnetlink.h>
  14 #include <linux/pkt_cls.h>
  15 #include <bpf/bpf.h>
  16 #include <bpf/libbpf.h>
  17 #include "unetd.h"
  18
  19 static int unetd_bpf_pr(enum libbpf_print_level level, const char *format,
  20                      va_list args)
  21 {
  22         return vfprintf(stderr, format, args);
  23 }
  24
  25 static void unetd_init_env(void)
  26 {
  27         struct rlimit limit = {
  28                 .rlim_cur = RLIM_INFINITY,
  29                 .rlim_max = RLIM_INFINITY,
  30         };
  31
  32         setrlimit(RLIMIT_MEMLOCK, &limit);
  33 }
  34
  35 static void
  36 unetd_set_prog_mtu(struct bpf_object *obj, uint32_t mtu)
  37 {
  38         struct bpf_map *map = NULL;
  39
  40         while ((map = bpf_object__next_map(obj, map)) != NULL) {
  41                 if (!strstr(bpf_map__name(map), ".rodata"))
  42                         continue;
  43
  44                 bpf_map__set_initial_value(map, &mtu, sizeof(mtu));
  45         }
  46 }
  47
  48 static int
  49 unetd_attach_bpf_prog(int ifindex, int fd, bool egress)
  50 {
  51         DECLARE_LIBBPF_OPTS(bpf_tc_hook, hook,
  52                             .attach_point = egress ? BPF_TC_EGRESS : BPF_TC_INGRESS,
  53                             .ifindex = ifindex);
  54         DECLARE_LIBBPF_OPTS(bpf_tc_opts, attach_tc,
  55                             .flags = BPF_TC_F_REPLACE,
  56                             .handle = 1,
  57                                 .prog_fd = fd,
  58                             .priority = UNETD_MSS_PRIO_BASE);
  59
  60         bpf_tc_hook_create(&hook);
  61
  62         return bpf_tc_attach(&hook, &attach_tc);
  63 }
  64
  65 int unetd_attach_mssfix(int ifindex, int mtu)
  66 {
  67         struct bpf_program *prog;
  68         struct bpf_object *obj;
  69         int prog_fd;
  70         int ret = -1;
  71
  72         if (rtnl_init())
  73                 return -1;
  74
  75         unetd_init_env();
  76         libbpf_set_print(unetd_bpf_pr);
  77
  78         obj = bpf_object__open_file(mssfix_path, NULL);
  79         if (libbpf_get_error(obj)) {
  80                 perror("bpf_object__open_file");
  81                 goto out;
  82         }
  83
  84         prog = bpf_object__find_program_by_name(obj, "mssfix");
  85         if (!prog) {
  86                 perror("bpf_object__find_program_by_name");
  87                 goto out;
  88         }
  89
  90         bpf_program__set_type(prog, BPF_PROG_TYPE_SCHED_CLS);
  91
  92         unetd_set_prog_mtu(obj, mtu);
  93
  94         if (bpf_object__load(obj)) {
  95                 perror("bpf_object__load");
  96                 goto out;
  97         }
  98
  99         prog_fd = bpf_program__fd(prog);
 100         unetd_attach_bpf_prog(ifindex, prog_fd, true);
 101         unetd_attach_bpf_prog(ifindex, prog_fd, false);
 102
 103         ret = 0;
 104
 105 out:
 106         bpf_object__close(obj);
 107
 108         return ret;
 109 }