LXR linux/tools/testing/selftests/bpf/progs/test_sysctl

   1// SPDX-License-Identifier: GPL-2.0
   2// Copyright (c) 2019 Facebook
   3
   4#include <stdint.h>
   5#include <string.h>
   6
   7#include <linux/stddef.h>
   8#include <linux/bpf.h>
   9
  10#include <bpf/bpf_helpers.h>
  11
  12/* Max supported length of a string with unsigned long in base 10 (pow2 - 1). */
  13#define MAX_ULONG_STR_LEN 0xF
  14
  15/* Max supported length of sysctl value string (pow2). */
  16#define MAX_VALUE_STR_LEN 0x40
  17
  18#ifndef ARRAY_SIZE
  19#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
  20#endif
  21
  22const char tcp_mem_name[] = "net/ipv4/tcp_mem";
  23static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
  24{
  25        unsigned char i;
  26        char name[sizeof(tcp_mem_name)];
  27        int ret;
  28
  29        memset(name, 0, sizeof(name));
  30        ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
  31        if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
  32                return 0;
  33
  34#pragma clang loop unroll(full)
  35        for (i = 0; i < sizeof(tcp_mem_name); ++i)
  36                if (name[i] != tcp_mem_name[i])
  37                        return 0;
  38
  39        return 1;
  40}
  41
  42SEC("cgroup/sysctl")
  43int sysctl_tcp_mem(struct bpf_sysctl *ctx)
  44{
  45        unsigned long tcp_mem[3] = {0, 0, 0};
  46        char value[MAX_VALUE_STR_LEN];
  47        unsigned char i, off = 0;
  48        volatile int ret;
  49
  50        if (ctx->write)
  51                return 0;
  52
  53        if (!is_tcp_mem(ctx))
  54                return 0;
  55
  56        ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
  57        if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
  58                return 0;
  59
  60#pragma clang loop unroll(full)
  61        for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
  62                ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
  63                                  tcp_mem + i);
  64                if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
  65                        return 0;
  66                off += ret & MAX_ULONG_STR_LEN;
  67        }
  68
  69
  70        return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
  71}
  72
  73char _license[] SEC("license") = "GPL";
  74