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#ifndef ARRAY_SIZE
  13#define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
  14#endif
  15
  16/* tcp_mem sysctl has only 3 ints, but this test is doing TCP_MEM_LOOPS */
  17#define TCP_MEM_LOOPS 28  /* because 30 doesn't fit into 512 bytes of stack */
  18#define MAX_ULONG_STR_LEN 7
  19#define MAX_VALUE_STR_LEN (TCP_MEM_LOOPS * MAX_ULONG_STR_LEN)
  20
  21const char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";
  22static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
  23{
  24        unsigned char i;
  25        char name[sizeof(tcp_mem_name)];
  26        int ret;
  27
  28        memset(name, 0, sizeof(name));
  29        ret = bpf_sysctl_get_name(ctx, name, sizeof(name), 0);
  30        if (ret < 0 || ret != sizeof(tcp_mem_name) - 1)
  31                return 0;
  32
  33#pragma clang loop unroll(disable)
  34        for (i = 0; i < sizeof(tcp_mem_name); ++i)
  35                if (name[i] != tcp_mem_name[i])
  36                        return 0;
  37
  38        return 1;
  39}
  40
  41SEC("cgroup/sysctl")
  42int sysctl_tcp_mem(struct bpf_sysctl *ctx)
  43{
  44        unsigned long tcp_mem[TCP_MEM_LOOPS] = {};
  45        char value[MAX_VALUE_STR_LEN];
  46        unsigned char i, off = 0;
  47        /* a workaround to prevent compiler from generating
  48         * codes verifier cannot handle yet.
  49         */
  50        volatile int ret;
  51
  52        if (ctx->write)
  53                return 0;
  54
  55        if (!is_tcp_mem(ctx))
  56                return 0;
  57
  58        ret = bpf_sysctl_get_current_value(ctx, value, MAX_VALUE_STR_LEN);
  59        if (ret < 0 || ret >= MAX_VALUE_STR_LEN)
  60                return 0;
  61
  62#pragma clang loop unroll(disable)
  63        for (i = 0; i < ARRAY_SIZE(tcp_mem); ++i) {
  64                ret = bpf_strtoul(value + off, MAX_ULONG_STR_LEN, 0,
  65                                  tcp_mem + i);
  66                if (ret <= 0 || ret > MAX_ULONG_STR_LEN)
  67                        return 0;
  68                off += ret & MAX_ULONG_STR_LEN;
  69        }
  70
  71        return tcp_mem[0] < tcp_mem[1] && tcp_mem[1] < tcp_mem[2];
  72}
  73
  74char _license[] SEC("license") = "GPL";
  75