root/tools/testing/selftests/bpf/progs/test_sysctl_loop1.c

DEFINITIONS

1. is_tcp_mem
2. SEC

   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_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 
  21 static __always_inline int is_tcp_mem(struct bpf_sysctl *ctx)
  22 {
  23         volatile char tcp_mem_name[] = "net/ipv4/tcp_mem/very_very_very_very_long_pointless_string";
  24         unsigned char i;
  25         char name[64];
  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 
  41 SEC("cgroup/sysctl")
  42 int 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 
  74 char _license[] SEC("license") = "GPL";