使用.net C#的SNMP项目发生封送错误

本文关键字：错误 项目 net SNMP 使用 | 更新日期: 2023-09-27 18:29:38

我必须构建一个SNMP项目来与各种设备通信。遗憾的是，除了用于SNMP的windows dll（mgmtapi.dll，snmpapi.dll，wsnmp32.dll）之外，我不能使用任何库。我已经为这些库和这些库的功能所需的所有结构制作了包装器，但在循环之后：

  • SnmpMgrOpen（初始化并获取会话）
  • SnmpVarBindList创建（使用SnmpMgrStrToOid、SnmpUtilMemAlloc和其他编组）以创建GET请求
  • SnmpMgrRequest以发出请求并填充SnmpVarBindList结构
  • SnmpMgrClose关闭会话

当我想使用查看SnmpVarBindList中的SnmpVarBinding内部的内容时

Marshal.PtrToStringAnsi(varBind.value.asnValue.text.stream, (int)varBind.value.asnValue.text.length + 1)

我收到错误：试图读取或写入受保护的内存。这通常表示其他内存已损坏。

从snmp.h头转换而来的结构是：

[StructLayout(LayoutKind.Sequential)]
public struct AsnOctetString
{
    public uint length;
    public int dynamic;
    public IntPtr stream;
}
[StructLayout(LayoutKind.Sequential)]
public struct AsnObjectIdentifier
{
    public uint idLength;
    public IntPtr ids;
}
[StructLayout(LayoutKind.Explicit)]
public struct AsnUnion
{
    [FieldOffset(0)]
    public int number;
    [FieldOffset(0)]
    public uint unsigned32;
    [FieldOffset(0)]
    public ulong counter64;
    [FieldOffset(0)]
    public AsnOctetString text;
    [FieldOffset(0)]
    public AsnOctetString bits;
    [FieldOffset(0)]
    public AsnObjectIdentifier objectID;
    [FieldOffset(0)]
    public AsnOctetString sequence;
    [FieldOffset(0)]
    public AsnOctetString address;
    [FieldOffset(0)]
    public uint counter;
    [FieldOffset(0)]
    public uint gauge;
    [FieldOffset(0)]
    public uint ticks;
    [FieldOffset(0)]
    public AsnOctetString arbitrary;
}
[StructLayout(LayoutKind.Sequential)]
public struct AsnAny
{
    public byte asnType;
    public AsnUnion asnValue;
}
[StructLayout(LayoutKind.Sequential)]
public struct SnmpVarBind
{
    public AsnObjectIdentifier name;
    public AsnAny value;
}
[StructLayout(LayoutKind.Sequential)]
public struct SnmpVarBindList
{
    public IntPtr list;
    public uint len;
}

有什么想法吗？我可以输入你想要/需要的代码。

使用.net C#的SNMP项目发生封送错误

我知道这个答案已经很晚了，但我最近遇到了SNMP API的封送处理问题。我曾假设这些结构是在字节边界上封装的，但这是错误的。如果您查看Snmp.h，您将看到#include <pshpack4.h>，它打开了4字节边界上的打包。这意味着场偏移不同。这就是我的AsnAny的样子：

[StructLayout(LayoutKind.Explicit)]
    private struct AsnAny
    {
        [FieldOffset(0)]
        public readonly byte Type;
        [FieldOffset(4)]
        public readonly Int32 Number;
        [FieldOffset(4)]
        public readonly UInt32 Unsigned32;
        [FieldOffset(4)]
        public readonly UInt64 Counter64;
        [FieldOffset(4)]
        public readonly AsnOctetString String;
        [FieldOffset(4)]
        public readonly AsnOctetString Bits;
        [FieldOffset(4)]
        public readonly AsnObjectIdentifier Object;
        [FieldOffset(4)]
        public readonly AsnOctetString Sequence;
        [FieldOffset(4)]
        public readonly AsnOctetString IPAddress;
        [FieldOffset(4)]
        public readonly UInt32 Counter32;
        [FieldOffset(4)]
        public readonly UInt32 Gauge32;
        [FieldOffset(4)]
        public readonly UInt32 Ticks;
        [FieldOffset(4)]
        public readonly AsnOctetString Arbitrary;
    }
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