> For the complete documentation index, see [llms.txt](https://book.bsdcn.org/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://book.bsdcn.org/man/man4/ng_deflate.4.md).

# ng\_deflate.4

`ng_deflate` — Deflate PPP 压缩（RFC 1979）netgraph 节点类型

## 名称

`ng_deflate`

## 概要

`#include <sys/types.h>`

`#include <netgraph/ng_deflate.h>`

## 描述

`deflate` 节点类型实现了压缩控制协议（CCP）的 Deflate 子协议。

节点有两个钩子：用于压缩的 `comp` 和用于解压缩的 `decomp`。同一时间只能连接其中一个，指定节点的操作模式。通常这些钩子会连接到 [ng\_ppp(4)](/man/man4/ng_ppp.4.md) 节点类型的同名钩子。相应的 [ng\_ppp(4)](/man/man4/ng_ppp.4.md) 节点钩子必须切换到 `NG_PPP_DECOMPRESS_FULL` 模式以允许发送未压缩帧。

## 钩子

此节点类型支持以下钩子：

**`comp`** 连接到 [ng\_ppp(4)](/man/man4/ng_ppp.4.md) `comp` 钩子。传入帧（如果可能）被压缩并从同一钩子发回。 **`decomp`** 连接到 [ng\_ppp(4)](/man/man4/ng_ppp.4.md) `decomp` 钩子。传入帧（如果已压缩）被解压缩并从同一钩子发回。

同一时间只能连接一个钩子，指定节点的操作模式。

## 控制消息

此节点类型支持通用控制消息，外加以下消息：

```sh
struct ng_deflate_config {
	u_char	enable;			/* 节点已启用 */
	u_char	windowBits;		/* log2(窗口大小) */
};
```

```sh
struct ng_deflate_stats {
	uint64_t	FramesPlain;
	uint64_t	FramesComp;
	uint64_t	FramesUncomp;
	uint64_t	InOctets;
	uint64_t	OutOctets;
	uint64_t	Errors;
};
```

**`NGM_DEFLATE_CONFIG`** (`config`) 此命令重置并为会话（即压缩或解压缩）配置节点。此命令以 `struct ng_deflate_config` 为参数：`enabled` 字段启用通过节点的流量。`windowBits` 指定由 PPP 中压缩控制协议（CCP）协商的压缩窗口大小。

**`NGM_DEFLATE_RESETREQ`** (`resetreq`) 此消息不含参数，且是双向的。如果在解压缩期间检测到错误，此消息由节点发送给发起该会话的 `NGM_DEFLATE_CONFIG` 消息的发起者。接收者应通过向对等方发送 PPP CCP Reset-Request 来响应。当本地 PPP 实体收到 CCP Reset-Request 或 Reset-Ack 时，此消息也可能被此节点类型接收。节点将通过刷新其压缩状态来响应，以便双方可以重新同步。

**`NGM_DEFLATE_GET_STATS`** (`getstats`) 此控制消息获取给定钩子的统计信息。统计信息以 `struct ng_deflate_stats` 返回：

**`NGM_DEFLATE_CLR_STATS`** (`clrstats`) 此控制消息清除给定钩子的统计信息。

**`NGM_DEFLATE_GETCLR_STATS`** (`getclrstats`) 此控制消息获取并清除给定钩子的统计信息。

## 关闭

此节点在收到 `NGM_SHUTDOWN` 控制消息时，或当钩子已断开时关闭。

## 参见

[netgraph(4)](/man/man4/netgraph.4.md), [ng\_ppp(4)](/man/man4/ng_ppp.4.md), ngctl(8)

> J. Woods, "PPP Deflate Protocol", RFC 1979.

> W. Simpson, "The Point-to-Point Protocol (PPP)", RFC 1661.

## 作者

Alexander Motin <mav@alkar.net>

## 缺陷

由于 netgraph PPP 实现的性质，在数据包丢失的情况下，数据包与 ResetAck CCP 数据包之间可能存在竞态条件。结果，数据包丢失可能产生比协议预期的更大的性能下降。


---

# Agent Instructions
This documentation is published with GitBook. GitBook is the documentation platform designed so that both humans and AI agents can read, navigate, and reason over technical content effectively. Learn more at gitbook.com.

## Querying This Documentation
If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter, and the optional `goal` query parameter:

```
GET https://book.bsdcn.org/man/man4/ng_deflate.4.md?ask=<question>&goal=<endgoal>
```

`ask` is the immediate question: it should be specific, self-contained, and written in natural language.
`goal` is optional and describes the broader end goal you are ultimately trying to accomplish on behalf of the user. GitBook uses it to tailor the answer towards what is most useful for that goal.

The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.