docs: inputs: forward: clarify buffer_max_size payload enforcement (#2524)

- Updated `buffer_max_size` description to note that the limit
    applies to incoming payloads and decompressed data, and that
    connections sending oversized payloads are rejected and closed
    (reflects enforcement added in in_forward source commit 4ffc5b0a0)

Signed-off-by: Eric D. Schabell <eric@schabell.org>

Author: eschabell

pipeline/inputs/forward.md

@@ -9,7 +9,7 @@ The plugin supports the following configuration parameters:
 | Key                 | Description  | Default   |
 |:--------------------|:-------------|:----------|
 | `buffer_chunk_size` | By default the buffer to store the incoming Forward messages, don't allocate the maximum memory allowed, instead it allocate memory when it's required. The rounds of allocations are set by `buffer_chunk_size`. The value must be according to the [Unit Size ](../../administration/configuring-fluent-bit.md#unit-sizes)specification. | `1024000` |
-| `buffer_max_size`   | Specify the maximum buffer memory size used to receive a Forward message. The value must be according to the [Unit Size](../../administration/configuring-fluent-bit.md#unit-sizes) specification.                                                                                                                                         | `6144000` |
+| `buffer_max_size`   | Specify the maximum buffer memory size used to receive a Forward message. This limit also applies to incoming payloads and decompressed data; payloads exceeding this size are rejected and the connection is closed. The value must be according to the [Unit Size](../../administration/configuring-fluent-bit.md#unit-sizes) specification. | `6144000` |
 | `empty_shared_key`  | Enable secure forward protocol with a zero-length shared key. Use this to enable user authentication without requiring a shared key, or to connect to Fluentd with a zero-length shared key.                                                                                                                                              | `false`   |
 | `listen`            | Listener network interface.                                                                                                                                                                                                                                                                                                                | `0.0.0.0` |
 | `port`              | TCP port to listen for incoming connections.                                                                                                                                                                                                                                                                                               | `24224`   |