Apache通过LimitInternalRecursion指令防止重写死循环

# ❌ 危险配置：无条件重写导致无限循环
RewriteEngine On
RewriteRule ^(.*)$ /index.php?page=$1 [L]
# 问题：/index.php 匹配 ^(.*)$，再次重写 → 死循环

# 默认配置（Apache 2.4+）
LimitInternalRecursion 10
# 生产环境建议（根据应用复杂度调整）
LimitInternalRecursion 5
# 调试时临时增大（配合 RewriteLogLevel）
<IfDefine DEBUG>
    LimitInternalRecursion 20
</IfDefine>

<VirtualHost *:80>
    ServerName example.com
    DocumentRoot /var/www/html
    # 核心：限制内部递归深度
    LimitInternalRecursion 5
    # 辅助：限制单请求子请求数（防止间接循环）
    LimitRequestFields 50
    LimitRequestFieldSize 8190
    <Directory /var/www/html>
        RewriteEngine On
        # 关键：使用 [END] 标志（Apache 2.4+）替代 [L]
        # [L] 仅停止当前轮，[END] 完全终止重写处理
        RewriteRule ^api/(.*)$ /api/index.php?path=$1 [END]
        # 传统 [L] 需配合条件避免循环
        RewriteCond %{ENV:REDIRECT_STATUS} ^$
        RewriteRule ^(.*)$ /index.php [L]
    </RewriteCond>
    </Directory>
</VirtualHost>

<Directory /var/www/app>
    RewriteEngine On
    # 防御层1：严格递归限制
    LimitInternalRecursion 3
    # 防御层2：标记已重写请求（双重保险）
    RewriteCond %{ENV:REDIRECT_STATUS} 200
    RewriteRule ^ - [L]
    # 防御层3：排除已处理 URI 模式
    RewriteCond %{REQUEST_URI} !\.php$
    RewriteCond %{REQUEST_URI} !^/(assets|uploads)/
    RewriteRule ^(.*)$ /router.php?uri=$1 [QSA,L]
    # 错误处理：递归超限返回 500
    ErrorDocument 500 /error/loop-detected.html
</Directory>

# 反向代理场景易触发多级重写
<VirtualHost *:443>
    SSLEngine on
    # 代理场景需更大递归深度（子请求+重写）
    LimitInternalRecursion 10
    RewriteEngine On
    # 关键：排除代理目标路径，防止回环
    RewriteCond %{REQUEST_URI} !^/proxy-backend/
    RewriteRule ^/api/(.*)$ /proxy-backend/api/$1 [P,L]
    ProxyPass /proxy-backend/ http://localhost:8080/
    ProxyPassReverse /proxy-backend/ http://localhost:8080/
    # 代理错误时停止递归
    RewriteCond %{HTTP:Upgrade} websocket [NC]
    RewriteRule ^/ws/(.*)$ ws://localhost:8081/$1 [P,L]
</VirtualHost>

# 开发/调试环境启用详细重写日志
<IfDefine DEBUG_REWRITE>
    LogLevel rewrite:trace8
    # 自定义日志格式包含递归深度
    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{REDIRECT_STATUS}e\" %{rewrite_uri}n" rewrite_log
    CustomLog logs/rewrite.log rewrite_log
</IfDefine>

# 错误日志中的循环迹象
[rewrite:trace4] ... (1) init rewrite engine
[rewrite:trace4] ... (1) applying pattern '^/(.*)$' to uri 'index.php'
[rewrite:trace4] ... (2) init rewrite engine  <-- 数字递增表示递归
[rewrite:trace4] ... (2) applying pattern '^/(.*)$' to uri 'index.php'
...
[rewrite:trace1] ... (11) init rewrite engine  <-- 超过 LimitInternalRecursion
[core:error] ... Request exceeded the limit of 10 internal redirects 
              due to probable configuration error. Use 'LimitInternalRecursion' 
              to increase the limit if necessary.

# Laravel / Symfony / 类似 MVC 框架
<Directory /var/www/laravel/public>
    RewriteEngine On
    # 严格递归限制（框架路由已处理多级逻辑）
    LimitInternalRecursion 2
    # 发送所有请求到 index.php（单次重写）
    RewriteCond %{HTTP:Authorization} .
    RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteRule ^ index.php [END]  # [END] 完全终止，比 [L] 更安全
</Directory>
# WordPress 典型配置
<Directory /var/www/wordpress>
    RewriteEngine On
    LimitInternalRecursion 3
    RewriteBase /
    RewriteRule ^index\.php$ - [L]
    RewriteCond %{REQUEST_FILENAME} !-f
    RewriteCond %{REQUEST_FILENAME} !-d
    RewriteRule . /index.php [L]
</Directory>