人狠话不多，直接上代码：
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local headers=ngx.req.get_headers()
        local clientIP = headers["x-forwarded-for"]
        if clientIP == nil or string.len(clientIP) == 0 or clientIP == "unknown" then
               clientIP = headers["Proxy-Client-IP"]
        end
        if clientIP == nil or string.len(clientIP) == 0 or clientIP == "unknown" then
               clientIP = headers["WL-Proxy-Client-IP"]
        end
        if clientIP == nil or string.len(clientIP) == 0 or clientIP == "unknown" then
               clientIP = ngx.var.remote_addr    
        end
        -- 对于通过多个代理的情况，第一个IP为客户端真实IP,多个IP按照','分割
        if clientIP ~= nil and string.len(clientIP) >15  then
               local pos  = string.find(clientIP, ",", 1)
               clientIP = string.sub(clientIP,1,pos-1)
        end