test_partial_packets.go

package main

import (
	"math/rand"
	"net"
	"time"

	"github.com/valyala/fasthttp"
)

const charset = "abcdefghijklmnopqrstuvwxyz0123456789"

func random() string {
	b := make([]byte, rand.Intn(100))
	for i := 0; i < len(b); i++ {
		b[i] = charset[rand.Intn(len(charset))]
	}
	return string(b)
}

func main() {
	go func() {
		if err := fasthttp.ListenAndServe(":7070", func(ctx *fasthttp.RequestCtx) {
			o := string(ctx.Request.Header.Peek("OriginalIP"))
			if o != "141.226.8.217" {
				println(o)
			}
		}); err != nil {
			panic(err)
		}
	}()

	time.Sleep(time.Second)

	addr, err := net.ResolveTCPAddr("tcp", "localhost:7070")
	if err != nil {
		panic(err)
	}

	for i := 0; i < 20; i++ {
		go func() {
			conn, err := net.DialTCP("tcp4", nil, addr)
			if err != nil {
				panic(err)
			}

			// Don't buffer writes to this conn, send it immediately.
			conn.SetNoDelay(true)

			for {
				req := "GET /" + random() + " HTTP/1.1\r\nUser-Agent: Dalvik/2.1.0 (Linux; U; Android 5.1.1; AOSP on p201 Build/LMY47V)\r\nHost: example.com\r\nConnection: Keep-Alive\r\nAccept-Encoding: gzip\r\nOriginalIP: 141.226.8.217  \r\n\r\n"
				var chunks []string

				// Split the request in small chunks.
				for len(req) > 0 {
					n := rand.Intn(20)
					if l := len(req); n > l {
						n = l
					}
					chunks = append(chunks, req[:n])
					req = req[n:]
				}

				// Send each chunk in a separate TCP packet.
				for _, c := range chunks {
					if _, err := conn.Write([]byte(c)); err != nil {
						panic(err)
					}
					// With a small delay in between.
					time.Sleep(time.Duration(rand.Intn(1000)) * time.Microsecond)
				}

				// Read the response.
				b := make([]byte, 4096)
				if _, err := conn.Read(b); err != nil {
					panic(err)
				}
			}
		}()
	}

	select {}
}