[#dict#epoll] #epoll #python #dict#namespace #docker

epoll模块的使用.md

import select
import socket

if __name__ == "__main__":
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM, 0)
    s.setblocking(False)
    s.setsockopt(socket.SOL_SOCKET, socket.SO_REUSEADDR, 1)

    s.bind(('', 4000))
    s.listen(64)
    ep = select.epoll()
    ep.register(s.fileno(), select.EPOLLIN)
    connections = {}

    while True:
        events = ep.poll(1)
        for fd, event in events:
            if fd == s.fileno() and event == select.EPOLLIN:
                conn, addr = s.accept()
                print "connection ", conn, "is connected"
                conn.setblocking(False)
                ep.register(conn.fileno(), select.EPOLLIN)
                connections[conn.fileno()] = conn
                continue
            if event == select.EPOLLIN:
                assert connections.get(fd) != None
                c = connections.get(fd)
                # recevie 1 byte from the tcp connection on purpose
                # it's to validate the idea of lt mode reading
                msg = c.recv(1)
                print msg

数据结构.md

如何创建一个字典和给字典赋值

创建一个字典，和给字典赋值都是比较简单的，按照下面，即可创建。

>>> dict1 = {}
>>> dict2 = {'name': 'earth','port': 80}

当然，我们也可以使用工厂方法来创建

>>> fdict = dict((['x',1],['y',2]))
>>>  fdict
{'y':2,'x':1}
>>> fdict = dict(name= "hello",sex ="male")
{"name":"hello","sex":"male"}

访问字典中的值

要遍历一个字典，使用in操作，然后通过字典键加上括号来访问其值

>>> dict2 = {'name': 'earth','port': 80}
>>> for key in dict2
>>>       print 'key= %s,value = %s' %(key,dict2[key])

如果访问一个不存在的键将会报错。

如何更新字典

可以有几种方式对一个字典做修改：添加一个数据项或者是新元素，修改一个已经存在的数据项，删除一个已经存在的数据项。

>>>dict2['name'] = 'venus'
>>>dict2['port'] = 6969

如果字典中该键已经存在，则字典中该键对应的值将被新值替代.

删除字典某元素和字典

通常删除整个字典的操作是不常见的，下面记录了删除的代码：

del dict2['name']#删除name的条目
dict2.clear()  #删除整个条目

字典方法文档搜索

在python字典中输入：dict.xxx。

字典方法

构造字典对象

字典构造

字典方法

• len(dict)获取字典项目
• clear() 清除所有的项
• copy() 浅拷贝复制
• fromkeys(seq,[,value]) 创建一个新的字典，键来自seq，值设置为value。
• get(key[,default])获取某个键的值，如果没有该键，默认返回None，当然你可以改变默认值
• items()将所有的字典项以列表的方式返回，其中每一项都是来自于键和值。（这个键和值共同组成元祖）但在返回的时候， 没有特殊顺序。
• iteritems()的作用相同，但是返回的是迭代器对象而不是列表。
• keys() 将字典中的键以列表的方式返回。
• pop(key[,default]) 如果键值存在，那么直接删除该键-值对，并且返回其值，如果default没有给，并且键不存在，那么会产生KeyError

设置key字典的pattern

my_dict.setdefault(key, []).append(new_value)

# 等价于
if key not in my_dict:
    my_dict[key] = []
my_dict[key].append(new_value)

string

def remove_prefix(text, prefix):
    if text.startswith(prefix):
        return text[len(prefix):]
    return text

系统工具简单脚本

• 来源

tcpdump or iptables or new net namespace

#  -*-coding:utf8 -*-
import atexit
import ctypes
import io
import os
import shlex
import signal
import socket
import subprocess
import sys
import tcp_info
import time


LIBC = ctypes.CDLL("libc.so.6")

CLONE_NEWNET = 0x40000000
original_net_ns = open("/proc/self/ns/net", 'rb')
if True:
    r = LIBC.unshare(CLONE_NEWNET)
    if r != 0:
        print("[!] Are you root? Need unshare() syscall.")
        sys.exit(-1)
    LIBC.setns(original_net_ns.fileno(), CLONE_NEWNET)

def new_ns():
    # 在一个新的名字中运行程序
    r = LIBC.unshare(CLONE_NEWNET)
    if r != 0:
        print("[!] Are you root? Need unshare() syscall.")
        sys.exit(-1)
    # Execute the command (a string) in a subshell.
    os.system("ip link set lo up")

def restore_ns():
    LIBC.setns(original_net_ns.fileno(), CLONE_NEWNET)


def do_iptables(action, sport, dport, extra):
    if sport:
        sport = '--sport %d' % (sport,)
        dport = ''
    else:
        sport = ''
        dport = '--dport %d' % (dport,)
    # 使用ip table
    os.system("iptables -%s INPUT -i lo -p tcp %s %s %s -j DROP" % (action, sport, dport, extra))

def drop_start(sport=None, dport=None, extra=''):
    do_iptables('I', sport, dport, extra)

def drop_stop(sport=None, dport=None, extra=''):
    do_iptables('D', sport, dport, extra)

# 执行一个shell的命令
tcpdump_bin = os.popen('which tcpdump').read().strip()
# 执行一个shell命令
ss_bin = os.popen('which ss').read().strip()

def tcpdump_start(port):
    # --packet-buffered 打印可打印字符
    # -n 不要主机地址转换成名字
    # Print a delta (micro-second resolution) between current and first line on each dump line
    p = subprocess.Popen(shlex.split('%s -B 16384 --packet-buffered -n -ttttt -i lo port %s' % (tcpdump_bin, port)))
    time.sleep(1)
    # 注册关掉回调
    def close():
        p.send_signal(signal.SIGINT)
        p.wait()
    p.close = close
    atexit.register(close)
    # 创建一个子进程
    return p

def ss(port):
    print(os.popen('%s -t -n -o -a dport = :%s or sport = :%s' % (ss_bin, port, port)).read())

def check_buffer(c):
    ti = tcp_info.from_socket(c)
    print("delivered, acked", ti.tcpi_bytes_acked-1)
    print("in-flight:", ti.tcpi_bytes_sent - ti.tcpi_bytes_retrans- ti.tcpi_bytes_acked+1)
    print("in queue, not in flight:", ti.tcpi_notsent_bytes)

def socket_info(c):
    ti = tcp_info.from_socket(c)
    acked = ti.tcpi_bytes_acked-1
    in_flight = ti.tcpi_bytes_sent - ti.tcpi_bytes_retrans- ti.tcpi_bytes_acked+1
    notsent = ti.tcpi_notsent_bytes
    return acked, in_flight, notsent

使用epoll的方式

这里需要hack的方式，将net库中epoll暴露出来

var epoller *epoll
func main() {
	setLimit()
	ln, err := net.Listen("tcp", ":8972")
	if err != nil {
		panic(err)
	}
	go func() {
		if err := http.ListenAndServe(":6060", nil); err != nil {
			log.Fatalf("pprof failed: %v", err)
		}
	}()
	epoller, err = MkEpoll()
	if err != nil {
		panic(err)
	}
	go start()
	for {
		conn, e := ln.Accept()
		if e != nil {
			if ne, ok := e.(net.Error); ok && ne.Temporary() {
				log.Printf("accept temp err: %v", ne)
				continue
			}
			log.Printf("accept err: %v", e)
			return
		}
		if err := epoller.Add(conn); err != nil {
			log.Printf("failed to add connection %v", err)
			conn.Close()
		}
	}
}
func start() {
	var buf = make([]byte, 8)
	for {
		connections, err := epoller.Wait()
		if err != nil {
			log.Printf("failed to epoll wait %v", err)
			continue
		}
		for _, conn := range connections {
			if conn == nil {
				break
			}
			if _, err := conn.Read(buf); err != nil {
				if err := epoller.Remove(conn); err != nil {
					log.Printf("failed to remove %v", err)
				}
				conn.Close()
			}
		}
	}
}

epoll的抽象

type epoll struct {
	fd          int
	connections map[int]net.Conn
	lock        *sync.RWMutex
}
func MkEpoll() (*epoll, error) {
	fd, err := unix.EpollCreate1(0)
	if err != nil {
		return nil, err
	}
	return &epoll{
		fd:          fd,
		lock:        &sync.RWMutex{},
		connections: make(map[int]net.Conn),
	}, nil
}
func (e *epoll) Add(conn net.Conn) error {
	// Extract file descriptor associated with the connection
	fd := socketFD(conn)
	err := unix.EpollCtl(e.fd, syscall.EPOLL_CTL_ADD, fd, &unix.EpollEvent{Events: unix.POLLIN | unix.POLLHUP, Fd: int32(fd)})
	if err != nil {
		return err
	}
	e.lock.Lock()
	defer e.lock.Unlock()
	e.connections[fd] = conn
	if len(e.connections)%100 == 0 {
		log.Printf("total number of connections: %v", len(e.connections))
	}
	return nil
}
func (e *epoll) Remove(conn net.Conn) error {
	fd := socketFD(conn)
	err := unix.EpollCtl(e.fd, syscall.EPOLL_CTL_DEL, fd, nil)
	if err != nil {
		return err
	}
	e.lock.Lock()
	defer e.lock.Unlock()
	delete(e.connections, fd)
	if len(e.connections)%100 == 0 {
		log.Printf("total number of connections: %v", len(e.connections))
	}
	return nil
}
func (e *epoll) Wait() ([]net.Conn, error) {
	events := make([]unix.EpollEvent, 100)
	n, err := unix.EpollWait(e.fd, events, 100)
	if err != nil {
		return nil, err
	}
	e.lock.RLock()
	defer e.lock.RUnlock()
	var connections []net.Conn
	for i := 0; i < n; i++ {
		conn := e.connections[int(events[i].Fd)]
		connections = append(connections, conn)
	}
	return connections, nil
}
func socketFD(conn net.Conn) int {
	//tls := reflect.TypeOf(conn.UnderlyingConn()) == reflect.TypeOf(&tls.Conn{})
	// Extract the file descriptor associated with the connection
	//connVal := reflect.Indirect(reflect.ValueOf(conn)).FieldByName("conn").Elem()
	tcpConn := reflect.Indirect(reflect.ValueOf(conn)).FieldByName("conn")
	//if tls {
	//	tcpConn = reflect.Indirect(tcpConn.Elem())
	//}
	fdVal := tcpConn.FieldByName("fd")
	pfdVal := reflect.Indirect(fdVal).FieldByName("pfd")
	return int(pfdVal.FieldByName("Sysfd").Int())
}

可以看到建立连接后大约占了10G的内存，CPU占用非常小。

• 封装好的库： https://github.com/tidwall/evio

Raw socket

• 使用BPF, 将Go网络程序的吞吐提升8倍

这里我们使用gopacket对各种协议层的包的定义，方便解析(或创建)TCP/IP各层的网络协议。

package main
import (
	"flag"
	"log"
	"net"
	"github.com/google/gopacket"
	"github.com/google/gopacket/layers"
	"github.com/smallnest/go-network-programming/codec"
	"golang.org/x/net/bpf"
	"golang.org/x/net/ipv4"
)
var (
	addr = flag.String("s", "localhost", "server address")
	port = flag.Int("p", 8972, "port")
)
var (
	stat         = make(map[string]int)
	lastStatTime = int64(0)
)
func main() {
	flag.Parse()
	conn, err := net.ListenPacket("ip4:udp", *addr)
	if err != nil {
		panic(err)
	}
	cc := conn.(*net.IPConn)
	cc.SetReadBuffer(20 * 1024 * 1024)
	cc.SetWriteBuffer(20 * 1024 * 1024)
	handleConn(conn)
}
func handleConn(conn net.PacketConn) {
	for {
		buffer := make([]byte, 1024)
		n, remoteaddr, err := conn.ReadFrom(buffer)
		if err != nil {
			log.Fatal(err)
		}
		buffer = buffer[:n]
		packet := gopacket.NewPacket(buffer, layers.LayerTypeUDP, gopacket.NoCopy)
		// Get the UDP layer from this packet
		if udpLayer := packet.Layer(layers.LayerTypeUDP); udpLayer != nil {
			udp, _ := udpLayer.(*layers.UDP)
			if app := packet.ApplicationLayer(); app != nil {
				data, err := codec.EncodeUDPPacket(net.ParseIP("127.0.0.1"), net.ParseIP("127.0.0.1"), uint16(udp.DstPort), uint16(udp.SrcPort), app.Payload())
				if err != nil {
					log.Printf("failed to EncodePacket: %v", err)
					return
				}
				if _, err := conn.WriteTo(data, remoteaddr); err != nil {
					log.Printf("failed to write packet: %v", err)
					conn.Close()
					return
				}
			}
		}
	}
}