dnsseeder/crawler.go

package main

import (
	"errors"
	"log"
	"net"
	"strconv"
	"time"

	"github.com/btcsuite/btcd/wire"
)

type crawlError struct {
	errLoc string
	Err    error
}

// Error returns a formatted error about a crawl
func (e *crawlError) Error() string {
	return "err: " + e.errLoc + ": " + e.Err.Error()
}

// crawlNode runs in a goroutine, crawls the remote ip and updates the master
// list of currently active addresses
func crawlNode(s *dnsseeder, nd *node) {

	nd.crawlActive = true
	nd.crawlStart = time.Now()

	defer crawlEnd(nd)

	if config.debug {
		log.Printf("%s - debug - start crawl: node %s status: %v:%v lastcrawl: %s\n",
			s.name,
			net.JoinHostPort(nd.na.IP.String(),
				strconv.Itoa(int(nd.na.Port))),
			nd.status,
			nd.rating,
			time.Since(nd.crawlStart).String())
	}

	// connect to the remote ip and ask them for their addr list
	rna, e := s.crawlIP(nd)

	if e != nil {
		// update the fact that we have not connected to this node
		nd.lastTry = time.Now()
		nd.connectFails++
		nd.statusStr = e.Error()

		// update the status of this failed node
		switch nd.status {
		case statusRG:
			// if we are full then any RG failures will skip directly to NG
			if s.isFull() {
				nd.status = statusNG // not able to connect to this node so ignore
				nd.statusTime = time.Now()
			} else {
				if nd.rating += 25; nd.rating > 30 {
					nd.status = statusWG
					nd.statusTime = time.Now()
				}
			}
		case statusCG:
			if nd.rating += 25; nd.rating >= 50 {
				nd.status = statusWG
				nd.statusTime = time.Now()
			}
		case statusWG:
			if nd.rating += 15; nd.rating >= 100 {
				nd.status = statusNG // not able to connect to this node so ignore
				nd.statusTime = time.Now()
			}
		}
		// no more to do so return which will shutdown the goroutine & call
		// the deffered cleanup
		if config.verbose {
			log.Printf("%s: failed crawl node: %s s:r:f: %v:%v:%v %s\n",
				s.name,
				net.JoinHostPort(nd.na.IP.String(),
					strconv.Itoa(int(nd.na.Port))),
				nd.status,
				nd.rating,
				nd.connectFails,
				nd.statusStr)
		}
		return
	}

	// succesful connection and addresses received so mark status
	if nd.status != statusCG {
		nd.status = statusCG
		nd.statusTime = time.Now()
	}
	cs := nd.lastConnect
	nd.rating = 0
	nd.connectFails = 0
	nd.lastConnect = time.Now()
	nd.lastTry = time.Now()
	nd.statusStr = "ok: received remote address list"

	added := 0
	// do not accept more than one third of maxSize addresses from one node
	oneThird := int(float64(s.maxSize / 3))

	// if we are full then skip adding more possible clients
	if s.isFull() == false {
		// loop through all the received network addresses and add to thelist if not present
		for _, na := range rna {
			// a new network address so add to the system
			if x := s.addNa(na); x == true {
				if added++; added > oneThird {
					break
				}
			}
		}
	}

	if config.verbose {
		log.Printf("%s: crawl done: node: %s s:r:f: %v:%v:%v addr: %v:%v CrawlTime: %s Last connect: %v ago\n",
			s.name,
			net.JoinHostPort(nd.na.IP.String(),
				strconv.Itoa(int(nd.na.Port))),
			nd.status,
			nd.rating,
			nd.connectFails,
			len(rna),
			added,
			time.Since(nd.crawlStart).String(),
			time.Since(cs).String())
	}

	// goroutine ends. deffered cleanup runs
}

// crawlEnd is a deffered func to update theList after a crawl is all done
func crawlEnd(nd *node) {
	nd.crawlActive = false
}

// crawlIP retrievs a slice of ip addresses from a client
func (s *dnsseeder) crawlIP(nd *node) ([]*wire.NetAddress, *crawlError) {

	ip := nd.na.IP.String()
	port := strconv.Itoa(int(nd.na.Port))
	// get correct formatting for ipv6 addresses
	dialString := net.JoinHostPort(ip, port)

	conn, err := net.DialTimeout("tcp", dialString, time.Second*10)
	if err != nil {
		if config.debug {
			log.Printf("%s - debug - Could not connect to %s - %v\n", s.name, ip, err)
		}
		return nil, &crawlError{"", err}
	}

	defer conn.Close()
	if config.debug {
		log.Printf("%s - debug - Connected to remote address: %s Last connect was %v ago\n", s.name, ip, time.Since(nd.lastConnect).String())
	}

	// set a deadline for all comms to be done by. After this all i/o will error
	conn.SetDeadline(time.Now().Add(time.Second * maxTo))

	// First command to remote end needs to be a version command
	// last parameter is lastblock
	msgver, err := wire.NewMsgVersionFromConn(conn, nounce, 0)
	if err != nil {
		return nil, &crawlError{"Create NewMsgVersionFromConn", err}
	}

	err = wire.WriteMessage(conn, msgver, s.pver, s.id)
	if err != nil {
		// Log and handle the error
		return nil, &crawlError{"Write Version Message", err}
	}

	// first message received should be version
	msg, _, err := wire.ReadMessage(conn, s.pver, s.id)
	if err != nil {
		// Log and handle the error
		return nil, &crawlError{"Read message after sending Version", err}
	}

	switch msg := msg.(type) {
	case *wire.MsgVersion:
		// The message is a pointer to a MsgVersion struct.
		if config.debug {
			log.Printf("%s - debug - %s - Remote version: %v\n", s.name, ip, msg.ProtocolVersion)
		}
		// fill the node struct with the remote details
		nd.version = msg.ProtocolVersion
		nd.services = msg.Services
		nd.lastBlock = msg.LastBlock
		if nd.strVersion != msg.UserAgent {
			// if the srtVersion is already the same then don't overwrite it.
			// saves the GC having to cleanup a perfectly good string
			nd.strVersion = msg.UserAgent
		}
	default:
		return nil, &crawlError{"Did not receive expected Version message from remote client", errors.New("")}
	}

	// send verack command
	msgverack := wire.NewMsgVerAck()

	err = wire.WriteMessage(conn, msgverack, s.pver, s.id)
	if err != nil {
		return nil, &crawlError{"writing message VerAck", err}
	}

	// second message received should be verack
	msg, _, err = wire.ReadMessage(conn, s.pver, s.id)
	if err != nil {
		return nil, &crawlError{"reading expected Ver Ack from remote client", err}
	}

	switch msg.(type) {
	case *wire.MsgVerAck:
		if config.debug {
			log.Printf("%s - debug - %s - received Version Ack\n", s.name, ip)
		}
	default:
		return nil, &crawlError{"Did not receive expected Ver Ack message from remote client", errors.New("")}
	}

	// if we get this far and if the seeder is full then don't ask for addresses. This will reduce bandwith usage while still
	// confirming that we can connect to the remote node
	if s.isFull() {
		return nil, nil
	}
	// send getaddr command
	msgGetAddr := wire.NewMsgGetAddr()

	err = wire.WriteMessage(conn, msgGetAddr, s.pver, s.id)
	if err != nil {
		return nil, &crawlError{"writing Addr message to remote client", err}
	}

	c := 0
	dowhile := true
	for dowhile == true {

		// Using the Bitcoin lib for the some networks means it does not understand some
		// of the commands and will error. We can ignore these as we are only
		// interested in the addr message and its content.
		msgaddr, _, _ := wire.ReadMessage(conn, s.pver, s.id)
		if msgaddr != nil {
			switch msg := msgaddr.(type) {
			case *wire.MsgAddr:
				// received the addr message so return the result
				if config.debug {
					log.Printf("%s - debug - %s - received valid addr message\n", s.name, ip)
				}
				dowhile = false
				return msg.AddrList, nil
			default:
				if config.debug {
					log.Printf("%s - debug - %s - ignoring message - %v\n", s.name, ip, msg.Command())
				}
			}
		}
		// if we get more than 25 messages before the addr we asked for then give up on this client
		if c++; c >= 25 {
			dowhile = false
		}
	}

	// received too many messages before requested Addr
	return nil, &crawlError{"message loop - did not receive remote addresses in first 25 messages from remote client", errors.New("")}
}

/*

 */