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Fallback to server IP if PASV IP is unrouteable #53

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Fallback to server IP if PASV IP is unrouteable #53

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38 changes: 38 additions & 0 deletions persistent_connection.go
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Original file line number Diff line number Diff line change
Expand Up @@ -7,6 +7,7 @@ package goftp
import (
"bufio"
"crypto/tls"
"errors"
"fmt"
"net"
"net/textproto"
Expand Down Expand Up @@ -345,9 +346,41 @@ PASV:
port |= portOctet << (byte(1-i) * 8)
}

pconn.debug("check returned IP routable: %s", ip.String())
isRoutable, err := isRoutableIP(ip.String())
if err != nil {
pconn.debug("failed to resolve whether IP %v is routable: %s", ip.String(), err)
}
if !isRoutable {
pconn.debug("returned IP %v is not routable, use server address instead", ip.String())

remoteHost, _, err = net.SplitHostPort(pconn.controlConn.RemoteAddr().String())
if err != nil {
pconn.debug("failed determining remote host: %s", err)

} else {
return net.JoinHostPort(remoteHost, strconv.Itoa(port)), nil
}
}

return net.JoinHostPort(ip.String(), strconv.Itoa(port)), nil
}

func isRoutableIP(ip string) (bool, error) {
var err error
private := false
IP := net.ParseIP(ip)
if IP == nil {
err = errors.New("Invalid IP")
} else {
_, private24BitBlock, _ := net.ParseCIDR("10.0.0.0/8")
_, private20BitBlock, _ := net.ParseCIDR("172.16.0.0/12")
_, private16BitBlock, _ := net.ParseCIDR("192.168.0.0/16")
private = private24BitBlock.Contains(IP) || private20BitBlock.Contains(IP) || private16BitBlock.Contains(IP)
}
return !private, err
}

type dataConn struct {
net.Conn
Timeout time.Duration
Expand Down Expand Up @@ -420,6 +453,11 @@ func (pconn *persistentConn) prepareDataConn() (func() (net.Conn, error), error)
pconn.debug("upgrading data connection to TLS")
dc = tls.Client(dc, pconn.config.TLSConfig)
}
if dc == nil {
pconn.debug("data connection lost after upgrade to TLS")
} else {
pconn.debug("connection available")
}

return func() (net.Conn, error) {
pconn.dataConn = &dataConn{
Expand Down