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Merge: - /control/dhcp/find_active_dhcp: fix DHCP server detection 

Close #704

* commit '68dc8a13411c09cd8c382a1bf986953659166506':
  * control: update "DHCP server not found" message
  * update openapi.yaml
  - /control/dhcp/find_active_dhcp: fix DHCP server detection
This commit is contained in:
Simon Zolin 2019-04-23 12:29:15 +03:00
parent 69c5f175e8 68dc8a1341
commit 173ab2a3c1
5 changed files with 132 additions and 47 deletions
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4
client/src/__locales/en.json
View File

@ -12,8 +12,8 @@
"dhcp_description": "If your router does not provide DHCP settings, you can use AdGuard's own built-in DHCP server.",
"dhcp_enable": "Enable DHCP server",
"dhcp_disable": "Disable DHCP server",
"dhcp_not_found": "No active DHCP servers found on the network. It is safe to enable the built-in DHCP server.",
"dhcp_found": "Some active DHCP servers found on the network. It is not safe to enable the built-in DHCP server.",
"dhcp_not_found": "It is safe to enable the built-in DHCP server - we didn't find any active DHCP servers on the network. However, we encourage you to re-check it manually as our automatic test currently doesn't give 100% guarantee.",
"dhcp_found": "An active DHCP server is found on the network. It is not safe to enable the built-in DHCP server.",
"dhcp_leases": "DHCP leases",
"dhcp_leases_not_found": "No DHCP leases found",
"dhcp_config_saved": "Saved DHCP server config",

87
dhcpd/check_other_dhcp.go
View File

@ -1,6 +1,7 @@
package dhcpd
import (
"bytes"
"crypto/rand"
"encoding/binary"
"fmt"
@ -11,6 +12,7 @@ import (
"github.com/AdguardTeam/golibs/log"
"github.com/krolaw/dhcp4"
"golang.org/x/net/ipv4"
)
// CheckIfOtherDHCPServersPresent sends a DHCP request to the specified network interface,
@ -32,13 +34,13 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
dst := "255.255.255.255:67"
// form a DHCP request packet, try to emulate existing client as much as possible
xID := make([]byte, 8)
xID := make([]byte, 4)
n, err := rand.Read(xID)
if n != 8 && err == nil {
err = fmt.Errorf("Generated less than 8 bytes")
if n != 4 && err == nil {
err = fmt.Errorf("Generated less than 4 bytes")
}
if err != nil {
return false, wrapErrPrint(err, "Couldn't generate 8 random bytes")
return false, wrapErrPrint(err, "Couldn't generate random bytes")
}
hostname, err := os.Hostname()
if err != nil {
@ -89,58 +91,63 @@ func CheckIfOtherDHCPServersPresent(ifaceName string) (bool, error) {
// bind to 0.0.0.0:68
log.Tracef("Listening to udp4 %+v", udpAddr)
c, err := net.ListenPacket("udp4", src)
c, err := newBroadcastPacketConn(net.IPv4(0, 0, 0, 0), 68, ifaceName)
if c != nil {
defer c.Close()
}
// spew.Dump(c, err)
// spew.Printf("net.ListenUDP returned %v, %v\n", c, err)
if err != nil {
return false, wrapErrPrint(err, "Couldn't listen to %s", src)
return false, wrapErrPrint(err, "Couldn't listen on :68")
}
// send to 255.255.255.255:67
_, err = c.WriteTo(packet, dstAddr)
cm := ipv4.ControlMessage{}
_, err = c.WriteTo(packet, &cm, dstAddr)
// spew.Dump(n, err)
if err != nil {
return false, wrapErrPrint(err, "Couldn't send a packet to %s", dst)
}
// wait for answer
log.Tracef("Waiting %v for an answer", defaultDiscoverTime)
// TODO: replicate dhclient's behaviour of retrying several times with progressively bigger timeouts
b := make([]byte, 1500)
c.SetReadDeadline(time.Now().Add(defaultDiscoverTime))
n, _, err = c.ReadFrom(b)
if isTimeout(err) {
// timed out -- no DHCP servers
return false, nil
}
if err != nil {
return false, wrapErrPrint(err, "Couldn't receive packet")
}
if n > 0 {
b = b[:n]
}
// spew.Dump(n, fromAddr, err, b)
for {
// wait for answer
log.Tracef("Waiting %v for an answer", defaultDiscoverTime)
// TODO: replicate dhclient's behaviour of retrying several times with progressively bigger timeouts
b := make([]byte, 1500)
_ = c.SetReadDeadline(time.Now().Add(defaultDiscoverTime))
n, _, _, err = c.ReadFrom(b)
if isTimeout(err) {
// timed out -- no DHCP servers
return false, nil
}
if err != nil {
return false, wrapErrPrint(err, "Couldn't receive packet")
}
// spew.Dump(n, fromAddr, err, b)
if n < 240 {
// packet too small for dhcp
return false, wrapErrPrint(err, "got packet that's too small for DHCP")
}
log.Tracef("Received packet (%v bytes)", n)
response := dhcp4.Packet(b[:n])
if response.HLen() > 16 {
// invalid size
return false, wrapErrPrint(err, "got malformed packet with HLen() > 16")
}
if n < 240 {
// packet too small for dhcp
continue
}
parsedOptions := response.ParseOptions()
_, ok := parsedOptions[dhcp4.OptionDHCPMessageType]
if !ok {
return false, wrapErrPrint(err, "got malformed packet without DHCP message type")
}
response := dhcp4.Packet(b[:n])
if response.OpCode() != dhcp4.BootReply ||
response.HType() != 1 /*Ethernet*/ ||
response.HLen() > 16 ||
!bytes.Equal(response.CHAddr(), iface.HardwareAddr) ||
!bytes.Equal(response.XId(), xID) {
continue
}
// that's a DHCP server there
return true, nil
parsedOptions := response.ParseOptions()
if t := parsedOptions[dhcp4.OptionDHCPMessageType]; len(t) != 1 {
continue //packet without DHCP message type
}
log.Tracef("The packet is from an active DHCP server")
// that's a DHCP server there
return true, nil
}
}

47
dhcpd/os_unix.go Normal file
View File

@ -0,0 +1,47 @@
// +build aix darwin dragonfly freebsd linux netbsd openbsd solaris
package dhcpd
import (
"net"
"os"
"syscall"
"golang.org/x/net/ipv4"
)
// Create a socket for receiving broadcast packets
func newBroadcastPacketConn(bindAddr net.IP, port int, ifname string) (*ipv4.PacketConn, error) {
s, err := syscall.Socket(syscall.AF_INET, syscall.SOCK_DGRAM, syscall.IPPROTO_UDP)
if err != nil {
return nil, err
}
if err := syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_BROADCAST, 1); err != nil {
return nil, err
}
if err := syscall.SetsockoptInt(s, syscall.SOL_SOCKET, syscall.SO_REUSEADDR, 1); err != nil {
return nil, err
}
if err := syscall.SetsockoptString(s, syscall.SOL_SOCKET, syscall.SO_BINDTODEVICE, ifname); err != nil {
return nil, err
}
addr := syscall.SockaddrInet4{Port: port}
copy(addr.Addr[:], bindAddr.To4())
err = syscall.Bind(s, &addr)
if err != nil {
syscall.Close(s)
return nil, err
}
f := os.NewFile(uintptr(s), "")
c, err := net.FilePacketConn(f)
f.Close()
if err != nil {
return nil, err
}
p := ipv4.NewPacketConn(c)
return p, nil
}

12
dhcpd/os_windows.go Normal file
View File

@ -0,0 +1,12 @@
package dhcpd
import (
"net"
"golang.org/x/net/ipv4"
)
// Create a socket for receiving broadcast packets
func newBroadcastPacketConn(bindAddr net.IP, port int, ifname string) (*ipv4.PacketConn, error) {
return nil, nil
}

29
openapi/openapi.yaml
View File

@ -1142,14 +1142,33 @@ definitions:
DhcpSearchResult:
type: "object"
description: "Information about a DHCP server discovered in the current network"
required:
- "found"
properties:
other_server:
$ref: "#/definitions/DhcpSearchResultOtherServer"
static_ip:
$ref: "#/definitions/DhcpSearchResultStaticIP"
DhcpSearchResultOtherServer:
type: "object"
properties:
found:
type: "boolean"
gateway_ip:
type: "string"
example: "192.168.1.1"
description: "yes|no|error"
example: "no"
error:
type: "string"
description: "Set if found=error"
example: ""
DhcpSearchResultStaticIP:
type: "object"
properties:
static:
type: "string"
description: "yes|no|error"
example: "yes"
ip:
type: "string"
description: "Set if static=no"
example: ""
DnsAnswer:
type: "object"
description: "DNS answer section"