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Change unicast connection of dhcpv4 client as a raw socket
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If the network manager in the operating system uses DHCP to obtain an IP
for the network card, it will occupy the DHCP client port. In this case
the release function will fail because the unicast connection with UDP
socket need the same port. Use a raw udp socket instead of a datagram
udp socket to solve it.

Signed-off-by: yaocw2020 <[email protected]>
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@yaocw2020
yaocw2020 committed Jan 23, 2022
1 parent 3c283ff commit 2386756
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Showing 4 changed files with 117 additions and 13 deletions.
12 changes: 3 additions & 9 deletions dhcpv4/nclient4/client.go
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Original file line number Diff line number Diff line change
Expand Up @@ -214,7 +214,7 @@ func new(iface string, conn net.PacketConn, ifaceHWAddr net.HardwareAddr, opts .
if iface == `` {
return nil, ErrNoConn
}
c.conn, err = NewRawUDPConn(iface, ClientPort) // broadcast
c.conn, err = NewRawUDPConn(iface, &net.UDPAddr{Port: ClientPort}, UDPBroadcast) // broadcast
if err != nil {
return nil, fmt.Errorf("unable to open a broadcasting socket: %w", err)
}
Expand Down Expand Up @@ -349,15 +349,9 @@ func WithLogger(newLogger Logger) ClientOpt {
// srcAddr is both:
// * The source address of outgoing frames.
// * The address to be listened for incoming frames.
func WithUnicast(srcAddr *net.UDPAddr) ClientOpt {
func WithUnicast(iface string, srcAddr *net.UDPAddr) ClientOpt {
return func(c *Client) (err error) {
if srcAddr == nil {
srcAddr = &net.UDPAddr{Port: ClientPort}
}
c.conn, err = net.ListenUDP("udp4", srcAddr)
if err != nil {
err = fmt.Errorf("unable to start listening UDP port: %w", err)
}
c.conn, err = NewRawUDPConn(iface, srcAddr, UDPUnicast)
return
}
}
Expand Down
106 changes: 102 additions & 4 deletions dhcpv4/nclient4/conn_unix.go
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Original file line number Diff line number Diff line change
Expand Up @@ -10,12 +10,29 @@ package nclient4

import (
"errors"
"fmt"
"io"
"net"

"github.com/mdlayher/arp"
"github.com/mdlayher/ethernet"
"github.com/mdlayher/raw"
"github.com/u-root/uio/uio"
"github.com/vishvananda/netlink"
)

// UDPConnType indicates the type of the udp conn.
type UDPConnType int

const (
// UDPBroadcast specifies the type of udp conn as broadcast.
//
// All the packets will be broadcasted.
UDPBroadcast UDPConnType = 0

// UDPUnicast specifies the type of udp conn as unicast.
// All the packets will be sent to a unicast MAC address.
UDPUnicast UDPConnType = 1
)

var (
Expand All @@ -28,13 +45,16 @@ var (
var (
// ErrUDPAddrIsRequired is an error used when a passed argument is not of type "*net.UDPAddr".
ErrUDPAddrIsRequired = errors.New("must supply UDPAddr")

// ErrHWAddrNotFound is an error used when getting MAC address failed.
ErrHWAddrNotFound = errors.New("hardware address not found")
)

// NewRawUDPConn returns a UDP connection bound to the interface and port
// given based on a raw packet socket. All packets are broadcasted.
// NewRawUDPConn returns a UDP connection bound to the interface and udp address
// given based on a raw packet socket.
//
// The interface can be completely unconfigured.
func NewRawUDPConn(iface string, port int) (net.PacketConn, error) {
func NewRawUDPConn(iface string, addr *net.UDPAddr, typ UDPConnType) (net.PacketConn, error) {
ifc, err := net.InterfaceByName(iface)
if err != nil {
return nil, err
Expand All @@ -43,7 +63,12 @@ func NewRawUDPConn(iface string, port int) (net.PacketConn, error) {
if err != nil {
return nil, err
}
return NewBroadcastUDPConn(rawConn, &net.UDPAddr{Port: port}), nil

if typ == UDPUnicast {
return NewUnicastRawUDPConn(rawConn, addr), nil
}

return NewBroadcastUDPConn(rawConn, addr), nil
}

// BroadcastRawUDPConn uses a raw socket to send UDP packets to the broadcast
Expand Down Expand Up @@ -157,3 +182,76 @@ func (upc *BroadcastRawUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
// Broadcasting is not always right, but hell, what the ARP do I know.
return upc.PacketConn.WriteTo(packet, &raw.Addr{HardwareAddr: BroadcastMac})
}

// UnicastRawUDPConn inherits from BroadcastRawUDPConn and override the WriteTo method
type UnicastRawUDPConn struct {
*BroadcastRawUDPConn
}

// NewUnicastRawUDPConn returns a PacketConn which sending the packets to a unicast MAC address.
func NewUnicastRawUDPConn(rawPacketConn net.PacketConn, boundAddr *net.UDPAddr) net.PacketConn {
return &UnicastRawUDPConn{
BroadcastRawUDPConn: NewBroadcastUDPConn(rawPacketConn, boundAddr).(*BroadcastRawUDPConn),
}
}

// WriteTo implements net.PacketConn.WriteTo.
//
// WriteTo try to get the MAC address of destination IP address before
// unicast all packets at the raw socket level.
func (upc *UnicastRawUDPConn) WriteTo(b []byte, addr net.Addr) (int, error) {
udpAddr, ok := addr.(*net.UDPAddr)
if !ok {
return 0, ErrUDPAddrIsRequired
}

// Using the boundAddr is not quite right here, but it works.
packet := udp4pkt(b, udpAddr, upc.boundAddr)
dstMac, err := getHwAddr(udpAddr.IP)
if err != nil {
return 0, ErrHWAddrNotFound
}

return upc.PacketConn.WriteTo(packet, &raw.Addr{HardwareAddr: dstMac})
}

// getHwAddr from local arp cache. If no existing, try to get it by arp protocol.
func getHwAddr(ip net.IP) (net.HardwareAddr, error) {
neighList, err := netlink.NeighListExecute(netlink.Ndmsg{
Family: netlink.FAMILY_V4,
State: netlink.NUD_REACHABLE,
})
if err != nil {
return nil, err
}

for _, neigh := range neighList {
if ip.Equal(neigh.IP) && neigh.HardwareAddr != nil {
return neigh.HardwareAddr, nil
}
}

return arpResolve(ip)
}

func arpResolve(dest net.IP) (net.HardwareAddr, error) {
// auto match the interface based on routes
routes, err := netlink.RouteGet(dest)
if err != nil {
return nil, err
}
if len(routes) == 0 {
return nil, fmt.Errorf("no route to %s found", dest.String())
}
ifc, err := net.InterfaceByIndex(routes[0].LinkIndex)
if err != nil {
return nil, err
}

c, err := arp.Dial(ifc)
if err != nil {
return nil, err
}

return c.Resolve(dest)
}
2 changes: 2 additions & 0 deletions go.mod
View file
Original file line number Diff line number Diff line change
Expand Up @@ -6,12 +6,14 @@ require (
github.com/fanliao/go-promise v0.0.0-20141029170127-1890db352a72
github.com/hugelgupf/socketpair v0.0.0-20190730060125-05d35a94e714
github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c
github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc
github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7
github.com/mdlayher/netlink v1.1.1
github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065
github.com/smartystreets/goconvey v1.6.4 // indirect
github.com/stretchr/testify v1.6.1
github.com/u-root/uio v0.0.0-20210528114334-82958018845c
github.com/vishvananda/netlink v1.1.0
golang.org/x/net v0.0.0-20201110031124-69a78807bb2b
golang.org/x/sys v0.0.0-20210525143221-35b2ab0089ea
)
10 changes: 10 additions & 0 deletions go.sum
View file
Original file line number Diff line number Diff line change
Expand Up @@ -19,13 +19,17 @@ github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c h1:7cpGGTQO6+
github.com/jsimonetti/rtnetlink v0.0.0-20201110080708-d2c240429e6c/go.mod h1:huN4d1phzjhlOsNIjFsw2SVRbwIHj3fJDMEU2SDPTmg=
github.com/jtolds/gls v4.20.0+incompatible h1:xdiiI2gbIgH/gLH7ADydsJ1uDOEzR8yvV7C0MuV77Wo=
github.com/jtolds/gls v4.20.0+incompatible/go.mod h1:QJZ7F/aHp+rZTRtaJ1ow/lLfFfVYBRgL+9YlvaHOwJU=
github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc h1:m7rJJJeXrYCFpsxXYapkDW53wJCDmf9bsIXUg0HoeQY=
github.com/mdlayher/arp v0.0.0-20191213142603-f72070a231fc/go.mod h1:eOj1DDj3NAZ6yv+WafaKzY37MFZ58TdfIhQ+8nQbiis=
github.com/mdlayher/ethernet v0.0.0-20190313224307-5b5fc417d966/go.mod h1:5s5p/sMJ6sNsFl6uCh85lkFGV8kLuIYJCRJLavVJwvg=
github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7 h1:lez6TS6aAau+8wXUP3G9I3TGlmPFEq2CTxBaRqY6AGE=
github.com/mdlayher/ethernet v0.0.0-20190606142754-0394541c37b7/go.mod h1:U6ZQobyTjI/tJyq2HG+i/dfSoFUt8/aZCM+GKtmFk/Y=
github.com/mdlayher/netlink v0.0.0-20190409211403-11939a169225/go.mod h1:eQB3mZE4aiYnlUsyGGCOpPETfdQq4Jhsgf1fk3cwQaA=
github.com/mdlayher/netlink v1.0.0/go.mod h1:KxeJAFOFLG6AjpyDkQ/iIhxygIUKD+vcwqcnu43w/+M=
github.com/mdlayher/netlink v1.1.0/go.mod h1:H4WCitaheIsdF9yOYu8CFmCgQthAPIWZmcKp9uZHgmY=
github.com/mdlayher/netlink v1.1.1 h1:VqG+Voq9V4uZ+04vjIrcSCWDpf91B1xxbP4QBUmUJE8=
github.com/mdlayher/netlink v1.1.1/go.mod h1:WTYpFb/WTvlRJAyKhZL5/uy69TDDpHHu2VZmb2XgV7o=
github.com/mdlayher/raw v0.0.0-20190313224157-43dbcdd7739d/go.mod h1:r1fbeITl2xL/zLbVnNHFyOzQJTgr/3fpf1lJX/cjzR8=
github.com/mdlayher/raw v0.0.0-20190606142536-fef19f00fc18/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065 h1:aFkJ6lx4FPip+S+Uw4aTegFMct9shDvP+79PsSxpm3w=
github.com/mdlayher/raw v0.0.0-20191009151244-50f2db8cc065/go.mod h1:7EpbotpCmVZcu+KCX4g9WaRNuu11uyhiW7+Le1dKawg=
Expand All @@ -41,9 +45,14 @@ github.com/stretchr/testify v1.6.1 h1:hDPOHmpOpP40lSULcqw7IrRb/u7w6RpDC9399XyoNd
github.com/stretchr/testify v1.6.1/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
github.com/u-root/uio v0.0.0-20210528114334-82958018845c h1:BFvcl34IGnw8yvJi8hlqLFo9EshRInwWBs2M5fGWzQA=
github.com/u-root/uio v0.0.0-20210528114334-82958018845c/go.mod h1:LpEX5FO/cB+WF4TYGY1V5qktpaZLkKkSegbr0V4eYXA=
github.com/vishvananda/netlink v1.1.0 h1:1iyaYNBLmP6L0220aDnYQpo1QEV4t4hJ+xEEhhJH8j0=
github.com/vishvananda/netlink v1.1.0/go.mod h1:cTgwzPIzzgDAYoQrMm0EdrjRUBkTqKYppBueQtXaqoE=
github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df h1:OviZH7qLw/7ZovXvuNyL3XQl8UFofeikI1NW1Gypu7k=
github.com/vishvananda/netns v0.0.0-20191106174202-0a2b9b5464df/go.mod h1:JP3t17pCcGlemwknint6hfoeCVQrEMVwxRLRjXpq+BU=
golang.org/x/crypto v0.0.0-20190308221718-c2843e01d9a2/go.mod h1:djNgcEr1/C05ACkg1iLfiJU5Ep61QUkGW8qpdssI0+w=
golang.org/x/crypto v0.0.0-20200622213623-75b288015ac9/go.mod h1:LzIPMQfyMNhhGPhUkYOs5KpL4U8rLKemX1yGLhDgUto=
golang.org/x/net v0.0.0-20190311183353-d8887717615a/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190313220215-9f648a60d977/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190404232315-eb5bcb51f2a3/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190419010253-1f3472d942ba/go.mod h1:t9HGtf8HONx5eT2rtn7q6eTqICYqUVnKs3thJo3Qplg=
golang.org/x/net v0.0.0-20190603091049-60506f45cf65/go.mod h1:HSz+uSET+XFnRR8LxR5pz3Of3rY3CfYBVs4xY44aLks=
Expand All @@ -59,6 +68,7 @@ golang.org/x/sys v0.0.0-20190411185658-b44545bcd369/go.mod h1:h1NjWce9XRLGQEsW7w
golang.org/x/sys v0.0.0-20190412213103-97732733099d/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190418153312-f0ce4c0180be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190606122018-79a91cf218c4/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190606203320-7fc4e5ec1444/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20190826190057-c7b8b68b1456/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20191008105621-543471e840be/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
golang.org/x/sys v0.0.0-20200202164722-d101bd2416d5/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
Expand Down

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