-
Notifications
You must be signed in to change notification settings - Fork 8
Commit
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
IP+UDP Stack over Ethernet for DHCP (#17)
* fix IP marshal bugs, begin adding DHCP * add tcpctl.Stack type * fix bug in IP marshal and add test to catch it * continue trying to add DHCP * add some more form to DoDHCP * move DHCPHeader to eth package * push work up until now. packets are malformed but it's what we got so far * latest changes * remove useless operation * DHCP seems to be well formed now. still no response * add more idiomatic dhcp option encoding * fix bugs in checksum; also length calculation * printing DHCP responses works! * add extra check in rxEvent * stack needs API redesign by the looks of it, good exploration though * huge refactor to DHCP stack; much nicer inner workings * add DHCP option parsing * redo DHCP request after 8 seconds * add pretty printing of DHCP options * DHCP is working with my test setup * add tcp sockets (#19)
- Loading branch information
Showing
13 changed files
with
1,377 additions
and
165 deletions.
There are no files selected for viewing
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,181 @@ | ||
| package tcpctl | ||
|
|
||
| import ( | ||
| "encoding/binary" | ||
| "errors" | ||
| "fmt" | ||
| "net" | ||
|
|
||
| "github.com/soypat/cyw43439/internal/tcpctl/eth" | ||
| ) | ||
|
|
||
| type DHCPClient struct { | ||
| ourHeader eth.DHCPHeader | ||
| State uint8 | ||
| MAC [6]byte | ||
| // The result IP of the DHCP transaction (our new IP). | ||
| YourIP [4]byte | ||
| // DHCP server IP | ||
| ServerIP [4]byte | ||
| } | ||
|
|
||
| const ( | ||
| dhcpStateNone = iota | ||
| dhcpStateWaitOffer | ||
| dhcpStateWaitAck | ||
| dhcpStateDone | ||
| ) | ||
|
|
||
| func (d *DHCPClient) HandleUDP(resp []byte, packet *UDPPacket) (_ int, err error) { | ||
| const ( | ||
| xid = 0x12345678 | ||
|
|
||
| sizeSName = 64 // Server name, part of BOOTP too. | ||
| sizeFILE = 128 // Boot file name, Legacy. | ||
| sizeOptions = 312 | ||
| dhcpOffset = eth.SizeEthernetHeader + eth.SizeIPv4Header + eth.SizeUDPHeader | ||
| optionsStart = dhcpOffset + eth.SizeDHCPHeader + sizeSName + sizeFILE | ||
| sizeDHCPTotal = eth.SizeDHCPHeader + sizeSName + sizeFILE + sizeOptions | ||
| ) | ||
| // First action is used to send data without having received a packet | ||
| // so hasPacket will be false. | ||
| hasPacket := packet.HasPacket() | ||
| incpayload := packet.Payload() | ||
| switch { | ||
| case len(resp) < sizeDHCPTotal: | ||
| return 0, errors.New("short payload to marshall DHCP") | ||
| case hasPacket && len(incpayload) < eth.SizeDHCPHeader: | ||
| return 0, errors.New("short payload to parse DHCP") | ||
| } | ||
|
|
||
| var rcvHdr eth.DHCPHeader | ||
| if hasPacket { | ||
| rcvHdr = eth.DecodeDHCPHeader(incpayload) | ||
| ptr := eth.SizeDHCPHeader + sizeSName + sizeFILE + 4 | ||
| for ptr+1 < len(incpayload) && int(incpayload[ptr+1]) < len(incpayload) { | ||
| if incpayload[ptr] == 0xff { | ||
| break | ||
| } | ||
| option := eth.DHCPOption(incpayload[ptr]) | ||
| optlen := incpayload[ptr+1] | ||
| // optionData := incpayload[ptr+2 : ptr+2+int(optlen)] | ||
|
|
||
| // print("DHCP Option received ", option.String()) | ||
| optionData := incpayload[ptr+2 : ptr+2+int(optlen)] | ||
| if d.State == dhcpStateWaitAck && option == eth.DHCP_MessageType && len(optionData) > 0 && optionData[0] == 5 { | ||
| d.State = dhcpStateDone | ||
| return 0, nil | ||
| } | ||
| println() | ||
| ptr += int(optlen) + 2 | ||
| } | ||
| } | ||
|
|
||
| // Switch statement prepares DHCP response depending on whether we're waiting | ||
| // for offer, ack or if we still need to send a discover (StateNone). | ||
| type option struct { | ||
| code byte | ||
| data []byte | ||
| } | ||
| var Options []option | ||
| switch { | ||
| case !hasPacket && d.State == dhcpStateNone: | ||
| d.initOurHeader(xid) | ||
| // DHCP options. | ||
| Options = []option{ | ||
| {53, []byte{1}}, // DHCP Message Type: Discover | ||
| {50, []byte{192, 168, 1, 69}}, // Requested IP | ||
| {55, []byte{1, 3, 15, 6}}, // Parameter request list | ||
| } | ||
| d.State = dhcpStateWaitOffer | ||
|
|
||
| case hasPacket && d.State == dhcpStateWaitOffer: | ||
| offer := net.IP(rcvHdr.YIAddr[:]) | ||
| Options = []option{ | ||
| {53, []byte{3}}, // DHCP Message Type: Request | ||
| {50, offer}, // Requested IP | ||
| {54, rcvHdr.SIAddr[:]}, // DHCP server IP | ||
| } | ||
| // Accept this server's offer. | ||
| copy(d.ourHeader.SIAddr[:], rcvHdr.SIAddr[:]) | ||
| copy(d.YourIP[:], offer) // Store our new IP. | ||
| d.State = dhcpStateWaitAck | ||
| default: | ||
| err = fmt.Errorf("UNHANDLED CASE %v %+v", hasPacket, d) | ||
| } | ||
| if err != nil { | ||
| return 0, nil | ||
| } | ||
| for i := dhcpOffset + 14; i < len(resp); i++ { | ||
| resp[i] = 0 // Zero out BOOTP and options fields. | ||
| } | ||
| // Encode DHCP header + options. | ||
| d.ourHeader.Put(resp[dhcpOffset:]) | ||
|
|
||
| ptr := optionsStart | ||
| binary.BigEndian.PutUint32(resp[ptr:], 0x63825363) // Magic cookie. | ||
| ptr += 4 | ||
| for _, opt := range Options { | ||
| ptr += encodeDHCPOption(resp[ptr:], opt.code, opt.data) | ||
| } | ||
| resp[ptr] = 0xff // endmark | ||
| // Set Ethernet+IP+UDP headers. | ||
| payload := resp[dhcpOffset : dhcpOffset+sizeDHCPTotal] | ||
| d.setResponseUDP(packet, payload) | ||
| packet.PutHeaders(resp) | ||
| return dhcpOffset + sizeDHCPTotal, nil | ||
| } | ||
|
|
||
| // initOurHeader zero's out most of header and sets the xid and MAC address along with OP=1. | ||
| func (d *DHCPClient) initOurHeader(xid uint32) { | ||
| dhdr := &d.ourHeader | ||
| dhdr.OP = 1 | ||
| dhdr.HType = 1 | ||
| dhdr.HLen = 6 | ||
| dhdr.HOps = 0 | ||
| dhdr.Secs = 0 | ||
| dhdr.Flags = 0 | ||
| dhdr.Xid = xid | ||
| dhdr.CIAddr = [4]byte{} | ||
| dhdr.YIAddr = [4]byte{} | ||
| dhdr.SIAddr = [4]byte{} | ||
| dhdr.GIAddr = [4]byte{} | ||
| copy(dhdr.CHAddr[:], d.MAC[:]) | ||
| } | ||
|
|
||
| func (d *DHCPClient) setResponseUDP(packet *UDPPacket, payload []byte) { | ||
| const ipWordLen = 5 | ||
| // Ethernet frame. | ||
| copy(packet.Eth.Destination[:], eth.BroadcastHW()) | ||
| copy(packet.Eth.Source[:], d.MAC[:]) | ||
| packet.Eth.SizeOrEtherType = uint16(eth.EtherTypeIPv4) | ||
|
|
||
| // IPv4 frame. | ||
| copy(packet.IP.Destination[:], eth.BroadcastHW()) | ||
| packet.IP.Source = [4]byte{} // Source IP is always zeroed when client sends. | ||
| packet.IP.Protocol = 17 // UDP | ||
| packet.IP.TTL = 64 | ||
| // 16bit Xorshift for prandom IP packet ID. https://en.wikipedia.org/wiki/Xorshift | ||
| packet.IP.ID ^= packet.IP.ID << 7 | ||
| packet.IP.ID ^= packet.IP.ID >> 9 | ||
| packet.IP.ID ^= packet.IP.ID << 8 | ||
| packet.IP.VersionAndIHL = ipWordLen // Sets IHL: No IP options. Version set automatically. | ||
| packet.IP.TotalLength = 4*ipWordLen + eth.SizeUDPHeader + uint16(len(payload)) | ||
| packet.IP.Checksum = packet.IP.CalculateChecksum() | ||
|
|
||
| // UDP frame. | ||
| packet.UDP.DestinationPort = 67 | ||
| packet.UDP.SourcePort = 68 | ||
| packet.UDP.Length = packet.IP.TotalLength - 4*ipWordLen | ||
| packet.UDP.Checksum = packet.UDP.CalculateChecksumIPv4(&packet.IP, payload) | ||
| } | ||
|
|
||
| func encodeDHCPOption(dst []byte, code byte, data []byte) int { | ||
| if len(data)+2 > len(dst) { | ||
| panic("small dst size for DHCP encoding") | ||
| } | ||
| dst[0] = code | ||
| dst[1] = byte(len(data)) | ||
| copy(dst[2:], data) | ||
| return 2 + len(data) | ||
| } |
Oops, something went wrong.