Userspace: Implement super simple DHCP client
This commit is contained in:
parent
102aa50a41
commit
2138eeb87f
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@ -8,6 +8,7 @@ set(USERSPACE_PROJECTS
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chmod
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cp
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dd
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dhcp-client
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echo
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id
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init
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@ -0,0 +1,16 @@
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cmake_minimum_required(VERSION 3.26)
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project(dhcp-client CXX)
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set(SOURCES
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main.cpp
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)
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add_executable(dhcp-client ${SOURCES})
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target_compile_options(dhcp-client PUBLIC -O2 -g)
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target_link_libraries(dhcp-client PUBLIC libc)
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add_custom_target(dhcp-client-install
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COMMAND ${CMAKE_COMMAND} -E copy ${CMAKE_CURRENT_BINARY_DIR}/dhcp-client ${BANAN_BIN}/
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DEPENDS dhcp-client
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)
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@ -0,0 +1,380 @@
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#include <BAN/Endianness.h>
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#include <BAN/IPv4.h>
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#include <BAN/MAC.h>
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#include <BAN/Vector.h>
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#include <fcntl.h>
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#include <net/if.h>
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#include <netinet/in.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <string.h>
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#include <stropts.h>
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#include <sys/socket.h>
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#define DEBUG_DHCP 0
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struct DHCPPacket
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{
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uint8_t op;
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uint8_t htype { 0x01 };
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uint8_t hlen { 0x06 };
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uint8_t hops { 0x00 };
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BAN::NetworkEndian<uint32_t> xid { 0x3903F326 };
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BAN::NetworkEndian<uint16_t> secs { 0x0000 };
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BAN::NetworkEndian<uint16_t> flags { 0x0000 };
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BAN::NetworkEndian<uint32_t> ciaddr { 0 };
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BAN::NetworkEndian<uint32_t> yiaddr { 0 };
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BAN::NetworkEndian<uint32_t> siaddr { 0 };
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BAN::NetworkEndian<uint32_t> giaddr { 0 };
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BAN::MACAddress chaddr;
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uint8_t padding[10] {};
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uint8_t legacy[192] {};
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BAN::NetworkEndian<uint32_t> magic_cookie { 0x63825363 };
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uint8_t options[0x100];
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};
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static_assert(offsetof(DHCPPacket, options) == 240);
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enum DHCPType
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{
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SubnetMask = 1,
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Router = 3,
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DomainNameServer = 6,
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RequestedIPv4Address= 50,
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DHCPMessageType = 53,
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ServerIdentifier = 54,
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ParameterRequestList = 55,
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End = 255,
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};
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enum DHCPMessageType
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{
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INVALID = 0,
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DHCPDISCOVER = 1,
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DHCPOFFER = 2,
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DHCPREQUEST = 3,
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DHCPDECLINE = 4,
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DHCPACK = 5,
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};
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BAN::MACAddress get_mac_address(int socket)
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{
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ifreq ifreq;
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if (ioctl(socket, SIOCGIFHWADDR, &ifreq) == -1)
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{
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perror("ioctl");
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exit(1);
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}
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BAN::MACAddress mac_address;
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memcpy(&mac_address, ifreq.ifr_ifru.ifru_hwaddr.sa_data, sizeof(mac_address));
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return mac_address;
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}
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void update_ipv4_info(int socket, BAN::IPv4Address address, BAN::IPv4Address subnet)
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{
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{
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ifreq ifreq;
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ifreq.ifr_ifru.ifru_addr.sa_family = AF_INET;
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*(uint32_t*)ifreq.ifr_ifru.ifru_addr.sa_data = address.as_u32();
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if (ioctl(socket, SIOCSIFADDR, &ifreq) == -1)
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{
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perror("ioctl");
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exit(1);
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}
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}
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{
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ifreq ifreq;
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ifreq.ifr_ifru.ifru_netmask.sa_family = AF_INET;
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*(uint32_t*)ifreq.ifr_ifru.ifru_netmask.sa_data = subnet.as_u32();
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if (ioctl(socket, SIOCSIFNETMASK, &ifreq) == -1)
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{
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perror("ioctl");
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exit(1);
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}
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}
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}
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void send_dhcp_packet(int socket, const DHCPPacket& dhcp_packet, BAN::IPv4Address server_ipv4)
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{
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sockaddr_in server_addr;
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server_addr.sin_family = AF_INET;
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server_addr.sin_port = 67;
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server_addr.sin_addr.s_addr = server_ipv4.as_u32();;
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if (sendto(socket, &dhcp_packet, sizeof(DHCPPacket), 0, (sockaddr*)&server_addr, sizeof(server_addr)) == -1)
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{
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perror("sendto");
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exit(1);
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}
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}
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void send_dhcp_discover(int socket, BAN::MACAddress mac_address)
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{
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DHCPPacket dhcp_packet;
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dhcp_packet.op = 0x01;
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dhcp_packet.chaddr = mac_address;
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size_t idx = 0;
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dhcp_packet.options[idx++] = DHCPMessageType;
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dhcp_packet.options[idx++] = 0x01;
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dhcp_packet.options[idx++] = DHCPDISCOVER;
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dhcp_packet.options[idx++] = ParameterRequestList;
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dhcp_packet.options[idx++] = 0x03;
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dhcp_packet.options[idx++] = DomainNameServer;
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dhcp_packet.options[idx++] = SubnetMask;
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dhcp_packet.options[idx++] = Router;
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dhcp_packet.options[idx++] = 0xFF;
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send_dhcp_packet(socket, dhcp_packet, BAN::IPv4Address { 0xFFFFFFFF });
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}
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void send_dhcp_request(int socket, BAN::MACAddress mac_address, BAN::IPv4Address offered_ipv4, BAN::IPv4Address server_ipv4)
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{
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DHCPPacket dhcp_packet;
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dhcp_packet.op = 0x01;
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dhcp_packet.siaddr = server_ipv4.as_u32();
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dhcp_packet.chaddr = mac_address;
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size_t idx = 0;
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dhcp_packet.options[idx++] = DHCPMessageType;
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dhcp_packet.options[idx++] = 0x01;
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dhcp_packet.options[idx++] = DHCPREQUEST;
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dhcp_packet.options[idx++] = RequestedIPv4Address;
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dhcp_packet.options[idx++] = 0x04;
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dhcp_packet.options[idx++] = offered_ipv4.address[0];
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dhcp_packet.options[idx++] = offered_ipv4.address[1];
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dhcp_packet.options[idx++] = offered_ipv4.address[2];
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dhcp_packet.options[idx++] = offered_ipv4.address[3];
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dhcp_packet.options[idx++] = 0xFF;
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send_dhcp_packet(socket, dhcp_packet, BAN::IPv4Address { 0xFFFFFFFF });
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}
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struct DHCPPacketInfo
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{
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enum DHCPMessageType message_type { INVALID };
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BAN::IPv4Address address { 0 };
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BAN::IPv4Address subnet { 0 };
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BAN::IPv4Address server { 0 };
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BAN::Vector<BAN::IPv4Address> routers;
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BAN::Vector<BAN::IPv4Address> dns;
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};
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DHCPPacketInfo parse_dhcp_packet(const DHCPPacket& packet)
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{
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DHCPPacketInfo packet_info;
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packet_info.address = BAN::IPv4Address(packet.yiaddr);
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const uint8_t* options = packet.options;
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while (*options != End)
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{
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uint8_t type = *options++;
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uint8_t length = *options++;
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switch (type)
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{
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case SubnetMask:
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{
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if (length != 4)
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{
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fprintf(stderr, "Subnet mask with invalid length %hhu\n", length);
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break;
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}
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uint32_t raw = *reinterpret_cast<const BAN::NetworkEndian<uint32_t>*>(options);
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packet_info.subnet = BAN::IPv4Address(raw);
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break;
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}
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case Router:
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{
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if (length % 4 != 0)
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{
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fprintf(stderr, "Router with invalid length %hhu\n", length);
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break;
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}
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for (int i = 0; i < length; i += 4)
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{
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uint32_t raw = *reinterpret_cast<const BAN::NetworkEndian<uint32_t>*>(options + i);
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MUST(packet_info.routers.emplace_back(raw));
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}
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break;
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}
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case DomainNameServer:
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{
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if (length % 4 != 0)
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{
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fprintf(stderr, "DNS with invalid length %hhu\n", length);
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break;
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}
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for (int i = 0; i < length; i += 4)
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{
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uint32_t raw = *reinterpret_cast<const BAN::NetworkEndian<uint32_t>*>(options + i);
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MUST(packet_info.dns.emplace_back(raw));
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}
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break;
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}
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case DHCPMessageType:
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{
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if (length != 1)
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{
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fprintf(stderr, "DHCP Message Type with invalid length %hhu\n", length);
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break;
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}
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switch (*options)
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{
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case DHCPDISCOVER: packet_info.message_type = DHCPDISCOVER; break;
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case DHCPOFFER: packet_info.message_type = DHCPOFFER; break;
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case DHCPREQUEST: packet_info.message_type = DHCPREQUEST; break;
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case DHCPDECLINE: packet_info.message_type = DHCPDECLINE; break;
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case DHCPACK: packet_info.message_type = DHCPACK; break;
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}
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break;
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}
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case ServerIdentifier:
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{
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if (length != 4)
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{
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fprintf(stderr, "Server identifier with invalid length %hhu\n", length);
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break;
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}
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uint32_t raw = *reinterpret_cast<const BAN::NetworkEndian<uint32_t>*>(options);
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packet_info.server = BAN::IPv4Address(raw);
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break;
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}
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}
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options += length;
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}
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return packet_info;
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}
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BAN::Optional<DHCPPacketInfo> read_dhcp_packet(int socket)
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{
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DHCPPacket dhcp_packet;
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ssize_t nrecv = recvfrom(socket, &dhcp_packet, sizeof(dhcp_packet), 0, nullptr, nullptr);
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if (nrecv == -1)
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{
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perror("revcfrom");
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return {};
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}
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if (nrecv <= (ssize_t)offsetof(DHCPPacket, options))
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{
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fprintf(stderr, "invalid DHCP offer\n");
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return {};
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}
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if (dhcp_packet.magic_cookie != 0x63825363)
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{
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fprintf(stderr, "invalid DHCP offer\n");
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return {};
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}
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return parse_dhcp_packet(dhcp_packet);
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}
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int main()
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{
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int socket = ::socket(AF_INET, SOCK_DGRAM, 0);
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if (socket == -1)
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{
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perror("socket");
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return 1;
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}
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sockaddr_in client_addr;
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client_addr.sin_family = AF_INET;
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client_addr.sin_port = 68;
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client_addr.sin_addr.s_addr = 0x00000000;
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if (bind(socket, (sockaddr*)&client_addr, sizeof(client_addr)) == -1)
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{
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perror("bind");
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return 1;
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}
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auto mac_address = get_mac_address(socket);
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#if DEBUG_DHCP
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BAN::Formatter::println(putchar, "MAC: {}", mac_address);
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#endif
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send_dhcp_discover(socket, mac_address);
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#if DEBUG_DHCP
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printf("DHCPDISCOVER sent\n");
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#endif
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auto dhcp_offer = read_dhcp_packet(socket);
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if (!dhcp_offer.has_value())
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return 1;
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if (dhcp_offer->message_type != DHCPOFFER)
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{
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fprintf(stderr, "DHCP server did not respond with DHCPOFFER\n");
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return 1;
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}
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#if DEBUG_DHCP
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BAN::Formatter::println(putchar, "DHCPOFFER");
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BAN::Formatter::println(putchar, " IP {}", dhcp_offer->address);
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BAN::Formatter::println(putchar, " SUBNET {}", dhcp_offer->subnet);
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BAN::Formatter::println(putchar, " SERVER {}", dhcp_offer->server);
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#endif
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send_dhcp_request(socket, mac_address, dhcp_offer->address, dhcp_offer->server);
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#if DEBUG_DHCP
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printf("DHCPREQUEST sent\n");
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#endif
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auto dhcp_ack = read_dhcp_packet(socket);
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if (!dhcp_ack.has_value())
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return 1;
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if (dhcp_ack->message_type != DHCPACK)
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{
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fprintf(stderr, "DHCP server did not respond with DHCPACK\n");
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return 1;
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}
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#if DEBUG_DHCP
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BAN::Formatter::println(putchar, "DHCPACK");
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BAN::Formatter::println(putchar, " IP {}", dhcp_ack->address);
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BAN::Formatter::println(putchar, " SUBNET {}", dhcp_ack->subnet);
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BAN::Formatter::println(putchar, " SERVER {}", dhcp_ack->server);
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#endif
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if (dhcp_offer->address != dhcp_ack->address)
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{
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fprintf(stderr, "DHCP server OFFER and ACK ips don't match\n");
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return 1;
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}
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update_ipv4_info(socket, dhcp_ack->address, dhcp_ack->subnet);
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if (true)
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{
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uint32_t packet = 0x12345678;
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sockaddr_in server_addr;
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server_addr.sin_family = AF_INET;
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server_addr.sin_port = 67;
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server_addr.sin_addr.s_addr = dhcp_ack->routers.front().as_u32();
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server_addr.sin_addr.s_addr = (192 << 24) | (168 << 16) | (1 << 8) | 203;
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if (sendto(socket, &packet, sizeof(packet), 0, (sockaddr*)&server_addr, sizeof(server_addr)) == -1)
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{
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perror("sendto");
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exit(1);
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}
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}
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close(socket);
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return 0;
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}
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@ -29,6 +29,12 @@ int main()
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if (load_keymap("/usr/share/keymaps/fi.keymap") == -1)
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perror("load_keymap");
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if (fork() == 0)
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{
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execl("/bin/dhcp-client", "dhcp-client", NULL);
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exit(1);
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}
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bool first = true;
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termios termios;
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