mirror of
https://github.com/Mathewnd/Astral.git
synced 2026-10-27 12:48:22 +00:00
netd: initial implementation (dhcp client)
This commit is contained in:
Matheus
@@ -0,0 +1,14 @@
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.phony: all install
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CC=x86_64-astral-gcc
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LD=x86_64-astral-gcc
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all: netd
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install:
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mkdir -p "$(DESTDIR)/$(PREFIX)/sbin/"
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cp netd "$(DESTDIR)/$(PREFIX)/sbin/netd"
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netd: main.o
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$(LD) $(LDFLAGS) -g -o $@ $^
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main.o: main.c
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$(CC) -c $(CFLAGS) -g -o $@ $<
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@@ -0,0 +1,474 @@
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#include <stdio.h>
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#include <stdlib.h>
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#include <stdbool.h>
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#include <string.h>
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#include <stdint.h>
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#include <stddef.h>
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#include <sys/socket.h>
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#include <stdio.h>
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#include <string.h>
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#include <netinet/in.h>
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#include <net/if.h>
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#include <sys/ioctl.h>
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#include <errno.h>
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#include <poll.h>
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#include <net/route.h>
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#ifndef SIOCADDRT
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#define SIOCADDRT 0x890B
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#endif
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#define DHCPHDR_TYPE_CLIENT 1
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#define DHCPHDR_TYPE_SERVER 2
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#define DHCPHDR_HTYPE_ETH 1
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#define DHCPHDR_HLEN_ETH 6
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#define DHCPHDR_COOKIE 0x63825363
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#define DHCPHDR_XID 0x12345678
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#define DHCP_CLIENT_PORT 68
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#define DHCP_SERVER_PORT 67
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typedef struct {
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uint8_t op;
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uint8_t htype;
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uint8_t hlen;
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uint8_t hops;
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uint32_t xid;
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uint16_t secs;
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uint16_t flags;
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uint32_t clientip;
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uint32_t responseip;
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uint32_t serverip;
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uint32_t relayip;
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uint8_t clienthw[16];
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uint8_t sname[64];
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uint8_t file[128];
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uint32_t cookie;
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} __attribute__((packed)) dhcphdr_t;
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#define OPTION_TYPE 53
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#define OPTION_TYPE_LENGTH 1
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#define OPTION_TYPE_DHCPDISCOVER 1
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#define OPTION_TYPE_DHCPOFFER 2
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#define OPTION_TYPE_DHCPREQUEST 3
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#define OPTION_TYPE_DHCPACK 5
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#define OPTION_REQUEST 55
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#define OPTION_REQUEST_LENGTH 2
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#define OPTION_MASK 1
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#define OPTION_ROUTER 3
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#define OPTION_LEASETIME 51
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#define OPTION_IPREQ 50
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#define OPTION_SERVER 54
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#define OPTION_END 0xff
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static uint8_t discoveropts[] = {
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OPTION_TYPE, OPTION_TYPE_LENGTH, OPTION_TYPE_DHCPDISCOVER,
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OPTION_REQUEST, OPTION_REQUEST_LENGTH, OPTION_MASK, OPTION_ROUTER,
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0xff
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};
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typedef struct {
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dhcphdr_t hdr;
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uint8_t opts[sizeof(discoveropts)];
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} __attribute__((packed)) dhcpdiscover_t;
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typedef struct {
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dhcphdr_t hdr;
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uint8_t opts[];
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} __attribute__((packed)) dhcpoffer_t;
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typedef struct {
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uint8_t type[3];
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uint8_t ipreqhdr[2];
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uint32_t ipreq;
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uint8_t dhcpserverhdr[2];
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uint32_t dhcpserver;
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uint8_t end;
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} __attribute__((packed)) requestopts_t;
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typedef struct {
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dhcphdr_t hdr;
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requestopts_t opts;
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} __attribute__((packed)) dhcprequest_t;
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typedef struct {
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dhcphdr_t hdr;
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uint8_t opts[];
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} __attribute__((packed)) dhcpack_t;
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static char *name;
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static int sockfd;
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static uint8_t hwaddr[DHCPHDR_HLEN_ETH];
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static void usage() {
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fprintf(stderr, "%s: usage: %s device\n", name, name);
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fprintf(stderr, "%s: example: %s vionet0\n", name, name);
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exit(EXIT_FAILURE);
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}
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static void logstrerror(char *msg) {
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fprintf(stderr, "%s: %s: %s\n", name, msg, strerror(errno));
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}
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static void logmsg(char *msg) {
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printf("%s: %s\n", name, msg);
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}
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static void logerr(char *msg) {
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fprintf(stderr, "%s: %s\n", name, msg);
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}
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int createsocket(char *device) {
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// initialize the DHCP socket and bind it to the client port
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sockfd = socket(AF_INET, SOCK_DGRAM, 0);
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if (sockfd < 0) {
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logstrerror("failed to create socket");
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return 1;
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}
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struct sockaddr_in addr;
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addr.sin_port = htons(DHCP_CLIENT_PORT);
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addr.sin_family = AF_INET;
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addr.sin_addr.s_addr = htonl(INADDR_ANY);
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if (bind(sockfd, (struct sockaddr *)&addr, sizeof(struct sockaddr_in))) {
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logstrerror("failed to bind socket");
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return 1;
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}
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// make the socket able to broadcast datagrams and bind it to the chosen device
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int broadcast = 1;
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if (setsockopt(sockfd, SOL_SOCKET, SO_BROADCAST, &broadcast, sizeof(broadcast))) {
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logstrerror("failed to make socket accept broadcasts");
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return 1;
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}
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if (setsockopt(sockfd, SOL_SOCKET, SO_BINDTODEVICE, device, strlen(device) + 1)) {
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logstrerror("failed to bind to device");
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return 1;
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}
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return 0;
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}
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int getdevicehwaddr(char *device) {
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// get hardware address of device
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struct ifreq buffer = {0};
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strcpy(buffer.ifr_name, device);
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if (ioctl(sockfd, SIOCGIFHWADDR, &buffer)) {
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logstrerror("failed to get device hardware address");
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return 1;
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}
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memcpy(hwaddr, buffer.ifr_hwaddr.sa_data, DHCPHDR_HLEN_ETH);
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char printbuff[50];
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snprintf(printbuff, 50, "hardware address: %02x:%02x:%02x:%02x:%02x:%02x", hwaddr[0], hwaddr[1], hwaddr[2], hwaddr[3], hwaddr[4], hwaddr[5]);
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logmsg(printbuff);
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return 0;
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}
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static int discover() {
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// send out the DHCPDISCOVER packet
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dhcpdiscover_t packet;
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memset(&packet, 0, sizeof(packet));
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packet.hdr.op = DHCPHDR_TYPE_CLIENT;
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packet.hdr.htype = DHCPHDR_HTYPE_ETH;
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packet.hdr.hlen = DHCPHDR_HLEN_ETH;
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packet.hdr.xid = htonl(DHCPHDR_XID);
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memcpy(packet.hdr.clienthw, hwaddr, DHCPHDR_HLEN_ETH);
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packet.hdr.cookie = htonl(DHCPHDR_COOKIE);
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memcpy(packet.opts, discoveropts, sizeof(packet.opts));
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// broadcast address
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struct sockaddr_in address = {
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.sin_family = AF_INET,
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.sin_port = htons(DHCP_SERVER_PORT),
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.sin_addr.s_addr = htonl(INADDR_BROADCAST)
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};
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if (sendto(sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&address, sizeof(address)) < 0) {
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logstrerror("sending DHCPDISCOVER failed");
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return 1;
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}
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return 0;
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}
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static int waitforserver(int timeout) {
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struct pollfd pollfd = {
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.fd = sockfd,
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.events = POLLIN
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};
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int pollr = poll(&pollfd, 1, timeout);
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return pollr <= 0 ? 1 : 0;
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}
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static inline uint32_t optget32(uint8_t *opt, int i) {
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return ((uint32_t)opt[i] << 24) | ((uint32_t)opt[i + 1] << 16) | ((uint32_t)opt[i + 2] << 8) | ((uint32_t)opt[i + 3]);
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}
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typedef struct {
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uint32_t clientip;
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uint32_t serverip;
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uint32_t netmask;
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uint32_t router;
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uint32_t leasetime;
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} offer_t;
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static int processoffer(offer_t *offer, uint32_t *xid) {
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uint8_t buffer[1024];
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dhcpoffer_t *dhcpoffer = (dhcpoffer_t *)buffer;
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memset(buffer, 0, sizeof(buffer));
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size_t nbytes = recv(sockfd, buffer, sizeof(buffer), 0);
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if (nbytes < 0) {
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logstrerror("failed to recv while processing offer");
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return 1;
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}
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// not from the server, ignore
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if (dhcpoffer->hdr.op != DHCPHDR_TYPE_SERVER) {
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*xid = 0;
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return 0;
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}
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size_t optsize = nbytes - sizeof(dhcphdr_t);
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// get the offered stuff in the options
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int i = 0;
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uint8_t *opts = dhcpoffer->opts;
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while (i < optsize) {
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switch (opts[i]) {
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case OPTION_TYPE:
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if (opts[i + 2] != OPTION_TYPE_DHCPOFFER) {
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// not a DHCPOFFER, ignore
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*xid = 0;
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return 0;
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}
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break;
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case OPTION_MASK:
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uint32_t mask = optget32(opts, i + 2);
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offer->netmask = mask;
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break;
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case OPTION_ROUTER :
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uint32_t router = optget32(opts, i + 2);
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offer->router = router;
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break;
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case OPTION_SERVER:
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uint32_t server = optget32(opts, i + 2);
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offer->serverip = server;
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break;
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case OPTION_LEASETIME:
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uint32_t leasetime = optget32(opts, i + 2);
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offer->leasetime = leasetime;
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break;
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case OPTION_END:
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goto leave;
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}
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uint8_t optlen = opts[i + 1];
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i += optlen + 2;
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}
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leave:
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offer->clientip = ntohl(dhcpoffer->hdr.responseip);
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*xid = ntohl(dhcpoffer->hdr.xid);
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return 0;
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}
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static int request(offer_t *offer) {
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// send out the DHCPREQUEST packet
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dhcprequest_t packet;
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memset(&packet, 0, sizeof(packet));
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packet.hdr.op = DHCPHDR_TYPE_CLIENT;
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packet.hdr.htype = DHCPHDR_HTYPE_ETH;
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packet.hdr.hlen = DHCPHDR_HLEN_ETH;
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packet.hdr.xid = htonl(DHCPHDR_XID);
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packet.hdr.clientip = htonl(offer->clientip);
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packet.hdr.serverip = htonl(offer->serverip);
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memcpy(packet.hdr.clienthw, hwaddr, DHCPHDR_HLEN_ETH);
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packet.hdr.cookie = htonl(DHCPHDR_COOKIE);
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packet.opts.type[0] = OPTION_TYPE;
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packet.opts.type[1] = OPTION_TYPE_LENGTH;
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packet.opts.type[2] = OPTION_TYPE_DHCPREQUEST;
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packet.opts.ipreqhdr[0] = OPTION_IPREQ;
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packet.opts.ipreqhdr[1] = 4;
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packet.opts.ipreq = htonl(offer->clientip);
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packet.opts.dhcpserverhdr[0] = OPTION_SERVER;
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packet.opts.dhcpserverhdr[1] = 4;
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packet.opts.dhcpserver = htonl(offer->serverip);
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packet.opts.end = 0xff;
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// broadcast address
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struct sockaddr_in address = {
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.sin_family = AF_INET,
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.sin_port = htons(DHCP_SERVER_PORT),
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.sin_addr.s_addr = htonl(INADDR_BROADCAST)
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};
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if (sendto(sockfd, &packet, sizeof(packet), 0, (struct sockaddr *)&address, sizeof(address)) < 0) {
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logstrerror("sending DHCPREQUEST failed");
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return 1;
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}
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return 0;
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}
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static int getack(uint32_t *xid) {
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uint8_t buffer[1024];
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dhcpoffer_t *dhcpack = (dhcpoffer_t *)buffer;
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memset(buffer, 0, sizeof(buffer));
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size_t nbytes = recv(sockfd, buffer, sizeof(buffer), 0);
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if (nbytes < 0) {
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logstrerror("failed to recv while processing ack");
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return 1;
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}
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// not from the server, ignore
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if (dhcpack->hdr.op != DHCPHDR_TYPE_SERVER) {
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*xid = 0;
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return 0;
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}
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size_t optsize = nbytes - sizeof(dhcphdr_t);
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// get the offered stuff in the options
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int i = 0;
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uint8_t *opts = dhcpack->opts;
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while (i < optsize) {
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switch (opts[i]) {
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case OPTION_TYPE:
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if (opts[i + 2] == OPTION_TYPE_DHCPACK) {
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*xid = ntohl(dhcpack->hdr.xid);
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return 0;
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}
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break;
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case OPTION_END:
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goto leave;
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}
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uint8_t optlen = opts[i + 1];
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i += optlen + 2;
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}
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leave:
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// if we reach this, its not an ack packet.
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*xid = 0;
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return 0;
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}
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static void printip(char *ipname, uint32_t ip) {
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struct in_addr addr;
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addr.s_addr = htonl(ip);
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char *ipstr = inet_ntoa(addr);
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printf("%s: %s: %s\n", name, ipname, ipstr);
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}
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static void printoffer(offer_t *offer) {
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printip("client ip", offer->clientip);
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printip("server ip", offer->serverip);
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printip("netmask", offer->netmask);
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printip("router", offer->router);
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printf("%s: lease time: %d seconds\n", name, offer->leasetime);
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}
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static void addroute(char *device, uint32_t addr, uint32_t gateway, uint32_t mask, int weight) {
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struct rtentry route;
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memset(&route, 0, sizeof(route));
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struct sockaddr_in sockaddr;
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struct sockaddr_in sockgateway;
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struct sockaddr_in sockmask;
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sockaddr.sin_family = AF_INET;
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sockaddr.sin_addr.s_addr = htonl(addr);
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sockgateway.sin_family = AF_INET;
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sockgateway.sin_addr.s_addr = htonl(gateway);
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sockmask.sin_family = AF_INET;
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sockmask.sin_addr.s_addr = htonl(mask);
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memcpy(&route.rt_dst, &sockaddr, sizeof(struct sockaddr_in));
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memcpy(&route.rt_gateway, &sockgateway, sizeof(struct sockaddr_in));
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memcpy(&route.rt_genmask, &sockmask, sizeof(struct sockaddr_in));
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route.rt_metric = weight;
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route.rt_dev = device;
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if (ioctl(sockfd, SIOCADDRT, &route) < 0)
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logstrerror("failed to add route");
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}
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int main(int argc, char *argv[]) {
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name = argv[0];
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if (argc != 2)
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usage();
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if (createsocket(argv[1]))
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return EXIT_FAILURE;
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if (getdevicehwaddr(argv[1]))
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return EXIT_FAILURE;
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offer_t offer;
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bool gotoffer = false;
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while (gotoffer == false) {
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if (discover())
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return EXIT_FAILURE;
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while (gotoffer == false) {
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if (waitforserver(10000))
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break;
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uint32_t xid;
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if (processoffer(&offer, &xid))
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return EXIT_FAILURE;
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// packet wasn't for this machine
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if (xid != DHCPHDR_XID)
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continue;
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gotoffer = true;
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}
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}
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bool gotack = false;
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while (gotack == false) {
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if (request(&offer))
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return EXIT_FAILURE;
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while (gotack == false) {
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if (waitforserver(10000))
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break;
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uint32_t xid;
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if (getack(&xid))
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return EXIT_FAILURE;
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if (xid != DHCPHDR_XID)
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continue;
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gotack = true;
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}
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}
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// TODO routing table information
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printoffer(&offer);
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addroute(argv[1], 0, offer.router, 0, 1);
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addroute(argv[1], offer.clientip, 0, offer.netmask, 10);
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return EXIT_SUCCESS;
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}
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