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netd: implement client id and hostname options for DHCPDISCOVER

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Matheus
2026-02-23 22:58:09 -03:00
parent 992cb07bc7
commit b25ab76048
1 changed files with 48 additions and 3 deletions
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tools/netd/main.c
+48 -3
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@@ -1,3 +1,4 @@
#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
@@ -16,6 +17,7 @@
#include <fcntl.h>
#include <unistd.h>
#include <time.h>
#include <limits.h>
#ifndef SIOCADDRT
#define SIOCADDRT 0x890B
@@ -61,6 +63,12 @@ typedef struct {
#define OPTION_REQUEST 55
#define OPTION_REQUEST_LENGTH 3
#define OPTION_CLIENT_ID 61
#define OPTION_CLIENT_ID_LENGTH 7
#define OPTION_HOSTNAME 12
#define OPTION_HOSTNAME_LENGTH 64
#define OPTION_MASK 1
#define OPTION_ROUTER 3
#define OPTION_DNS 6
@@ -69,16 +77,23 @@ typedef struct {
#define OPTION_SERVER 54
#define OPTION_END 0xff
#define DISCOVEROPTS_OFFSET_CLIENT_ID 11
#define DISCOVEROPTS_OFFSET_HOSTNAME 19
static uint8_t discoveropts[] = {
OPTION_TYPE, OPTION_TYPE_LENGTH, OPTION_TYPE_DHCPDISCOVER,
OPTION_REQUEST, OPTION_REQUEST_LENGTH, OPTION_MASK, OPTION_ROUTER, OPTION_DNS,
0xff
OPTION_CLIENT_ID, OPTION_CLIENT_ID_LENGTH, 1, 0, 0, 0, 0, 0, 0,
OPTION_HOSTNAME, OPTION_HOSTNAME_LENGTH,
// 64 bytes for hostname
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
OPTION_END
};
typedef struct {
dhcphdr_t hdr;
uint8_t opts[sizeof(discoveropts)];
uint8_t padding[300 - sizeof(dhcphdr_t) - sizeof(discoveropts)];
} __attribute__((packed)) dhcpdiscover_t;
typedef struct {
@@ -92,13 +107,19 @@ typedef struct {
uint32_t ipreq;
uint8_t dhcpserverhdr[2];
uint32_t dhcpserver;
uint8_t userid;
uint8_t useridlen;
uint8_t useridtype;
uint8_t useridhwaddr[6];
uint8_t hn;
uint8_t hnlen;
uint8_t hndata[64];
uint8_t end;
} __attribute__((packed)) requestopts_t;
typedef struct {
dhcphdr_t hdr;
requestopts_t opts;
uint8_t padding[300 - sizeof(dhcphdr_t) - sizeof(requestopts_t)];
} __attribute__((packed)) dhcprequest_t;
typedef struct {
@@ -323,6 +344,13 @@ static int request(offer_t *offer) {
packet.opts.dhcpserverhdr[0] = OPTION_SERVER;
packet.opts.dhcpserverhdr[1] = 4;
packet.opts.dhcpserver = htonl(offer->serverip);
packet.opts.userid = OPTION_CLIENT_ID;
packet.opts.useridlen = OPTION_CLIENT_ID_LENGTH;
packet.opts.useridtype = 1;
memcpy(packet.opts.useridhwaddr, hwaddr, 6);
packet.opts.hn = OPTION_HOSTNAME;
gethostname(packet.opts.hndata, 64);
packet.opts.hnlen = packet.opts.hndata[63] ? 64 : strlen(packet.opts.hndata);
packet.opts.end = 0xff;
// broadcast address
@@ -475,48 +503,65 @@ int main(int argc, char *argv[]) {
xid = ((uint32_t)rand() << 16) ^ (uint32_t)rand();
discoverstart = time(NULL);
memcpy(&discoveropts[DISCOVEROPTS_OFFSET_CLIENT_ID], hwaddr, 6);
gethostname(&discoveropts[DISCOVEROPTS_OFFSET_HOSTNAME], 64);
if (discoveropts[DISCOVEROPTS_OFFSET_HOSTNAME + 63] == '\0')
discoveropts[DISCOVEROPTS_OFFSET_HOSTNAME - 1] = strlen(&discoveropts[DISCOVEROPTS_OFFSET_HOSTNAME]);
offer_t offer;
bool gotoffer = false;
while (gotoffer == false) {
printf("sending discover...\n");
if (discover())
return EXIT_FAILURE;
printf("waiting for offer...\n");
while (gotoffer == false) {
if (waitforserver(10000))
break;
printf("got offer!\n");
uint32_t rxid;
if (processoffer(&offer, &rxid))
return EXIT_FAILURE;
printf("processed offer!\n");
// packet wasn't for this machine
if (rxid != xid)
continue;
printf("packet id ok\n");
gotoffer = true;
}
}
bool gotack = false;
while (gotack == false) {
printf("sending request...\n");
if (request(&offer))
return EXIT_FAILURE;
printf("waiting for ack...\n");
while (gotack == false) {
if (waitforserver(10000))
break;
uint32_t rxid;
printf("got ack\n");
if (getack(&rxid))
return EXIT_FAILURE;
printf("ack ok\n");
if (rxid != xid)
continue;
printf("ack id ok\n");
gotack = true;
}
}