1 #include <assert.h>
2 #include <stdio.h>
3 #include <stdlib.h>
4 #include <string.h>
5
6 #include <uv.h>
7
8 uv_loop_t *loop;
9 uv_udp_t send_socket;
10 uv_udp_t recv_socket;
11
alloc_buffer(uv_handle_t * handle,size_t suggested_size,uv_buf_t * buf)12 void alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) {
13 buf->base = malloc(suggested_size);
14 buf->len = suggested_size;
15 }
16
on_read(uv_udp_t * req,ssize_t nread,const uv_buf_t * buf,const struct sockaddr * addr,unsigned flags)17 void on_read(uv_udp_t *req, ssize_t nread, const uv_buf_t *buf, const struct sockaddr *addr, unsigned flags) {
18 if (nread < 0) {
19 fprintf(stderr, "Read error %s\n", uv_err_name(nread));
20 uv_close((uv_handle_t*) req, NULL);
21 free(buf->base);
22 return;
23 }
24
25 char sender[17] = { 0 };
26 uv_ip4_name((const struct sockaddr_in*) addr, sender, 16);
27 fprintf(stderr, "Recv from %s\n", sender);
28
29 // ... DHCP specific code
30 unsigned int *as_integer = (unsigned int*)buf->base;
31 unsigned int ipbin = ntohl(as_integer[4]);
32 unsigned char ip[4] = {0};
33 int i;
34 for (i = 0; i < 4; i++)
35 ip[i] = (ipbin >> i*8) & 0xff;
36 fprintf(stderr, "Offered IP %d.%d.%d.%d\n", ip[3], ip[2], ip[1], ip[0]);
37
38 free(buf->base);
39 uv_udp_recv_stop(req);
40 }
41
make_discover_msg()42 uv_buf_t make_discover_msg() {
43 uv_buf_t buffer;
44 alloc_buffer(NULL, 256, &buffer);
45 memset(buffer.base, 0, buffer.len);
46
47 // BOOTREQUEST
48 buffer.base[0] = 0x1;
49 // HTYPE ethernet
50 buffer.base[1] = 0x1;
51 // HLEN
52 buffer.base[2] = 0x6;
53 // HOPS
54 buffer.base[3] = 0x0;
55 // XID 4 bytes
56 if (uv_random(NULL, NULL, &buffer.base[4], 4, 0, NULL))
57 abort();
58 // SECS
59 buffer.base[8] = 0x0;
60 // FLAGS
61 buffer.base[10] = 0x80;
62 // CIADDR 12-15 is all zeros
63 // YIADDR 16-19 is all zeros
64 // SIADDR 20-23 is all zeros
65 // GIADDR 24-27 is all zeros
66 // CHADDR 28-43 is the MAC address, use your own
67 buffer.base[28] = 0xe4;
68 buffer.base[29] = 0xce;
69 buffer.base[30] = 0x8f;
70 buffer.base[31] = 0x13;
71 buffer.base[32] = 0xf6;
72 buffer.base[33] = 0xd4;
73 // SNAME 64 bytes zero
74 // FILE 128 bytes zero
75 // OPTIONS
76 // - magic cookie
77 buffer.base[236] = 99;
78 buffer.base[237] = 130;
79 buffer.base[238] = 83;
80 buffer.base[239] = 99;
81
82 // DHCP Message type
83 buffer.base[240] = 53;
84 buffer.base[241] = 1;
85 buffer.base[242] = 1; // DHCPDISCOVER
86
87 // DHCP Parameter request list
88 buffer.base[243] = 55;
89 buffer.base[244] = 4;
90 buffer.base[245] = 1;
91 buffer.base[246] = 3;
92 buffer.base[247] = 15;
93 buffer.base[248] = 6;
94
95 return buffer;
96 }
97
on_send(uv_udp_send_t * req,int status)98 void on_send(uv_udp_send_t *req, int status) {
99 if (status) {
100 fprintf(stderr, "Send error %s\n", uv_strerror(status));
101 return;
102 }
103 }
104
main()105 int main() {
106 loop = uv_default_loop();
107
108 uv_udp_init(loop, &recv_socket);
109 struct sockaddr_in recv_addr;
110 uv_ip4_addr("0.0.0.0", 68, &recv_addr);
111 uv_udp_bind(&recv_socket, (const struct sockaddr *)&recv_addr, UV_UDP_REUSEADDR);
112 uv_udp_recv_start(&recv_socket, alloc_buffer, on_read);
113
114 uv_udp_init(loop, &send_socket);
115 struct sockaddr_in broadcast_addr;
116 uv_ip4_addr("0.0.0.0", 0, &broadcast_addr);
117 uv_udp_bind(&send_socket, (const struct sockaddr *)&broadcast_addr, 0);
118 uv_udp_set_broadcast(&send_socket, 1);
119
120 uv_udp_send_t send_req;
121 uv_buf_t discover_msg = make_discover_msg();
122
123 struct sockaddr_in send_addr;
124 uv_ip4_addr("255.255.255.255", 67, &send_addr);
125 uv_udp_send(&send_req, &send_socket, &discover_msg, 1, (const struct sockaddr *)&send_addr, on_send);
126
127 return uv_run(loop, UV_RUN_DEFAULT);
128 }
129
