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160
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1 #include <assert.h>
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2 #include <stdio.h>
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3 #include <stdlib.h>
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4 #include <string.h>
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5
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6 #include <uv.h>
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7
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8 uv_loop_t *loop;
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9 uv_udp_t send_socket;
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10 uv_udp_t recv_socket;
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11
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12 void alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) {
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13 buf->base = malloc(suggested_size);
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14 buf->len = suggested_size;
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15 }
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16
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17 void on_read(uv_udp_t *req, ssize_t nread, const uv_buf_t *buf, const struct sockaddr *addr, unsigned flags) {
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18 if (nread < 0) {
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19 fprintf(stderr, "Read error %s\n", uv_err_name(nread));
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20 uv_close((uv_handle_t*) req, NULL);
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21 free(buf->base);
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22 return;
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23 }
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24
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25 char sender[17] = { 0 };
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26 uv_ip4_name((const struct sockaddr_in*) addr, sender, 16);
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27 fprintf(stderr, "Recv from %s\n", sender);
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28
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29 // ... DHCP specific code
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30 unsigned int *as_integer = (unsigned int*)buf->base;
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31 unsigned int ipbin = ntohl(as_integer[4]);
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32 unsigned char ip[4] = {0};
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33 int i;
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34 for (i = 0; i < 4; i++)
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35 ip[i] = (ipbin >> i*8) & 0xff;
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36 fprintf(stderr, "Offered IP %d.%d.%d.%d\n", ip[3], ip[2], ip[1], ip[0]);
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37
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38 free(buf->base);
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39 uv_udp_recv_stop(req);
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40 }
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41
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42 uv_buf_t make_discover_msg() {
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43 uv_buf_t buffer;
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44 alloc_buffer(NULL, 256, &buffer);
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45 memset(buffer.base, 0, buffer.len);
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46
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47 // BOOTREQUEST
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48 buffer.base[0] = 0x1;
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49 // HTYPE ethernet
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50 buffer.base[1] = 0x1;
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51 // HLEN
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52 buffer.base[2] = 0x6;
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53 // HOPS
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54 buffer.base[3] = 0x0;
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55 // XID 4 bytes
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56 if (uv_random(NULL, NULL, &buffer.base[4], 4, 0, NULL))
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57 abort();
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58 // SECS
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59 buffer.base[8] = 0x0;
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60 // FLAGS
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61 buffer.base[10] = 0x80;
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62 // CIADDR 12-15 is all zeros
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63 // YIADDR 16-19 is all zeros
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64 // SIADDR 20-23 is all zeros
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65 // GIADDR 24-27 is all zeros
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66 // CHADDR 28-43 is the MAC address, use your own
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67 buffer.base[28] = 0xe4;
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68 buffer.base[29] = 0xce;
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69 buffer.base[30] = 0x8f;
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70 buffer.base[31] = 0x13;
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71 buffer.base[32] = 0xf6;
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72 buffer.base[33] = 0xd4;
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73 // SNAME 64 bytes zero
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74 // FILE 128 bytes zero
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75 // OPTIONS
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76 // - magic cookie
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77 buffer.base[236] = 99;
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78 buffer.base[237] = 130;
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79 buffer.base[238] = 83;
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80 buffer.base[239] = 99;
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81
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82 // DHCP Message type
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83 buffer.base[240] = 53;
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84 buffer.base[241] = 1;
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85 buffer.base[242] = 1; // DHCPDISCOVER
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86
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87 // DHCP Parameter request list
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88 buffer.base[243] = 55;
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89 buffer.base[244] = 4;
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90 buffer.base[245] = 1;
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91 buffer.base[246] = 3;
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92 buffer.base[247] = 15;
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93 buffer.base[248] = 6;
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94
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95 return buffer;
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96 }
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97
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98 void on_send(uv_udp_send_t *req, int status) {
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99 if (status) {
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100 fprintf(stderr, "Send error %s\n", uv_strerror(status));
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101 return;
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102 }
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103 }
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104
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105 int main() {
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106 loop = uv_default_loop();
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107
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108 uv_udp_init(loop, &recv_socket);
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109 struct sockaddr_in recv_addr;
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110 uv_ip4_addr("0.0.0.0", 68, &recv_addr);
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111 uv_udp_bind(&recv_socket, (const struct sockaddr *)&recv_addr, UV_UDP_REUSEADDR);
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112 uv_udp_recv_start(&recv_socket, alloc_buffer, on_read);
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113
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114 uv_udp_init(loop, &send_socket);
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115 struct sockaddr_in broadcast_addr;
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116 uv_ip4_addr("0.0.0.0", 0, &broadcast_addr);
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117 uv_udp_bind(&send_socket, (const struct sockaddr *)&broadcast_addr, 0);
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118 uv_udp_set_broadcast(&send_socket, 1);
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119
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120 uv_udp_send_t send_req;
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121 uv_buf_t discover_msg = make_discover_msg();
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122
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123 struct sockaddr_in send_addr;
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124 uv_ip4_addr("255.255.255.255", 67, &send_addr);
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125 uv_udp_send(&send_req, &send_socket, &discover_msg, 1, (const struct sockaddr *)&send_addr, on_send);
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126
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127 return uv_run(loop, UV_RUN_DEFAULT);
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128 }
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