#include #include #include #include #include uv_loop_t *loop; uv_udp_t send_socket; uv_udp_t recv_socket; void alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) { buf->base = malloc(suggested_size); buf->len = suggested_size; } void on_read(uv_udp_t *req, ssize_t nread, const uv_buf_t *buf, const struct sockaddr *addr, unsigned flags) { if (nread < 0) { fprintf(stderr, "Read error %s\n", uv_err_name(nread)); uv_close((uv_handle_t*) req, NULL); free(buf->base); return; } char sender[17] = { 0 }; uv_ip4_name((const struct sockaddr_in*) addr, sender, 16); fprintf(stderr, "Recv from %s\n", sender); // ... DHCP specific code unsigned int *as_integer = (unsigned int*)buf->base; unsigned int ipbin = ntohl(as_integer[4]); unsigned char ip[4] = {0}; int i; for (i = 0; i < 4; i++) ip[i] = (ipbin >> i*8) & 0xff; fprintf(stderr, "Offered IP %d.%d.%d.%d\n", ip[3], ip[2], ip[1], ip[0]); free(buf->base); uv_udp_recv_stop(req); } uv_buf_t make_discover_msg() { uv_buf_t buffer; alloc_buffer(NULL, 256, &buffer); memset(buffer.base, 0, buffer.len); // BOOTREQUEST buffer.base[0] = 0x1; // HTYPE ethernet buffer.base[1] = 0x1; // HLEN buffer.base[2] = 0x6; // HOPS buffer.base[3] = 0x0; // XID 4 bytes if (uv_random(NULL, NULL, &buffer.base[4], 4, 0, NULL)) abort(); // SECS buffer.base[8] = 0x0; // FLAGS buffer.base[10] = 0x80; // CIADDR 12-15 is all zeros // YIADDR 16-19 is all zeros // SIADDR 20-23 is all zeros // GIADDR 24-27 is all zeros // CHADDR 28-43 is the MAC address, use your own buffer.base[28] = 0xe4; buffer.base[29] = 0xce; buffer.base[30] = 0x8f; buffer.base[31] = 0x13; buffer.base[32] = 0xf6; buffer.base[33] = 0xd4; // SNAME 64 bytes zero // FILE 128 bytes zero // OPTIONS // - magic cookie buffer.base[236] = 99; buffer.base[237] = 130; buffer.base[238] = 83; buffer.base[239] = 99; // DHCP Message type buffer.base[240] = 53; buffer.base[241] = 1; buffer.base[242] = 1; // DHCPDISCOVER // DHCP Parameter request list buffer.base[243] = 55; buffer.base[244] = 4; buffer.base[245] = 1; buffer.base[246] = 3; buffer.base[247] = 15; buffer.base[248] = 6; return buffer; } void on_send(uv_udp_send_t *req, int status) { if (status) { fprintf(stderr, "Send error %s\n", uv_strerror(status)); return; } } int main() { loop = uv_default_loop(); uv_udp_init(loop, &recv_socket); struct sockaddr_in recv_addr; uv_ip4_addr("0.0.0.0", 68, &recv_addr); uv_udp_bind(&recv_socket, (const struct sockaddr *)&recv_addr, UV_UDP_REUSEADDR); uv_udp_recv_start(&recv_socket, alloc_buffer, on_read); uv_udp_init(loop, &send_socket); struct sockaddr_in broadcast_addr; uv_ip4_addr("0.0.0.0", 0, &broadcast_addr); uv_udp_bind(&send_socket, (const struct sockaddr *)&broadcast_addr, 0); uv_udp_set_broadcast(&send_socket, 1); uv_udp_send_t send_req; uv_buf_t discover_msg = make_discover_msg(); struct sockaddr_in send_addr; uv_ip4_addr("255.255.255.255", 67, &send_addr); uv_udp_send(&send_req, &send_socket, &discover_msg, 1, (const struct sockaddr *)&send_addr, on_send); return uv_run(loop, UV_RUN_DEFAULT); }