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/* Copyright Joyent, Inc. and other Node contributors. All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to
* deal in the Software without restriction, including without limitation the
* rights to use, copy, modify, merge, publish, distribute, sublicense, and/or
* sell copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
* FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS
* IN THE SOFTWARE.
*/
#include "uv.h"
#include "task.h"
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
typedef struct {
uv_write_t req;
uv_buf_t buf;
} write_req_t;
/* used to track multiple DNS requests received */
typedef struct {
char* prevbuf_ptr;
int prevbuf_pos;
int prevbuf_rem;
} dnsstate;
/* modify handle to append dnsstate */
typedef struct {
uv_tcp_t handle;
dnsstate state;
} dnshandle;
static uv_loop_t* loop;
static uv_tcp_t server;
static void after_write(uv_write_t* req, int status);
static void after_read(uv_stream_t*, ssize_t nread, const uv_buf_t* buf);
static void on_close(uv_handle_t* peer);
static void on_connection(uv_stream_t*, int status);
#define WRITE_BUF_LEN (64*1024)
#define DNSREC_LEN (4)
#define LEN_OFFSET 0
#define QUERYID_OFFSET 2
static unsigned char DNSRsp[] = {
0, 43, 0, 0, 0x81, 0x80, 0, 1, 0, 1, 0, 0, 0, 0
};
static unsigned char qrecord[] = {
5, 'e', 'c', 'h', 'o', 's', 3, 's', 'r', 'v', 0, 0, 1, 0, 1
};
static unsigned char arecord[] = {
0xc0, 0x0c, 0, 1, 0, 1, 0, 0, 5, 0xbd, 0, 4, 10, 0, 1, 1
};
static void after_write(uv_write_t* req, int status) {
write_req_t* wr;
if (status) {
fprintf(stderr, "uv_write error: %s\n", uv_strerror(status));
ASSERT(0);
}
wr = (write_req_t*) req;
/* Free the read/write buffer and the request */
free(wr->buf.base);
free(wr);
}
static void after_shutdown(uv_shutdown_t* req, int status) {
uv_close((uv_handle_t*) req->handle, on_close);
free(req);
}
static void addrsp(write_req_t* wr, char* hdr) {
char * dnsrsp;
short int rsplen;
short int* reclen;
rsplen = sizeof(DNSRsp) + sizeof(qrecord) + sizeof(arecord);
ASSERT (rsplen + wr->buf.len < WRITE_BUF_LEN);
dnsrsp = wr->buf.base + wr->buf.len;
/* copy stock response */
memcpy(dnsrsp, DNSRsp, sizeof(DNSRsp));
memcpy(dnsrsp + sizeof(DNSRsp), qrecord, sizeof(qrecord));
memcpy(dnsrsp + sizeof(DNSRsp) + sizeof(qrecord), arecord, sizeof(arecord));
/* overwrite with network order length and id from request header */
reclen = (short int*)dnsrsp;
*reclen = htons(rsplen-2);
dnsrsp[QUERYID_OFFSET] = hdr[QUERYID_OFFSET];
dnsrsp[QUERYID_OFFSET+1] = hdr[QUERYID_OFFSET+1];
wr->buf.len += rsplen;
}
static void process_req(uv_stream_t* handle,
ssize_t nread,
const uv_buf_t* buf) {
write_req_t* wr;
dnshandle* dns = (dnshandle*)handle;
char hdrbuf[DNSREC_LEN];
int hdrbuf_remaining = DNSREC_LEN;
int rec_remaining = 0;
int readbuf_remaining;
char* dnsreq;
char* hdrstart;
int usingprev = 0;
wr = (write_req_t*) malloc(sizeof *wr);
wr->buf.base = (char*)malloc(WRITE_BUF_LEN);
wr->buf.len = 0;
if (dns->state.prevbuf_ptr != NULL) {
dnsreq = dns->state.prevbuf_ptr + dns->state.prevbuf_pos;
readbuf_remaining = dns->state.prevbuf_rem;
usingprev = 1;
} else {
dnsreq = buf->base;
readbuf_remaining = nread;
}
hdrstart = dnsreq;
while (dnsreq != NULL) {
/* something to process */
while (readbuf_remaining > 0) {
/* something to process in current buffer */
if (hdrbuf_remaining > 0) {
/* process len and id */
if (readbuf_remaining < hdrbuf_remaining) {
/* too little to get request header. save for next buffer */
memcpy(&hdrbuf[DNSREC_LEN - hdrbuf_remaining],
dnsreq,
readbuf_remaining);
hdrbuf_remaining = DNSREC_LEN - readbuf_remaining;
break;
} else {
/* save header */
memcpy(&hdrbuf[DNSREC_LEN - hdrbuf_remaining],
dnsreq,
hdrbuf_remaining);
dnsreq += hdrbuf_remaining;
readbuf_remaining -= hdrbuf_remaining;
hdrbuf_remaining = 0;
/* get record length */
rec_remaining = (unsigned) hdrbuf[0] * 256 + (unsigned) hdrbuf[1];
rec_remaining -= (DNSREC_LEN - 2);
}
}
if (rec_remaining <= readbuf_remaining) {
/* prepare reply */
addrsp(wr, hdrbuf);
/* move to next record */
dnsreq += rec_remaining;
hdrstart = dnsreq;
readbuf_remaining -= rec_remaining;
rec_remaining = 0;
hdrbuf_remaining = DNSREC_LEN;
} else {
/* otherwise this buffer is done. */
rec_remaining -= readbuf_remaining;
break;
}
}
/* If we had to use bytes from prev buffer, start processing the current
* one.
*/
if (usingprev == 1) {
/* free previous buffer */
free(dns->state.prevbuf_ptr);
dnsreq = buf->base;
readbuf_remaining = nread;
usingprev = 0;
} else {
dnsreq = NULL;
}
}
/* send write buffer */
if (wr->buf.len > 0) {
if (uv_write((uv_write_t*) &wr->req, handle, &wr->buf, 1, after_write)) {
FATAL("uv_write failed");
}
}
if (readbuf_remaining > 0) {
/* save start of record position, so we can continue on next read */
dns->state.prevbuf_ptr = buf->base;
dns->state.prevbuf_pos = hdrstart - buf->base;
dns->state.prevbuf_rem = nread - dns->state.prevbuf_pos;
} else {
/* nothing left in this buffer */
dns->state.prevbuf_ptr = NULL;
dns->state.prevbuf_pos = 0;
dns->state.prevbuf_rem = 0;
free(buf->base);
}
}
static void after_read(uv_stream_t* handle,
ssize_t nread,
const uv_buf_t* buf) {
uv_shutdown_t* req;
if (nread < 0) {
/* Error or EOF */
ASSERT(nread == UV_EOF);
if (buf->base) {
free(buf->base);
}
req = malloc(sizeof *req);
uv_shutdown(req, handle, after_shutdown);
return;
}
if (nread == 0) {
/* Everything OK, but nothing read. */
free(buf->base);
return;
}
/* process requests and send responses */
process_req(handle, nread, buf);
}
static void on_close(uv_handle_t* peer) {
free(peer);
}
static void buf_alloc(uv_handle_t* handle,
size_t suggested_size,
uv_buf_t* buf) {
buf->base = malloc(suggested_size);
buf->len = suggested_size;
}
static void on_connection(uv_stream_t* server, int status) {
dnshandle* handle;
int r;
ASSERT(status == 0);
handle = (dnshandle*) malloc(sizeof *handle);
ASSERT(handle != NULL);
/* initialize read buffer state */
handle->state.prevbuf_ptr = 0;
handle->state.prevbuf_pos = 0;
handle->state.prevbuf_rem = 0;
r = uv_tcp_init(loop, (uv_tcp_t*)handle);
ASSERT(r == 0);
r = uv_accept(server, (uv_stream_t*)handle);
ASSERT(r == 0);
r = uv_read_start((uv_stream_t*)handle, buf_alloc, after_read);
ASSERT(r == 0);
}
static int dns_start(int port) {
struct sockaddr_in addr;
int r;
ASSERT(0 == uv_ip4_addr("0.0.0.0", port, &addr));
r = uv_tcp_init(loop, &server);
if (r) {
/* TODO: Error codes */
fprintf(stderr, "Socket creation error\n");
return 1;
}
r = uv_tcp_bind(&server, (const struct sockaddr*) &addr, 0);
if (r) {
/* TODO: Error codes */
fprintf(stderr, "Bind error\n");
return 1;
}
r = uv_listen((uv_stream_t*)&server, 128, on_connection);
if (r) {
/* TODO: Error codes */
fprintf(stderr, "Listen error\n");
return 1;
}
return 0;
}
HELPER_IMPL(dns_server) {
loop = uv_default_loop();
if (dns_start(TEST_PORT_2))
return 1;
uv_run(loop, UV_RUN_DEFAULT);
return 0;
}