lokinet/llarp/dnsc.cpp

// why dnsd? what do you need from that?
#include "dnsd.hpp"
#include "buffer.hpp"

#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>		/* getaddrinfo, getnameinfo */
#include <stdlib.h>		/* exit */
#include <string.h>		/* memset */
#include <unistd.h>   /* close */

#include <netinet/in.h>
#include <arpa/inet.h>

#include "logger.hpp"
#include <llarp/dns.h>
#include "net.hpp" // for llarp::Addr
#include "net.hpp" // for llarp::Addr

// FIXME: make configurable
#define SERVER "8.8.8.8"
#define PORT 53

struct sockaddr *resolveHost(const char *url) {
  char* sUrl = strdup(url);
  struct dns_query dnsQuery;
  dnsQuery.length  = 12;
  dnsQuery.url     = sUrl;
  dnsQuery.reqType = 0x01;
  // dnsQuery.request  = { 0xDB, 0x42, 0x01, 0x00, 0x00, 0x01, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 };
  dnsQuery.request[ 0] = 0xDB;
  dnsQuery.request[ 1] = 0x42;
  dnsQuery.request[ 2] = 0x01;
  dnsQuery.request[ 3] = 0x00;
  dnsQuery.request[ 4] = 0x00;
  dnsQuery.request[ 5] = 0x01;
  dnsQuery.request[ 6] = 0x00;
  dnsQuery.request[ 7] = 0x00;
  dnsQuery.request[ 8] = 0x00;
  dnsQuery.request[ 9] = 0x00;
  dnsQuery.request[10] = 0x00;
  dnsQuery.request[11] = 0x00;

  char * word;
  unsigned int i;
  llarp::LogDebug("Asking DNS server %s about %s\n", SERVER, url);
  //dnsQuery.reqType = 0x01;

  word = strtok(sUrl, ".");
  while (word) {
    llarp::LogDebug("parsing hostname: \"%s\" is %zu characters\n", word, strlen(word));
    dnsQuery.request[dnsQuery.length++] = strlen(word);
    for (i = 0; i < strlen(word); i++) {
      dnsQuery.request[dnsQuery.length++] = word[i];
    }
    word = strtok(NULL, ".");
  }

  dnsQuery.request[dnsQuery.length++] = 0x00; // End of the host name
  dnsQuery.request[dnsQuery.length++] = 0x00; // 0x0001 - Query is a Type A query (host address)
  dnsQuery.request[dnsQuery.length++] = dnsQuery.reqType;
  dnsQuery.request[dnsQuery.length++] = 0x00; // 0x0001 - Query is class IN (Internet address)
  dnsQuery.request[dnsQuery.length++] = 0x01;

  struct sockaddr_in addr;
  //int socket;
  ssize_t ret;
  int rcode;
  socklen_t size;
  int ip = 0;
  int length;
  unsigned char buffer[DNC_BUF_SIZE];
  //unsigned char tempBuf[3];
  uint16_t QDCOUNT; //No. of items in Question Section
  uint16_t ANCOUNT; //No. of items in Answer Section
  uint16_t NSCOUNT; //No. of items in Authority Section
  uint16_t ARCOUNT; //No. of items in Additional Section
  uint16_t QCLASS; //Specifies the class of the query
  uint16_t ATYPE; //Specifies the meaning of the data in the RDATA field
  uint16_t ACLASS; //Specifies the class of the data in the RDATA field
  uint32_t TTL; //The number of seconds the results can be cached
  uint16_t RDLENGTH; //The length of the RDATA field
  uint16_t MSGID;

  int sockfd;

  sockfd = socket(AF_INET, SOCK_DGRAM, 0);
  if (sockfd < 0) {
    llarp::LogWarn("Error creating socket!\n");
    return nullptr;
  }
  //socket = sockfd;

  memset(&addr, 0, sizeof(addr));
  addr.sin_family = AF_INET;
  addr.sin_addr.s_addr = inet_addr(SERVER);
  addr.sin_port = htons(PORT);
  size = sizeof(addr);

  //hexdump("sending packet", &dnsQuery.request, dnsQuery.length);
  ret = sendto(sockfd, dnsQuery.request, dnsQuery.length, 0, (struct sockaddr*)&addr, size);
  if (ret < 0) {
    llarp::LogWarn("Error Sending Request");
    return nullptr;
  }
  //printf("Sent\n");

  memset(&buffer, 0, DNC_BUF_SIZE);
  ret = recvfrom(sockfd, buffer, DNC_BUF_SIZE, 0, (struct sockaddr*)&addr, &size);
  if (ret < 0) {
    llarp::LogWarn("Error Receiving Response");
    return nullptr;
  }

  //hexdump("received packet", &buffer, ret);

  close(sockfd);

  rcode = (buffer[3] & 0x0F);

  //tempBuf[0] = buffer[4];
  //tempBuf[1] = buffer[5];
  //tempBuf[2] = '\0';

  //printf("%0x %0x %0x %0x\n", buffer[4], buffer[5], tempBuf[0], tempBuf[1]);

  //QDCOUNT = (uint16_t) strtol(tempBuf, NULL, 16);
  QDCOUNT = (uint16_t)  buffer[4] * 0x100 + buffer[5];
  llarp::LogDebug("entries in question section: %u\n", QDCOUNT);
  ANCOUNT = (uint16_t)  buffer[6] * 0x100 + buffer[7];
  llarp::LogDebug("records in answer section: %u\n", ANCOUNT);
  NSCOUNT = (uint16_t)  buffer[8] * 0x100 + buffer[9];
  llarp::LogDebug("name server resource record count: %u\n", NSCOUNT);
  ARCOUNT = (uint16_t)  buffer[10] * 0x100 + buffer[11];
  llarp::LogDebug("additional records count: %u\n", ARCOUNT);

  llarp::LogDebug("query type: %u\n", dnsQuery.reqType);
  QCLASS = (uint16_t) dnsQuery.request[dnsQuery.length - 2] * 0x100 + dnsQuery.request[dnsQuery.length - 1];
  llarp::LogDebug("query class: %u\n", QCLASS);
  length = dnsQuery.length + 1;	 // to skip 0xc00c
  ATYPE = (uint16_t) buffer[length + 1] * 0x100 + buffer[length + 2];
  llarp::LogDebug("answer type: %u\n", ATYPE);
  ACLASS = (uint16_t) buffer[length + 3] * 0x100 + buffer[length + 4];
  llarp::LogDebug("answer class: %u\n", ACLASS);
  TTL = (uint32_t) buffer[length + 5] * 0x1000000 + buffer[length + 6] * 0x10000 + buffer[length + 7] * 0x100 + buffer[length + 8];
  llarp::LogDebug("seconds to cache: %u\n", TTL);
  RDLENGTH = (uint16_t) buffer[length + 9] * 0x100 + buffer[length + 10];
  llarp::LogDebug("bytes in answer: %u\n", RDLENGTH);
  MSGID = (uint16_t) buffer[0] * 0x100 + buffer[1];
  llarp::LogDebug("answer msg id: %u\n", MSGID);



  if (rcode == 2) {
    llarp::LogWarn("nameserver %s returned SERVFAIL:\n", SERVER);
    llarp::LogWarn("  the name server was unable to process this query due to a\n  problem with the name server.\n");
    return nullptr;
  } else if (rcode == 3) {
    llarp::LogWarn("nameserver %s returned NXDOMAIN for %s:\n", SERVER, dnsQuery.url);
    llarp::LogWarn("  the domain name referenced in the query does not exist\n");
    return nullptr;
  }

  /* search for and print IPv4 addresses */
  if (dnsQuery.reqType == 0x01) {
    llarp::LogDebug("DNS server's answer is: (type#=%u):", ATYPE);
    //printf("IPv4 address(es) for %s:\n", dnsQuery.url);
    for (i = 0 ; i < ret ; i++) {
      if (buffer[i] == 0xC0 && buffer[i+3] == 0x01) {
        ip++; i += 12; /* ! += buf[i+1]; */
        llarp::LogDebug(" %u.%u.%u.%u\n", buffer[i], buffer[i+1], buffer[i+2], buffer[i+3]);
        struct sockaddr *g_addr = new sockaddr;
        g_addr->sa_family = AF_INET;
        g_addr->sa_len = sizeof(in_addr);
        struct in_addr *addr = &((struct sockaddr_in *)g_addr)->sin_addr;
        unsigned char * ip;

        //have ip point to s_addr
        ip = (unsigned char *) &(addr->s_addr);

        ip[0]=buffer[i + 0];
        ip[1]=buffer[i + 1];
        ip[2]=buffer[i + 2];
        ip[3]=buffer[i + 3];

        return g_addr;
      }
    }

    if (!ip) {
      llarp::LogWarn("  No IPv4 address found in the DNS response!\n");
      return nullptr;
    }
  }
  return nullptr;
}

void
llarp_handle_dnsclient_recvfrom(struct llarp_udp_io *udp, const struct sockaddr *saddr,
                      const void *buf, ssize_t sz)
{
  //llarp::LogInfo("got a response, udp user is ", udp->user);
  struct dns_client_request *request = (struct dns_client_request *)udp->user;
  if (!request)
  {
    llarp::LogError("User data to DNS Client response not a dns_client_request");
    // we can't call back the hook
    return;
  }
  llarp_dnsc_unbind(request);

  if (sz < 0) {
    llarp::LogWarn("Error Receiving DNS Client Response");
    request->resolved(request);
    return;
  }

  unsigned char *castBuf = (unsigned char *)buf;
  auto buffer = llarp::StackBuffer< decltype(castBuf) >(castBuf);

  //hexdump("received packet", &buffer, ret);

  uint16_t QDCOUNT; //No. of items in Question Section
  uint16_t ANCOUNT; //No. of items in Answer Section
  uint16_t NSCOUNT; //No. of items in Authority Section
  uint16_t ARCOUNT; //No. of items in Additional Section
  uint16_t QCLASS; //Specifies the class of the query
  uint16_t ATYPE; //Specifies the meaning of the data in the RDATA field
  uint16_t ACLASS; //Specifies the class of the data in the RDATA field
  uint32_t TTL; //The number of seconds the results can be cached
  uint16_t RDLENGTH; //The length of the RDATA field
  uint16_t MSGID;
  int rcode;
  int length;

  struct dns_query *dnsQuery = &request->query;
  
  rcode = (buffer[3] & 0x0F);

  //tempBuf[0] = buffer[4];
  //tempBuf[1] = buffer[5];
  //tempBuf[2] = '\0';

  //printf("%0x %0x %0x %0x\n", buffer[4], buffer[5], tempBuf[0], tempBuf[1]);

  //QDCOUNT = (uint16_t) strtol(tempBuf, NULL, 16);
  QDCOUNT = (uint16_t)  buffer[4] * 0x100 + buffer[5];
  //llarp::LogDebug("entries in question section: %u\n", QDCOUNT);
  ANCOUNT = (uint16_t)  buffer[6] * 0x100 + buffer[7];
  //llarp::LogDebug("records in answer section: %u\n", ANCOUNT);
  NSCOUNT = (uint16_t)  buffer[8] * 0x100 + buffer[9];
  //llarp::LogDebug("name server resource record count: %u\n", NSCOUNT);
  ARCOUNT = (uint16_t)  buffer[10] * 0x100 + buffer[11];
  //llarp::LogDebug("additional records count: %u\n", ARCOUNT);

  //llarp::LogDebug("query type: %u\n", dnsQuery->reqType);
  QCLASS = (uint16_t) dnsQuery->request[dnsQuery->length - 2] * 0x100 + dnsQuery->request[dnsQuery->length - 1];
  //llarp::LogDebug("query class: %u\n", QCLASS);
  length = dnsQuery->length + 1;	 // to skip 0xc00c
  ATYPE = (uint16_t) buffer[length + 1] * 0x100 + buffer[length + 2];
  //llarp::LogDebug("answer type: %u\n", ATYPE);
  ACLASS = (uint16_t) buffer[length + 3] * 0x100 + buffer[length + 4];
  //llarp::LogDebug("answer class: %u\n", ACLASS);
  TTL = (uint32_t) buffer[length + 5] * 0x1000000 + buffer[length + 6] * 0x10000 + buffer[length + 7] * 0x100 + buffer[length + 8];
  //llarp::LogDebug("seconds to cache: %u\n", TTL);
  RDLENGTH = (uint16_t) buffer[length + 9] * 0x100 + buffer[length + 10];
  //llarp::LogDebug("bytes in answer: %u\n", RDLENGTH);
  MSGID = (uint16_t) buffer[0] * 0x100 + buffer[1];
  //llarp::LogDebug("answer msg id: %u\n", MSGID);

  if (rcode == 2) {
    llarp::LogWarn("nameserver %s returned SERVFAIL:\n", SERVER);
    llarp::LogWarn("  the name server was unable to process this query due to a\n  problem with the name server.\n");
    request->resolved(request);
    return;
  } else if (rcode == 3) {
    llarp::LogWarn("nameserver %s returned NXDOMAIN for %s:\n", SERVER, dnsQuery->url);
    llarp::LogWarn("  the domain name referenced in the query does not exist\n");
    request->resolved(request);
    return;
  }

  int ip = 0;

  /* search for and print IPv4 addresses */
  if (dnsQuery->reqType == 0x01) {
    llarp::LogInfo("DNS server's answer is: (type#=%u):", ATYPE);
    printf("IPv4 address(es) for %s:\n", dnsQuery->url);
    for (unsigned int i = 0 ; i < sz ; i++) {
      if (buffer[i] == 0xC0 && buffer[i+3] == 0x01) {
        ip++; i += 12; /* ! += buf[i+1]; */
        //llarp::LogInfo(" %u.%u.%u.%u\n", buffer[i], buffer[i+1], buffer[i+2], buffer[i+3]);
        
        /*
        struct sockaddr *g_addr = new sockaddr;
        g_addr->sa_family = AF_INET;
        g_addr->sa_len = sizeof(in_addr);
        struct in_addr *addr = &((struct sockaddr_in *)g_addr)->sin_addr;
        */

        unsigned char * ip;

        //have ip point to s_addr
        request->result.sa_family = AF_INET;
        request->result.sa_len = sizeof(in_addr);
        struct in_addr *addr = &((struct sockaddr_in *) &request->result)->sin_addr;

        //ip = (unsigned char *) &request->result.sa_data;
        ip = (unsigned char *) &(addr->s_addr);

        ip[0]=buffer[i + 0];
        ip[1]=buffer[i + 1];
        ip[2]=buffer[i + 2];
        ip[3]=buffer[i + 3];
        llarp::Addr test(request->result);
        llarp::LogInfo("IP Address ", test);

        //return g_addr;
        //request->result = g_addr;
        request->found = true;
        request->resolved(request);
        return;
      }
    }

    if (!ip) {
      llarp::LogWarn("  No IPv4 address found in the DNS response!\n");
      request->resolved(request);
      return;
    }
  }
}

void build_dns_query(struct dns_query *dnsQuery)
{
  dnsQuery->length  = 12;
  dnsQuery->reqType = 0x01;
  dnsQuery->request[ 0] = 0xDB;
  dnsQuery->request[ 1] = 0x42;
  dnsQuery->request[ 2] = 0x01;
  dnsQuery->request[ 3] = 0x00;
  dnsQuery->request[ 4] = 0x00;
  dnsQuery->request[ 5] = 0x01;
  dnsQuery->request[ 6] = 0x00;
  dnsQuery->request[ 7] = 0x00;
  dnsQuery->request[ 8] = 0x00;
  dnsQuery->request[ 9] = 0x00;
  dnsQuery->request[10] = 0x00;
  dnsQuery->request[11] = 0x00;

  char * word;
  //llarp::LogDebug("Asking DNS server %s about %s\n", SERVER, dnsQuery->url);
  
  char * strTemp = strdup(dnsQuery->url);
  word = strtok(strTemp, ".");
  while (word) {
    //llarp::LogDebug("parsing hostname: \"%s\" is %zu characters\n", word, strlen(word));
    dnsQuery->request[dnsQuery->length++] = strlen(word);
    for (unsigned int i = 0; i < strlen(word); i++) {
      dnsQuery->request[dnsQuery->length++] = word[i];
    }
    word = strtok(NULL, ".");
  }

  dnsQuery->request[dnsQuery->length++] = 0x00; // End of the host name
  dnsQuery->request[dnsQuery->length++] = 0x00; // 0x0001 - Query is a Type A query (host address)
  dnsQuery->request[dnsQuery->length++] = dnsQuery->reqType;
  dnsQuery->request[dnsQuery->length++] = 0x00; // 0x0001 - Query is class IN (Internet address)
  dnsQuery->request[dnsQuery->length++] = 0x01;
}

bool llarp_resolve_host(struct dnsc_context *dnsc, const char *url, resolve_dns_hook_func resolved, void *user)
{
  dns_client_request *request = new dns_client_request;
  request->sock      = (void *)&request->udp;
  request->user      = user;
  // configure query
  request->query.url = strdup(url);
  request->resolved  = resolved;
  request->found     = false;
  
  // request address holds through the packet recv
  request->udp.user = request;
  
  // finish setting up our query
  struct dns_query *dnsQuery = &request->query;
  build_dns_query(dnsQuery);
  
  // build a socket per request because we're multithreaded and will have many inflight
  if (!llarp_dnsc_bind(dnsc->netloop, request))
  {
    llarp::LogWarn("Error binding");
    return false;
  }
  
  ssize_t ret = llarp_ev_udp_sendto(&request->udp, dnsc->server, dnsQuery->request, dnsQuery->length);
  if (ret < 0) {
    llarp::LogWarn("Error Sending Request");
    return false;
  }
  
  return true;
}

void
llarp_host_resolved(dns_client_request *request)
{
  delete request;
}

bool
llarp_dnsc_bind(struct llarp_ev_loop *netloop, struct dns_client_request *request)
{
  // just grab a random open port
  struct sockaddr_in srcaddr;
  srcaddr.sin_addr.s_addr = inet_addr("0.0.0.0");
  srcaddr.sin_family = AF_INET;
  // we'll need to make sure the port is >1024 if not root

  request->udp.user      = request;
  request->udp.recvfrom  = &llarp_handle_dnsclient_recvfrom;
  request->udp.tick      = nullptr;

  // create new listener for this request
  return llarp_ev_add_udp(netloop, &request->udp, (const sockaddr *)&srcaddr) != -1;
}

// FIXME: drop the bool
bool
llarp_dnsc_unbind(struct dns_client_request *request)
{
  llarp_ev_close_udp(&request->udp); // stop listening
  return true;
}

bool
llarp_dnsc_init(struct dnsc_context *dnsc, struct llarp_ev_loop *netloop,
               const char *dnsc_hostname, uint16_t dnsc_port)
{
  sockaddr_in *trgaddr = new sockaddr_in;
  trgaddr->sin_addr.s_addr = inet_addr(dnsc_hostname);
  trgaddr->sin_port = htons(dnsc_port);
  trgaddr->sin_family = AF_INET;
  dnsc->server = (sockaddr *)trgaddr;
  dnsc->netloop = netloop;
  return true;
}

bool
llarp_dnsc_stop(struct dnsc_context *dnsc)
{
  //llarp_ev_close_udp(&dnsc->udp); // stop listening
  delete (sockaddr_in *)dnsc->server; // deallocation
  return true;
}