serval-dna/overlay_mdp.c

/*
Copyright (C) 2010-2012 Paul Gardner-Stephen, Serval Project.
 
This program is free software; you can redistribute it and/or
modify it under the terms of the GNU General Public License
as published by the Free Software Foundation; either version 2
of the License, or (at your option) any later version.
 
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
GNU General Public License for more details.
 
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
*/

#include "serval.h"
#include <sys/stat.h>

int mdp_abstract_socket=-1;
int mdp_named_socket=-1;
int overlay_mdp_setup_sockets()
{
  struct sockaddr_un name;
  int len;
  
  name.sun_family = AF_UNIX;
  
#ifndef HAVE_LINUX_IF_H
  /* Abstrack name space (i.e., non-file represented) unix domain sockets are a
     linux-only thing. */
  mdp_abstract_socket = -1;
#else
  if (mdp_abstract_socket==-1) {
    /* Abstract name space unix sockets is a special Linux thing, which is
       convenient for us because Android is Linux, but does not have a shared
       writable path that is on a UFS partition, so we cannot use traditional
       named unix domain sockets. So the abstract name space gives us a solution. */
    name.sun_path[0]=0;
    /* XXX The 100 should be replaced with the actual maximum allowed.
       Apparently POSIX requires it to be at least 100, but I would still feel
       more comfortable with using the appropriate constant. */
    snprintf(&name.sun_path[1],100,"org.servalproject.mesh.overlay.mdp");
    len = 1+strlen(&name.sun_path[1]) + sizeof(name.sun_family);
    
    mdp_abstract_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
    if (mdp_abstract_socket>-1) {
      int dud=0;
      int r=bind(mdp_abstract_socket, (struct sockaddr *)&name, len);
      if (r) { dud=1; r=0; WHY("bind() of abstract name space socket failed (not an error on non-linux systems"); }
      if (dud) {
	close(mdp_abstract_socket);
	mdp_abstract_socket=-1;
	WHY("Could not open abstract name-space socket (only a problem on Linux).");
      }
    }
  }
#endif
  if (mdp_named_socket==-1) {
    char *instancepath=serval_instancepath();
    if (strlen(instancepath)>85) return WHY("Instance path too long to allow construction of named unix domain socket.");
    snprintf(&name.sun_path[0],100,"%s/mdp.socket",instancepath);
    unlink(&name.sun_path[0]);
    len = 0+strlen(&name.sun_path[0]) + sizeof(name.sun_family)+1;
    mdp_named_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
    if (mdp_named_socket>-1) {
      int dud=0;
      int r=bind(mdp_named_socket, (struct sockaddr *)&name, len);
      if (r) { dud=1; r=0; WHY("bind() of named unix domain socket failed"); }
      if (dud) {
	close(mdp_named_socket);
	mdp_named_socket=-1;
	WHY("Could not open named unix domain socket.");
      }
    }
  }

  return 0;
  
}

int overlay_mdp_get_fds(struct pollfd *fds,int *fdcount,int fdmax)
{
  /* Make sure sockets are open */
  overlay_mdp_setup_sockets();

  if ((*fdcount)>=fdmax) return -1;
  if (mdp_abstract_socket>-1)
    {
      if (1||debug&DEBUG_IO) {
	fprintf(stderr,"MDP abstract name space socket is poll() slot #%d (fd %d)\n",
		*fdcount,mdp_abstract_socket);
      }
      fds[*fdcount].fd=mdp_abstract_socket;
      fds[*fdcount].events=POLLIN;
      (*fdcount)++;
    }
  if ((*fdcount)>=fdmax) return -1;
  if (mdp_named_socket>-1)
    {
      if (1||debug&DEBUG_IO) {
	fprintf(stderr,"MDP named unix domain socket is poll() slot #%d (fd %d)\n",
		*fdcount,mdp_named_socket);
      }
      fds[*fdcount].fd=mdp_named_socket;
      fds[*fdcount].events=POLLIN;
      (*fdcount)++;
    }


  return 0;
}

#define MDP_MAX_BINDINGS 100
#define MDP_MAX_SOCKET_NAME_LEN 110
int mdp_bindings_initialised=0;
sockaddr_mdp mdp_bindings[MDP_MAX_BINDINGS];
char mdp_bindings_sockets[MDP_MAX_BINDINGS][MDP_MAX_SOCKET_NAME_LEN];
int mdp_bindings_socket_name_lengths[MDP_MAX_BINDINGS];

int overlay_mdp_reply_error(int sock,
			    struct sockaddr_un *recvaddr,int recvaddrlen,
			    int error_number,char *message)
{
  overlay_mdp_frame mdpreply;

  mdpreply.packetTypeAndFlags=MDP_ERROR;
  mdpreply.error.error=error_number;
  if (error_number==0||message)
    snprintf(&mdpreply.error.message[0],128,"%s",message?message:"Success");
  else
    snprintf(&mdpreply.error.message[0],128,"Error code #%d",error_number);
  mdpreply.error.message[127]=0;
  int replylen=4+4+strlen(mdpreply.error.message)+1;
  errno=0;
  int r=sendto(sock,(char *)&mdpreply,replylen,0,
	       (struct sockaddr *)recvaddr,recvaddrlen);
  if (r<0) { 
    perror("sendto"); 
    WHY("sendto() failed when sending MDP reply"); 
    printf("sock=%d, r=%d\n",sock,r);
    return -1;
  }
  return 0;  
}

int overlay_mdp_reply_ok(int sock,
			 struct sockaddr_un *recvaddr,int recvaddrlen,
			 char *message)
{
  return overlay_mdp_reply_error(sock,recvaddr,recvaddrlen,0,message);
}

int overlay_mdp_process_bind_request(int sock,overlay_mdp_frame *mdp,
				     struct sockaddr_un *recvaddr,int recvaddrlen)
{
  int i;
  if (!mdp_bindings_initialised) {
    /* Mark all slots as unused */
    for(i=0;i<MDP_MAX_BINDINGS;i++) mdp_bindings[i].port=0;
    mdp_bindings_initialised=1;
  }

  /* See if binding already exists */
  int found=-1;
  int free=-1;
  for(i=0;i<MDP_MAX_BINDINGS;i++) {
    /* Look for duplicate bindings */
    if (mdp_bindings[i].port==mdp->bind.port_number)
      if (!memcmp(mdp_bindings[i].sid,mdp->bind.sid,SID_SIZE))
	{ found=i; break; }
    /* Look for free slots in case we need one */
    if ((free==-1)&&(mdp_bindings[i].port==0)) free=i;
  }
 
  /* Binding was found.  See if it is us, if so, then all is well,
     else we check flags to see if we should override the existing binding. */
  if (found>-1) {
    if (mdp_bindings_socket_name_lengths[found]==recvaddrlen)
      if (!memcmp(mdp_bindings_sockets[found],recvaddr->sun_path,recvaddrlen))
	{
	  fprintf(stderr,"Identical binding exists");
	  return overlay_mdp_reply_ok(sock,recvaddr,recvaddrlen,"Port bound (actually, it was already bound to you)");
	}
    /* Okay, so there is an existing binding.  Either replace it (if requested) or
       return an error */
    if (!(mdp->packetTypeAndFlags&MDP_FORCE))
      {
	fprintf(stderr,"Port already in use.\n");
	return overlay_mdp_reply_error(sock,recvaddr,recvaddrlen,3,
				       "Port already in use");
      }
    else {
      /* Cause existing binding to be replaced.
	 XXX - We should notify the existing binding holder that their binding
	 has been snaffled. */
      WHY("Warn socket holder about port-snatch");
      free=found;
    }
  }

  /* Okay, so no binding exists.  Make one, and return success.
     If we have too many bindings, we should return an error.
     XXX - We don't find out when the socket responsible for a binding has died,
     so stale bindings can hang around.  We really need a solution to this, e.g., 
     probing the sockets periodically (by sending an MDP NOOP frame perhaps?) and
     destroying any socket that reports an error.
  */
  if (free==-1) {
    /* XXX Should we probe for stale bindings here and now, since this is when
       we want the spare slots ? */
    WHY("Should probe existing bindings to see if any can be freed");
    fprintf(stderr,"No free port binding slots.  Close other connections and try again?");
    return overlay_mdp_reply_error(sock,recvaddr,recvaddrlen,4,"All binding slots in use. Close old connections and try again, or increase MDP_MAX_BINDINGS.");
  }

  /* Okay, record binding and report success */
  mdp_bindings[free].port=mdp->bind.port_number;
  memcpy(&mdp_bindings[free].sid[0],&mdp->bind.sid[0],SID_SIZE);
  mdp_bindings_socket_name_lengths[free]=recvaddrlen-2;
  memcpy(&mdp_bindings_sockets[free][0],&recvaddr->sun_path[0],
	 mdp_bindings_socket_name_lengths[free]);
  fprintf(stderr,"Port bound\n");
  return overlay_mdp_reply_ok(sock,recvaddr,recvaddrlen,"Port bound");
}

int overlay_saw_mdp_frame(int interface,overlay_frame *f,long long now)
{
  return WHY("Not implemented");
}

int overlay_mdp_poll()
{
  unsigned char buffer[16384];
  int ttl;
  unsigned char recvaddrbuffer[1024];
  struct sockaddr *recvaddr=(struct sockaddr *)&recvaddrbuffer[0];
  socklen_t recvaddrlen=sizeof(recvaddrbuffer);
  struct sockaddr_un *recvaddr_un=NULL;

  if (mdp_named_socket>-1) {
    ttl=-1;
    bzero((void *)recvaddrbuffer,sizeof(recvaddrbuffer));
    fcntl(mdp_named_socket, F_SETFL, 
	  fcntl(mdp_named_socket, F_GETFL, NULL)|O_NONBLOCK); 
    int len = recvwithttl(mdp_named_socket,buffer,sizeof(buffer),&ttl,
			  recvaddr,&recvaddrlen);
    recvaddr_un=(struct sockaddr_un *)recvaddr;

    if (len>0) {
      /* Look at overlay_mdp_frame we have received */
      overlay_mdp_frame *mdp=(overlay_mdp_frame *)&buffer[0];
      switch(mdp->packetTypeAndFlags&MDP_TYPE_MASK) {
      case MDP_TX: /* Send payload */
	break;
      case MDP_BIND: /* Bind to port */
	return overlay_mdp_process_bind_request(mdp_named_socket,mdp,
						recvaddr_un,recvaddrlen);
	break;
      default:
	/* Client is not allowed to send any other frame type */
	WHY("Illegal frame type.");
	mdp->packetTypeAndFlags=MDP_ERROR;
	mdp->error.error=2;
	snprintf(mdp->error.message,128,"Illegal request type.  Clients may use only MDP_TX or MDP_BIND.");
	int len=4+4+strlen(mdp->error.message)+1;
	errno=0;
	/* We ignore the result of the following, because it is just sending an
	   error message back to the client.  If this fails, where would we report
	   the error to? My point exactly. */
	sendto(mdp_named_socket,mdp,len,0,(struct sockaddr *)recvaddr,recvaddrlen);
      }
    }

    fcntl(mdp_named_socket, F_SETFL, 
	  fcntl(mdp_named_socket, F_GETFL, NULL)&(~O_NONBLOCK)); 
  }

  if (!(random()&0xff)) WHY("Not implemented");
  return -1;
}

int mdp_client_socket=-1;
int overlay_mdp_dispatch(overlay_mdp_frame *mdp,int flags,int timeout_ms)
{
  int len=4;
 
  if (mdp_client_socket==-1) overlay_mdp_client_init();

  /* Minimise frame length to save work and prevent accidental disclosure of
     memory contents. */
  switch(mdp->packetTypeAndFlags)
    {
    case MDP_TX: len=4+sizeof(mdp->out)+mdp->out.payload_length; break;
    case MDP_RX: len=4+sizeof(mdp->in)+mdp->out.payload_length; break;
    case MDP_BIND: len=4+4; break;
    case MDP_ERROR: len=4+4+strlen(mdp->error.message)+1; break;
    default:
      return WHY("Illegal MDP frame type.");
    }

  /* Construct name of socket to send to. */
  char mdp_socket_name[101];
  mdp_socket_name[100]=0;
  snprintf(mdp_socket_name,100,"%s/mdp.socket",serval_instancepath());
  if (mdp_socket_name[100]) {    
    return WHY("instance path is too long (unix domain named sockets have a short maximum path length)");
  }
  struct sockaddr_un name;
  name.sun_family = AF_UNIX;
  strcpy(name.sun_path, mdp_socket_name); 

  int result=sendto(mdp_client_socket, mdp, len, 0,
		    (struct sockaddr *)&name, sizeof(struct sockaddr_un));
  if (result<0) {
    mdp->packetTypeAndFlags=MDP_ERROR;
    mdp->error.error=1;
    snprintf(mdp->error.message,128,"Error sending frame to MDP server.");
    /* Clear socket so that we have the chance of reconnecting */
    overlay_mdp_client_done();
    return -1;
  } else {
    WHY("packet sent");
    if (!(flags&MDP_AWAITREPLY)) {       
      return 0;
    }
  }

  /* Wait for a reply until timeout */
  struct pollfd fds[1];
  int fdcount=1;
  fds[0].fd=mdp_client_socket; fds[0].events=POLLIN;
  result = poll(fds,fdcount,timeout_ms);
  if (result==0) {
    /* Timeout */
    mdp->packetTypeAndFlags=MDP_ERROR;
    mdp->error.error=1;
    snprintf(mdp->error.message,128,"Timeout waiting for reply to MDP packet (packet was successfully sent).");    
    return -1;
  }

  /* Check if reply available */
  unsigned char replybuffer[2048];
  fcntl(mdp_client_socket, F_SETFL, 
	fcntl(mdp_client_socket, F_GETFL, NULL)|O_NONBLOCK); 
  int ttl=-1;
  unsigned char recvaddrbuffer[1024];
  struct sockaddr *recvaddr=(struct sockaddr *)recvaddrbuffer;
  unsigned int recvaddrlen=sizeof(recvaddrbuffer);
  struct sockaddr_un *recvaddr_un;
  mdp->packetTypeAndFlags=0;
  len = recvwithttl(mdp_client_socket,(unsigned char *)mdp,
		    sizeof(overlay_mdp_frame),&ttl,recvaddr,&recvaddrlen);
  recvaddr_un=(struct sockaddr_un *)recvaddr;
  if (len>0) {
    /* Make sure recvaddr matches who we sent it to */
    if (strcmp(mdp_socket_name,recvaddr_un->sun_path)) {
      /* Okay, reply was PROBABLY not from the server, but on OSX if the path
	 has a symlink in it, it is resolved in the reply path, but might not
	 be in the request path (mdp_socket_name), thus we need to stat() and
	 compare inode numbers etc */
      struct stat sb1,sb2;
      if (stat(mdp_socket_name,&sb1)) return WHY("stat(mdp_socket_name) failed, so could not verify that reply came from MDP server");
      if (stat(recvaddr_un->sun_path,&sb2)) return WHY("stat(ra->sun_path) failed, so could not verify that reply came from MDP server");
      if ((sb1.st_ino!=sb2.st_ino)||(sb1.st_dev!=sb2.st_dev))
	return WHY("Reply did not come from server");
    }

    /* If all is well, examine result and return error code provided */
    WHY("Got a reply from server");
    if ((mdp->packetTypeAndFlags&MDP_TYPE_MASK)==MDP_ERROR)
	return mdp->error.error;
    else
      return WHY("MDP server replied with something unexpected");
  } else {
    /* poll() said that there was data, but there isn't.
       So we will abort. */
    return WHY("poll() aborted");
  }
}

int overlay_mdp_client_init()
{
  char mdp_temporary_socket[1024];
  mdp_temporary_socket[0]=0;
  if (mdp_client_socket==-1) {
    /* Open socket to MDP server (thus connection is always local) */
    WHY("Use of abstract name space socket for Linux not implemented");
    
    mdp_client_socket = socket(AF_UNIX, SOCK_DGRAM, 0);
    if (mdp_client_socket < 0) {
      perror("socket");
      return WHY("Could not open socket to MDP server");
    }

    /* We must bind to a temporary file name */
    snprintf(mdp_temporary_socket,1024,"%s/mdp-client.socket",serval_instancepath());
    unlink(mdp_temporary_socket);    
    struct sockaddr_un name;
    name.sun_family = AF_UNIX;
    snprintf(&name.sun_path[0],100,"%s",mdp_temporary_socket);
    int len = 1+strlen(&name.sun_path[0]) + sizeof(name.sun_family)+1;
    int r=bind(mdp_client_socket, (struct sockaddr *)&name, len);
    if (r) {
      WHY("Could not bind MDP client socket to file name");
      perror("bind");
      return -1;
    }
  }
  
  return 0;
}

int overlay_mdp_client_done()
{
  char mdp_temporary_socket[1024];
  snprintf(mdp_temporary_socket,1024,"%s/mdp-client.socket",serval_instancepath());
  unlink(mdp_temporary_socket);
  if (mdp_client_socket!=-1) close(mdp_client_socket);
  mdp_client_socket=-1;
  return 0;
}

int overlay_mdp_client_poll(long long timeout_ms)
{
  if (timeout_ms<0) timeout_ms=0;
  printf("waiting for %lldms on client socket.\n",timeout_ms);
  struct pollfd fds[1];
  int fdcount=1;
  fds[0].fd=mdp_client_socket; fds[0].events=POLLIN;

  return poll(fds,fdcount,timeout_ms);
}