I have a small program that uses the POSIX API calls like open(), read() to read a file. This file is "managed" by my 
resource manager. (ie, it is under my resource manager's mount point).

I want to find a non POSIX way to read from the file.

C program fragment (error checking code omitted):

int fd = open("/home/narrow/if.txt", O_RDONLY);
read(fd, buf, 20);

The kernel event trace is below, with some of my questions:

Event, Time, Owner, Type, Data
74272, 2s 576ms 892us, MyTestProgram Thread 1, ConnectAttach Enter, nd 0x0 pid 1 chid 0x1 index 0 flags 0x1 process 
procnto-smp-instr
	--> seems like it is making contact with the Process Manager. why?
74273, 2s 576ms 894us, MyTestProgram Thread 1, ConnectAttach Exit, coid 0x3
	--> seems like it got a connecton id 3
74274, 2s 576ms 895us, MyTestProgram Thread 1, MsgSendv Enter, coid 0x3 sparts 2 rparts 2 msg0 0x20100 msg1 0x0 msg2 
0x100a18 function _IO_CONNECT_OPEN
	--> seems like the POSIX open() call resulted in a Message Send to procnto. Why?
74357, 2s 577ms 121us, MyTestProgram Thread 1, MsgSendv Exit, status 2148204544 rmsg 0x20100
	--> how do I interpet the return value?
74366, 2s 577ms 154us, MyTestProgram Thread 1, ConnectAttach Enter, nd 0x0 pid 630794 chid 0x1 index 0 flags 0x1 process
 MyResourceManager
	--> seems like the POSIX open() call resulted in a Message Send to MyResourceManager. This was expected.
74368, 2s 577ms 158us, MyTestProgram Thread 1, ConnectAttach Exit, coid 0x3
	--> seems like it got a connecton id 3
74369, 2s 577ms 159us, MyTestProgram Thread 1, MsgSendv Enter, coid 0x3 sparts 2 rparts 2 msg0 0x20100 msg1 0x0 msg2 
0xf0998 function _IO_CONNECT_OPEN
	--> seems like it now sends a message (_IO_CONNECT) to my resource manager. Expected. How do I know the contents of the
 _IO_CONNECT? 
	--> Is it a two part IOV? if so, what is in those two parts?
134486, 3s 579ms 311us, MyTestProgram Thread 1, MsgSendv Exit, status 4294967295 rmsg 0x1

In this case, my registered callout for open(0 does get invoked.

QNX native fragment (error checking code omitted):

typedef struct
{
	uint16_t msg_type;
	unsigned data_size;
} header_t;

coid = ConnectAttach(0, 630794, 1, 0, 1); // I know that the pid of MyResourceManager is 630794

iov_t siov[2];

header_t hdr;
hdr.msg_type = _IO_CONNECT;
hdr.data_size = strlen("if.txt");
SETIOV (&siov[0], &hdr, sizeof hdr);
SETIOV (&siov[1],"if.txt", hdr.data_size);

char rec_msg[100];
int status = MsgSendvs(coid, siov, 2,rec_msg, sizeof (rec_msg) );
if(-1 == status)
{   //was there an error sending to server?
	printf("could not send message with errorno = %d and error string %s \n", errno, strerror(errno));
}

It prints the program output as: "could not send message with errorno = 89 and error string Function not implemented"

The corresponding kernel trace is:
Event, Time, Owner, Type, Data
49992, 1s 818ms 265us, ReaderAppSansPosix Thread 1, ConnectAttach Enter, nd 0x0 pid 1 chid 0x1 index 1073741824 flags 
0x0 process procnto-smp-instr
50054, 1s 819ms 153us, ReaderAppSansPosix Thread 1, ConnectAttach Exit, coid 0x40000000
	--> seems like it got a connecton id 0x40000000, different than the 3 in the above case
Event, Time, Owner, Type, Data
52646, 1s 824ms 422us, ReaderAppSansPosix Thread 1, ConnectAttach Enter, nd 0x0 pid 630794 chid 0x1 index 0 flags 0x1 
process MyResourceManager
52647, 1s 824ms 423us, ReaderAppSansPosix Thread 1, ConnectAttach Exit, coid 0x3
52648, 1s 824ms 425us, ReaderAppSansPosix Thread 1, MsgSendv Enter, coid 0x3 sparts 2 rparts 1 msg0 0x8040100 msg1 0x6 
msg2 0x0 function _IO_CONNECT
	--> this should have caused the message to show up in MyResourceManager (in the myio_open() which I specify during 
resmgr_attach())
	--> but this does not happen. Why?
	
What is the format of the _IO_CONNECT messsage that goes from the libc implementation of open() to a resource manager? I
 do not have the source code for libc....