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Re: RPC clnt_create() adress already in use




Hello Mark,

i downloaded the sources of libtirpc from this url: https://sourceforge.net/projects/libtirpc/files/libtirpc/1.0.1/ and unpacked it in the local subdirectory libtirpc-1.0.1.
I had to make the following changes:

libtirpc-1.0.1/src/clnt_bcast.c (because POLLRDNORM, POLLRDBAND are already defined in /usr/include/sys/poll.h) :

--> #ifndef POLLRDNORM
--> # define POLLRDNORM     0x040           /* Normal data may be read.  */
--> # define POLLRDBAND     0x080           /* Priority data may be read.  */
--> #endif

libtirpc-1.0.1/tirpc/rpc/xdr.h (typedefs where missed):

--> #include <rpc/types.h>

--> typedef __uint64_t      u_quad_t;
--> typedef __int64_t       quad_t;


I linked the necessary source files with my testprogram:

gcc -D__GLIBC__ -D__linux__ -I/c/dh-progs/tstdir/libtirpc-1.0.1/tirpc \
tst_rpc.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/clnt_bcast.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/clnt_dg.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/clnt_generic.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/clnt_perror.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/clnt_vc.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpc_callmsg.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpc_commondata.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpc_generic.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpc_prot.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpcb_clnt.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/rpcb_prot.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/xdr.c  \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/xdr_array.c  \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/xdr_mem.c  \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/xdr_rec.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/xdr_reference.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/getnetconfig.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/getnetpath.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/auth_none.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/auth_unix.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/authunix_prot.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/mt_misc.c \
/c/dh-progs/tstdir/libtirpc-1.0.1/src/debug.c \
-o tst_rpc-libtirpc-1-0-1

The program works perfectly (no errors is test cases 1 and 2).

I assume, there must be a difference between the downloaded lib-files and the Cygwin-libtirpc.

Raimund Paulus


-----Ursprüngliche Nachricht-----
Von: cygwin-owner@xxxxxxxxxx [mailto:cygwin-owner@xxxxxxxxxx] Im Auftrag von Mark Geisert
Gesendet: Mittwoch, 27. September 2017 11:50
An: cygwin@xxxxxxxxxx
Betreff: Re: RPC clnt_create() adress already in use

Hello Raimund,
Let's keep this on the mailing list please.

PAULUS, Raimund, TI-ABN wrote:
> Hallo Mark Geisert,
>
> many thanks for your answer. I supposed this too.
>
> I included in my source code the following function calls after clnt_create():
>
> int fd = 0;
> bool bool_ret = clnt_control(cl, CLGET_FD, &fd); if(bool_ret == true) {
>   printf("fd: %d\n", fd);
>
>   int enable = 1;
>   retval = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &enable, sizeof(int));
>   if(retval < 0)
>     fprintf(stderr, "Fehler setsockopt(): %s\n", strerror(errno)); }
>
> The function clnt_control() delivers the socket of the RPC-Client-Handle.
> The result is the same as before. Moreover i think, the effect of setsockopt() would be valid only during the process is running (my test scenarios 1 and 2).
> But it wouldn't change anything regarding my test scenario 3 (several restarts).
>
> Raimund

I looked through the libtirpc source code and nowhere is SO_REUSEADDR being set. 
  You are on the right track with how to do it, but by the time clnt_create() returns to you it is already too late.  As far as I can tell there is no way to get access to the socket between the time it's created within libtirpc and the time it's made available to you by clnt_create().

I did try running your testcase (thanks for supplying that) but I don't have a local machine running RPC services and don't wish to poke at random machines on the Internet ;-).  I had to compile it as so:
     gcc -g -o test_rpc -I/usr/include/tirpc test_rpc.c -ltirpc You are taking care to compile against the correct RPC-package includes and link against the correct RPC-package libraries, yes?

Speculation: There might be a way to decompose what clnt_create() does into other libtirpc functions that accomplish the same thing, but in smaller pieces such that you could set the socket option before bind() is called.  That would be a fair amount of work though and given my cursory look at the source I don't know if it's even possible.

..mark

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