From mboxrd@z Thu Jan  1 00:00:00 1970
Date: Mon, 29 Feb 2016 22:08:42 +0100
From: Gilles Chanteperdrix <gilles.chanteperdrix@xenomai.org>
Message-ID: <20160229210842.GD26312@hermes.click-hack.org>
References: <56d4b0f131fc36.79352149@wp.pl>
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Subject: Re: [Xenomai] RTnet -- receive broadcast frame at the local machine
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To: Mariusz Janiak <mariuszjaniak@wp.pl>
Cc: Xenomai <xenomai@xenomai.org>

On Mon, Feb 29, 2016 at 09:58:25PM +0100, Mariusz Janiak wrote:
> Dnia Poniedzia=B3ek, 29 Lutego 2016 21:29 Gilles Chanteperdrix <gilles.ch=
anteperdrix@xenomai.org> napisa=B3(a)=20
> > On Mon, Feb 29, 2016 at 09:24:11PM +0100, Mariusz Janiak wrote:
> > > Dear Xenomai users,
> > >=20
> > > Since RTnet has been integrated with Xenomai I address this question =
to you. The question is, how to receive a broadcast frame at the local mach=
ine without using the localhost? The issue is following, we have two proces=
s with separate rtsockets at the single machine (of course we have differen=
t machines in the network but this is not a case). One process send a broad=
cast UDP frame to the specified UDP port -- we have one rteth device on the=
 machine. The second process listen on that port=20
> > > (receivefrom) and does not receive the broadcast frame sent by first =
process. I have found the following thread on the RTnet mailing list=20
> > >=20
> > > https://sourceforge.net/p/rtnet/mailman/message/6787561/
> > >=20
> > > Could you please point me the place which should be hacked to duplica=
te outgoing packets if there are multiple
> > > matching routes?
> >=20
> > I ma not sure I understand what you are looking for, but to receive
> > on a host the frames sent by that host, you need to enable and load
> > the loopback module. When you do that, no hack should be needed.
> >=20
> > --=20
> > 					    Gilles.
> > https://click-hack.org
>=20
> Hi Gilles,
>=20
> I am pretty sure that loopback module has been loaded, this is standard R=
Tnet configuration that has not been changed by me. Beside that, there is r=
tlo (127.0.0.1) device which is created when RT_LOOPBACK=3D"yes" in rtnet.c=
onf.=20
>=20
> Below you will find simple testcase. Compile this using Xenomai posix ski=
n.=20
>=20
> 1) receiver.c
> #include <stdio.h>
> #include <unistd.h>
> #include <stdlib.h>
> #include <sys/mman.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <arpa/inet.h>
> #include <rtnet.h>
> #define DEF_REC_PORT 1883
>=20
> int sock;
> struct sockaddr_in rec_addr;
>=20
> int main()
> {
>   int enable =3D 1;
>   int buffer[100];
>   socklen_t len =3D sizeof(rec_addr);
>=20
>   mlockall(MCL_CURRENT|MCL_FUTURE);

1->

>=20
>   sock =3D socket(AF_INET, SOCK_DGRAM, 0);

2->

>   setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &enable, sizeof(enable));

3->

>=20
>   memset(&rec_addr, 0, sizeof(struct sockaddr_in));
>   rec_addr.sin_family      =3D AF_INET;
>   rec_addr.sin_port        =3D htons(DEF_REC_PORT);
>   rec_addr.sin_addr.s_addr =3D INADDR_ANY;
>   bind(sock, (struct sockaddr *) &rec_addr, sizeof(struct
>   sockaddr_in));

4->

>=20
>   while (1) {
>     memset(buffer, 0, 100);
>     recvfrom(sock, buffer, 100, 0, &rec_addr, &len);

5->

>     printf("%s\n", buffer);
>   }
>   close(sock);
>   return 0;
> }
>=20
>=20
> 2. sender.c
> #include <unistd.h>
> #include <stdlib.h>
> #include <sys/mman.h>
> #include <sys/socket.h>
> #include <netinet/in.h>
> #include <arpa/inet.h>
> #include <rtnet.h>
> #include <rtnet_config.h>
> #define DEF_SND_PORT 1883
> #define DEF_SND_IP   "10.0.0.255"
>=20
> int sock;
> struct sockaddr_in snd_addr;
> int ret, size;
>=20
> int main()
> {
>   int enable =3D 1;
>   struct in_addr  snd_ip;
>   char buffer[] =3D "Hello";
>   socklen_t len =3D sizeof(snd_addr);
>=20
>   mlockall(MCL_CURRENT|MCL_FUTURE);

6->

>=20
>   inet_aton(DEF_SND_IP, &snd_ip);

7->

>   sock =3D socket(AF_INET, SOCK_DGRAM, 0);

8->

>   setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &enable,
>   sizeof(enable));

9->

>=20
>   memset(&snd_addr, 0, sizeof(struct sockaddr_in));
>   snd_addr.sin_family =3D AF_INET;
>   snd_addr.sin_port =3D htons(DEF_SND_PORT);
>   snd_addr.sin_addr =3D snd_ip;
>=20
>   while (1) {
>     ret =3D sendto(sock, buffer, 6, 0 , &snd_addr, len);

10->

So, that is 10 function calls without checking the return value.
Please check the function return values.

--=20
					    Gilles.
https://click-hack.org