Re: [RFC] small app for aiding non-MII card link detection on idle networks

[Paul Ionescu <i_p_a_u_l yahoo com>]

Hi,

--- Dan Williams <dcbw redhat com> wrote:

> Hi,
> 
> As far as I know, some cards actually just loop even Ethernet loopback packets 
> back to the box without sending them over the wire...  Though that's probably 
> not your average garden-variety cards in desktop computers.
> 
Could be. But those are exceptions, I hope.
I don't know how many cards of this type exists, and if it's the card fault or the driver's, but
if they are not the average cards in desktops, then they are not impacting the target of NM.
Anyway, if they are not too many, we can probably make a blacklist of them.
If you have several non-MII cards, you can see if it works on all of them or not.
I only tested with my e100/e1000 cards (which are actually MII cards) because I don't have anymore
any old non-MII card.

Thanks,
Paul

> Dan
> 
> On Tue, 8 Feb 2005, Paul Ionescu wrote:
> 
> > Hi Dan,
> > 
> > Here is a small program to send a LOOPBACK packet on an interface.
> > I tested on my systems (FC2/FC3) and it works.
> > Launch it with an ethernet interface argument for sending a loopback
> > packet on that interface.
> > If the link is up, then you will have growing RX_bytes on the interface.
> > We should run this only if there is no network activity, ie RX_bytes on
> > the interface is not growing.
> > At one point we may want this in HAL, and HAL will export to everybody the
> > link status of the non-MII card.
> > 
> > The program bellow can be improved, but it is a working start.
> > Comments ?
> > 
> > #include <unistd.h>
> > #include <stdlib.h>
> > #include <stdio.h>
> > #include <errno.h>
> > #include <ctype.h>
> > #include <string.h>
> > #include <sys/socket.h>
> > #include <sys/types.h>
> > #include <sys/ioctl.h>
> > #include <linux/if.h>
> > 
> > char outpack[30];
> > 
> > int main(int argc, char *argv[])
> > {
> >         struct sockaddr whereto;
> >         char *ifname = "eth0" ;
> >         int s;
> > 
> >         if (argc == 2) ifname = argv[1] ;
> >                 else
> >                         {
> >                         puts ("Usage : loop NETWORK_INTERFACE \n\
> > where NETWORK_INTERFACE is a valid ethernet device \n\
> > default NETWORK_INTERFACE is eth0, all other arguments are ignored");
> >                         }
> > 
> >         if ((s = socket(AF_INET, SOCK_PACKET, SOCK_PACKET)) < 0) {
> >                 if (errno == EPERM)
> >                         fprintf(stderr, "must run me as root\n");
> >                 else
> >                         perror("error socket");
> >         }
> >         /* Don't revert if debugging allows a normal user to get the raw socket. */
> >         setuid(getuid());
> > 
> >         struct ifreq if_hwaddr;
> >         unsigned char *hwaddr = if_hwaddr.ifr_hwaddr.sa_data;
> > 
> >                 strcpy(if_hwaddr.ifr_name, ifname);
> >                 if (ioctl(s, SIOCGIFHWADDR, &if_hwaddr) < 0) {
> >                         fprintf(stderr, "SIOCGIFHWADDR on %s failed: %s\n", ifname,
> >                                         strerror(errno));
> >                         return 1;
> >                 }
> > 
> > /* set destination and source MAC address as our own */
> > 
> >                 memcpy(outpack, if_hwaddr.ifr_hwaddr.sa_data, 6);
> >                 memcpy(outpack+6, if_hwaddr.ifr_hwaddr.sa_data, 6);
> > 
> > /* set ETHER-TYPE to 0x9000 meaning LOOPBACK packet */
> >                 outpack[12]=0x90;
> >                 outpack[13]=0x00;
> > 
> > /* set loop.function to Replay  */
> >                 outpack[16]=0x01;
> > 
> >         whereto.sa_family = 0;
> >         strcpy(whereto.sa_data, ifname);
> > 
> > /* send the whole packet which is 20 bytes long */
> > 
> >         if (sendto(s, outpack, 20 , 0, &whereto, sizeof(whereto)) < 0)
> >                 perror("sendto");
> > }
> > 
> > 
> > 
> 


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