[lkml]   [2002]   [Mar]   [6]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
Messages in this thread
Subjectproblem with ioctl SIOCSARP or is it?
Hi, can anybody from the linux kernel developers tell me what is wrong with 
proxy arp in kernel 2.4. I just want to configure my machine so as to act as
an arp proxy. When I do arp -s <ipaddr> <hwaddr> pub the kernel adds the
following line to my arp cache:
Address HWtype HWaddress Flags Mask Iface
ipaddr * * MP eth0
and when I am trying to ping the newly configured node I receive destination
unrichable message.
On the other hand I have the following programme which is supposed to do the
same task, however it adds exactly the same entry in the arp cache, and I
have also the same result as before when I try to ping the new node

main(argc, argv)
int argc;
char **argv;
int tunfd;
IP_addr ip_addr;
struct ifreq ifreq;
struct arpreq arp;
struct ether_addr ea;
struct sockaddr_in *paddr;

if( argc != 2){
printf("Usage: tunnel <IP ADDRESS>\n");

if( (inet_pton(AF_INET, *(argv + 1), &ip_addr)) < 0)
err_sys("inet_pton error");

if( (tunfd = socket(PF_INET, SOCK_DGRAM, 0)) < 0)
err_sys("socket error");

strcpy(ifreq.ifr_name, "eth0");
if( ioctl(tunfd, SIOCGIFHWADDR, &ifreq))
err_sys("ioctl error");

memcpy(&ea, ifreq.ifr_hwaddr.sa_data, ETH_ALEN);

memset(&arp, 0x00, sizeof(arp));

paddr = (struct sockaddr_in*) &arp.arp_pa;
bzero(paddr, sizeof(Sockaddr_in));
paddr->sin_family = AF_INET;
memcpy(&paddr->sin_addr, &ip_addr, sizeof(IP_addr));

arp.arp_ha.sa_family = ARPHRD_ETHER;
/*I tryied also AF_UNSPEC*/

memcpy(arp.arp_ha.sa_data, ea.ether_addr_octet, ETH_ALEN);

arp.arp_flags |= ATF_PUBL;

strcpy(arp.arp_dev, "eth0");

if( ioctl(tunfd, SIOCSARP, &arp))
err_sys("ioctl error");

err_sys("close error");

return 0;

All I want to know is if there is a problem with ioctl SIOCSARP. Is there any
other way to add entries to my arp cache? I heard about netlink sockets but
except the manual page I found nothing else.

PS1. The net.ipv4.conf.all.proxy_arp flag is set.
PS2. I subscribed to the kernel mailing list a few hours ago but still
haven't received any mail, so please if somebody answers include me in the cc:
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to
More majordomo info at
Please read the FAQ at

 \ /
  Last update: 2005-03-22 13:21    [W:0.027 / U:1.876 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site