Date: Mon, 18 Jul 2011 17:04:27 +0300 From: Daniel Braniss <danny@cs.huji.ac.il> To: freebsd-net@freebsd.org Cc: freebsd-hackers@freebsd.org Subject: broadcast oddity Message-ID: <E1QioQt-000MJQ-T9@kabab.cs.huji.ac.il>
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this code behaves correctly when run from a diskless host which booted via PXE,
but fails on a host that was booted from disk.
hint: the non working sends a packet with a non ethernet broadcast address and
an ip address of 255.255.255.255, the working version sets the ethernet address
to 0xffffffff and the ip to the network broadcast address.
what am I doing wrong?
danny
PS: what is the correct way to obtain the network broadcast address?
#include <sys/types.h>
#include <netinet/in.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <stdio.h>
void
bcast()
{
int so, on;
char msg[BUFSIZ];
struct timespec t2;
struct sockaddr_in soin;
if((so = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP)) < 0) {
perror("socket");
exit(-1);
}
on = 1;
if(setsockopt(so, SOL_SOCKET, SO_BROADCAST, &on, sizeof(on))) {
perror("setsockopt");
exit(-1);
}
bzero(&soin, sizeof(struct sockaddr_in));
soin.sin_len = sizeof(struct sockaddr_in);
soin.sin_family = AF_INET;
soin.sin_addr.s_addr = INADDR_BROADCAST;
soin.sin_port = htons(12345);
while(1) {
clock_gettime(CLOCK_REALTIME, &t2);
sprintf(msg, "0x%016x", t2.tv_sec);
if(sendto(so, msg, strlen(msg)+1,
0, (struct sockaddr *)&soin, sizeof(struct sockaddr)) < 0) {
perror("sendto");
break;
}
sleep(10);
}
}
main(int cc, char **vv)
{
bcast();
}
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