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timeout on gethostbyaddr() function

I got the following "dns lookup with timeout" code from:

http://orange.kame.net/dev/cvsweb.cgi/wwwoffle/ sockets4.c?rev=1.1&cvsroot=apps-obsoleted

If my connection to the internet is ok, then it works great, but if I disrupt my connection to check that the timeout is working, my app dies with signal 10.

Anyone see the problem or know another way to specify a timeout on gethostbyaddr()?

Thanks.

- Philip


static void sigalarm(int signum) {
longjmp(dns_jmp_env,1);
}

- (NSString *)dnsLookupForIP:(NSString *)ip {
struct sigaction action;

start:

if(!timeout_dns) {
host = gethostbyaddr((const void*)&MYaddr, sizeof(struct in_addr), AF_INET);
if (host) {
return [NSString stringWithCString:host->h_name];
} else {
return @"n/a";
}
}

action.sa_handler = sigalarm;
sigemptyset (&action.sa_mask);
action.sa_flags = 0;
if (sigaction(SIGALRM, &action, NULL) != 0) {
printf("Failed to set SIGALRM; cancelling timeout for DNS.\n");
timeout_dns=0;
goto start;
}

alarm(timeout_dns);

if (setjmp(dns_jmp_env)) {
host=NULL;
errno=ETIMEDOUT;
} else {
inet_aton([ip cString], &MYaddr);
host = gethostbyaddr((const void*)&MYaddr, sizeof(struct in_addr), AF_INET);
}

alarm(0);
action.sa_handler = SIG_IGN;
sigemptyset (&action.sa_mask);
action.sa_flags = 0;
if (sigaction(SIGALRM, &action, NULL) != 0)
printf("Failed to clear SIGALRM.\n");

if (host) {
return [NSString stringWithCString:host->h_name];
} else {
return @"n/a";
}
}
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