iOS timeout of ping and ttl - iphone

Question

I want make ping with timeout and TTL. I use code by Apple ("Simple Ping"). I read it
"iOS ping with timeout". I change code:
CFSocketNativeHandle sock = CFSocketGetNative(self->_socket);
struct timeval tv;
tv.tv_sec = 0;
tv.tv_usec = 100000; // 0.1 sec
setsockopt(sock, SOL_SOCKET, SO_SNDTIMEO, (void *)&tv, sizeof(tv));
bytesSent = sendto(
sock,
[packet bytes],
[packet length],
0,
(struct sockaddr *) [self.hostAddress bytes],
(socklen_t) [self.hostAddress length]
);
But I don't understand where I should put code that will show me timeout of receiving packets. Also I need to make ping with TTL (time-to-live) information. I want get information based on this pattern: icmp_seq=count from=ip_address ttl=value_of_ttl time=value_of_replytime_ms

Answer 1

To modify the default TTL in the IP Header, call setsockopt with IP_TTL as parameter (tested with IPv4):
- (BOOL)setTTL:(int)ttl{
CFSocketNativeHandle sock = CFSocketGetNative(self->_socket);
int status = setsockopt(sock, IPPROTO_IP, IP_TTL, &ttl, sizeof(ttl));
if(status < 0)
{
return NO;
}
return YES;
}
The "iOS ping with timeout" example add a output timeout to the socket. From what I understand, it will timeout if the packet is not been sent by the socket within this period. I could be wrong, but I cannot find this "timeout" value from the ICMP header and IPv4 header (ICMP Packet format).
Here are the console log and request, response packet captured using apple's simple ping:
If you only want to know the response time of the ping, I guess you can track it yourself in the delegate methods. Get timestamps when "didSendPacket" and "didReceivePingResponsePacket" functions called and then compare the difference.

Answer 2

You can always put some limit time on the receivefrom:
tv.tv_sec = 0;
tv.tv_usec = 10000;
setsockopt(recv_sock, SOL_SOCKET, SO_RCVTIMEO, (char *)&tv,sizeof(struct timeval));