Date: Sun, 5 Jan 2003 05:31:35 -0600 (CST) From: Abdul Basit <basit@basit.cc> To: net@freebsd.org Subject: raw socket/icmp-echo Message-ID: <20030105052449.K49935-100000@wireless.cs.twsu.edu>
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Hello,
I was trying to learn raw sockets, I wrote a simple program
to get all icmp packets and display ..
-- program
int
main(void)
{
int sockfd;
int ip_len;
char *buf;
int n;
struct icmp *icmp;
struct ip *ip;
buf = (char*) malloc(sizeof(struct ip)+sizeof(struct icmp));
sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_ICMP);
for (;;) {
n = recv(sockfd, buf, sizeof(buf),0);
ip = (struct ip *) buf;
ip_len = ip->ip_hl << 2; // ip header length
icmp = (struct icmp *) (buf + ip_len);
if (icmp->icmp_type == ICMP_ECHO) {
printf("ping request arrived\n");
}
}
}
-- end
The program compiles fine, but it can't recieve echo request , seems like
the BSD kernel is not passing icmp echo type requests to raw socket?
I beleive this is NOT the case in Linux, why this behaviour exists in BSD?
is there any way to circumvent this ?
Also, if anyone know any good tutorial on bpf , let me know the url (some
simple example for capturing will be good .. i read bpf manpage, it seems
little obscure to me).
-- basit
Graduate Stdudent
Dept. Of Computer science.
Wichita state university
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