packets dropped by kernel?
hi.
i was into raw sockets the last time so i wrote a simple
program that would create a single packet and send it
to the destination.
Code:
#include <netinet/in.h>
#include <sys/socket.h>
#include <netinet/ip.h>
#include <netinet/tcp.h>
int main ()
{
int tcp_socket;
struct sockaddr_in peer;
struct send_tcp
{
struct iphdr ip;
struct tcphdr tcp;
} packet;
packet.ip.version = 4;
packet.ip.ihl = 5;
packet.ip.tos = 0;
packet.ip.tot_len = htons(40);
packet.ip.id = 1;
packet.ip.frag_off = 0;
packet.ip.ttl = 255;
packet.ip.protocol = IPPROTO_TCP;
packet.ip.check = 14536;
packet.ip.saddr = inet_addr("192.168.0.10");
packet.ip.daddr = inet_addr("192.168.0.1");
packet.tcp.source = htons(8000);
packet.tcp.dest = htons(23);
packet.tcp.seq = 1;
packet.tcp.ack_seq = 2;
packet.tcp.doff = 5;
packet.tcp.res1 = 0;
packet.tcp.fin = 0;
packet.tcp.syn = 1;
packet.tcp.rst = 0;
packet.tcp.psh = 0;
packet.tcp.ack = 0;
packet.tcp.urg = 0;
packet.tcp.res2 = 0;
packet.tcp.window = htons(512);
packet.tcp.check = 8889;
packet.tcp.urg_ptr = 0;
peer.sin_family = AF_INET;
peer.sin_port = htons(25);
peer.sin_addr.s_addr = inet_addr("192.168.0.1");
tcp_socket = socket(AF_INET, SOCK_RAW, IPPROTO_RAW);
sendto(tcp_socket, &packet, sizeof(packet), 0, (struct sockaddr *)&peer, sizeof(peer));
close(tcp_socket);
return 0;
}
with that code i want to establish a connection to my gateway on port 23. so i switched on tcpdump on the gateway and sent the packet. the was successfully sent but the gateway wasnt replying to that syn packet.
why that?
thanks
ps. i have the port openend i want to connect to.
