mydatagram.c

一个基于linux的TCP/IP协议栈的实现

static inline int myip_route_connect(struct rtable **rp, u32 dst,
				   u32 src, u32 tos, int oif, u8 protocol,
				   u16 sport, u16 dport, struct sock *sk)
{
	struct flowi fl = { .oif = oif,
			    .nl_u = { .ip4_u = { .daddr = dst,
						 .saddr = src,
						 .tos   = tos } },
			    .proto = protocol,
			    .uli_u = { .ports =
				       { .sport = sport,
					 .dport = dport } } };

	int err;
	if (!dst || !src) {
		err = __myip_route_output_key(rp, &fl);
		if (err)
			return err;
		fl.fl4_dst = (*rp)->rt_dst;
		fl.fl4_src = (*rp)->rt_src;
		ip_rt_put(*rp);
		*rp = NULL;
	}
	return myip_route_output_flow(rp, &fl, sk, 0);
}

int myip4_datagram_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len )
{
	struct inet_sock *inet = inet_sk(sk);
	struct sockaddr_in *usin = (struct sockaddr_in *) uaddr;
	struct rtable *rt;
	u32 saddr;
	int oif;
	int err;

	if (addr_len < sizeof(*usin)) 
	  	return -EINVAL;

	if (usin->sin_family != MY_AF_INET) 
	  	return -EAFNOSUPPORT;
	
	sk_dst_reset(sk);

	oif = sk->sk_bound_dev_if;
	saddr = inet->saddr;
	if (MULTICAST(usin->sin_addr.s_addr)) {
		if (!oif)
			oif = inet->mc_index;
		if (!saddr)
			saddr = inet->mc_addr;
	}
	err = myip_route_connect(&rt, usin->sin_addr.s_addr, saddr,
					RT_CONN_FLAGS(sk), oif,
					sk->sk_protocol,
					inet->sport, usin->sin_port, sk);
	if( err )
		return err;
	if( (rt->rt_flags & RTCF_BROADCAST) && !sock_flag(sk, SOCK_BROADCAST) ){
		ip_rt_put(rt);
		return -EACCES;
	}

	if (!inet->saddr)
		inet->saddr = rt->rt_src;
	if (!inet->rcv_saddr)
		inet->rcv_saddr = rt->rt_src;
	inet->daddr = rt->rt_dst;
	inet->dport = usin->sin_port;
	sk->sk_state = TCP_ESTABLISHED;

	inet->id = jiffies;
	sk_dst_set(sk, &rt->u.dst);
	return 0;
}