af_inet.c

	if (inet->opt && inet->opt->srr)
		daddr = inet->opt->faddr;

	/* Query new route. */
	err = ip_route_connect(&rt, daddr, 0,
			       RT_CONN_FLAGS(sk),
			       sk->sk_bound_dev_if,
			       sk->sk_protocol,
			       inet->sport, inet->dport, sk);
	if (err)
		return err;

	sk_setup_caps(sk, &rt->u.dst);

	new_saddr = rt->rt_src;

	if (new_saddr == old_saddr)
		return 0;

	if (sysctl_ip_dynaddr > 1) {
		printk(KERN_INFO "%s(): shifting inet->"
				 "saddr from %d.%d.%d.%d to %d.%d.%d.%d\n",
		       __FUNCTION__,
		       NIPQUAD(old_saddr),
		       NIPQUAD(new_saddr));
	}

	inet->saddr = inet->rcv_saddr = new_saddr;

	/*
	 * XXX The only one ugly spot where we need to
	 * XXX really change the sockets identity after
	 * XXX it has entered the hashes. -DaveM
	 *
	 * Besides that, it does not check for connection
	 * uniqueness. Wait for troubles.
	 */
	__sk_prot_rehash(sk);
	return 0;
}

int inet_sk_rebuild_header(struct sock *sk)
{
	struct inet_sock *inet = inet_sk(sk);
	struct rtable *rt = (struct rtable *)__sk_dst_check(sk, 0);
	u32 daddr;
	int err;

	/* Route is OK, nothing to do. */
	if (rt)
		return 0;

	/* Reroute. */
	daddr = inet->daddr;
	if (inet->opt && inet->opt->srr)
		daddr = inet->opt->faddr;
{
	struct flowi fl = {
		.oif = sk->sk_bound_dev_if,
		.nl_u = {
			.ip4_u = {
				.daddr	= daddr,
				.saddr	= inet->saddr,
				.tos	= RT_CONN_FLAGS(sk),
			},
		},
		.proto = sk->sk_protocol,
		.uli_u = {
			.ports = {
				.sport = inet->sport,
				.dport = inet->dport,
			},
		},
	};
						
	security_sk_classify_flow(sk, &fl);
	err = ip_route_output_flow(&rt, &fl, sk, 0);
}
	if (!err)
		sk_setup_caps(sk, &rt->u.dst);
	else {
		/* Routing failed... */
		sk->sk_route_caps = 0;
		/*
		 * Other protocols have to map its equivalent state to TCP_SYN_SENT.
		 * DCCP maps its DCCP_REQUESTING state to TCP_SYN_SENT. -acme
		 */
		if (!sysctl_ip_dynaddr ||
		    sk->sk_state != TCP_SYN_SENT ||
		    (sk->sk_userlocks & SOCK_BINDADDR_LOCK) ||
		    (err = inet_sk_reselect_saddr(sk)) != 0)
			sk->sk_err_soft = -err;
	}

	return err;
}

EXPORT_SYMBOL(inet_sk_rebuild_header);

static int inet_gso_send_check(struct sk_buff *skb)
{
	struct iphdr *iph;
	struct net_protocol *ops;
	int proto;
	int ihl;
	int err = -EINVAL;

	if (unlikely(!pskb_may_pull(skb, sizeof(*iph))))
		goto out;

	iph = skb->nh.iph;
	ihl = iph->ihl * 4;
	if (ihl < sizeof(*iph))
		goto out;

	if (unlikely(!pskb_may_pull(skb, ihl)))
		goto out;

	skb->h.raw = __skb_pull(skb, ihl);
	iph = skb->nh.iph;
	proto = iph->protocol & (MAX_INET_PROTOS - 1);
	err = -EPROTONOSUPPORT;

	rcu_read_lock();
	ops = rcu_dereference(inet_protos[proto]);
	if (likely(ops && ops->gso_send_check))
		err = ops->gso_send_check(skb);
	rcu_read_unlock();

out:
	return err;
}

static struct sk_buff *inet_gso_segment(struct sk_buff *skb, int features)
{
	struct sk_buff *segs = ERR_PTR(-EINVAL);
	struct iphdr *iph;
	struct net_protocol *ops;
	int proto;
	int ihl;
	int id;

	if (unlikely(skb_shinfo(skb)->gso_type &
		     ~(SKB_GSO_TCPV4 |
		       SKB_GSO_UDP |
		       SKB_GSO_DODGY |
		       SKB_GSO_TCP_ECN |
		       0)))
		goto out;

	if (unlikely(!pskb_may_pull(skb, sizeof(*iph))))
		goto out;

	iph = skb->nh.iph;
	ihl = iph->ihl * 4;
	if (ihl < sizeof(*iph))
		goto out;

	if (unlikely(!pskb_may_pull(skb, ihl)))
		goto out;

	skb->h.raw = __skb_pull(skb, ihl);
	iph = skb->nh.iph;
	id = ntohs(iph->id);
	proto = iph->protocol & (MAX_INET_PROTOS - 1);
	segs = ERR_PTR(-EPROTONOSUPPORT);

	rcu_read_lock();
	ops = rcu_dereference(inet_protos[proto]);
	if (likely(ops && ops->gso_segment))
		segs = ops->gso_segment(skb, features);
	rcu_read_unlock();

	if (!segs || unlikely(IS_ERR(segs)))
		goto out;

	skb = segs;
	do {
		iph = skb->nh.iph;
		iph->id = htons(id++);
		iph->tot_len = htons(skb->len - skb->mac_len);
		iph->check = 0;
		iph->check = ip_fast_csum(skb->nh.raw, iph->ihl);
	} while ((skb = skb->next));

out:
	return segs;
}

#ifdef CONFIG_IP_MULTICAST
static struct net_protocol igmp_protocol = {
	.handler =	igmp_rcv,
};
#endif

static struct net_protocol tcp_protocol = {
	.handler =	tcp_v4_rcv,
	.err_handler =	tcp_v4_err,
	.gso_send_check = tcp_v4_gso_send_check,
	.gso_segment =	tcp_tso_segment,
	.no_policy =	1,
};

static struct net_protocol udp_protocol = {
	.handler =	udp_rcv,
	.err_handler =	udp_err,
	.no_policy =	1,
};

static struct net_protocol icmp_protocol = {
	.handler =	icmp_rcv,
};

static int __init init_ipv4_mibs(void)
{
	net_statistics[0] = alloc_percpu(struct linux_mib);
	net_statistics[1] = alloc_percpu(struct linux_mib);
	ip_statistics[0] = alloc_percpu(struct ipstats_mib);
	ip_statistics[1] = alloc_percpu(struct ipstats_mib);
	icmp_statistics[0] = alloc_percpu(struct icmp_mib);
	icmp_statistics[1] = alloc_percpu(struct icmp_mib);
	tcp_statistics[0] = alloc_percpu(struct tcp_mib);
	tcp_statistics[1] = alloc_percpu(struct tcp_mib);
	udp_statistics[0] = alloc_percpu(struct udp_mib);
	udp_statistics[1] = alloc_percpu(struct udp_mib);
	if (!
	    (net_statistics[0] && net_statistics[1] && ip_statistics[0]
	     && ip_statistics[1] && tcp_statistics[0] && tcp_statistics[1]
	     && udp_statistics[0] && udp_statistics[1]))
		return -ENOMEM;

	(void) tcp_mib_init();

	return 0;
}

static int ipv4_proc_init(void);

/*
 *	IP protocol layer initialiser
 */

static struct packet_type ip_packet_type = {
	.type = __constant_htons(ETH_P_IP),
	.func = ip_rcv,
	.gso_send_check = inet_gso_send_check,
	.gso_segment = inet_gso_segment,
};

static int __init inet_init(void)
{
	struct sk_buff *dummy_skb;
	struct inet_protosw *q;
	struct list_head *r;
	int rc = -EINVAL;

	BUILD_BUG_ON(sizeof(struct inet_skb_parm) > sizeof(dummy_skb->cb));

	rc = proto_register(&tcp_prot, 1);
	if (rc)
		goto out;

	rc = proto_register(&udp_prot, 1);
	if (rc)
		goto out_unregister_tcp_proto;

	rc = proto_register(&raw_prot, 1);
	if (rc)
		goto out_unregister_udp_proto;

	/*
	 *	Tell SOCKET that we are alive... 
	 */

  	(void)sock_register(&inet_family_ops);

	/*
	 *	Add all the base protocols.
	 */

	if (inet_add_protocol(&icmp_protocol, IPPROTO_ICMP) < 0)
		printk(KERN_CRIT "inet_init: Cannot add ICMP protocol\n");
	if (inet_add_protocol(&udp_protocol, IPPROTO_UDP) < 0)
		printk(KERN_CRIT "inet_init: Cannot add UDP protocol\n");
	if (inet_add_protocol(&tcp_protocol, IPPROTO_TCP) < 0)
		printk(KERN_CRIT "inet_init: Cannot add TCP protocol\n");
#ifdef CONFIG_IP_MULTICAST
	if (inet_add_protocol(&igmp_protocol, IPPROTO_IGMP) < 0)
		printk(KERN_CRIT "inet_init: Cannot add IGMP protocol\n");
#endif

	/* Register the socket-side information for inet_create. */
	for (r = &inetsw[0]; r < &inetsw[SOCK_MAX]; ++r)
		INIT_LIST_HEAD(r);

	for (q = inetsw_array; q < &inetsw_array[INETSW_ARRAY_LEN]; ++q)
		inet_register_protosw(q);

	/*
	 *	Set the ARP module up
	 */

	arp_init();

  	/*
  	 *	Set the IP module up
  	 */

	ip_init();

	tcp_v4_init(&inet_family_ops);

	/* Setup TCP slab cache for open requests. */
	tcp_init();


	/*
	 *	Set the ICMP layer up
	 */

	icmp_init(&inet_family_ops);

	/*
	 *	Initialise the multicast router
	 */
#if defined(CONFIG_IP_MROUTE)
	ip_mr_init();
#endif
	/*
	 *	Initialise per-cpu ipv4 mibs
	 */ 

	if(init_ipv4_mibs())
		printk(KERN_CRIT "inet_init: Cannot init ipv4 mibs\n"); ;
	
	ipv4_proc_init();

	ipfrag_init();

	dev_add_pack(&ip_packet_type);

	rc = 0;
out:
	return rc;
out_unregister_udp_proto:
	proto_unregister(&udp_prot);
out_unregister_tcp_proto:
	proto_unregister(&tcp_prot);
	goto out;
}

fs_initcall(inet_init);

/* ------------------------------------------------------------------------ */

#ifdef CONFIG_PROC_FS
static int __init ipv4_proc_init(void)
{
	int rc = 0;

	if (raw_proc_init())
		goto out_raw;
	if (tcp4_proc_init())
		goto out_tcp;
	if (udp4_proc_init())
		goto out_udp;
	if (fib_proc_init())
		goto out_fib;
	if (ip_misc_proc_init())
		goto out_misc;
out:
	return rc;
out_misc:
	fib_proc_exit();
out_fib:
	udp4_proc_exit();
out_udp:
	tcp4_proc_exit();
out_tcp:
	raw_proc_exit();
out_raw:
	rc = -ENOMEM;
	goto out;
}

#else /* CONFIG_PROC_FS */
static int __init ipv4_proc_init(void)
{
	return 0;
}
#endif /* CONFIG_PROC_FS */

MODULE_ALIAS_NETPROTO(PF_INET);

EXPORT_SYMBOL(inet_accept);
EXPORT_SYMBOL(inet_bind);
EXPORT_SYMBOL(inet_dgram_connect);
EXPORT_SYMBOL(inet_dgram_ops);
EXPORT_SYMBOL(inet_getname);
EXPORT_SYMBOL(inet_ioctl);
EXPORT_SYMBOL(inet_listen);
EXPORT_SYMBOL(inet_register_protosw);
EXPORT_SYMBOL(inet_release);
EXPORT_SYMBOL(inet_sendmsg);
EXPORT_SYMBOL(inet_shutdown);
EXPORT_SYMBOL(inet_sock_destruct);
EXPORT_SYMBOL(inet_stream_connect);
EXPORT_SYMBOL(inet_stream_ops);
EXPORT_SYMBOL(inet_unregister_protosw);
EXPORT_SYMBOL(net_statistics);
EXPORT_SYMBOL(sysctl_ip_nonlocal_bind);