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/*
* INET An implementation of the TCP/IP protocol suite for the LINUX
* operating system. INET is implemented using the BSD Socket
* interface as the means of communication with the user level.
*
* The IP forwarding functionality.
*
* Version: $Id: ip_forward.c,v 1.43 1999/03/21 05:22:37 davem Exp $
*
* Authors: see ip.c
*
* Fixes:
* Many : Split from ip.c , see ip_input.c for
* history.
* Dave Gregorich : NULL ip_rt_put fix for multicast
* routing.
* Jos Vos : Add call_out_firewall before sending,
* use output device for accounting.
* Jos Vos : Call forward firewall after routing
* (always use output device).
* Mike McLagan : Routing by source
*/
#include <linux/config.h>
#include <linux/types.h>
#include <linux/mm.h>
#include <linux/sched.h>
#include <linux/skbuff.h>
#include <linux/ip.h>
#include <linux/icmp.h>
#include <linux/netdevice.h>
#include <net/sock.h>
#include <net/ip.h>
#include <net/tcp.h>
#include <net/udp.h>
#include <net/icmp.h>
#include <linux/tcp.h>
#include <linux/udp.h>
#include <linux/firewall.h>
#include <linux/ip_fw.h>
#ifdef CONFIG_IP_MASQUERADE
#include <net/ip_masq.h>
#endif
#include <net/checksum.h>
#include <linux/route.h>
#include <net/route.h>
#ifdef CONFIG_IP_TRANSPARENT_PROXY
/*
* Check the packet against our socket administration to see
* if it is related to a connection on our system.
* Needed for transparent proxying.
*/
int ip_chksock(struct sk_buff *skb)
{
switch (skb->nh.iph->protocol) {
case IPPROTO_ICMP:
return icmp_chkaddr(skb);
case IPPROTO_TCP:
return tcp_chkaddr(skb);
case IPPROTO_UDP:
return udp_chkaddr(skb);
default:
return 0;
}
}
#endif
int ip_forward(struct sk_buff *skb)
{
struct device *dev2; /* Output device */
struct iphdr *iph; /* Our header */
struct rtable *rt; /* Route we use */
struct ip_options * opt = &(IPCB(skb)->opt);
unsigned short mtu;
#if defined(CONFIG_FIREWALL) || defined(CONFIG_IP_MASQUERADE)
int fw_res = 0;
#endif
if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
return 0;
if (skb->pkt_type != PACKET_HOST)
goto drop;
/*
* According to the RFC, we must first decrease the TTL field. If
* that reaches zero, we must reply an ICMP control message telling
* that the packet's lifetime expired.
*/
iph = skb->nh.iph;
rt = (struct rtable*)skb->dst;
#ifdef CONFIG_CPU_IS_SLOW
if (net_cpu_congestion > 1 && !(iph->tos&IPTOS_RELIABILITY) &&
IPTOS_PREC(iph->tos) < IPTOS_PREC_INTERNETCONTROL) {
if (((xtime.tv_usec&0xF)<<net_cpu_congestion) > 0x1C)
goto drop;
}
#endif
#ifdef CONFIG_IP_TRANSPARENT_PROXY
if (ip_chksock(skb))
goto local_pkt;
#endif
if (iph->ttl <= 1)
goto too_many_hops;
if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
goto sr_failed;
/*
* Having picked a route we can now send the frame out
* after asking the firewall permission to do so.
*/
skb->priority = rt_tos2priority(iph->tos);
dev2 = rt->u.dst.dev;
mtu = rt->u.dst.pmtu;
#ifdef CONFIG_NET_SECURITY
call_fw_firewall(PF_SECURITY, dev2, NULL, &mtu, NULL);
#endif
/*
* We now generate an ICMP HOST REDIRECT giving the route
* we calculated.
*/
if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr)
ip_rt_send_redirect(skb);
/* We are about to mangle packet. Copy it! */
if ((skb = skb_cow(skb, dev2->hard_header_len)) == NULL)
return -1;
iph = skb->nh.iph;
opt = &(IPCB(skb)->opt);
/* Decrease ttl after skb cow done */
ip_decrease_ttl(iph);
/*
* We now may allocate a new buffer, and copy the datagram into it.
* If the indicated interface is up and running, kick it.
*/
if (skb->len > mtu && (ntohs(iph->frag_off) & IP_DF))
goto frag_needed;
#ifdef CONFIG_IP_ROUTE_NAT
if (rt->rt_flags & RTCF_NAT) {
if (ip_do_nat(skb)) {
kfree_skb(skb);
return -1;
}
}
#endif
#ifdef CONFIG_IP_MASQUERADE
if(!(IPCB(skb)->flags&IPSKB_MASQUERADED)) {
/*
* Check that any ICMP packets are not for a
* masqueraded connection. If so rewrite them
* and skip the firewall checks
*/
if (iph->protocol == IPPROTO_ICMP) {
__u32 maddr;
#ifdef CONFIG_IP_MASQUERADE_ICMP
struct icmphdr *icmph = (struct icmphdr *)((char*)iph + (iph->ihl << 2));
if ((icmph->type==ICMP_DEST_UNREACH)||
(icmph->type==ICMP_SOURCE_QUENCH)||
(icmph->type==ICMP_TIME_EXCEEDED))
{
#endif
maddr = inet_select_addr(dev2, rt->rt_gateway, RT_SCOPE_UNIVERSE);
fw_res = ip_fw_masq_icmp(&skb, maddr);
if (fw_res < 0) {
kfree_skb(skb);
return -1;
}
if (fw_res)
/* ICMP matched - skip firewall */
goto skip_call_fw_firewall;
#ifdef CONFIG_IP_MASQUERADE_ICMP
}
#endif
}
if (rt->rt_flags&RTCF_MASQ)
goto skip_call_fw_firewall;
#endif /* CONFIG_IP_MASQUERADE */
#ifdef CONFIG_FIREWALL
fw_res=call_fw_firewall(PF_INET, dev2, iph, NULL, &skb);
switch (fw_res) {
case FW_ACCEPT:
case FW_MASQUERADE:
break;
case FW_REJECT:
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
/* fall thru */
default:
kfree_skb(skb);
return -1;
}
#endif
#ifdef CONFIG_IP_MASQUERADE
}
skip_call_fw_firewall:
/*
* If this fragment needs masquerading, make it so...
* (Don't masquerade de-masqueraded fragments)
*/
if (!(IPCB(skb)->flags&IPSKB_MASQUERADED) &&
(fw_res==FW_MASQUERADE || rt->rt_flags&RTCF_MASQ)) {
u32 maddr;
#ifdef CONFIG_IP_ROUTE_NAT
maddr = (rt->rt_flags&RTCF_MASQ) ? rt->rt_src_map : 0;
if (maddr == 0)
#endif
maddr = inet_select_addr(dev2, rt->rt_gateway, RT_SCOPE_UNIVERSE);
if (ip_fw_masquerade(&skb, maddr) < 0) {
kfree_skb(skb);
return -1;
} else {
/*
* Masquerader may have changed skb
*/
iph = skb->nh.iph;
opt = &(IPCB(skb)->opt);
}
}
#endif
#ifdef CONFIG_FIREWALL
if ((fw_res = call_out_firewall(PF_INET, dev2, iph, NULL,&skb)) < FW_ACCEPT) {
/* FW_ACCEPT and FW_MASQUERADE are treated equal:
masquerading is only supported via forward rules */
if (fw_res == FW_REJECT)
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_HOST_UNREACH, 0);
kfree_skb(skb);
return -1;
}
#endif
ip_statistics.IpForwDatagrams++;
if (opt->optlen == 0) {
#ifdef CONFIG_NET_FASTROUTE
if (rt->rt_flags&RTCF_FAST && !netdev_fastroute_obstacles) {
unsigned h = ((*(u8*)&rt->key.dst)^(*(u8*)&rt->key.src))&NETDEV_FASTROUTE_HMASK;
/* Time to switch to functional programming :-) */
dst_release_irqwait(xchg(&skb->dev->fastpath[h], dst_clone(&rt->u.dst)));
}
#endif
ip_send(skb);
return 0;
}
ip_forward_options(skb);
ip_send(skb);
return 0;
#ifdef CONFIG_IP_TRANSPARENT_PROXY
local_pkt:
return ip_local_deliver(skb);
#endif
frag_needed:
ip_statistics.IpFragFails++;
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, htonl(mtu));
goto drop;
sr_failed:
/*
* Strict routing permits no gatewaying
*/
icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
goto drop;
too_many_hops:
/* Tell the sender its packet died... */
icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
drop:
kfree_skb(skb);
return -1;
}
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