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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 1.48 2000/12/13 18:31:48 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/netfilter_ipv4.h>
#include <net/checksum.h>
#include <linux/route.h>
#include <net/route.h>
static inline int ip_forward_finish(struct sk_buff *skb)
{
struct ip_options * opt = &(IPCB(skb)->opt);
IP_INC_STATS_BH(IpForwDatagrams);
if (opt->optlen == 0) {
#ifdef CONFIG_NET_FASTROUTE
struct rtable *rt = (struct rtable*)skb->dst;
if (rt->rt_flags&RTCF_FAST && !netdev_fastroute_obstacles) {
struct dst_entry *old_dst;
unsigned h = ((*(u8*)&rt->key.dst)^(*(u8*)&rt->key.src))&NETDEV_FASTROUTE_HMASK;
write_lock_irq(&skb->dev->fastpath_lock);
old_dst = skb->dev->fastpath[h];
skb->dev->fastpath[h] = dst_clone(&rt->u.dst);
write_unlock_irq(&skb->dev->fastpath_lock);
dst_release(old_dst);
}
#endif
return (ip_send(skb));
}
ip_forward_options(skb);
return (ip_send(skb));
}
int ip_forward(struct sk_buff *skb)
{
struct net_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 (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
return NET_RX_SUCCESS;
if (skb->pkt_type != PACKET_HOST)
goto drop;
skb->ip_summed = CHECKSUM_NONE;
/*
* 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;
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;
/*
* 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_cow(skb, dev2->hard_header_len))
goto drop;
iph = skb->nh.iph;
/* 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 NET_RX_BAD;
}
}
#endif
return NF_HOOK(PF_INET, NF_IP_FORWARD, skb, skb->dev, dev2,
ip_forward_finish);
frag_needed:
IP_INC_STATS_BH(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 NET_RX_DROP;
}
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