blob: 877da3ed52e2bef524d12cc88f2d23aa33b69502 [file] [log] [blame]
Linus Torvalds1da177e2005-04-16 15:20:36 -07001/*
2 * INET An implementation of the TCP/IP protocol suite for the LINUX
3 * operating system. INET is implemented using the BSD Socket
4 * interface as the means of communication with the user level.
5 *
6 * The IP forwarding functionality.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +09007 *
Linus Torvalds1da177e2005-04-16 15:20:36 -07008 * Version: $Id: ip_forward.c,v 1.48 2000/12/13 18:31:48 davem Exp $
9 *
10 * Authors: see ip.c
11 *
12 * Fixes:
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090013 * Many : Split from ip.c , see ip_input.c for
Linus Torvalds1da177e2005-04-16 15:20:36 -070014 * history.
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090015 * Dave Gregorich : NULL ip_rt_put fix for multicast
Linus Torvalds1da177e2005-04-16 15:20:36 -070016 * routing.
17 * Jos Vos : Add call_out_firewall before sending,
18 * use output device for accounting.
19 * Jos Vos : Call forward firewall after routing
20 * (always use output device).
21 * Mike McLagan : Routing by source
22 */
23
Linus Torvalds1da177e2005-04-16 15:20:36 -070024#include <linux/types.h>
25#include <linux/mm.h>
Linus Torvalds1da177e2005-04-16 15:20:36 -070026#include <linux/skbuff.h>
27#include <linux/ip.h>
28#include <linux/icmp.h>
29#include <linux/netdevice.h>
30#include <net/sock.h>
31#include <net/ip.h>
32#include <net/tcp.h>
33#include <net/udp.h>
34#include <net/icmp.h>
35#include <linux/tcp.h>
36#include <linux/udp.h>
37#include <linux/netfilter_ipv4.h>
38#include <net/checksum.h>
39#include <linux/route.h>
40#include <net/route.h>
41#include <net/xfrm.h>
42
Patrick McHardy861d0482007-10-15 01:48:39 -070043static int ip_forward_finish(struct sk_buff *skb)
Linus Torvalds1da177e2005-04-16 15:20:36 -070044{
45 struct ip_options * opt = &(IPCB(skb)->opt);
46
47 IP_INC_STATS_BH(IPSTATS_MIB_OUTFORWDATAGRAMS);
48
49 if (unlikely(opt->optlen))
50 ip_forward_options(skb);
51
52 return dst_output(skb);
53}
54
55int ip_forward(struct sk_buff *skb)
56{
57 struct iphdr *iph; /* Our header */
58 struct rtable *rt; /* Route we use */
59 struct ip_options * opt = &(IPCB(skb)->opt);
60
61 if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
62 goto drop;
63
64 if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
65 return NET_RX_SUCCESS;
66
67 if (skb->pkt_type != PACKET_HOST)
68 goto drop;
69
Herbert Xu35fc92a2007-03-26 23:22:20 -070070 skb_forward_csum(skb);
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090071
Linus Torvalds1da177e2005-04-16 15:20:36 -070072 /*
73 * According to the RFC, we must first decrease the TTL field. If
74 * that reaches zero, we must reply an ICMP control message telling
75 * that the packet's lifetime expired.
76 */
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -070077 if (ip_hdr(skb)->ttl <= 1)
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +090078 goto too_many_hops;
Linus Torvalds1da177e2005-04-16 15:20:36 -070079
80 if (!xfrm4_route_forward(skb))
81 goto drop;
82
Linus Torvalds1da177e2005-04-16 15:20:36 -070083 rt = (struct rtable*)skb->dst;
84
85 if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
86 goto sr_failed;
87
John Heffner9af39122007-03-25 23:32:29 -070088 if (unlikely(skb->len > dst_mtu(&rt->u.dst) &&
YOSHIFUJI Hideaki9c681b42007-07-19 10:43:47 +090089 (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
John Heffner9af39122007-03-25 23:32:29 -070090 IP_INC_STATS(IPSTATS_MIB_FRAGFAILS);
91 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
92 htonl(dst_mtu(&rt->u.dst)));
93 goto drop;
94 }
95
Linus Torvalds1da177e2005-04-16 15:20:36 -070096 /* We are about to mangle packet. Copy it! */
97 if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
98 goto drop;
Arnaldo Carvalho de Meloeddc9ec2007-04-20 22:47:35 -070099 iph = ip_hdr(skb);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700100
101 /* Decrease ttl after skb cow done */
102 ip_decrease_ttl(iph);
103
104 /*
105 * We now generate an ICMP HOST REDIRECT giving the route
106 * we calculated.
107 */
Masahide NAKAMURA3b26a9a2007-08-24 23:33:01 -0700108 if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb->sp)
Linus Torvalds1da177e2005-04-16 15:20:36 -0700109 ip_rt_send_redirect(skb);
110
111 skb->priority = rt_tos2priority(iph->tos);
112
113 return NF_HOOK(PF_INET, NF_IP_FORWARD, skb, skb->dev, rt->u.dst.dev,
114 ip_forward_finish);
115
116sr_failed:
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900117 /*
Linus Torvalds1da177e2005-04-16 15:20:36 -0700118 * Strict routing permits no gatewaying
119 */
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900120 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
121 goto drop;
Linus Torvalds1da177e2005-04-16 15:20:36 -0700122
123too_many_hops:
YOSHIFUJI Hideakie905a9e2007-02-09 23:24:47 +0900124 /* Tell the sender its packet died... */
125 IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS);
126 icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
Linus Torvalds1da177e2005-04-16 15:20:36 -0700127drop:
128 kfree_skb(skb);
129 return NET_RX_DROP;
130}