netfilter: ipv4: use NFPROTO values for NF_HOOK invocation
[linux-2.6.git] / net / ipv4 / ip_forward.c
1 /*
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.
7  *
8  * Authors:     see ip.c
9  *
10  * Fixes:
11  *              Many            :       Split from ip.c , see ip_input.c for
12  *                                      history.
13  *              Dave Gregorich  :       NULL ip_rt_put fix for multicast
14  *                                      routing.
15  *              Jos Vos         :       Add call_out_firewall before sending,
16  *                                      use output device for accounting.
17  *              Jos Vos         :       Call forward firewall after routing
18  *                                      (always use output device).
19  *              Mike McLagan    :       Routing by source
20  */
21
22 #include <linux/types.h>
23 #include <linux/mm.h>
24 #include <linux/skbuff.h>
25 #include <linux/ip.h>
26 #include <linux/icmp.h>
27 #include <linux/netdevice.h>
28 #include <net/sock.h>
29 #include <net/ip.h>
30 #include <net/tcp.h>
31 #include <net/udp.h>
32 #include <net/icmp.h>
33 #include <linux/tcp.h>
34 #include <linux/udp.h>
35 #include <linux/netfilter_ipv4.h>
36 #include <net/checksum.h>
37 #include <linux/route.h>
38 #include <net/route.h>
39 #include <net/xfrm.h>
40
41 static int ip_forward_finish(struct sk_buff *skb)
42 {
43         struct ip_options * opt = &(IPCB(skb)->opt);
44
45         IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS);
46
47         if (unlikely(opt->optlen))
48                 ip_forward_options(skb);
49
50         return dst_output(skb);
51 }
52
53 int ip_forward(struct sk_buff *skb)
54 {
55         struct iphdr *iph;      /* Our header */
56         struct rtable *rt;      /* Route we use */
57         struct ip_options * opt = &(IPCB(skb)->opt);
58
59         if (skb_warn_if_lro(skb))
60                 goto drop;
61
62         if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
63                 goto drop;
64
65         if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
66                 return NET_RX_SUCCESS;
67
68         if (skb->pkt_type != PACKET_HOST)
69                 goto drop;
70
71         skb_forward_csum(skb);
72
73         /*
74          *      According to the RFC, we must first decrease the TTL field. If
75          *      that reaches zero, we must reply an ICMP control message telling
76          *      that the packet's lifetime expired.
77          */
78         if (ip_hdr(skb)->ttl <= 1)
79                 goto too_many_hops;
80
81         if (!xfrm4_route_forward(skb))
82                 goto drop;
83
84         rt = skb_rtable(skb);
85
86         if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
87                 goto sr_failed;
88
89         if (unlikely(skb->len > dst_mtu(&rt->u.dst) && !skb_is_gso(skb) &&
90                      (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) {
91                 IP_INC_STATS(dev_net(rt->u.dst.dev), IPSTATS_MIB_FRAGFAILS);
92                 icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED,
93                           htonl(dst_mtu(&rt->u.dst)));
94                 goto drop;
95         }
96
97         /* We are about to mangle packet. Copy it! */
98         if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
99                 goto drop;
100         iph = ip_hdr(skb);
101
102         /* Decrease ttl after skb cow done */
103         ip_decrease_ttl(iph);
104
105         /*
106          *      We now generate an ICMP HOST REDIRECT giving the route
107          *      we calculated.
108          */
109         if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb_sec_path(skb))
110                 ip_rt_send_redirect(skb);
111
112         skb->priority = rt_tos2priority(iph->tos);
113
114         return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, skb, skb->dev,
115                        rt->u.dst.dev, ip_forward_finish);
116
117 sr_failed:
118         /*
119          *      Strict routing permits no gatewaying
120          */
121          icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
122          goto drop;
123
124 too_many_hops:
125         /* Tell the sender its packet died... */
126         IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS);
127         icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
128 drop:
129         kfree_skb(skb);
130         return NET_RX_DROP;
131 }