[NET]: dev_put/dev_hold cleanup
[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  * 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:
13  *              Many            :       Split from ip.c , see ip_input.c for 
14  *                                      history.
15  *              Dave Gregorich  :       NULL ip_rt_put fix for multicast 
16  *                                      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
24 #include <linux/config.h>
25 #include <linux/types.h>
26 #include <linux/mm.h>
27 #include <linux/sched.h>
28 #include <linux/skbuff.h>
29 #include <linux/ip.h>
30 #include <linux/icmp.h>
31 #include <linux/netdevice.h>
32 #include <net/sock.h>
33 #include <net/ip.h>
34 #include <net/tcp.h>
35 #include <net/udp.h>
36 #include <net/icmp.h>
37 #include <linux/tcp.h>
38 #include <linux/udp.h>
39 #include <linux/netfilter_ipv4.h>
40 #include <net/checksum.h>
41 #include <linux/route.h>
42 #include <net/route.h>
43 #include <net/xfrm.h>
44
45 static inline int ip_forward_finish(struct sk_buff *skb)
46 {
47         struct ip_options * opt = &(IPCB(skb)->opt);
48
49         IP_INC_STATS_BH(IPSTATS_MIB_OUTFORWDATAGRAMS);
50
51         if (unlikely(opt->optlen))
52                 ip_forward_options(skb);
53
54         return dst_output(skb);
55 }
56
57 int ip_forward(struct sk_buff *skb)
58 {
59         struct iphdr *iph;      /* Our header */
60         struct rtable *rt;      /* Route we use */
61         struct ip_options * opt = &(IPCB(skb)->opt);
62
63         if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb))
64                 goto drop;
65
66         if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb))
67                 return NET_RX_SUCCESS;
68
69         if (skb->pkt_type != PACKET_HOST)
70                 goto drop;
71
72         skb->ip_summed = CHECKSUM_NONE;
73         
74         /*
75          *      According to the RFC, we must first decrease the TTL field. If
76          *      that reaches zero, we must reply an ICMP control message telling
77          *      that the packet's lifetime expired.
78          */
79         if (skb->nh.iph->ttl <= 1)
80                 goto too_many_hops;
81
82         if (!xfrm4_route_forward(skb))
83                 goto drop;
84
85         rt = (struct rtable*)skb->dst;
86
87         if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway)
88                 goto sr_failed;
89
90         /* We are about to mangle packet. Copy it! */
91         if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len))
92                 goto drop;
93         iph = skb->nh.iph;
94
95         /* Decrease ttl after skb cow done */
96         ip_decrease_ttl(iph);
97
98         /*
99          *      We now generate an ICMP HOST REDIRECT giving the route
100          *      we calculated.
101          */
102         if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr)
103                 ip_rt_send_redirect(skb);
104
105         skb->priority = rt_tos2priority(iph->tos);
106
107         return NF_HOOK(PF_INET, NF_IP_FORWARD, skb, skb->dev, rt->u.dst.dev,
108                        ip_forward_finish);
109
110 sr_failed:
111         /*
112          *      Strict routing permits no gatewaying
113          */
114          icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0);
115          goto drop;
116
117 too_many_hops:
118         /* Tell the sender its packet died... */
119         icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0);
120 drop:
121         kfree_skb(skb);
122         return NET_RX_DROP;
123 }