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1da177e4 LT |
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 | ||
1da177e4 LT |
24 | #include <linux/types.h> |
25 | #include <linux/mm.h> | |
26 | #include <linux/sched.h> | |
27 | #include <linux/skbuff.h> | |
28 | #include <linux/ip.h> | |
29 | #include <linux/icmp.h> | |
30 | #include <linux/netdevice.h> | |
31 | #include <net/sock.h> | |
32 | #include <net/ip.h> | |
33 | #include <net/tcp.h> | |
34 | #include <net/udp.h> | |
35 | #include <net/icmp.h> | |
36 | #include <linux/tcp.h> | |
37 | #include <linux/udp.h> | |
38 | #include <linux/netfilter_ipv4.h> | |
39 | #include <net/checksum.h> | |
40 | #include <linux/route.h> | |
41 | #include <net/route.h> | |
42 | #include <net/xfrm.h> | |
43 | ||
44 | static inline int ip_forward_finish(struct sk_buff *skb) | |
45 | { | |
46 | struct ip_options * opt = &(IPCB(skb)->opt); | |
47 | ||
48 | IP_INC_STATS_BH(IPSTATS_MIB_OUTFORWDATAGRAMS); | |
49 | ||
50 | if (unlikely(opt->optlen)) | |
51 | ip_forward_options(skb); | |
52 | ||
53 | return dst_output(skb); | |
54 | } | |
55 | ||
56 | int ip_forward(struct sk_buff *skb) | |
57 | { | |
58 | struct iphdr *iph; /* Our header */ | |
59 | struct rtable *rt; /* Route we use */ | |
60 | struct ip_options * opt = &(IPCB(skb)->opt); | |
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->ip_summed = CHECKSUM_NONE; | |
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 | */ | |
9070683b | 78 | if (skb->nh.iph->ttl <= 1) |
1da177e4 LT |
79 | goto too_many_hops; |
80 | ||
81 | if (!xfrm4_route_forward(skb)) | |
82 | goto drop; | |
83 | ||
1da177e4 LT |
84 | rt = (struct rtable*)skb->dst; |
85 | ||
86 | if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway) | |
87 | goto sr_failed; | |
88 | ||
89 | /* We are about to mangle packet. Copy it! */ | |
90 | if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+rt->u.dst.header_len)) | |
91 | goto drop; | |
92 | iph = skb->nh.iph; | |
93 | ||
94 | /* Decrease ttl after skb cow done */ | |
95 | ip_decrease_ttl(iph); | |
96 | ||
97 | /* | |
98 | * We now generate an ICMP HOST REDIRECT giving the route | |
99 | * we calculated. | |
100 | */ | |
101 | if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr) | |
102 | ip_rt_send_redirect(skb); | |
103 | ||
104 | skb->priority = rt_tos2priority(iph->tos); | |
105 | ||
106 | return NF_HOOK(PF_INET, NF_IP_FORWARD, skb, skb->dev, rt->u.dst.dev, | |
107 | ip_forward_finish); | |
108 | ||
109 | sr_failed: | |
110 | /* | |
111 | * Strict routing permits no gatewaying | |
112 | */ | |
113 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0); | |
114 | goto drop; | |
115 | ||
116 | too_many_hops: | |
117 | /* Tell the sender its packet died... */ | |
42d1d52e | 118 | IP_INC_STATS_BH(IPSTATS_MIB_INHDRERRORS); |
1da177e4 LT |
119 | icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0); |
120 | drop: | |
121 | kfree_skb(skb); | |
122 | return NET_RX_DROP; | |
123 | } |