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Commit | Line | Data |
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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. | |
e905a9ed | 7 | * |
1da177e4 LT |
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: | |
e905a9ed | 13 | * Many : Split from ip.c , see ip_input.c for |
1da177e4 | 14 | * history. |
e905a9ed | 15 | * Dave Gregorich : NULL ip_rt_put fix for multicast |
1da177e4 LT |
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> | |
1da177e4 LT |
26 | #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 | ||
861d0486 | 43 | static int ip_forward_finish(struct sk_buff *skb) |
1da177e4 LT |
44 | { |
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 | ||
55 | int 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 | ||
35fc92a9 | 70 | skb_forward_csum(skb); |
e905a9ed | 71 | |
1da177e4 LT |
72 | /* |
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 | */ | |
eddc9ec5 | 77 | if (ip_hdr(skb)->ttl <= 1) |
e905a9ed | 78 | goto too_many_hops; |
1da177e4 LT |
79 | |
80 | if (!xfrm4_route_forward(skb)) | |
81 | goto drop; | |
82 | ||
ee6b9673 | 83 | rt = skb->rtable; |
1da177e4 LT |
84 | |
85 | if (opt->is_strictroute && rt->rt_dst != rt->rt_gateway) | |
86 | goto sr_failed; | |
87 | ||
9af3912e | 88 | if (unlikely(skb->len > dst_mtu(&rt->u.dst) && |
9c681b43 | 89 | (ip_hdr(skb)->frag_off & htons(IP_DF))) && !skb->local_df) { |
9af3912e JH |
90 | 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 | ||
1da177e4 LT |
96 | /* 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; | |
eddc9ec5 | 99 | iph = ip_hdr(skb); |
1da177e4 LT |
100 | |
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 | */ | |
3b26a9a6 | 108 | if (rt->rt_flags&RTCF_DOREDIRECT && !opt->srr && !skb->sp) |
1da177e4 LT |
109 | ip_rt_send_redirect(skb); |
110 | ||
111 | skb->priority = rt_tos2priority(iph->tos); | |
112 | ||
6e23ae2a | 113 | return NF_HOOK(PF_INET, NF_INET_FORWARD, skb, skb->dev, rt->u.dst.dev, |
1da177e4 LT |
114 | ip_forward_finish); |
115 | ||
116 | sr_failed: | |
e905a9ed | 117 | /* |
1da177e4 LT |
118 | * Strict routing permits no gatewaying |
119 | */ | |
e905a9ed YH |
120 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0); |
121 | goto drop; | |
1da177e4 LT |
122 | |
123 | too_many_hops: | |
e905a9ed YH |
124 | /* 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); | |
1da177e4 LT |
127 | drop: |
128 | kfree_skb(skb); | |
129 | return NET_RX_DROP; | |
130 | } |