Commit | Line | Data |
---|---|---|
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 | * Authors: see ip.c |
9 | * | |
10 | * Fixes: | |
e905a9ed | 11 | * Many : Split from ip.c , see ip_input.c for |
1da177e4 | 12 | * history. |
e905a9ed | 13 | * Dave Gregorich : NULL ip_rt_put fix for multicast |
1da177e4 LT |
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 | ||
1da177e4 LT |
22 | #include <linux/types.h> |
23 | #include <linux/mm.h> | |
1da177e4 LT |
24 | #include <linux/skbuff.h> |
25 | #include <linux/ip.h> | |
26 | #include <linux/icmp.h> | |
27 | #include <linux/netdevice.h> | |
5a0e3ad6 | 28 | #include <linux/slab.h> |
1da177e4 LT |
29 | #include <net/sock.h> |
30 | #include <net/ip.h> | |
31 | #include <net/tcp.h> | |
32 | #include <net/udp.h> | |
33 | #include <net/icmp.h> | |
34 | #include <linux/tcp.h> | |
35 | #include <linux/udp.h> | |
36 | #include <linux/netfilter_ipv4.h> | |
37 | #include <net/checksum.h> | |
38 | #include <linux/route.h> | |
39 | #include <net/route.h> | |
40 | #include <net/xfrm.h> | |
41 | ||
fe6cc55f FW |
42 | static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) |
43 | { | |
ca6c5d4a | 44 | if (skb->len <= mtu) |
fe6cc55f FW |
45 | return false; |
46 | ||
cf826244 FW |
47 | if (unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)) |
48 | return false; | |
49 | ||
50 | /* original fragment exceeds mtu and DF is set */ | |
51 | if (unlikely(IPCB(skb)->frag_max_size > mtu)) | |
52 | return true; | |
53 | ||
54 | if (skb->ignore_df) | |
55 | return false; | |
56 | ||
fe6cc55f FW |
57 | if (skb_is_gso(skb) && skb_gso_network_seglen(skb) <= mtu) |
58 | return false; | |
59 | ||
60 | return true; | |
61 | } | |
62 | ||
fe6cc55f | 63 | |
7026b1dd | 64 | static int ip_forward_finish(struct sock *sk, struct sk_buff *skb) |
1da177e4 | 65 | { |
5e73ea1a | 66 | struct ip_options *opt = &(IPCB(skb)->opt); |
1da177e4 | 67 | |
adf30907 | 68 | IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTFORWDATAGRAMS); |
2d8dbb04 | 69 | IP_ADD_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_OUTOCTETS, skb->len); |
1da177e4 LT |
70 | |
71 | if (unlikely(opt->optlen)) | |
72 | ip_forward_options(skb); | |
73 | ||
c29390c6 | 74 | skb_sender_cpu_clear(skb); |
7026b1dd | 75 | return dst_output_sk(sk, skb); |
1da177e4 LT |
76 | } |
77 | ||
78 | int ip_forward(struct sk_buff *skb) | |
79 | { | |
f87c10a8 | 80 | u32 mtu; |
1da177e4 LT |
81 | struct iphdr *iph; /* Our header */ |
82 | struct rtable *rt; /* Route we use */ | |
5e73ea1a | 83 | struct ip_options *opt = &(IPCB(skb)->opt); |
1da177e4 | 84 | |
d4f2fa6a DK |
85 | /* that should never happen */ |
86 | if (skb->pkt_type != PACKET_HOST) | |
87 | goto drop; | |
88 | ||
2ab95749 SP |
89 | if (unlikely(skb->sk)) |
90 | goto drop; | |
91 | ||
4497b076 BH |
92 | if (skb_warn_if_lro(skb)) |
93 | goto drop; | |
94 | ||
1da177e4 LT |
95 | if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb)) |
96 | goto drop; | |
97 | ||
98 | if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb)) | |
99 | return NET_RX_SUCCESS; | |
100 | ||
35fc92a9 | 101 | skb_forward_csum(skb); |
e905a9ed | 102 | |
1da177e4 LT |
103 | /* |
104 | * According to the RFC, we must first decrease the TTL field. If | |
105 | * that reaches zero, we must reply an ICMP control message telling | |
106 | * that the packet's lifetime expired. | |
107 | */ | |
eddc9ec5 | 108 | if (ip_hdr(skb)->ttl <= 1) |
e905a9ed | 109 | goto too_many_hops; |
1da177e4 LT |
110 | |
111 | if (!xfrm4_route_forward(skb)) | |
112 | goto drop; | |
113 | ||
511c3f92 | 114 | rt = skb_rtable(skb); |
1da177e4 | 115 | |
155e8336 | 116 | if (opt->is_strictroute && rt->rt_uses_gateway) |
1da177e4 LT |
117 | goto sr_failed; |
118 | ||
f87c10a8 HFS |
119 | IPCB(skb)->flags |= IPSKB_FORWARDED; |
120 | mtu = ip_dst_mtu_maybe_forward(&rt->dst, true); | |
cf826244 | 121 | if (ip_exceeds_mtu(skb, mtu)) { |
d8d1f30b | 122 | IP_INC_STATS(dev_net(rt->dst.dev), IPSTATS_MIB_FRAGFAILS); |
9af3912e | 123 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, |
f87c10a8 | 124 | htonl(mtu)); |
9af3912e JH |
125 | goto drop; |
126 | } | |
127 | ||
1da177e4 | 128 | /* We are about to mangle packet. Copy it! */ |
d8d1f30b | 129 | if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len)) |
1da177e4 | 130 | goto drop; |
eddc9ec5 | 131 | iph = ip_hdr(skb); |
1da177e4 LT |
132 | |
133 | /* Decrease ttl after skb cow done */ | |
134 | ip_decrease_ttl(iph); | |
135 | ||
136 | /* | |
137 | * We now generate an ICMP HOST REDIRECT giving the route | |
138 | * we calculated. | |
139 | */ | |
df4d9254 HFS |
140 | if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr && |
141 | !skb_sec_path(skb)) | |
1da177e4 LT |
142 | ip_rt_send_redirect(skb); |
143 | ||
144 | skb->priority = rt_tos2priority(iph->tos); | |
145 | ||
7026b1dd DM |
146 | return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, NULL, skb, |
147 | skb->dev, rt->dst.dev, ip_forward_finish); | |
1da177e4 LT |
148 | |
149 | sr_failed: | |
e905a9ed | 150 | /* |
1da177e4 LT |
151 | * Strict routing permits no gatewaying |
152 | */ | |
e905a9ed YH |
153 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0); |
154 | goto drop; | |
1da177e4 LT |
155 | |
156 | too_many_hops: | |
e905a9ed | 157 | /* Tell the sender its packet died... */ |
adf30907 | 158 | IP_INC_STATS_BH(dev_net(skb_dst(skb)->dev), IPSTATS_MIB_INHDRERRORS); |
e905a9ed | 159 | icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0); |
1da177e4 LT |
160 | drop: |
161 | kfree_skb(skb); | |
162 | return NET_RX_DROP; | |
163 | } |