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b2441318 | 1 | // SPDX-License-Identifier: GPL-2.0 |
1da177e4 LT |
2 | /* |
3 | * INET An implementation of the TCP/IP protocol suite for the LINUX | |
4 | * operating system. INET is implemented using the BSD Socket | |
5 | * interface as the means of communication with the user level. | |
6 | * | |
7 | * The IP forwarding functionality. | |
e905a9ed | 8 | * |
1da177e4 LT |
9 | * Authors: see ip.c |
10 | * | |
11 | * Fixes: | |
e905a9ed | 12 | * Many : Split from ip.c , see ip_input.c for |
1da177e4 | 13 | * history. |
e905a9ed | 14 | * Dave Gregorich : NULL ip_rt_put fix for multicast |
1da177e4 LT |
15 | * routing. |
16 | * Jos Vos : Add call_out_firewall before sending, | |
17 | * use output device for accounting. | |
18 | * Jos Vos : Call forward firewall after routing | |
19 | * (always use output device). | |
20 | * Mike McLagan : Routing by source | |
21 | */ | |
22 | ||
1da177e4 LT |
23 | #include <linux/types.h> |
24 | #include <linux/mm.h> | |
1da177e4 LT |
25 | #include <linux/skbuff.h> |
26 | #include <linux/ip.h> | |
27 | #include <linux/icmp.h> | |
28 | #include <linux/netdevice.h> | |
5a0e3ad6 | 29 | #include <linux/slab.h> |
1da177e4 LT |
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 | ||
fe6cc55f FW |
43 | static bool ip_exceeds_mtu(const struct sk_buff *skb, unsigned int mtu) |
44 | { | |
ca6c5d4a | 45 | if (skb->len <= mtu) |
fe6cc55f FW |
46 | return false; |
47 | ||
cf826244 FW |
48 | if (unlikely((ip_hdr(skb)->frag_off & htons(IP_DF)) == 0)) |
49 | return false; | |
50 | ||
51 | /* original fragment exceeds mtu and DF is set */ | |
52 | if (unlikely(IPCB(skb)->frag_max_size > mtu)) | |
53 | return true; | |
54 | ||
55 | if (skb->ignore_df) | |
56 | return false; | |
57 | ||
779b7931 | 58 | if (skb_is_gso(skb) && skb_gso_validate_network_len(skb, mtu)) |
fe6cc55f FW |
59 | return false; |
60 | ||
61 | return true; | |
62 | } | |
63 | ||
fe6cc55f | 64 | |
0c4b51f0 | 65 | static int ip_forward_finish(struct net *net, struct sock *sk, struct sk_buff *skb) |
1da177e4 | 66 | { |
5e73ea1a | 67 | struct ip_options *opt = &(IPCB(skb)->opt); |
1da177e4 | 68 | |
b45386ef | 69 | __IP_INC_STATS(net, IPSTATS_MIB_OUTFORWDATAGRAMS); |
98f61995 | 70 | __IP_ADD_STATS(net, IPSTATS_MIB_OUTOCTETS, skb->len); |
1da177e4 | 71 | |
f839a6c9 IS |
72 | #ifdef CONFIG_NET_SWITCHDEV |
73 | if (skb->offload_l3_fwd_mark) { | |
74 | consume_skb(skb); | |
75 | return 0; | |
76 | } | |
77 | #endif | |
78 | ||
1da177e4 LT |
79 | if (unlikely(opt->optlen)) |
80 | ip_forward_options(skb); | |
81 | ||
de799101 | 82 | skb_clear_tstamp(skb); |
13206b6b | 83 | return dst_output(net, sk, skb); |
1da177e4 LT |
84 | } |
85 | ||
86 | int ip_forward(struct sk_buff *skb) | |
87 | { | |
f87c10a8 | 88 | u32 mtu; |
1da177e4 LT |
89 | struct iphdr *iph; /* Our header */ |
90 | struct rtable *rt; /* Route we use */ | |
5e73ea1a | 91 | struct ip_options *opt = &(IPCB(skb)->opt); |
fcad0ac2 | 92 | struct net *net; |
2edc1a38 | 93 | SKB_DR(reason); |
1da177e4 | 94 | |
d4f2fa6a DK |
95 | /* that should never happen */ |
96 | if (skb->pkt_type != PACKET_HOST) | |
97 | goto drop; | |
98 | ||
2ab95749 SP |
99 | if (unlikely(skb->sk)) |
100 | goto drop; | |
101 | ||
4497b076 BH |
102 | if (skb_warn_if_lro(skb)) |
103 | goto drop; | |
104 | ||
2edc1a38 MD |
105 | if (!xfrm4_policy_check(NULL, XFRM_POLICY_FWD, skb)) { |
106 | SKB_DR_SET(reason, XFRM_POLICY); | |
1da177e4 | 107 | goto drop; |
2edc1a38 | 108 | } |
1da177e4 LT |
109 | |
110 | if (IPCB(skb)->opt.router_alert && ip_call_ra_chain(skb)) | |
111 | return NET_RX_SUCCESS; | |
112 | ||
35fc92a9 | 113 | skb_forward_csum(skb); |
fcad0ac2 | 114 | net = dev_net(skb->dev); |
e905a9ed | 115 | |
1da177e4 LT |
116 | /* |
117 | * According to the RFC, we must first decrease the TTL field. If | |
118 | * that reaches zero, we must reply an ICMP control message telling | |
119 | * that the packet's lifetime expired. | |
120 | */ | |
eddc9ec5 | 121 | if (ip_hdr(skb)->ttl <= 1) |
e905a9ed | 122 | goto too_many_hops; |
1da177e4 | 123 | |
2edc1a38 MD |
124 | if (!xfrm4_route_forward(skb)) { |
125 | SKB_DR_SET(reason, XFRM_POLICY); | |
1da177e4 | 126 | goto drop; |
2edc1a38 | 127 | } |
1da177e4 | 128 | |
511c3f92 | 129 | rt = skb_rtable(skb); |
1da177e4 | 130 | |
77d5bc7e | 131 | if (opt->is_strictroute && rt->rt_uses_gateway) |
1da177e4 LT |
132 | goto sr_failed; |
133 | ||
9ee6c5dc | 134 | IPCB(skb)->flags |= IPSKB_FORWARDED; |
f87c10a8 | 135 | mtu = ip_dst_mtu_maybe_forward(&rt->dst, true); |
cf826244 | 136 | if (ip_exceeds_mtu(skb, mtu)) { |
fcad0ac2 | 137 | IP_INC_STATS(net, IPSTATS_MIB_FRAGFAILS); |
9af3912e | 138 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_FRAG_NEEDED, |
f87c10a8 | 139 | htonl(mtu)); |
2edc1a38 | 140 | SKB_DR_SET(reason, PKT_TOO_BIG); |
9af3912e JH |
141 | goto drop; |
142 | } | |
143 | ||
1da177e4 | 144 | /* We are about to mangle packet. Copy it! */ |
d8d1f30b | 145 | if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+rt->dst.header_len)) |
1da177e4 | 146 | goto drop; |
eddc9ec5 | 147 | iph = ip_hdr(skb); |
1da177e4 LT |
148 | |
149 | /* Decrease ttl after skb cow done */ | |
150 | ip_decrease_ttl(iph); | |
151 | ||
152 | /* | |
153 | * We now generate an ICMP HOST REDIRECT giving the route | |
154 | * we calculated. | |
155 | */ | |
df4d9254 HFS |
156 | if (IPCB(skb)->flags & IPSKB_DOREDIRECT && !opt->srr && |
157 | !skb_sec_path(skb)) | |
1da177e4 LT |
158 | ip_rt_send_redirect(skb); |
159 | ||
7bf9e18d | 160 | if (READ_ONCE(net->ipv4.sysctl_ip_fwd_update_priority)) |
432e05d3 | 161 | skb->priority = rt_tos2priority(iph->tos); |
1da177e4 | 162 | |
29a26a56 EB |
163 | return NF_HOOK(NFPROTO_IPV4, NF_INET_FORWARD, |
164 | net, NULL, skb, skb->dev, rt->dst.dev, | |
165 | ip_forward_finish); | |
1da177e4 LT |
166 | |
167 | sr_failed: | |
e905a9ed | 168 | /* |
1da177e4 LT |
169 | * Strict routing permits no gatewaying |
170 | */ | |
e905a9ed YH |
171 | icmp_send(skb, ICMP_DEST_UNREACH, ICMP_SR_FAILED, 0); |
172 | goto drop; | |
1da177e4 LT |
173 | |
174 | too_many_hops: | |
e905a9ed | 175 | /* Tell the sender its packet died... */ |
b45386ef | 176 | __IP_INC_STATS(net, IPSTATS_MIB_INHDRERRORS); |
e905a9ed | 177 | icmp_send(skb, ICMP_TIME_EXCEEDED, ICMP_EXC_TTL, 0); |
2edc1a38 | 178 | SKB_DR_SET(reason, IP_INHDR); |
1da177e4 | 179 | drop: |
2edc1a38 | 180 | kfree_skb_reason(skb, reason); |
1da177e4 LT |
181 | return NET_RX_DROP; |
182 | } |