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c8d7b98b PNA |
1 | /* (C) 1999-2001 Paul `Rusty' Russell |
2 | * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org> | |
3 | * | |
4 | * This program is free software; you can redistribute it and/or modify | |
5 | * it under the terms of the GNU General Public License version 2 as | |
6 | * published by the Free Software Foundation. | |
7 | */ | |
8 | ||
ab2d7251 | 9 | #include <linux/module.h> |
c8d7b98b PNA |
10 | #include <net/ip.h> |
11 | #include <net/tcp.h> | |
12 | #include <net/route.h> | |
13 | #include <net/dst.h> | |
56768644 | 14 | #include <net/netfilter/ipv4/nf_reject.h> |
c8d7b98b | 15 | #include <linux/netfilter_ipv4.h> |
c737b7c4 | 16 | #include <linux/netfilter_bridge.h> |
052b9498 | 17 | #include <net/netfilter/ipv4/nf_reject.h> |
c8d7b98b | 18 | |
052b9498 PNA |
19 | const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb, |
20 | struct tcphdr *_oth, int hook) | |
c8d7b98b | 21 | { |
c8d7b98b | 22 | const struct tcphdr *oth; |
c8d7b98b PNA |
23 | |
24 | /* IP header checks: fragment. */ | |
25 | if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET)) | |
052b9498 | 26 | return NULL; |
c8d7b98b PNA |
27 | |
28 | oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb), | |
052b9498 | 29 | sizeof(struct tcphdr), _oth); |
c8d7b98b | 30 | if (oth == NULL) |
052b9498 | 31 | return NULL; |
c8d7b98b PNA |
32 | |
33 | /* No RST for RST. */ | |
34 | if (oth->rst) | |
052b9498 | 35 | return NULL; |
c8d7b98b PNA |
36 | |
37 | /* Check checksum */ | |
38 | if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP)) | |
052b9498 | 39 | return NULL; |
c8d7b98b | 40 | |
052b9498 PNA |
41 | return oth; |
42 | } | |
43 | EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get); | |
c8d7b98b | 44 | |
052b9498 PNA |
45 | struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb, |
46 | const struct sk_buff *oldskb, | |
a03a8dbe | 47 | __u8 protocol, int ttl) |
052b9498 PNA |
48 | { |
49 | struct iphdr *niph, *oiph = ip_hdr(oldskb); | |
c8d7b98b PNA |
50 | |
51 | skb_reset_network_header(nskb); | |
52 | niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr)); | |
53 | niph->version = 4; | |
54 | niph->ihl = sizeof(struct iphdr) / 4; | |
55 | niph->tos = 0; | |
56 | niph->id = 0; | |
57 | niph->frag_off = htons(IP_DF); | |
052b9498 | 58 | niph->protocol = protocol; |
c8d7b98b PNA |
59 | niph->check = 0; |
60 | niph->saddr = oiph->daddr; | |
61 | niph->daddr = oiph->saddr; | |
052b9498 PNA |
62 | niph->ttl = ttl; |
63 | ||
64 | nskb->protocol = htons(ETH_P_IP); | |
65 | ||
66 | return niph; | |
67 | } | |
68 | EXPORT_SYMBOL_GPL(nf_reject_iphdr_put); | |
69 | ||
70 | void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb, | |
71 | const struct tcphdr *oth) | |
72 | { | |
73 | struct iphdr *niph = ip_hdr(nskb); | |
74 | struct tcphdr *tcph; | |
c8d7b98b PNA |
75 | |
76 | skb_reset_transport_header(nskb); | |
77 | tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr)); | |
78 | memset(tcph, 0, sizeof(*tcph)); | |
79 | tcph->source = oth->dest; | |
80 | tcph->dest = oth->source; | |
81 | tcph->doff = sizeof(struct tcphdr) / 4; | |
82 | ||
052b9498 | 83 | if (oth->ack) { |
c8d7b98b | 84 | tcph->seq = oth->ack_seq; |
052b9498 | 85 | } else { |
c8d7b98b PNA |
86 | tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin + |
87 | oldskb->len - ip_hdrlen(oldskb) - | |
88 | (oth->doff << 2)); | |
89 | tcph->ack = 1; | |
90 | } | |
91 | ||
92 | tcph->rst = 1; | |
93 | tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr, | |
94 | niph->daddr, 0); | |
95 | nskb->ip_summed = CHECKSUM_PARTIAL; | |
96 | nskb->csum_start = (unsigned char *)tcph - nskb->head; | |
97 | nskb->csum_offset = offsetof(struct tcphdr, check); | |
052b9498 PNA |
98 | } |
99 | EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put); | |
100 | ||
101 | /* Send RST reply */ | |
372892ec | 102 | void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook) |
052b9498 PNA |
103 | { |
104 | struct sk_buff *nskb; | |
105 | const struct iphdr *oiph; | |
106 | struct iphdr *niph; | |
107 | const struct tcphdr *oth; | |
108 | struct tcphdr _oth; | |
109 | ||
110 | oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook); | |
111 | if (!oth) | |
112 | return; | |
113 | ||
114 | if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST)) | |
115 | return; | |
116 | ||
117 | oiph = ip_hdr(oldskb); | |
118 | ||
119 | nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) + | |
120 | LL_MAX_HEADER, GFP_ATOMIC); | |
121 | if (!nskb) | |
122 | return; | |
c8d7b98b PNA |
123 | |
124 | /* ip_route_me_harder expects skb->dst to be set */ | |
125 | skb_dst_set_noref(nskb, skb_dst(oldskb)); | |
126 | ||
052b9498 PNA |
127 | skb_reserve(nskb, LL_MAX_HEADER); |
128 | niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP, | |
129 | ip4_dst_hoplimit(skb_dst(nskb))); | |
130 | nf_reject_ip_tcphdr_put(nskb, oldskb, oth); | |
131 | ||
c8d7b98b PNA |
132 | if (ip_route_me_harder(nskb, RTN_UNSPEC)) |
133 | goto free_nskb; | |
134 | ||
c8d7b98b PNA |
135 | /* "Never happens" */ |
136 | if (nskb->len > dst_mtu(skb_dst(nskb))) | |
137 | goto free_nskb; | |
138 | ||
139 | nf_ct_attach(nskb, oldskb); | |
140 | ||
141 | #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER) | |
142 | /* If we use ip_local_out for bridged traffic, the MAC source on | |
143 | * the RST will be ours, instead of the destination's. This confuses | |
144 | * some routers/firewalls, and they drop the packet. So we need to | |
145 | * build the eth header using the original destination's MAC as the | |
146 | * source, and send the RST packet directly. | |
147 | */ | |
148 | if (oldskb->nf_bridge) { | |
149 | struct ethhdr *oeth = eth_hdr(oldskb); | |
c737b7c4 FW |
150 | |
151 | nskb->dev = nf_bridge_get_physindev(oldskb); | |
c8d7b98b PNA |
152 | niph->tot_len = htons(nskb->len); |
153 | ip_send_check(niph); | |
154 | if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol), | |
155 | oeth->h_source, oeth->h_dest, nskb->len) < 0) | |
156 | goto free_nskb; | |
157 | dev_queue_xmit(nskb); | |
158 | } else | |
159 | #endif | |
160 | ip_local_out(nskb); | |
161 | ||
162 | return; | |
163 | ||
164 | free_nskb: | |
165 | kfree_skb(nskb); | |
166 | } | |
167 | EXPORT_SYMBOL_GPL(nf_send_reset); | |
ab2d7251 | 168 | |
ee586bbc FW |
169 | void nf_send_unreach(struct sk_buff *skb_in, int code, int hook) |
170 | { | |
171 | struct iphdr *iph = ip_hdr(skb_in); | |
172 | u8 proto; | |
173 | ||
174 | if (skb_in->csum_bad || iph->frag_off & htons(IP_OFFSET)) | |
175 | return; | |
176 | ||
177 | if (skb_csum_unnecessary(skb_in)) { | |
178 | icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); | |
179 | return; | |
180 | } | |
181 | ||
182 | if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP) | |
183 | proto = iph->protocol; | |
184 | else | |
185 | proto = 0; | |
186 | ||
187 | if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0) | |
188 | icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0); | |
189 | } | |
190 | EXPORT_SYMBOL_GPL(nf_send_unreach); | |
191 | ||
ab2d7251 | 192 | MODULE_LICENSE("GPL"); |