Merge git://git.kernel.org/pub/scm/linux/kernel/git/pablo/nf
[sfrench/cifs-2.6.git] / net / ipv4 / netfilter / nf_reject_ipv4.c
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
9 #include <linux/module.h>
10 #include <net/ip.h>
11 #include <net/tcp.h>
12 #include <net/route.h>
13 #include <net/dst.h>
14 #include <linux/netfilter_ipv4.h>
15 #include <net/netfilter/ipv4/nf_reject.h>
16
17 const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
18                                              struct tcphdr *_oth, int hook)
19 {
20         const struct tcphdr *oth;
21
22         /* IP header checks: fragment. */
23         if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
24                 return NULL;
25
26         oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
27                                  sizeof(struct tcphdr), _oth);
28         if (oth == NULL)
29                 return NULL;
30
31         /* No RST for RST. */
32         if (oth->rst)
33                 return NULL;
34
35         /* Check checksum */
36         if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
37                 return NULL;
38
39         return oth;
40 }
41 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get);
42
43 struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,
44                                   const struct sk_buff *oldskb,
45                                   __be16 protocol, int ttl)
46 {
47         struct iphdr *niph, *oiph = ip_hdr(oldskb);
48
49         skb_reset_network_header(nskb);
50         niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
51         niph->version   = 4;
52         niph->ihl       = sizeof(struct iphdr) / 4;
53         niph->tos       = 0;
54         niph->id        = 0;
55         niph->frag_off  = htons(IP_DF);
56         niph->protocol  = protocol;
57         niph->check     = 0;
58         niph->saddr     = oiph->daddr;
59         niph->daddr     = oiph->saddr;
60         niph->ttl       = ttl;
61
62         nskb->protocol = htons(ETH_P_IP);
63
64         return niph;
65 }
66 EXPORT_SYMBOL_GPL(nf_reject_iphdr_put);
67
68 void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb,
69                           const struct tcphdr *oth)
70 {
71         struct iphdr *niph = ip_hdr(nskb);
72         struct tcphdr *tcph;
73
74         skb_reset_transport_header(nskb);
75         tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
76         memset(tcph, 0, sizeof(*tcph));
77         tcph->source    = oth->dest;
78         tcph->dest      = oth->source;
79         tcph->doff      = sizeof(struct tcphdr) / 4;
80
81         if (oth->ack) {
82                 tcph->seq = oth->ack_seq;
83         } else {
84                 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
85                                       oldskb->len - ip_hdrlen(oldskb) -
86                                       (oth->doff << 2));
87                 tcph->ack = 1;
88         }
89
90         tcph->rst       = 1;
91         tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
92                                     niph->daddr, 0);
93         nskb->ip_summed = CHECKSUM_PARTIAL;
94         nskb->csum_start = (unsigned char *)tcph - nskb->head;
95         nskb->csum_offset = offsetof(struct tcphdr, check);
96 }
97 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put);
98
99 /* Send RST reply */
100 void nf_send_reset(struct sk_buff *oldskb, int hook)
101 {
102         struct sk_buff *nskb;
103         const struct iphdr *oiph;
104         struct iphdr *niph;
105         const struct tcphdr *oth;
106         struct tcphdr _oth;
107
108         oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
109         if (!oth)
110                 return;
111
112         if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
113                 return;
114
115         oiph = ip_hdr(oldskb);
116
117         nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
118                          LL_MAX_HEADER, GFP_ATOMIC);
119         if (!nskb)
120                 return;
121
122         /* ip_route_me_harder expects skb->dst to be set */
123         skb_dst_set_noref(nskb, skb_dst(oldskb));
124
125         skb_reserve(nskb, LL_MAX_HEADER);
126         niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
127                                    ip4_dst_hoplimit(skb_dst(nskb)));
128         nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
129
130         if (ip_route_me_harder(nskb, RTN_UNSPEC))
131                 goto free_nskb;
132
133         /* "Never happens" */
134         if (nskb->len > dst_mtu(skb_dst(nskb)))
135                 goto free_nskb;
136
137         nf_ct_attach(nskb, oldskb);
138
139 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
140         /* If we use ip_local_out for bridged traffic, the MAC source on
141          * the RST will be ours, instead of the destination's.  This confuses
142          * some routers/firewalls, and they drop the packet.  So we need to
143          * build the eth header using the original destination's MAC as the
144          * source, and send the RST packet directly.
145          */
146         if (oldskb->nf_bridge) {
147                 struct ethhdr *oeth = eth_hdr(oldskb);
148                 nskb->dev = oldskb->nf_bridge->physindev;
149                 niph->tot_len = htons(nskb->len);
150                 ip_send_check(niph);
151                 if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
152                                     oeth->h_source, oeth->h_dest, nskb->len) < 0)
153                         goto free_nskb;
154                 dev_queue_xmit(nskb);
155         } else
156 #endif
157                 ip_local_out(nskb);
158
159         return;
160
161  free_nskb:
162         kfree_skb(nskb);
163 }
164 EXPORT_SYMBOL_GPL(nf_send_reset);
165
166 MODULE_LICENSE("GPL");