1 /* (C) 1999-2001 Paul `Rusty' Russell
2 * (C) 2002-2004 Netfilter Core Team <coreteam@netfilter.org>
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.
9 #include <linux/module.h>
12 #include <net/route.h>
14 #include <net/netfilter/ipv4/nf_reject.h>
15 #include <linux/netfilter_ipv4.h>
16 #include <linux/netfilter_bridge.h>
18 const struct tcphdr *nf_reject_ip_tcphdr_get(struct sk_buff *oldskb,
19 struct tcphdr *_oth, int hook)
21 const struct tcphdr *oth;
23 /* IP header checks: fragment. */
24 if (ip_hdr(oldskb)->frag_off & htons(IP_OFFSET))
27 if (ip_hdr(oldskb)->protocol != IPPROTO_TCP)
30 oth = skb_header_pointer(oldskb, ip_hdrlen(oldskb),
31 sizeof(struct tcphdr), _oth);
40 if (nf_ip_checksum(oldskb, hook, ip_hdrlen(oldskb), IPPROTO_TCP))
45 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get);
47 struct iphdr *nf_reject_iphdr_put(struct sk_buff *nskb,
48 const struct sk_buff *oldskb,
49 __u8 protocol, int ttl)
51 struct iphdr *niph, *oiph = ip_hdr(oldskb);
53 skb_reset_network_header(nskb);
54 niph = (struct iphdr *)skb_put(nskb, sizeof(struct iphdr));
56 niph->ihl = sizeof(struct iphdr) / 4;
59 niph->frag_off = htons(IP_DF);
60 niph->protocol = protocol;
62 niph->saddr = oiph->daddr;
63 niph->daddr = oiph->saddr;
66 nskb->protocol = htons(ETH_P_IP);
70 EXPORT_SYMBOL_GPL(nf_reject_iphdr_put);
72 void nf_reject_ip_tcphdr_put(struct sk_buff *nskb, const struct sk_buff *oldskb,
73 const struct tcphdr *oth)
75 struct iphdr *niph = ip_hdr(nskb);
78 skb_reset_transport_header(nskb);
79 tcph = (struct tcphdr *)skb_put(nskb, sizeof(struct tcphdr));
80 memset(tcph, 0, sizeof(*tcph));
81 tcph->source = oth->dest;
82 tcph->dest = oth->source;
83 tcph->doff = sizeof(struct tcphdr) / 4;
86 tcph->seq = oth->ack_seq;
88 tcph->ack_seq = htonl(ntohl(oth->seq) + oth->syn + oth->fin +
89 oldskb->len - ip_hdrlen(oldskb) -
95 tcph->check = ~tcp_v4_check(sizeof(struct tcphdr), niph->saddr,
97 nskb->ip_summed = CHECKSUM_PARTIAL;
98 nskb->csum_start = (unsigned char *)tcph - nskb->head;
99 nskb->csum_offset = offsetof(struct tcphdr, check);
101 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put);
104 void nf_send_reset(struct net *net, struct sk_buff *oldskb, int hook)
106 struct sk_buff *nskb;
107 const struct iphdr *oiph;
109 const struct tcphdr *oth;
112 oth = nf_reject_ip_tcphdr_get(oldskb, &_oth, hook);
116 if (skb_rtable(oldskb)->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST))
119 oiph = ip_hdr(oldskb);
121 nskb = alloc_skb(sizeof(struct iphdr) + sizeof(struct tcphdr) +
122 LL_MAX_HEADER, GFP_ATOMIC);
126 /* ip_route_me_harder expects skb->dst to be set */
127 skb_dst_set_noref(nskb, skb_dst(oldskb));
129 nskb->mark = IP4_REPLY_MARK(net, oldskb->mark);
131 skb_reserve(nskb, LL_MAX_HEADER);
132 niph = nf_reject_iphdr_put(nskb, oldskb, IPPROTO_TCP,
133 ip4_dst_hoplimit(skb_dst(nskb)));
134 nf_reject_ip_tcphdr_put(nskb, oldskb, oth);
136 if (ip_route_me_harder(net, nskb, RTN_UNSPEC))
139 /* "Never happens" */
140 if (nskb->len > dst_mtu(skb_dst(nskb)))
143 nf_ct_attach(nskb, oldskb);
145 #if IS_ENABLED(CONFIG_BRIDGE_NETFILTER)
146 /* If we use ip_local_out for bridged traffic, the MAC source on
147 * the RST will be ours, instead of the destination's. This confuses
148 * some routers/firewalls, and they drop the packet. So we need to
149 * build the eth header using the original destination's MAC as the
150 * source, and send the RST packet directly.
152 if (oldskb->nf_bridge) {
153 struct ethhdr *oeth = eth_hdr(oldskb);
155 nskb->dev = nf_bridge_get_physindev(oldskb);
156 niph->tot_len = htons(nskb->len);
158 if (dev_hard_header(nskb, nskb->dev, ntohs(nskb->protocol),
159 oeth->h_source, oeth->h_dest, nskb->len) < 0)
161 dev_queue_xmit(nskb);
164 ip_local_out(net, nskb->sk, nskb);
171 EXPORT_SYMBOL_GPL(nf_send_reset);
173 void nf_send_unreach(struct sk_buff *skb_in, int code, int hook)
175 struct iphdr *iph = ip_hdr(skb_in);
178 if (skb_in->csum_bad || iph->frag_off & htons(IP_OFFSET))
181 if (skb_csum_unnecessary(skb_in)) {
182 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
186 if (iph->protocol == IPPROTO_TCP || iph->protocol == IPPROTO_UDP)
187 proto = iph->protocol;
191 if (nf_ip_checksum(skb_in, hook, ip_hdrlen(skb_in), proto) == 0)
192 icmp_send(skb_in, ICMP_DEST_UNREACH, code, 0);
194 EXPORT_SYMBOL_GPL(nf_send_unreach);
196 MODULE_LICENSE("GPL");