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>
17 #include <net/netfilter/ipv4/nf_reject.h>
19 const struct tcphdr
*nf_reject_ip_tcphdr_get(struct sk_buff
*oldskb
,
20 struct tcphdr
*_oth
, int hook
)
22 const struct tcphdr
*oth
;
24 /* IP header checks: fragment. */
25 if (ip_hdr(oldskb
)->frag_off
& htons(IP_OFFSET
))
28 oth
= skb_header_pointer(oldskb
, ip_hdrlen(oldskb
),
29 sizeof(struct tcphdr
), _oth
);
38 if (nf_ip_checksum(oldskb
, hook
, ip_hdrlen(oldskb
), IPPROTO_TCP
))
43 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_get
);
45 struct iphdr
*nf_reject_iphdr_put(struct sk_buff
*nskb
,
46 const struct sk_buff
*oldskb
,
47 __u8 protocol
, int ttl
)
49 struct iphdr
*niph
, *oiph
= ip_hdr(oldskb
);
51 skb_reset_network_header(nskb
);
52 niph
= (struct iphdr
*)skb_put(nskb
, sizeof(struct iphdr
));
54 niph
->ihl
= sizeof(struct iphdr
) / 4;
57 niph
->frag_off
= htons(IP_DF
);
58 niph
->protocol
= protocol
;
60 niph
->saddr
= oiph
->daddr
;
61 niph
->daddr
= oiph
->saddr
;
64 nskb
->protocol
= htons(ETH_P_IP
);
68 EXPORT_SYMBOL_GPL(nf_reject_iphdr_put
);
70 void nf_reject_ip_tcphdr_put(struct sk_buff
*nskb
, const struct sk_buff
*oldskb
,
71 const struct tcphdr
*oth
)
73 struct iphdr
*niph
= ip_hdr(nskb
);
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;
84 tcph
->seq
= oth
->ack_seq
;
86 tcph
->ack_seq
= htonl(ntohl(oth
->seq
) + oth
->syn
+ oth
->fin
+
87 oldskb
->len
- ip_hdrlen(oldskb
) -
93 tcph
->check
= ~tcp_v4_check(sizeof(struct tcphdr
), niph
->saddr
,
95 nskb
->ip_summed
= CHECKSUM_PARTIAL
;
96 nskb
->csum_start
= (unsigned char *)tcph
- nskb
->head
;
97 nskb
->csum_offset
= offsetof(struct tcphdr
, check
);
99 EXPORT_SYMBOL_GPL(nf_reject_ip_tcphdr_put
);
102 void nf_send_reset(struct net
*net
, struct sk_buff
*oldskb
, int hook
)
104 struct sk_buff
*nskb
;
105 const struct iphdr
*oiph
;
107 const struct tcphdr
*oth
;
110 oth
= nf_reject_ip_tcphdr_get(oldskb
, &_oth
, hook
);
114 if (skb_rtable(oldskb
)->rt_flags
& (RTCF_BROADCAST
| RTCF_MULTICAST
))
117 oiph
= ip_hdr(oldskb
);
119 nskb
= alloc_skb(sizeof(struct iphdr
) + sizeof(struct tcphdr
) +
120 LL_MAX_HEADER
, GFP_ATOMIC
);
124 /* ip_route_me_harder expects skb->dst to be set */
125 skb_dst_set_noref(nskb
, skb_dst(oldskb
));
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
);
132 if (ip_route_me_harder(nskb
, RTN_UNSPEC
))
135 /* "Never happens" */
136 if (nskb
->len
> dst_mtu(skb_dst(nskb
)))
139 nf_ct_attach(nskb
, oldskb
);
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.
148 if (oldskb
->nf_bridge
) {
149 struct ethhdr
*oeth
= eth_hdr(oldskb
);
151 nskb
->dev
= nf_bridge_get_physindev(oldskb
);
152 niph
->tot_len
= htons(nskb
->len
);
154 if (dev_hard_header(nskb
, nskb
->dev
, ntohs(nskb
->protocol
),
155 oeth
->h_source
, oeth
->h_dest
, nskb
->len
) < 0)
157 dev_queue_xmit(nskb
);
167 EXPORT_SYMBOL_GPL(nf_send_reset
);
169 void nf_send_unreach(struct sk_buff
*skb_in
, int code
, int hook
)
171 struct iphdr
*iph
= ip_hdr(skb_in
);
174 if (skb_in
->csum_bad
|| iph
->frag_off
& htons(IP_OFFSET
))
177 if (skb_csum_unnecessary(skb_in
)) {
178 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
182 if (iph
->protocol
== IPPROTO_TCP
|| iph
->protocol
== IPPROTO_UDP
)
183 proto
= iph
->protocol
;
187 if (nf_ip_checksum(skb_in
, hook
, ip_hdrlen(skb_in
), proto
) == 0)
188 icmp_send(skb_in
, ICMP_DEST_UNREACH
, code
, 0);
190 EXPORT_SYMBOL_GPL(nf_send_unreach
);
192 MODULE_LICENSE("GPL");
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