Commit | Line | Data |
---|---|---|
d2912cb1 | 1 | // SPDX-License-Identifier: GPL-2.0-only |
c7232c99 | 2 | /* nf_nat_helper.c - generic support functions for NAT helpers |
5b1158e9 JK |
3 | * |
4 | * (C) 2000-2002 Harald Welte <laforge@netfilter.org> | |
5 | * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org> | |
f229f6ce | 6 | * (C) 2007-2012 Patrick McHardy <kaber@trash.net> |
5b1158e9 JK |
7 | */ |
8 | #include <linux/module.h> | |
5a0e3ad6 | 9 | #include <linux/gfp.h> |
5b1158e9 | 10 | #include <linux/types.h> |
5b1158e9 JK |
11 | #include <linux/skbuff.h> |
12 | #include <linux/tcp.h> | |
13 | #include <linux/udp.h> | |
5b1158e9 JK |
14 | #include <net/tcp.h> |
15 | ||
5b1158e9 JK |
16 | #include <net/netfilter/nf_conntrack.h> |
17 | #include <net/netfilter/nf_conntrack_helper.h> | |
13eae15a | 18 | #include <net/netfilter/nf_conntrack_ecache.h> |
5b1158e9 | 19 | #include <net/netfilter/nf_conntrack_expect.h> |
41d73ec0 | 20 | #include <net/netfilter/nf_conntrack_seqadj.h> |
5b1158e9 | 21 | #include <net/netfilter/nf_nat.h> |
5b1158e9 JK |
22 | #include <net/netfilter/nf_nat_helper.h> |
23 | ||
5b1158e9 JK |
24 | /* Frobs data inside this packet, which is linear. */ |
25 | static void mangle_contents(struct sk_buff *skb, | |
26 | unsigned int dataoff, | |
27 | unsigned int match_offset, | |
28 | unsigned int match_len, | |
29 | const char *rep_buffer, | |
30 | unsigned int rep_len) | |
31 | { | |
32 | unsigned char *data; | |
33 | ||
f8b0a3ab | 34 | SKB_LINEAR_ASSERT(skb); |
eddc9ec5 | 35 | data = skb_network_header(skb) + dataoff; |
5b1158e9 JK |
36 | |
37 | /* move post-replacement */ | |
38 | memmove(data + match_offset + rep_len, | |
39 | data + match_offset + match_len, | |
938177e9 | 40 | skb_tail_pointer(skb) - (skb_network_header(skb) + dataoff + |
27a884dc | 41 | match_offset + match_len)); |
5b1158e9 JK |
42 | |
43 | /* insert data from buffer */ | |
44 | memcpy(data + match_offset, rep_buffer, rep_len); | |
45 | ||
46 | /* update skb info */ | |
47 | if (rep_len > match_len) { | |
0d53778e PM |
48 | pr_debug("nf_nat_mangle_packet: Extending packet by " |
49 | "%u from %u bytes\n", rep_len - match_len, skb->len); | |
5b1158e9 JK |
50 | skb_put(skb, rep_len - match_len); |
51 | } else { | |
0d53778e PM |
52 | pr_debug("nf_nat_mangle_packet: Shrinking packet from " |
53 | "%u from %u bytes\n", match_len - rep_len, skb->len); | |
5b1158e9 JK |
54 | __skb_trim(skb, skb->len + rep_len - match_len); |
55 | } | |
56 | ||
cb9c6836 | 57 | if (nf_ct_l3num((struct nf_conn *)skb_nfct(skb)) == NFPROTO_IPV4) { |
c7232c99 PM |
58 | /* fix IP hdr checksum information */ |
59 | ip_hdr(skb)->tot_len = htons(skb->len); | |
60 | ip_send_check(ip_hdr(skb)); | |
61 | } else | |
62 | ipv6_hdr(skb)->payload_len = | |
63 | htons(skb->len - sizeof(struct ipv6hdr)); | |
5b1158e9 JK |
64 | } |
65 | ||
66 | /* Unusual, but possible case. */ | |
cba81cc4 | 67 | static bool enlarge_skb(struct sk_buff *skb, unsigned int extra) |
5b1158e9 | 68 | { |
3db05fea | 69 | if (skb->len + extra > 65535) |
cba81cc4 | 70 | return false; |
5b1158e9 | 71 | |
3db05fea | 72 | if (pskb_expand_head(skb, 0, extra - skb_tailroom(skb), GFP_ATOMIC)) |
cba81cc4 | 73 | return false; |
5b1158e9 | 74 | |
cba81cc4 | 75 | return true; |
5b1158e9 JK |
76 | } |
77 | ||
78 | /* Generic function for mangling variable-length address changes inside | |
79 | * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX | |
80 | * command in FTP). | |
81 | * | |
82 | * Takes care about all the nasty sequence number changes, checksumming, | |
83 | * skb enlargement, ... | |
84 | * | |
85 | * */ | |
cba81cc4 GF |
86 | bool __nf_nat_mangle_tcp_packet(struct sk_buff *skb, |
87 | struct nf_conn *ct, | |
88 | enum ip_conntrack_info ctinfo, | |
89 | unsigned int protoff, | |
90 | unsigned int match_offset, | |
91 | unsigned int match_len, | |
92 | const char *rep_buffer, | |
93 | unsigned int rep_len, bool adjust) | |
5b1158e9 | 94 | { |
5b1158e9 JK |
95 | struct tcphdr *tcph; |
96 | int oldlen, datalen; | |
97 | ||
86f04538 | 98 | if (skb_ensure_writable(skb, skb->len)) |
cba81cc4 | 99 | return false; |
5b1158e9 JK |
100 | |
101 | if (rep_len > match_len && | |
3db05fea HX |
102 | rep_len - match_len > skb_tailroom(skb) && |
103 | !enlarge_skb(skb, rep_len - match_len)) | |
cba81cc4 | 104 | return false; |
5b1158e9 | 105 | |
c7232c99 | 106 | tcph = (void *)skb->data + protoff; |
5b1158e9 | 107 | |
c7232c99 PM |
108 | oldlen = skb->len - protoff; |
109 | mangle_contents(skb, protoff + tcph->doff*4, | |
5b1158e9 JK |
110 | match_offset, match_len, rep_buffer, rep_len); |
111 | ||
c7232c99 PM |
112 | datalen = skb->len - protoff; |
113 | ||
dac3fe72 FW |
114 | nf_nat_csum_recalc(skb, nf_ct_l3num(ct), IPPROTO_TCP, |
115 | tcph, &tcph->check, datalen, oldlen); | |
5b1158e9 | 116 | |
010c0b9f | 117 | if (adjust && rep_len != match_len) |
41d73ec0 PM |
118 | nf_ct_seqadj_set(ct, ctinfo, tcph->seq, |
119 | (int)rep_len - (int)match_len); | |
010c0b9f | 120 | |
cba81cc4 | 121 | return true; |
5b1158e9 | 122 | } |
010c0b9f | 123 | EXPORT_SYMBOL(__nf_nat_mangle_tcp_packet); |
5b1158e9 JK |
124 | |
125 | /* Generic function for mangling variable-length address changes inside | |
126 | * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX | |
127 | * command in the Amanda protocol) | |
128 | * | |
129 | * Takes care about all the nasty sequence number changes, checksumming, | |
130 | * skb enlargement, ... | |
131 | * | |
132 | * XXX - This function could be merged with nf_nat_mangle_tcp_packet which | |
133 | * should be fairly easy to do. | |
134 | */ | |
cba81cc4 | 135 | bool |
3db05fea | 136 | nf_nat_mangle_udp_packet(struct sk_buff *skb, |
5b1158e9 JK |
137 | struct nf_conn *ct, |
138 | enum ip_conntrack_info ctinfo, | |
051966c0 | 139 | unsigned int protoff, |
5b1158e9 JK |
140 | unsigned int match_offset, |
141 | unsigned int match_len, | |
142 | const char *rep_buffer, | |
143 | unsigned int rep_len) | |
144 | { | |
5b1158e9 JK |
145 | struct udphdr *udph; |
146 | int datalen, oldlen; | |
147 | ||
86f04538 | 148 | if (skb_ensure_writable(skb, skb->len)) |
cba81cc4 | 149 | return false; |
5b1158e9 JK |
150 | |
151 | if (rep_len > match_len && | |
3db05fea HX |
152 | rep_len - match_len > skb_tailroom(skb) && |
153 | !enlarge_skb(skb, rep_len - match_len)) | |
cba81cc4 | 154 | return false; |
5b1158e9 | 155 | |
c7232c99 | 156 | udph = (void *)skb->data + protoff; |
5b1158e9 | 157 | |
c7232c99 PM |
158 | oldlen = skb->len - protoff; |
159 | mangle_contents(skb, protoff + sizeof(*udph), | |
5b1158e9 JK |
160 | match_offset, match_len, rep_buffer, rep_len); |
161 | ||
162 | /* update the length of the UDP packet */ | |
c7232c99 | 163 | datalen = skb->len - protoff; |
5b1158e9 JK |
164 | udph->len = htons(datalen); |
165 | ||
166 | /* fix udp checksum if udp checksum was previously calculated */ | |
3db05fea | 167 | if (!udph->check && skb->ip_summed != CHECKSUM_PARTIAL) |
cba81cc4 | 168 | return true; |
5b1158e9 | 169 | |
6bac76db | 170 | nf_nat_csum_recalc(skb, nf_ct_l3num(ct), IPPROTO_UDP, |
dac3fe72 | 171 | udph, &udph->check, datalen, oldlen); |
5b1158e9 | 172 | |
cba81cc4 | 173 | return true; |
5b1158e9 JK |
174 | } |
175 | EXPORT_SYMBOL(nf_nat_mangle_udp_packet); | |
176 | ||
5b1158e9 JK |
177 | /* Setup NAT on this expected conntrack so it follows master. */ |
178 | /* If we fail to get a free NAT slot, we'll get dropped on confirm */ | |
179 | void nf_nat_follow_master(struct nf_conn *ct, | |
180 | struct nf_conntrack_expect *exp) | |
181 | { | |
2eb0f624 | 182 | struct nf_nat_range2 range; |
5b1158e9 JK |
183 | |
184 | /* This must be a fresh one. */ | |
185 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); | |
186 | ||
187 | /* Change src to where master sends to */ | |
cbc9f2f4 | 188 | range.flags = NF_NAT_RANGE_MAP_IPS; |
c7232c99 PM |
189 | range.min_addr = range.max_addr |
190 | = ct->master->tuplehash[!exp->dir].tuple.dst.u3; | |
cbc9f2f4 | 191 | nf_nat_setup_info(ct, &range, NF_NAT_MANIP_SRC); |
5b1158e9 JK |
192 | |
193 | /* For DST manip, map port here to where it's expected. */ | |
cbc9f2f4 | 194 | range.flags = (NF_NAT_RANGE_MAP_IPS | NF_NAT_RANGE_PROTO_SPECIFIED); |
c7232c99 PM |
195 | range.min_proto = range.max_proto = exp->saved_proto; |
196 | range.min_addr = range.max_addr | |
197 | = ct->master->tuplehash[!exp->dir].tuple.src.u3; | |
cbc9f2f4 | 198 | nf_nat_setup_info(ct, &range, NF_NAT_MANIP_DST); |
5b1158e9 JK |
199 | } |
200 | EXPORT_SYMBOL(nf_nat_follow_master); | |
c92c2717 FW |
201 | |
202 | u16 nf_nat_exp_find_port(struct nf_conntrack_expect *exp, u16 port) | |
203 | { | |
adda60cc FW |
204 | static const unsigned int max_attempts = 128; |
205 | int range, attempts_left; | |
206 | u16 min = port; | |
207 | ||
208 | range = USHRT_MAX - port; | |
209 | attempts_left = range; | |
210 | ||
211 | if (attempts_left > max_attempts) | |
212 | attempts_left = max_attempts; | |
213 | ||
c92c2717 | 214 | /* Try to get same port: if not, try to change it. */ |
adda60cc | 215 | for (;;) { |
c92c2717 FW |
216 | int res; |
217 | ||
218 | exp->tuple.dst.u.tcp.port = htons(port); | |
219 | res = nf_ct_expect_related(exp, 0); | |
220 | if (res == 0) | |
221 | return port; | |
222 | ||
adda60cc | 223 | if (res != -EBUSY || (--attempts_left < 0)) |
c92c2717 | 224 | break; |
adda60cc FW |
225 | |
226 | port = min + prandom_u32_max(range); | |
c92c2717 FW |
227 | } |
228 | ||
229 | return 0; | |
230 | } | |
231 | EXPORT_SYMBOL_GPL(nf_nat_exp_find_port); |