Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 1 | /* ip_nat_helper.c - generic support functions for NAT helpers |
| 2 | * |
| 3 | * (C) 2000-2002 Harald Welte <laforge@netfilter.org> |
| 4 | * (C) 2003-2006 Netfilter Core Team <coreteam@netfilter.org> |
| 5 | * |
| 6 | * This program is free software; you can redistribute it and/or modify |
| 7 | * it under the terms of the GNU General Public License version 2 as |
| 8 | * published by the Free Software Foundation. |
| 9 | */ |
| 10 | #include <linux/module.h> |
| 11 | #include <linux/kmod.h> |
| 12 | #include <linux/types.h> |
| 13 | #include <linux/timer.h> |
| 14 | #include <linux/skbuff.h> |
| 15 | #include <linux/tcp.h> |
| 16 | #include <linux/udp.h> |
| 17 | #include <net/checksum.h> |
| 18 | #include <net/tcp.h> |
| 19 | |
| 20 | #include <linux/netfilter_ipv4.h> |
| 21 | #include <net/netfilter/nf_conntrack.h> |
| 22 | #include <net/netfilter/nf_conntrack_helper.h> |
| 23 | #include <net/netfilter/nf_conntrack_expect.h> |
| 24 | #include <net/netfilter/nf_nat.h> |
| 25 | #include <net/netfilter/nf_nat_protocol.h> |
| 26 | #include <net/netfilter/nf_nat_core.h> |
| 27 | #include <net/netfilter/nf_nat_helper.h> |
| 28 | |
| 29 | #if 0 |
| 30 | #define DEBUGP printk |
| 31 | #define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos); |
| 32 | #else |
| 33 | #define DEBUGP(format, args...) |
| 34 | #define DUMP_OFFSET(x) |
| 35 | #endif |
| 36 | |
| 37 | static DEFINE_SPINLOCK(nf_nat_seqofs_lock); |
| 38 | |
| 39 | /* Setup TCP sequence correction given this change at this sequence */ |
| 40 | static inline void |
| 41 | adjust_tcp_sequence(u32 seq, |
| 42 | int sizediff, |
| 43 | struct nf_conn *ct, |
| 44 | enum ip_conntrack_info ctinfo) |
| 45 | { |
| 46 | int dir; |
| 47 | struct nf_nat_seq *this_way, *other_way; |
| 48 | struct nf_conn_nat *nat = nfct_nat(ct); |
| 49 | |
| 50 | DEBUGP("nf_nat_resize_packet: old_size = %u, new_size = %u\n", |
| 51 | (*skb)->len, new_size); |
| 52 | |
| 53 | dir = CTINFO2DIR(ctinfo); |
| 54 | |
| 55 | this_way = &nat->info.seq[dir]; |
| 56 | other_way = &nat->info.seq[!dir]; |
| 57 | |
| 58 | DEBUGP("nf_nat_resize_packet: Seq_offset before: "); |
| 59 | DUMP_OFFSET(this_way); |
| 60 | |
| 61 | spin_lock_bh(&nf_nat_seqofs_lock); |
| 62 | |
| 63 | /* SYN adjust. If it's uninitialized, or this is after last |
| 64 | * correction, record it: we don't handle more than one |
| 65 | * adjustment in the window, but do deal with common case of a |
| 66 | * retransmit */ |
| 67 | if (this_way->offset_before == this_way->offset_after || |
| 68 | before(this_way->correction_pos, seq)) { |
| 69 | this_way->correction_pos = seq; |
| 70 | this_way->offset_before = this_way->offset_after; |
| 71 | this_way->offset_after += sizediff; |
| 72 | } |
| 73 | spin_unlock_bh(&nf_nat_seqofs_lock); |
| 74 | |
| 75 | DEBUGP("nf_nat_resize_packet: Seq_offset after: "); |
| 76 | DUMP_OFFSET(this_way); |
| 77 | } |
| 78 | |
| 79 | /* Frobs data inside this packet, which is linear. */ |
| 80 | static void mangle_contents(struct sk_buff *skb, |
| 81 | unsigned int dataoff, |
| 82 | unsigned int match_offset, |
| 83 | unsigned int match_len, |
| 84 | const char *rep_buffer, |
| 85 | unsigned int rep_len) |
| 86 | { |
| 87 | unsigned char *data; |
| 88 | |
| 89 | BUG_ON(skb_is_nonlinear(skb)); |
| 90 | data = (unsigned char *)skb->nh.iph + dataoff; |
| 91 | |
| 92 | /* move post-replacement */ |
| 93 | memmove(data + match_offset + rep_len, |
| 94 | data + match_offset + match_len, |
| 95 | skb->tail - (data + match_offset + match_len)); |
| 96 | |
| 97 | /* insert data from buffer */ |
| 98 | memcpy(data + match_offset, rep_buffer, rep_len); |
| 99 | |
| 100 | /* update skb info */ |
| 101 | if (rep_len > match_len) { |
| 102 | DEBUGP("nf_nat_mangle_packet: Extending packet by " |
| 103 | "%u from %u bytes\n", rep_len - match_len, |
| 104 | skb->len); |
| 105 | skb_put(skb, rep_len - match_len); |
| 106 | } else { |
| 107 | DEBUGP("nf_nat_mangle_packet: Shrinking packet from " |
| 108 | "%u from %u bytes\n", match_len - rep_len, |
| 109 | skb->len); |
| 110 | __skb_trim(skb, skb->len + rep_len - match_len); |
| 111 | } |
| 112 | |
| 113 | /* fix IP hdr checksum information */ |
| 114 | skb->nh.iph->tot_len = htons(skb->len); |
| 115 | ip_send_check(skb->nh.iph); |
| 116 | } |
| 117 | |
| 118 | /* Unusual, but possible case. */ |
| 119 | static int enlarge_skb(struct sk_buff **pskb, unsigned int extra) |
| 120 | { |
| 121 | struct sk_buff *nskb; |
| 122 | |
| 123 | if ((*pskb)->len + extra > 65535) |
| 124 | return 0; |
| 125 | |
| 126 | nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC); |
| 127 | if (!nskb) |
| 128 | return 0; |
| 129 | |
| 130 | /* Transfer socket to new skb. */ |
| 131 | if ((*pskb)->sk) |
| 132 | skb_set_owner_w(nskb, (*pskb)->sk); |
| 133 | kfree_skb(*pskb); |
| 134 | *pskb = nskb; |
| 135 | return 1; |
| 136 | } |
| 137 | |
| 138 | /* Generic function for mangling variable-length address changes inside |
| 139 | * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX |
| 140 | * command in FTP). |
| 141 | * |
| 142 | * Takes care about all the nasty sequence number changes, checksumming, |
| 143 | * skb enlargement, ... |
| 144 | * |
| 145 | * */ |
| 146 | int |
| 147 | nf_nat_mangle_tcp_packet(struct sk_buff **pskb, |
| 148 | struct nf_conn *ct, |
| 149 | enum ip_conntrack_info ctinfo, |
| 150 | unsigned int match_offset, |
| 151 | unsigned int match_len, |
| 152 | const char *rep_buffer, |
| 153 | unsigned int rep_len) |
| 154 | { |
| 155 | struct iphdr *iph; |
| 156 | struct tcphdr *tcph; |
| 157 | int oldlen, datalen; |
| 158 | |
| 159 | if (!skb_make_writable(pskb, (*pskb)->len)) |
| 160 | return 0; |
| 161 | |
| 162 | if (rep_len > match_len && |
| 163 | rep_len - match_len > skb_tailroom(*pskb) && |
| 164 | !enlarge_skb(pskb, rep_len - match_len)) |
| 165 | return 0; |
| 166 | |
| 167 | SKB_LINEAR_ASSERT(*pskb); |
| 168 | |
| 169 | iph = (*pskb)->nh.iph; |
| 170 | tcph = (void *)iph + iph->ihl*4; |
| 171 | |
| 172 | oldlen = (*pskb)->len - iph->ihl*4; |
| 173 | mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4, |
| 174 | match_offset, match_len, rep_buffer, rep_len); |
| 175 | |
| 176 | datalen = (*pskb)->len - iph->ihl*4; |
| 177 | if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) { |
| 178 | tcph->check = 0; |
Frederik Deweerdt | ba7808e | 2007-02-04 20:15:27 -0800 | [diff] [blame] | 179 | tcph->check = tcp_v4_check(datalen, |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 180 | iph->saddr, iph->daddr, |
| 181 | csum_partial((char *)tcph, |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 182 | datalen, 0)); |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 183 | } else |
| 184 | nf_proto_csum_replace2(&tcph->check, *pskb, |
| 185 | htons(oldlen), htons(datalen), 1); |
| 186 | |
| 187 | if (rep_len != match_len) { |
| 188 | set_bit(IPS_SEQ_ADJUST_BIT, &ct->status); |
| 189 | adjust_tcp_sequence(ntohl(tcph->seq), |
| 190 | (int)rep_len - (int)match_len, |
| 191 | ct, ctinfo); |
| 192 | /* Tell TCP window tracking about seq change */ |
Arnaldo Carvalho de Melo | c9bdd4b | 2007-03-12 20:09:15 -0300 | [diff] [blame] | 193 | nf_conntrack_tcp_update(*pskb, ip_hdrlen(*pskb), |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 194 | ct, CTINFO2DIR(ctinfo)); |
| 195 | } |
| 196 | return 1; |
| 197 | } |
| 198 | EXPORT_SYMBOL(nf_nat_mangle_tcp_packet); |
| 199 | |
| 200 | /* Generic function for mangling variable-length address changes inside |
| 201 | * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX |
| 202 | * command in the Amanda protocol) |
| 203 | * |
| 204 | * Takes care about all the nasty sequence number changes, checksumming, |
| 205 | * skb enlargement, ... |
| 206 | * |
| 207 | * XXX - This function could be merged with nf_nat_mangle_tcp_packet which |
| 208 | * should be fairly easy to do. |
| 209 | */ |
| 210 | int |
| 211 | nf_nat_mangle_udp_packet(struct sk_buff **pskb, |
| 212 | struct nf_conn *ct, |
| 213 | enum ip_conntrack_info ctinfo, |
| 214 | unsigned int match_offset, |
| 215 | unsigned int match_len, |
| 216 | const char *rep_buffer, |
| 217 | unsigned int rep_len) |
| 218 | { |
| 219 | struct iphdr *iph; |
| 220 | struct udphdr *udph; |
| 221 | int datalen, oldlen; |
| 222 | |
| 223 | /* UDP helpers might accidentally mangle the wrong packet */ |
| 224 | iph = (*pskb)->nh.iph; |
| 225 | if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) + |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 226 | match_offset + match_len) |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 227 | return 0; |
| 228 | |
| 229 | if (!skb_make_writable(pskb, (*pskb)->len)) |
| 230 | return 0; |
| 231 | |
| 232 | if (rep_len > match_len && |
| 233 | rep_len - match_len > skb_tailroom(*pskb) && |
| 234 | !enlarge_skb(pskb, rep_len - match_len)) |
| 235 | return 0; |
| 236 | |
| 237 | iph = (*pskb)->nh.iph; |
| 238 | udph = (void *)iph + iph->ihl*4; |
| 239 | |
| 240 | oldlen = (*pskb)->len - iph->ihl*4; |
| 241 | mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph), |
| 242 | match_offset, match_len, rep_buffer, rep_len); |
| 243 | |
| 244 | /* update the length of the UDP packet */ |
| 245 | datalen = (*pskb)->len - iph->ihl*4; |
| 246 | udph->len = htons(datalen); |
| 247 | |
| 248 | /* fix udp checksum if udp checksum was previously calculated */ |
| 249 | if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL) |
| 250 | return 1; |
| 251 | |
| 252 | if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) { |
| 253 | udph->check = 0; |
| 254 | udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr, |
YOSHIFUJI Hideaki | e905a9e | 2007-02-09 23:24:47 +0900 | [diff] [blame] | 255 | datalen, IPPROTO_UDP, |
| 256 | csum_partial((char *)udph, |
| 257 | datalen, 0)); |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 258 | if (!udph->check) |
| 259 | udph->check = CSUM_MANGLED_0; |
| 260 | } else |
| 261 | nf_proto_csum_replace2(&udph->check, *pskb, |
| 262 | htons(oldlen), htons(datalen), 1); |
| 263 | |
| 264 | return 1; |
| 265 | } |
| 266 | EXPORT_SYMBOL(nf_nat_mangle_udp_packet); |
| 267 | |
| 268 | /* Adjust one found SACK option including checksum correction */ |
| 269 | static void |
| 270 | sack_adjust(struct sk_buff *skb, |
| 271 | struct tcphdr *tcph, |
| 272 | unsigned int sackoff, |
| 273 | unsigned int sackend, |
| 274 | struct nf_nat_seq *natseq) |
| 275 | { |
| 276 | while (sackoff < sackend) { |
| 277 | struct tcp_sack_block_wire *sack; |
| 278 | __be32 new_start_seq, new_end_seq; |
| 279 | |
| 280 | sack = (void *)skb->data + sackoff; |
| 281 | if (after(ntohl(sack->start_seq) - natseq->offset_before, |
| 282 | natseq->correction_pos)) |
| 283 | new_start_seq = htonl(ntohl(sack->start_seq) |
| 284 | - natseq->offset_after); |
| 285 | else |
| 286 | new_start_seq = htonl(ntohl(sack->start_seq) |
| 287 | - natseq->offset_before); |
| 288 | |
| 289 | if (after(ntohl(sack->end_seq) - natseq->offset_before, |
| 290 | natseq->correction_pos)) |
| 291 | new_end_seq = htonl(ntohl(sack->end_seq) |
| 292 | - natseq->offset_after); |
| 293 | else |
| 294 | new_end_seq = htonl(ntohl(sack->end_seq) |
| 295 | - natseq->offset_before); |
| 296 | |
| 297 | DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n", |
| 298 | ntohl(sack->start_seq), new_start_seq, |
| 299 | ntohl(sack->end_seq), new_end_seq); |
| 300 | |
| 301 | nf_proto_csum_replace4(&tcph->check, skb, |
| 302 | sack->start_seq, new_start_seq, 0); |
| 303 | nf_proto_csum_replace4(&tcph->check, skb, |
| 304 | sack->end_seq, new_end_seq, 0); |
| 305 | sack->start_seq = new_start_seq; |
| 306 | sack->end_seq = new_end_seq; |
| 307 | sackoff += sizeof(*sack); |
| 308 | } |
| 309 | } |
| 310 | |
| 311 | /* TCP SACK sequence number adjustment */ |
| 312 | static inline unsigned int |
| 313 | nf_nat_sack_adjust(struct sk_buff **pskb, |
| 314 | struct tcphdr *tcph, |
| 315 | struct nf_conn *ct, |
| 316 | enum ip_conntrack_info ctinfo) |
| 317 | { |
| 318 | unsigned int dir, optoff, optend; |
| 319 | struct nf_conn_nat *nat = nfct_nat(ct); |
| 320 | |
Arnaldo Carvalho de Melo | c9bdd4b | 2007-03-12 20:09:15 -0300 | [diff] [blame] | 321 | optoff = ip_hdrlen(*pskb) + sizeof(struct tcphdr); |
| 322 | optend = ip_hdrlen(*pskb) + tcph->doff * 4; |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 323 | |
| 324 | if (!skb_make_writable(pskb, optend)) |
| 325 | return 0; |
| 326 | |
| 327 | dir = CTINFO2DIR(ctinfo); |
| 328 | |
| 329 | while (optoff < optend) { |
| 330 | /* Usually: option, length. */ |
| 331 | unsigned char *op = (*pskb)->data + optoff; |
| 332 | |
| 333 | switch (op[0]) { |
| 334 | case TCPOPT_EOL: |
| 335 | return 1; |
| 336 | case TCPOPT_NOP: |
| 337 | optoff++; |
| 338 | continue; |
| 339 | default: |
| 340 | /* no partial options */ |
| 341 | if (optoff + 1 == optend || |
| 342 | optoff + op[1] > optend || |
| 343 | op[1] < 2) |
| 344 | return 0; |
| 345 | if (op[0] == TCPOPT_SACK && |
| 346 | op[1] >= 2+TCPOLEN_SACK_PERBLOCK && |
| 347 | ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0) |
| 348 | sack_adjust(*pskb, tcph, optoff+2, |
| 349 | optoff+op[1], |
| 350 | &nat->info.seq[!dir]); |
| 351 | optoff += op[1]; |
| 352 | } |
| 353 | } |
| 354 | return 1; |
| 355 | } |
| 356 | |
| 357 | /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */ |
| 358 | int |
| 359 | nf_nat_seq_adjust(struct sk_buff **pskb, |
| 360 | struct nf_conn *ct, |
| 361 | enum ip_conntrack_info ctinfo) |
| 362 | { |
| 363 | struct tcphdr *tcph; |
| 364 | int dir; |
| 365 | __be32 newseq, newack; |
| 366 | struct nf_conn_nat *nat = nfct_nat(ct); |
| 367 | struct nf_nat_seq *this_way, *other_way; |
| 368 | |
| 369 | dir = CTINFO2DIR(ctinfo); |
| 370 | |
| 371 | this_way = &nat->info.seq[dir]; |
| 372 | other_way = &nat->info.seq[!dir]; |
| 373 | |
Arnaldo Carvalho de Melo | c9bdd4b | 2007-03-12 20:09:15 -0300 | [diff] [blame] | 374 | if (!skb_make_writable(pskb, ip_hdrlen(*pskb) + sizeof(*tcph))) |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 375 | return 0; |
| 376 | |
Arnaldo Carvalho de Melo | c9bdd4b | 2007-03-12 20:09:15 -0300 | [diff] [blame] | 377 | tcph = (void *)(*pskb)->data + ip_hdrlen(*pskb); |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 378 | if (after(ntohl(tcph->seq), this_way->correction_pos)) |
| 379 | newseq = htonl(ntohl(tcph->seq) + this_way->offset_after); |
| 380 | else |
| 381 | newseq = htonl(ntohl(tcph->seq) + this_way->offset_before); |
| 382 | |
| 383 | if (after(ntohl(tcph->ack_seq) - other_way->offset_before, |
| 384 | other_way->correction_pos)) |
| 385 | newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after); |
| 386 | else |
| 387 | newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before); |
| 388 | |
| 389 | nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0); |
| 390 | nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0); |
| 391 | |
| 392 | DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n", |
| 393 | ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq), |
| 394 | ntohl(newack)); |
| 395 | |
| 396 | tcph->seq = newseq; |
| 397 | tcph->ack_seq = newack; |
| 398 | |
| 399 | if (!nf_nat_sack_adjust(pskb, tcph, ct, ctinfo)) |
| 400 | return 0; |
| 401 | |
Arnaldo Carvalho de Melo | c9bdd4b | 2007-03-12 20:09:15 -0300 | [diff] [blame] | 402 | nf_conntrack_tcp_update(*pskb, ip_hdrlen(*pskb), ct, dir); |
Jozsef Kadlecsik | 5b1158e | 2006-12-02 22:07:13 -0800 | [diff] [blame] | 403 | |
| 404 | return 1; |
| 405 | } |
| 406 | EXPORT_SYMBOL(nf_nat_seq_adjust); |
| 407 | |
| 408 | /* Setup NAT on this expected conntrack so it follows master. */ |
| 409 | /* If we fail to get a free NAT slot, we'll get dropped on confirm */ |
| 410 | void nf_nat_follow_master(struct nf_conn *ct, |
| 411 | struct nf_conntrack_expect *exp) |
| 412 | { |
| 413 | struct nf_nat_range range; |
| 414 | |
| 415 | /* This must be a fresh one. */ |
| 416 | BUG_ON(ct->status & IPS_NAT_DONE_MASK); |
| 417 | |
| 418 | /* Change src to where master sends to */ |
| 419 | range.flags = IP_NAT_RANGE_MAP_IPS; |
| 420 | range.min_ip = range.max_ip |
| 421 | = ct->master->tuplehash[!exp->dir].tuple.dst.u3.ip; |
| 422 | /* hook doesn't matter, but it has to do source manip */ |
| 423 | nf_nat_setup_info(ct, &range, NF_IP_POST_ROUTING); |
| 424 | |
| 425 | /* For DST manip, map port here to where it's expected. */ |
| 426 | range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); |
| 427 | range.min = range.max = exp->saved_proto; |
| 428 | range.min_ip = range.max_ip |
| 429 | = ct->master->tuplehash[!exp->dir].tuple.src.u3.ip; |
| 430 | /* hook doesn't matter, but it has to do destination manip */ |
| 431 | nf_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING); |
| 432 | } |
| 433 | EXPORT_SYMBOL(nf_nat_follow_master); |