| /* ip_nat_helper.c - generic support functions for NAT helpers |
| * |
| * (C) 2000-2002 Harald Welte <laforge@netfilter.org> |
| * (C) 2003-2004 Netfilter Core Team <coreteam@netfilter.org> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| * |
| * 14 Jan 2002 Harald Welte <laforge@gnumonks.org>: |
| * - add support for SACK adjustment |
| * 14 Mar 2002 Harald Welte <laforge@gnumonks.org>: |
| * - merge SACK support into newnat API |
| * 16 Aug 2002 Brian J. Murrell <netfilter@interlinx.bc.ca>: |
| * - make ip_nat_resize_packet more generic (TCP and UDP) |
| * - add ip_nat_mangle_udp_packet |
| */ |
| #include <linux/module.h> |
| #include <linux/kmod.h> |
| #include <linux/types.h> |
| #include <linux/timer.h> |
| #include <linux/skbuff.h> |
| #include <linux/netfilter_ipv4.h> |
| #include <net/checksum.h> |
| #include <net/icmp.h> |
| #include <net/ip.h> |
| #include <net/tcp.h> |
| #include <net/udp.h> |
| |
| #include <linux/netfilter_ipv4/ip_conntrack.h> |
| #include <linux/netfilter_ipv4/ip_conntrack_helper.h> |
| #include <linux/netfilter_ipv4/ip_nat.h> |
| #include <linux/netfilter_ipv4/ip_nat_protocol.h> |
| #include <linux/netfilter_ipv4/ip_nat_core.h> |
| #include <linux/netfilter_ipv4/ip_nat_helper.h> |
| |
| #if 0 |
| #define DEBUGP printk |
| #define DUMP_OFFSET(x) printk("offset_before=%d, offset_after=%d, correction_pos=%u\n", x->offset_before, x->offset_after, x->correction_pos); |
| #else |
| #define DEBUGP(format, args...) |
| #define DUMP_OFFSET(x) |
| #endif |
| |
| static DEFINE_SPINLOCK(ip_nat_seqofs_lock); |
| |
| /* Setup TCP sequence correction given this change at this sequence */ |
| static inline void |
| adjust_tcp_sequence(u32 seq, |
| int sizediff, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo) |
| { |
| int dir; |
| struct ip_nat_seq *this_way, *other_way; |
| |
| DEBUGP("ip_nat_resize_packet: old_size = %u, new_size = %u\n", |
| (*skb)->len, new_size); |
| |
| dir = CTINFO2DIR(ctinfo); |
| |
| this_way = &ct->nat.info.seq[dir]; |
| other_way = &ct->nat.info.seq[!dir]; |
| |
| DEBUGP("ip_nat_resize_packet: Seq_offset before: "); |
| DUMP_OFFSET(this_way); |
| |
| spin_lock_bh(&ip_nat_seqofs_lock); |
| |
| /* SYN adjust. If it's uninitialized, or this is after last |
| * correction, record it: we don't handle more than one |
| * adjustment in the window, but do deal with common case of a |
| * retransmit */ |
| if (this_way->offset_before == this_way->offset_after |
| || before(this_way->correction_pos, seq)) { |
| this_way->correction_pos = seq; |
| this_way->offset_before = this_way->offset_after; |
| this_way->offset_after += sizediff; |
| } |
| spin_unlock_bh(&ip_nat_seqofs_lock); |
| |
| DEBUGP("ip_nat_resize_packet: Seq_offset after: "); |
| DUMP_OFFSET(this_way); |
| } |
| |
| /* Frobs data inside this packet, which is linear. */ |
| static void mangle_contents(struct sk_buff *skb, |
| unsigned int dataoff, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len) |
| { |
| unsigned char *data; |
| |
| BUG_ON(skb_is_nonlinear(skb)); |
| data = (unsigned char *)skb->nh.iph + dataoff; |
| |
| /* move post-replacement */ |
| memmove(data + match_offset + rep_len, |
| data + match_offset + match_len, |
| skb->tail - (data + match_offset + match_len)); |
| |
| /* insert data from buffer */ |
| memcpy(data + match_offset, rep_buffer, rep_len); |
| |
| /* update skb info */ |
| if (rep_len > match_len) { |
| DEBUGP("ip_nat_mangle_packet: Extending packet by " |
| "%u from %u bytes\n", rep_len - match_len, |
| skb->len); |
| skb_put(skb, rep_len - match_len); |
| } else { |
| DEBUGP("ip_nat_mangle_packet: Shrinking packet from " |
| "%u from %u bytes\n", match_len - rep_len, |
| skb->len); |
| __skb_trim(skb, skb->len + rep_len - match_len); |
| } |
| |
| /* fix IP hdr checksum information */ |
| skb->nh.iph->tot_len = htons(skb->len); |
| ip_send_check(skb->nh.iph); |
| } |
| |
| /* Unusual, but possible case. */ |
| static int enlarge_skb(struct sk_buff **pskb, unsigned int extra) |
| { |
| struct sk_buff *nskb; |
| |
| if ((*pskb)->len + extra > 65535) |
| return 0; |
| |
| nskb = skb_copy_expand(*pskb, skb_headroom(*pskb), extra, GFP_ATOMIC); |
| if (!nskb) |
| return 0; |
| |
| /* Transfer socket to new skb. */ |
| if ((*pskb)->sk) |
| skb_set_owner_w(nskb, (*pskb)->sk); |
| kfree_skb(*pskb); |
| *pskb = nskb; |
| return 1; |
| } |
| |
| /* Generic function for mangling variable-length address changes inside |
| * NATed TCP connections (like the PORT XXX,XXX,XXX,XXX,XXX,XXX |
| * command in FTP). |
| * |
| * Takes care about all the nasty sequence number changes, checksumming, |
| * skb enlargement, ... |
| * |
| * */ |
| int |
| ip_nat_mangle_tcp_packet(struct sk_buff **pskb, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len) |
| { |
| struct iphdr *iph; |
| struct tcphdr *tcph; |
| int oldlen, datalen; |
| |
| if (!skb_make_writable(pskb, (*pskb)->len)) |
| return 0; |
| |
| if (rep_len > match_len |
| && rep_len - match_len > skb_tailroom(*pskb) |
| && !enlarge_skb(pskb, rep_len - match_len)) |
| return 0; |
| |
| SKB_LINEAR_ASSERT(*pskb); |
| |
| iph = (*pskb)->nh.iph; |
| tcph = (void *)iph + iph->ihl*4; |
| |
| oldlen = (*pskb)->len - iph->ihl*4; |
| mangle_contents(*pskb, iph->ihl*4 + tcph->doff*4, |
| match_offset, match_len, rep_buffer, rep_len); |
| |
| datalen = (*pskb)->len - iph->ihl*4; |
| if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) { |
| tcph->check = 0; |
| tcph->check = tcp_v4_check(tcph, datalen, |
| iph->saddr, iph->daddr, |
| csum_partial((char *)tcph, |
| datalen, 0)); |
| } else |
| nf_proto_csum_replace2(&tcph->check, *pskb, |
| htons(oldlen), htons(datalen), 1); |
| |
| if (rep_len != match_len) { |
| set_bit(IPS_SEQ_ADJUST_BIT, &ct->status); |
| adjust_tcp_sequence(ntohl(tcph->seq), |
| (int)rep_len - (int)match_len, |
| ct, ctinfo); |
| /* Tell TCP window tracking about seq change */ |
| ip_conntrack_tcp_update(*pskb, ct, CTINFO2DIR(ctinfo)); |
| } |
| return 1; |
| } |
| EXPORT_SYMBOL(ip_nat_mangle_tcp_packet); |
| |
| /* Generic function for mangling variable-length address changes inside |
| * NATed UDP connections (like the CONNECT DATA XXXXX MESG XXXXX INDEX XXXXX |
| * command in the Amanda protocol) |
| * |
| * Takes care about all the nasty sequence number changes, checksumming, |
| * skb enlargement, ... |
| * |
| * XXX - This function could be merged with ip_nat_mangle_tcp_packet which |
| * should be fairly easy to do. |
| */ |
| int |
| ip_nat_mangle_udp_packet(struct sk_buff **pskb, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo, |
| unsigned int match_offset, |
| unsigned int match_len, |
| const char *rep_buffer, |
| unsigned int rep_len) |
| { |
| struct iphdr *iph; |
| struct udphdr *udph; |
| int datalen, oldlen; |
| |
| /* UDP helpers might accidentally mangle the wrong packet */ |
| iph = (*pskb)->nh.iph; |
| if ((*pskb)->len < iph->ihl*4 + sizeof(*udph) + |
| match_offset + match_len) |
| return 0; |
| |
| if (!skb_make_writable(pskb, (*pskb)->len)) |
| return 0; |
| |
| if (rep_len > match_len |
| && rep_len - match_len > skb_tailroom(*pskb) |
| && !enlarge_skb(pskb, rep_len - match_len)) |
| return 0; |
| |
| iph = (*pskb)->nh.iph; |
| udph = (void *)iph + iph->ihl*4; |
| |
| oldlen = (*pskb)->len - iph->ihl*4; |
| mangle_contents(*pskb, iph->ihl*4 + sizeof(*udph), |
| match_offset, match_len, rep_buffer, rep_len); |
| |
| /* update the length of the UDP packet */ |
| datalen = (*pskb)->len - iph->ihl*4; |
| udph->len = htons(datalen); |
| |
| /* fix udp checksum if udp checksum was previously calculated */ |
| if (!udph->check && (*pskb)->ip_summed != CHECKSUM_PARTIAL) |
| return 1; |
| |
| if ((*pskb)->ip_summed != CHECKSUM_PARTIAL) { |
| udph->check = 0; |
| udph->check = csum_tcpudp_magic(iph->saddr, iph->daddr, |
| datalen, IPPROTO_UDP, |
| csum_partial((char *)udph, |
| datalen, 0)); |
| if (!udph->check) |
| udph->check = CSUM_MANGLED_0; |
| } else |
| nf_proto_csum_replace2(&udph->check, *pskb, |
| htons(oldlen), htons(datalen), 1); |
| return 1; |
| } |
| EXPORT_SYMBOL(ip_nat_mangle_udp_packet); |
| |
| /* Adjust one found SACK option including checksum correction */ |
| static void |
| sack_adjust(struct sk_buff *skb, |
| struct tcphdr *tcph, |
| unsigned int sackoff, |
| unsigned int sackend, |
| struct ip_nat_seq *natseq) |
| { |
| while (sackoff < sackend) { |
| struct tcp_sack_block_wire *sack; |
| __be32 new_start_seq, new_end_seq; |
| |
| sack = (void *)skb->data + sackoff; |
| if (after(ntohl(sack->start_seq) - natseq->offset_before, |
| natseq->correction_pos)) |
| new_start_seq = htonl(ntohl(sack->start_seq) |
| - natseq->offset_after); |
| else |
| new_start_seq = htonl(ntohl(sack->start_seq) |
| - natseq->offset_before); |
| |
| if (after(ntohl(sack->end_seq) - natseq->offset_before, |
| natseq->correction_pos)) |
| new_end_seq = htonl(ntohl(sack->end_seq) |
| - natseq->offset_after); |
| else |
| new_end_seq = htonl(ntohl(sack->end_seq) |
| - natseq->offset_before); |
| |
| DEBUGP("sack_adjust: start_seq: %d->%d, end_seq: %d->%d\n", |
| ntohl(sack->start_seq), new_start_seq, |
| ntohl(sack->end_seq), new_end_seq); |
| |
| nf_proto_csum_replace4(&tcph->check, skb, |
| sack->start_seq, new_start_seq, 0); |
| nf_proto_csum_replace4(&tcph->check, skb, |
| sack->end_seq, new_end_seq, 0); |
| sack->start_seq = new_start_seq; |
| sack->end_seq = new_end_seq; |
| sackoff += sizeof(*sack); |
| } |
| } |
| |
| /* TCP SACK sequence number adjustment */ |
| static inline unsigned int |
| ip_nat_sack_adjust(struct sk_buff **pskb, |
| struct tcphdr *tcph, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo) |
| { |
| unsigned int dir, optoff, optend; |
| |
| optoff = (*pskb)->nh.iph->ihl*4 + sizeof(struct tcphdr); |
| optend = (*pskb)->nh.iph->ihl*4 + tcph->doff*4; |
| |
| if (!skb_make_writable(pskb, optend)) |
| return 0; |
| |
| dir = CTINFO2DIR(ctinfo); |
| |
| while (optoff < optend) { |
| /* Usually: option, length. */ |
| unsigned char *op = (*pskb)->data + optoff; |
| |
| switch (op[0]) { |
| case TCPOPT_EOL: |
| return 1; |
| case TCPOPT_NOP: |
| optoff++; |
| continue; |
| default: |
| /* no partial options */ |
| if (optoff + 1 == optend |
| || optoff + op[1] > optend |
| || op[1] < 2) |
| return 0; |
| if (op[0] == TCPOPT_SACK |
| && op[1] >= 2+TCPOLEN_SACK_PERBLOCK |
| && ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0) |
| sack_adjust(*pskb, tcph, optoff+2, |
| optoff+op[1], |
| &ct->nat.info.seq[!dir]); |
| optoff += op[1]; |
| } |
| } |
| return 1; |
| } |
| |
| /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */ |
| int |
| ip_nat_seq_adjust(struct sk_buff **pskb, |
| struct ip_conntrack *ct, |
| enum ip_conntrack_info ctinfo) |
| { |
| struct tcphdr *tcph; |
| int dir; |
| __be32 newseq, newack; |
| struct ip_nat_seq *this_way, *other_way; |
| |
| dir = CTINFO2DIR(ctinfo); |
| |
| this_way = &ct->nat.info.seq[dir]; |
| other_way = &ct->nat.info.seq[!dir]; |
| |
| if (!skb_make_writable(pskb, (*pskb)->nh.iph->ihl*4+sizeof(*tcph))) |
| return 0; |
| |
| tcph = (void *)(*pskb)->data + (*pskb)->nh.iph->ihl*4; |
| if (after(ntohl(tcph->seq), this_way->correction_pos)) |
| newseq = htonl(ntohl(tcph->seq) + this_way->offset_after); |
| else |
| newseq = htonl(ntohl(tcph->seq) + this_way->offset_before); |
| |
| if (after(ntohl(tcph->ack_seq) - other_way->offset_before, |
| other_way->correction_pos)) |
| newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_after); |
| else |
| newack = htonl(ntohl(tcph->ack_seq) - other_way->offset_before); |
| |
| nf_proto_csum_replace4(&tcph->check, *pskb, tcph->seq, newseq, 0); |
| nf_proto_csum_replace4(&tcph->check, *pskb, tcph->ack_seq, newack, 0); |
| |
| DEBUGP("Adjusting sequence number from %u->%u, ack from %u->%u\n", |
| ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq), |
| ntohl(newack)); |
| |
| tcph->seq = newseq; |
| tcph->ack_seq = newack; |
| |
| if (!ip_nat_sack_adjust(pskb, tcph, ct, ctinfo)) |
| return 0; |
| |
| ip_conntrack_tcp_update(*pskb, ct, dir); |
| |
| return 1; |
| } |
| EXPORT_SYMBOL(ip_nat_seq_adjust); |
| |
| /* Setup NAT on this expected conntrack so it follows master. */ |
| /* If we fail to get a free NAT slot, we'll get dropped on confirm */ |
| void ip_nat_follow_master(struct ip_conntrack *ct, |
| struct ip_conntrack_expect *exp) |
| { |
| struct ip_nat_range range; |
| |
| /* This must be a fresh one. */ |
| BUG_ON(ct->status & IPS_NAT_DONE_MASK); |
| |
| /* Change src to where master sends to */ |
| range.flags = IP_NAT_RANGE_MAP_IPS; |
| range.min_ip = range.max_ip |
| = ct->master->tuplehash[!exp->dir].tuple.dst.ip; |
| /* hook doesn't matter, but it has to do source manip */ |
| ip_nat_setup_info(ct, &range, NF_IP_POST_ROUTING); |
| |
| /* For DST manip, map port here to where it's expected. */ |
| range.flags = (IP_NAT_RANGE_MAP_IPS | IP_NAT_RANGE_PROTO_SPECIFIED); |
| range.min = range.max = exp->saved_proto; |
| range.min_ip = range.max_ip |
| = ct->master->tuplehash[!exp->dir].tuple.src.ip; |
| /* hook doesn't matter, but it has to do destination manip */ |
| ip_nat_setup_info(ct, &range, NF_IP_PRE_ROUTING); |
| } |
| EXPORT_SYMBOL(ip_nat_follow_master); |