1#include <linux/types.h>
2#include <linux/netfilter.h>
3#include <net/tcp.h>
4
5#include <net/netfilter/nf_conntrack.h>
6#include <net/netfilter/nf_conntrack_extend.h>
7#include <net/netfilter/nf_conntrack_seqadj.h>
8
9int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
10 s32 off)
11{
12 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
13 struct nf_conn_seqadj *seqadj;
14 struct nf_ct_seqadj *this_way;
15
16 if (off == 0)
17 return 0;
18
19 set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
20
21 seqadj = nfct_seqadj(ct);
22 this_way = &seqadj->seq[dir];
23 this_way->offset_before = off;
24 this_way->offset_after = off;
25 return 0;
26}
27EXPORT_SYMBOL_GPL(nf_ct_seqadj_init);
28
29int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
30 __be32 seq, s32 off)
31{
32 struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
33 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
34 struct nf_ct_seqadj *this_way;
35
36 if (off == 0)
37 return 0;
38
39 if (unlikely(!seqadj)) {
40 WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
41 return 0;
42 }
43
44 set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
45
46 spin_lock_bh(&ct->lock);
47 this_way = &seqadj->seq[dir];
48 if (this_way->offset_before == this_way->offset_after ||
49 before(this_way->correction_pos, ntohl(seq))) {
50 this_way->correction_pos = ntohl(seq);
51 this_way->offset_before = this_way->offset_after;
52 this_way->offset_after += off;
53 }
54 spin_unlock_bh(&ct->lock);
55 return 0;
56}
57EXPORT_SYMBOL_GPL(nf_ct_seqadj_set);
58
59void nf_ct_tcp_seqadj_set(struct sk_buff *skb,
60 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
61 s32 off)
62{
63 const struct tcphdr *th;
64
65 if (nf_ct_protonum(ct) != IPPROTO_TCP)
66 return;
67
68 th = (struct tcphdr *)(skb_network_header(skb) + ip_hdrlen(skb));
69 nf_ct_seqadj_set(ct, ctinfo, th->seq, off);
70}
71EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set);
72
73
74static void nf_ct_sack_block_adjust(struct sk_buff *skb,
75 struct tcphdr *tcph,
76 unsigned int sackoff,
77 unsigned int sackend,
78 struct nf_ct_seqadj *seq)
79{
80 while (sackoff < sackend) {
81 struct tcp_sack_block_wire *sack;
82 __be32 new_start_seq, new_end_seq;
83
84 sack = (void *)skb->data + sackoff;
85 if (after(ntohl(sack->start_seq) - seq->offset_before,
86 seq->correction_pos))
87 new_start_seq = htonl(ntohl(sack->start_seq) -
88 seq->offset_after);
89 else
90 new_start_seq = htonl(ntohl(sack->start_seq) -
91 seq->offset_before);
92
93 if (after(ntohl(sack->end_seq) - seq->offset_before,
94 seq->correction_pos))
95 new_end_seq = htonl(ntohl(sack->end_seq) -
96 seq->offset_after);
97 else
98 new_end_seq = htonl(ntohl(sack->end_seq) -
99 seq->offset_before);
100
101 pr_debug("sack_adjust: start_seq: %u->%u, end_seq: %u->%u\n",
102 ntohl(sack->start_seq), ntohl(new_start_seq),
103 ntohl(sack->end_seq), ntohl(new_end_seq));
104
105 inet_proto_csum_replace4(&tcph->check, skb,
106 sack->start_seq, new_start_seq, false);
107 inet_proto_csum_replace4(&tcph->check, skb,
108 sack->end_seq, new_end_seq, false);
109 sack->start_seq = new_start_seq;
110 sack->end_seq = new_end_seq;
111 sackoff += sizeof(*sack);
112 }
113}
114
115
116static unsigned int nf_ct_sack_adjust(struct sk_buff *skb,
117 unsigned int protoff,
118 struct tcphdr *tcph,
119 struct nf_conn *ct,
120 enum ip_conntrack_info ctinfo)
121{
122 unsigned int dir, optoff, optend;
123 struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
124
125 optoff = protoff + sizeof(struct tcphdr);
126 optend = protoff + tcph->doff * 4;
127
128 if (!skb_make_writable(skb, optend))
129 return 0;
130
131 dir = CTINFO2DIR(ctinfo);
132
133 while (optoff < optend) {
134
135 unsigned char *op = skb->data + optoff;
136
137 switch (op[0]) {
138 case TCPOPT_EOL:
139 return 1;
140 case TCPOPT_NOP:
141 optoff++;
142 continue;
143 default:
144
145 if (optoff + 1 == optend ||
146 optoff + op[1] > optend ||
147 op[1] < 2)
148 return 0;
149 if (op[0] == TCPOPT_SACK &&
150 op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
151 ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
152 nf_ct_sack_block_adjust(skb, tcph, optoff + 2,
153 optoff+op[1],
154 &seqadj->seq[!dir]);
155 optoff += op[1];
156 }
157 }
158 return 1;
159}
160
161
162int nf_ct_seq_adjust(struct sk_buff *skb,
163 struct nf_conn *ct, enum ip_conntrack_info ctinfo,
164 unsigned int protoff)
165{
166 enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
167 struct tcphdr *tcph;
168 __be32 newseq, newack;
169 s32 seqoff, ackoff;
170 struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
171 struct nf_ct_seqadj *this_way, *other_way;
172 int res;
173
174 this_way = &seqadj->seq[dir];
175 other_way = &seqadj->seq[!dir];
176
177 if (!skb_make_writable(skb, protoff + sizeof(*tcph)))
178 return 0;
179
180 tcph = (void *)skb->data + protoff;
181 spin_lock_bh(&ct->lock);
182 if (after(ntohl(tcph->seq), this_way->correction_pos))
183 seqoff = this_way->offset_after;
184 else
185 seqoff = this_way->offset_before;
186
187 if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
188 other_way->correction_pos))
189 ackoff = other_way->offset_after;
190 else
191 ackoff = other_way->offset_before;
192
193 newseq = htonl(ntohl(tcph->seq) + seqoff);
194 newack = htonl(ntohl(tcph->ack_seq) - ackoff);
195
196 inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
197 inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
198 false);
199
200 pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n",
201 ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
202 ntohl(newack));
203
204 tcph->seq = newseq;
205 tcph->ack_seq = newack;
206
207 res = nf_ct_sack_adjust(skb, protoff, tcph, ct, ctinfo);
208 spin_unlock_bh(&ct->lock);
209
210 return res;
211}
212EXPORT_SYMBOL_GPL(nf_ct_seq_adjust);
213
214s32 nf_ct_seq_offset(const struct nf_conn *ct,
215 enum ip_conntrack_dir dir,
216 u32 seq)
217{
218 struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
219 struct nf_ct_seqadj *this_way;
220
221 if (!seqadj)
222 return 0;
223
224 this_way = &seqadj->seq[dir];
225 return after(seq, this_way->correction_pos) ?
226 this_way->offset_after : this_way->offset_before;
227}
228EXPORT_SYMBOL_GPL(nf_ct_seq_offset);
229
230static struct nf_ct_ext_type nf_ct_seqadj_extend __read_mostly = {
231 .len = sizeof(struct nf_conn_seqadj),
232 .align = __alignof__(struct nf_conn_seqadj),
233 .id = NF_CT_EXT_SEQADJ,
234};
235
236int nf_conntrack_seqadj_init(void)
237{
238 return nf_ct_extend_register(&nf_ct_seqadj_extend);
239}
240
241void nf_conntrack_seqadj_fini(void)
242{
243 nf_ct_extend_unregister(&nf_ct_seqadj_extend);
244}
245
