| 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 | |
| 9 | int 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 | } |
| 27 | EXPORT_SYMBOL_GPL(nf_ct_seqadj_init); |
| 28 | |
| 29 | int 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 | } |
| 57 | EXPORT_SYMBOL_GPL(nf_ct_seqadj_set); |
| 58 | |
| 59 | void 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 | } |
| 71 | EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set); |
| 72 | |
| 73 | /* Adjust one found SACK option including checksum correction */ |
| 74 | static 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, 0); |
| 107 | inet_proto_csum_replace4(&tcph->check, skb, |
| 108 | sack->end_seq, new_end_seq, 0); |
| 109 | sack->start_seq = new_start_seq; |
| 110 | sack->end_seq = new_end_seq; |
| 111 | sackoff += sizeof(*sack); |
| 112 | } |
| 113 | } |
| 114 | |
| 115 | /* TCP SACK sequence number adjustment */ |
| 116 | static 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 | /* Usually: option, length. */ |
| 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 | /* no partial options */ |
| 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 | /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */ |
| 162 | int 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, 0); |
| 197 | inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack, 0); |
| 198 | |
| 199 | pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n", |
| 200 | ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq), |
| 201 | ntohl(newack)); |
| 202 | |
| 203 | tcph->seq = newseq; |
| 204 | tcph->ack_seq = newack; |
| 205 | |
| 206 | res = nf_ct_sack_adjust(skb, protoff, tcph, ct, ctinfo); |
| 207 | spin_unlock_bh(&ct->lock); |
| 208 | |
| 209 | return res; |
| 210 | } |
| 211 | EXPORT_SYMBOL_GPL(nf_ct_seq_adjust); |
| 212 | |
| 213 | s32 nf_ct_seq_offset(const struct nf_conn *ct, |
| 214 | enum ip_conntrack_dir dir, |
| 215 | u32 seq) |
| 216 | { |
| 217 | struct nf_conn_seqadj *seqadj = nfct_seqadj(ct); |
| 218 | struct nf_ct_seqadj *this_way; |
| 219 | |
| 220 | if (!seqadj) |
| 221 | return 0; |
| 222 | |
| 223 | this_way = &seqadj->seq[dir]; |
| 224 | return after(seq, this_way->correction_pos) ? |
| 225 | this_way->offset_after : this_way->offset_before; |
| 226 | } |
| 227 | EXPORT_SYMBOL_GPL(nf_ct_seq_offset); |
| 228 | |
| 229 | static struct nf_ct_ext_type nf_ct_seqadj_extend __read_mostly = { |
| 230 | .len = sizeof(struct nf_conn_seqadj), |
| 231 | .align = __alignof__(struct nf_conn_seqadj), |
| 232 | .id = NF_CT_EXT_SEQADJ, |
| 233 | }; |
| 234 | |
| 235 | int nf_conntrack_seqadj_init(void) |
| 236 | { |
| 237 | return nf_ct_extend_register(&nf_ct_seqadj_extend); |
| 238 | } |
| 239 | |
| 240 | void nf_conntrack_seqadj_fini(void) |
| 241 | { |
| 242 | nf_ct_extend_unregister(&nf_ct_seqadj_extend); |
| 243 | } |