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, 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 /* 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, 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 } 212 EXPORT_SYMBOL_GPL(nf_ct_seq_adjust); 213 214 s32 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 } 228 EXPORT_SYMBOL_GPL(nf_ct_seq_offset); 229 230 static 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 }; 235 236 int nf_conntrack_seqadj_init(void) 237 { 238 return nf_ct_extend_register(&nf_ct_seqadj_extend); 239 } 240 241 void nf_conntrack_seqadj_fini(void) 242 { 243 nf_ct_extend_unregister(&nf_ct_seqadj_extend); 244 } 245