net/netfilter/nf_conntrack_seqadj.c

   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 = 1;
 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         newseq = htonl(ntohl(tcph->seq) + seqoff);
 188         inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
 189         pr_debug("Adjusting sequence number from %u->%u\n",
 190                  ntohl(tcph->seq), ntohl(newseq));
 191         tcph->seq = newseq;
 192
 193         if (!tcph->ack)
 194                 goto out;
 195
 196         if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
 197                   other_way->correction_pos))
 198                 ackoff = other_way->offset_after;
 199         else
 200                 ackoff = other_way->offset_before;
 201
 202         newack = htonl(ntohl(tcph->ack_seq) - ackoff);
 203         inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
 204                                  false);
 205         pr_debug("Adjusting ack number from %u->%u, ack from %u->%u\n",
 206                  ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
 207                  ntohl(newack));
 208         tcph->ack_seq = newack;
 209
 210         res = nf_ct_sack_adjust(skb, protoff, tcph, ct, ctinfo);
 211 out:
 212         spin_unlock_bh(&ct->lock);
 213
 214         return res;
 215 }
 216 EXPORT_SYMBOL_GPL(nf_ct_seq_adjust);
 217
 218 s32 nf_ct_seq_offset(const struct nf_conn *ct,
 219                      enum ip_conntrack_dir dir,
 220                      u32 seq)
 221 {
 222         struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
 223         struct nf_ct_seqadj *this_way;
 224
 225         if (!seqadj)
 226                 return 0;
 227
 228         this_way = &seqadj->seq[dir];
 229         return after(seq, this_way->correction_pos) ?
 230                  this_way->offset_after : this_way->offset_before;
 231 }
 232 EXPORT_SYMBOL_GPL(nf_ct_seq_offset);
 233
 234 static struct nf_ct_ext_type nf_ct_seqadj_extend __read_mostly = {
 235         .len    = sizeof(struct nf_conn_seqadj),
 236         .align  = __alignof__(struct nf_conn_seqadj),
 237         .id     = NF_CT_EXT_SEQADJ,
 238 };
 239
 240 int nf_conntrack_seqadj_init(void)
 241 {
 242         return nf_ct_extend_register(&nf_ct_seqadj_extend);
 243 }
 244
 245 void nf_conntrack_seqadj_fini(void)
 246 {
 247         nf_ct_extend_unregister(&nf_ct_seqadj_extend);
 248 }