linux/net/netfilter/nf_conntrack_seqadj.c
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   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/* Adjust one found SACK option including checksum correction */
  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/* TCP SACK sequence number adjustment */
 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                /* 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 */
 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