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- #include <linux/types.h>
- #include <linux/netfilter.h>
- #include <net/tcp.h>
- #include <net/netfilter/nf_conntrack.h>
- #include <net/netfilter/nf_conntrack_extend.h>
- #include <net/netfilter/nf_conntrack_seqadj.h>
- int nf_ct_seqadj_init(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
- s32 off)
- {
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- struct nf_conn_seqadj *seqadj;
- struct nf_ct_seqadj *this_way;
- if (off == 0)
- return 0;
- set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
- seqadj = nfct_seqadj(ct);
- this_way = &seqadj->seq[dir];
- this_way->offset_before = off;
- this_way->offset_after = off;
- return 0;
- }
- EXPORT_SYMBOL_GPL(nf_ct_seqadj_init);
- int nf_ct_seqadj_set(struct nf_conn *ct, enum ip_conntrack_info ctinfo,
- __be32 seq, s32 off)
- {
- struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- struct nf_ct_seqadj *this_way;
- if (off == 0)
- return 0;
- if (unlikely(!seqadj)) {
- WARN_ONCE(1, "Missing nfct_seqadj_ext_add() setup call\n");
- return 0;
- }
- set_bit(IPS_SEQ_ADJUST_BIT, &ct->status);
- spin_lock_bh(&ct->lock);
- this_way = &seqadj->seq[dir];
- if (this_way->offset_before == this_way->offset_after ||
- before(this_way->correction_pos, ntohl(seq))) {
- this_way->correction_pos = ntohl(seq);
- this_way->offset_before = this_way->offset_after;
- this_way->offset_after += off;
- }
- spin_unlock_bh(&ct->lock);
- return 0;
- }
- EXPORT_SYMBOL_GPL(nf_ct_seqadj_set);
- void nf_ct_tcp_seqadj_set(struct sk_buff *skb,
- struct nf_conn *ct, enum ip_conntrack_info ctinfo,
- s32 off)
- {
- const struct tcphdr *th;
- if (nf_ct_protonum(ct) != IPPROTO_TCP)
- return;
- th = (struct tcphdr *)(skb_network_header(skb) + ip_hdrlen(skb));
- nf_ct_seqadj_set(ct, ctinfo, th->seq, off);
- }
- EXPORT_SYMBOL_GPL(nf_ct_tcp_seqadj_set);
- /* Adjust one found SACK option including checksum correction */
- static void nf_ct_sack_block_adjust(struct sk_buff *skb,
- struct tcphdr *tcph,
- unsigned int sackoff,
- unsigned int sackend,
- struct nf_ct_seqadj *seq)
- {
- while (sackoff < sackend) {
- struct tcp_sack_block_wire *sack;
- __be32 new_start_seq, new_end_seq;
- sack = (void *)skb->data + sackoff;
- if (after(ntohl(sack->start_seq) - seq->offset_before,
- seq->correction_pos))
- new_start_seq = htonl(ntohl(sack->start_seq) -
- seq->offset_after);
- else
- new_start_seq = htonl(ntohl(sack->start_seq) -
- seq->offset_before);
- if (after(ntohl(sack->end_seq) - seq->offset_before,
- seq->correction_pos))
- new_end_seq = htonl(ntohl(sack->end_seq) -
- seq->offset_after);
- else
- new_end_seq = htonl(ntohl(sack->end_seq) -
- seq->offset_before);
- pr_debug("sack_adjust: start_seq: %u->%u, end_seq: %u->%u\n",
- ntohl(sack->start_seq), ntohl(new_start_seq),
- ntohl(sack->end_seq), ntohl(new_end_seq));
- inet_proto_csum_replace4(&tcph->check, skb,
- sack->start_seq, new_start_seq, false);
- inet_proto_csum_replace4(&tcph->check, skb,
- sack->end_seq, new_end_seq, false);
- sack->start_seq = new_start_seq;
- sack->end_seq = new_end_seq;
- sackoff += sizeof(*sack);
- }
- }
- /* TCP SACK sequence number adjustment */
- static unsigned int nf_ct_sack_adjust(struct sk_buff *skb,
- unsigned int protoff,
- struct tcphdr *tcph,
- struct nf_conn *ct,
- enum ip_conntrack_info ctinfo)
- {
- unsigned int dir, optoff, optend;
- struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
- optoff = protoff + sizeof(struct tcphdr);
- optend = protoff + tcph->doff * 4;
- if (!skb_make_writable(skb, optend))
- return 0;
- dir = CTINFO2DIR(ctinfo);
- while (optoff < optend) {
- /* Usually: option, length. */
- unsigned char *op = skb->data + optoff;
- switch (op[0]) {
- case TCPOPT_EOL:
- return 1;
- case TCPOPT_NOP:
- optoff++;
- continue;
- default:
- /* no partial options */
- if (optoff + 1 == optend ||
- optoff + op[1] > optend ||
- op[1] < 2)
- return 0;
- if (op[0] == TCPOPT_SACK &&
- op[1] >= 2+TCPOLEN_SACK_PERBLOCK &&
- ((op[1] - 2) % TCPOLEN_SACK_PERBLOCK) == 0)
- nf_ct_sack_block_adjust(skb, tcph, optoff + 2,
- optoff+op[1],
- &seqadj->seq[!dir]);
- optoff += op[1];
- }
- }
- return 1;
- }
- /* TCP sequence number adjustment. Returns 1 on success, 0 on failure */
- int nf_ct_seq_adjust(struct sk_buff *skb,
- struct nf_conn *ct, enum ip_conntrack_info ctinfo,
- unsigned int protoff)
- {
- enum ip_conntrack_dir dir = CTINFO2DIR(ctinfo);
- struct tcphdr *tcph;
- __be32 newseq, newack;
- s32 seqoff, ackoff;
- struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
- struct nf_ct_seqadj *this_way, *other_way;
- int res;
- this_way = &seqadj->seq[dir];
- other_way = &seqadj->seq[!dir];
- if (!skb_make_writable(skb, protoff + sizeof(*tcph)))
- return 0;
- tcph = (void *)skb->data + protoff;
- spin_lock_bh(&ct->lock);
- if (after(ntohl(tcph->seq), this_way->correction_pos))
- seqoff = this_way->offset_after;
- else
- seqoff = this_way->offset_before;
- if (after(ntohl(tcph->ack_seq) - other_way->offset_before,
- other_way->correction_pos))
- ackoff = other_way->offset_after;
- else
- ackoff = other_way->offset_before;
- newseq = htonl(ntohl(tcph->seq) + seqoff);
- newack = htonl(ntohl(tcph->ack_seq) - ackoff);
- inet_proto_csum_replace4(&tcph->check, skb, tcph->seq, newseq, false);
- inet_proto_csum_replace4(&tcph->check, skb, tcph->ack_seq, newack,
- false);
- pr_debug("Adjusting sequence number from %u->%u, ack from %u->%u\n",
- ntohl(tcph->seq), ntohl(newseq), ntohl(tcph->ack_seq),
- ntohl(newack));
- tcph->seq = newseq;
- tcph->ack_seq = newack;
- res = nf_ct_sack_adjust(skb, protoff, tcph, ct, ctinfo);
- spin_unlock_bh(&ct->lock);
- return res;
- }
- EXPORT_SYMBOL_GPL(nf_ct_seq_adjust);
- s32 nf_ct_seq_offset(const struct nf_conn *ct,
- enum ip_conntrack_dir dir,
- u32 seq)
- {
- struct nf_conn_seqadj *seqadj = nfct_seqadj(ct);
- struct nf_ct_seqadj *this_way;
- if (!seqadj)
- return 0;
- this_way = &seqadj->seq[dir];
- return after(seq, this_way->correction_pos) ?
- this_way->offset_after : this_way->offset_before;
- }
- EXPORT_SYMBOL_GPL(nf_ct_seq_offset);
- static struct nf_ct_ext_type nf_ct_seqadj_extend __read_mostly = {
- .len = sizeof(struct nf_conn_seqadj),
- .align = __alignof__(struct nf_conn_seqadj),
- .id = NF_CT_EXT_SEQADJ,
- };
- int nf_conntrack_seqadj_init(void)
- {
- return nf_ct_extend_register(&nf_ct_seqadj_extend);
- }
- void nf_conntrack_seqadj_fini(void)
- {
- nf_ct_extend_unregister(&nf_ct_seqadj_extend);
- }
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