| /* |
| * Copyright (c) 2013 Patrick McHardy <kaber@trash.net> |
| * |
| * This program is free software; you can redistribute it and/or modify |
| * it under the terms of the GNU General Public License version 2 as |
| * published by the Free Software Foundation. |
| */ |
| |
| #include <linux/module.h> |
| #include <linux/skbuff.h> |
| #include <asm/unaligned.h> |
| #include <net/tcp.h> |
| #include <net/netns/generic.h> |
| #include <linux/proc_fs.h> |
| |
| #include <linux/netfilter_ipv4/ip_tables.h> |
| #include <linux/netfilter/x_tables.h> |
| #include <linux/netfilter/xt_tcpudp.h> |
| #include <linux/netfilter/xt_SYNPROXY.h> |
| |
| #include <net/netfilter/nf_conntrack.h> |
| #include <net/netfilter/nf_conntrack_extend.h> |
| #include <net/netfilter/nf_conntrack_seqadj.h> |
| #include <net/netfilter/nf_conntrack_synproxy.h> |
| #include <net/netfilter/nf_conntrack_zones.h> |
| |
| unsigned int synproxy_net_id; |
| EXPORT_SYMBOL_GPL(synproxy_net_id); |
| |
| bool |
| synproxy_parse_options(const struct sk_buff *skb, unsigned int doff, |
| const struct tcphdr *th, struct synproxy_options *opts) |
| { |
| int length = (th->doff * 4) - sizeof(*th); |
| u8 buf[40], *ptr; |
| |
| ptr = skb_header_pointer(skb, doff + sizeof(*th), length, buf); |
| if (ptr == NULL) |
| return false; |
| |
| opts->options = 0; |
| while (length > 0) { |
| int opcode = *ptr++; |
| int opsize; |
| |
| switch (opcode) { |
| case TCPOPT_EOL: |
| return true; |
| case TCPOPT_NOP: |
| length--; |
| continue; |
| default: |
| opsize = *ptr++; |
| if (opsize < 2) |
| return true; |
| if (opsize > length) |
| return true; |
| |
| switch (opcode) { |
| case TCPOPT_MSS: |
| if (opsize == TCPOLEN_MSS) { |
| opts->mss = get_unaligned_be16(ptr); |
| opts->options |= XT_SYNPROXY_OPT_MSS; |
| } |
| break; |
| case TCPOPT_WINDOW: |
| if (opsize == TCPOLEN_WINDOW) { |
| opts->wscale = *ptr; |
| if (opts->wscale > TCP_MAX_WSCALE) |
| opts->wscale = TCP_MAX_WSCALE; |
| opts->options |= XT_SYNPROXY_OPT_WSCALE; |
| } |
| break; |
| case TCPOPT_TIMESTAMP: |
| if (opsize == TCPOLEN_TIMESTAMP) { |
| opts->tsval = get_unaligned_be32(ptr); |
| opts->tsecr = get_unaligned_be32(ptr + 4); |
| opts->options |= XT_SYNPROXY_OPT_TIMESTAMP; |
| } |
| break; |
| case TCPOPT_SACK_PERM: |
| if (opsize == TCPOLEN_SACK_PERM) |
| opts->options |= XT_SYNPROXY_OPT_SACK_PERM; |
| break; |
| } |
| |
| ptr += opsize - 2; |
| length -= opsize; |
| } |
| } |
| return true; |
| } |
| EXPORT_SYMBOL_GPL(synproxy_parse_options); |
| |
| unsigned int synproxy_options_size(const struct synproxy_options *opts) |
| { |
| unsigned int size = 0; |
| |
| if (opts->options & XT_SYNPROXY_OPT_MSS) |
| size += TCPOLEN_MSS_ALIGNED; |
| if (opts->options & XT_SYNPROXY_OPT_TIMESTAMP) |
| size += TCPOLEN_TSTAMP_ALIGNED; |
| else if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) |
| size += TCPOLEN_SACKPERM_ALIGNED; |
| if (opts->options & XT_SYNPROXY_OPT_WSCALE) |
| size += TCPOLEN_WSCALE_ALIGNED; |
| |
| return size; |
| } |
| EXPORT_SYMBOL_GPL(synproxy_options_size); |
| |
| void |
| synproxy_build_options(struct tcphdr *th, const struct synproxy_options *opts) |
| { |
| __be32 *ptr = (__be32 *)(th + 1); |
| u8 options = opts->options; |
| |
| if (options & XT_SYNPROXY_OPT_MSS) |
| *ptr++ = htonl((TCPOPT_MSS << 24) | |
| (TCPOLEN_MSS << 16) | |
| opts->mss); |
| |
| if (options & XT_SYNPROXY_OPT_TIMESTAMP) { |
| if (options & XT_SYNPROXY_OPT_SACK_PERM) |
| *ptr++ = htonl((TCPOPT_SACK_PERM << 24) | |
| (TCPOLEN_SACK_PERM << 16) | |
| (TCPOPT_TIMESTAMP << 8) | |
| TCPOLEN_TIMESTAMP); |
| else |
| *ptr++ = htonl((TCPOPT_NOP << 24) | |
| (TCPOPT_NOP << 16) | |
| (TCPOPT_TIMESTAMP << 8) | |
| TCPOLEN_TIMESTAMP); |
| |
| *ptr++ = htonl(opts->tsval); |
| *ptr++ = htonl(opts->tsecr); |
| } else if (options & XT_SYNPROXY_OPT_SACK_PERM) |
| *ptr++ = htonl((TCPOPT_NOP << 24) | |
| (TCPOPT_NOP << 16) | |
| (TCPOPT_SACK_PERM << 8) | |
| TCPOLEN_SACK_PERM); |
| |
| if (options & XT_SYNPROXY_OPT_WSCALE) |
| *ptr++ = htonl((TCPOPT_NOP << 24) | |
| (TCPOPT_WINDOW << 16) | |
| (TCPOLEN_WINDOW << 8) | |
| opts->wscale); |
| } |
| EXPORT_SYMBOL_GPL(synproxy_build_options); |
| |
| void synproxy_init_timestamp_cookie(const struct xt_synproxy_info *info, |
| struct synproxy_options *opts) |
| { |
| opts->tsecr = opts->tsval; |
| opts->tsval = tcp_time_stamp_raw() & ~0x3f; |
| |
| if (opts->options & XT_SYNPROXY_OPT_WSCALE) { |
| opts->tsval |= opts->wscale; |
| opts->wscale = info->wscale; |
| } else |
| opts->tsval |= 0xf; |
| |
| if (opts->options & XT_SYNPROXY_OPT_SACK_PERM) |
| opts->tsval |= 1 << 4; |
| |
| if (opts->options & XT_SYNPROXY_OPT_ECN) |
| opts->tsval |= 1 << 5; |
| } |
| EXPORT_SYMBOL_GPL(synproxy_init_timestamp_cookie); |
| |
| void synproxy_check_timestamp_cookie(struct synproxy_options *opts) |
| { |
| opts->wscale = opts->tsecr & 0xf; |
| if (opts->wscale != 0xf) |
| opts->options |= XT_SYNPROXY_OPT_WSCALE; |
| |
| opts->options |= opts->tsecr & (1 << 4) ? XT_SYNPROXY_OPT_SACK_PERM : 0; |
| |
| opts->options |= opts->tsecr & (1 << 5) ? XT_SYNPROXY_OPT_ECN : 0; |
| } |
| EXPORT_SYMBOL_GPL(synproxy_check_timestamp_cookie); |
| |
| unsigned int synproxy_tstamp_adjust(struct sk_buff *skb, |
| unsigned int protoff, |
| struct tcphdr *th, |
| struct nf_conn *ct, |
| enum ip_conntrack_info ctinfo, |
| const struct nf_conn_synproxy *synproxy) |
| { |
| unsigned int optoff, optend; |
| __be32 *ptr, old; |
| |
| if (synproxy->tsoff == 0) |
| return 1; |
| |
| optoff = protoff + sizeof(struct tcphdr); |
| optend = protoff + th->doff * 4; |
| |
| if (!skb_make_writable(skb, optend)) |
| return 0; |
| |
| while (optoff < optend) { |
| unsigned char *op = skb->data + optoff; |
| |
| switch (op[0]) { |
| case TCPOPT_EOL: |
| return 1; |
| case TCPOPT_NOP: |
| optoff++; |
| continue; |
| default: |
| if (optoff + 1 == optend || |
| optoff + op[1] > optend || |
| op[1] < 2) |
| return 0; |
| if (op[0] == TCPOPT_TIMESTAMP && |
| op[1] == TCPOLEN_TIMESTAMP) { |
| if (CTINFO2DIR(ctinfo) == IP_CT_DIR_REPLY) { |
| ptr = (__be32 *)&op[2]; |
| old = *ptr; |
| *ptr = htonl(ntohl(*ptr) - |
| synproxy->tsoff); |
| } else { |
| ptr = (__be32 *)&op[6]; |
| old = *ptr; |
| *ptr = htonl(ntohl(*ptr) + |
| synproxy->tsoff); |
| } |
| inet_proto_csum_replace4(&th->check, skb, |
| old, *ptr, false); |
| return 1; |
| } |
| optoff += op[1]; |
| } |
| } |
| return 1; |
| } |
| EXPORT_SYMBOL_GPL(synproxy_tstamp_adjust); |
| |
| static struct nf_ct_ext_type nf_ct_synproxy_extend __read_mostly = { |
| .len = sizeof(struct nf_conn_synproxy), |
| .align = __alignof__(struct nf_conn_synproxy), |
| .id = NF_CT_EXT_SYNPROXY, |
| }; |
| |
| #ifdef CONFIG_PROC_FS |
| static void *synproxy_cpu_seq_start(struct seq_file *seq, loff_t *pos) |
| { |
| struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); |
| int cpu; |
| |
| if (*pos == 0) |
| return SEQ_START_TOKEN; |
| |
| for (cpu = *pos - 1; cpu < nr_cpu_ids; cpu++) { |
| if (!cpu_possible(cpu)) |
| continue; |
| *pos = cpu + 1; |
| return per_cpu_ptr(snet->stats, cpu); |
| } |
| |
| return NULL; |
| } |
| |
| static void *synproxy_cpu_seq_next(struct seq_file *seq, void *v, loff_t *pos) |
| { |
| struct synproxy_net *snet = synproxy_pernet(seq_file_net(seq)); |
| int cpu; |
| |
| for (cpu = *pos; cpu < nr_cpu_ids; cpu++) { |
| if (!cpu_possible(cpu)) |
| continue; |
| *pos = cpu + 1; |
| return per_cpu_ptr(snet->stats, cpu); |
| } |
| |
| return NULL; |
| } |
| |
| static void synproxy_cpu_seq_stop(struct seq_file *seq, void *v) |
| { |
| return; |
| } |
| |
| static int synproxy_cpu_seq_show(struct seq_file *seq, void *v) |
| { |
| struct synproxy_stats *stats = v; |
| |
| if (v == SEQ_START_TOKEN) { |
| seq_puts(seq, "entries\t\tsyn_received\t" |
| "cookie_invalid\tcookie_valid\t" |
| "cookie_retrans\tconn_reopened\n"); |
| return 0; |
| } |
| |
| seq_printf(seq, "%08x\t%08x\t%08x\t%08x\t%08x\t%08x\n", 0, |
| stats->syn_received, |
| stats->cookie_invalid, |
| stats->cookie_valid, |
| stats->cookie_retrans, |
| stats->conn_reopened); |
| |
| return 0; |
| } |
| |
| static const struct seq_operations synproxy_cpu_seq_ops = { |
| .start = synproxy_cpu_seq_start, |
| .next = synproxy_cpu_seq_next, |
| .stop = synproxy_cpu_seq_stop, |
| .show = synproxy_cpu_seq_show, |
| }; |
| |
| static int __net_init synproxy_proc_init(struct net *net) |
| { |
| if (!proc_create_net("synproxy", 0444, net->proc_net_stat, |
| &synproxy_cpu_seq_ops, sizeof(struct seq_net_private))) |
| return -ENOMEM; |
| return 0; |
| } |
| |
| static void __net_exit synproxy_proc_exit(struct net *net) |
| { |
| remove_proc_entry("synproxy", net->proc_net_stat); |
| } |
| #else |
| static int __net_init synproxy_proc_init(struct net *net) |
| { |
| return 0; |
| } |
| |
| static void __net_exit synproxy_proc_exit(struct net *net) |
| { |
| return; |
| } |
| #endif /* CONFIG_PROC_FS */ |
| |
| static int __net_init synproxy_net_init(struct net *net) |
| { |
| struct synproxy_net *snet = synproxy_pernet(net); |
| struct nf_conn *ct; |
| int err = -ENOMEM; |
| |
| ct = nf_ct_tmpl_alloc(net, &nf_ct_zone_dflt, GFP_KERNEL); |
| if (!ct) |
| goto err1; |
| |
| if (!nfct_seqadj_ext_add(ct)) |
| goto err2; |
| if (!nfct_synproxy_ext_add(ct)) |
| goto err2; |
| |
| __set_bit(IPS_CONFIRMED_BIT, &ct->status); |
| nf_conntrack_get(&ct->ct_general); |
| snet->tmpl = ct; |
| |
| snet->stats = alloc_percpu(struct synproxy_stats); |
| if (snet->stats == NULL) |
| goto err2; |
| |
| err = synproxy_proc_init(net); |
| if (err < 0) |
| goto err3; |
| |
| return 0; |
| |
| err3: |
| free_percpu(snet->stats); |
| err2: |
| nf_ct_tmpl_free(ct); |
| err1: |
| return err; |
| } |
| |
| static void __net_exit synproxy_net_exit(struct net *net) |
| { |
| struct synproxy_net *snet = synproxy_pernet(net); |
| |
| nf_ct_put(snet->tmpl); |
| synproxy_proc_exit(net); |
| free_percpu(snet->stats); |
| } |
| |
| static struct pernet_operations synproxy_net_ops = { |
| .init = synproxy_net_init, |
| .exit = synproxy_net_exit, |
| .id = &synproxy_net_id, |
| .size = sizeof(struct synproxy_net), |
| }; |
| |
| static int __init synproxy_core_init(void) |
| { |
| int err; |
| |
| err = nf_ct_extend_register(&nf_ct_synproxy_extend); |
| if (err < 0) |
| goto err1; |
| |
| err = register_pernet_subsys(&synproxy_net_ops); |
| if (err < 0) |
| goto err2; |
| |
| return 0; |
| |
| err2: |
| nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
| err1: |
| return err; |
| } |
| |
| static void __exit synproxy_core_exit(void) |
| { |
| unregister_pernet_subsys(&synproxy_net_ops); |
| nf_ct_extend_unregister(&nf_ct_synproxy_extend); |
| } |
| |
| module_init(synproxy_core_init); |
| module_exit(synproxy_core_exit); |
| |
| MODULE_LICENSE("GPL"); |
| MODULE_AUTHOR("Patrick McHardy <kaber@trash.net>"); |