net/sched/em_ipt.c

   1 /*
   2  * net/sched/em_ipt.c IPtables matches Ematch
   3  *
   4  * (c) 2018 Eyal Birger <eyal.birger@gmail.com>
   5  *
   6  * This program is free software; you can redistribute it and/or
   7  * modify it under the terms of the GNU General Public License
   8  * as published by the Free Software Foundation; either version
   9  * 2 of the License, or (at your option) any later version.
  10  */
  11
  12 #include <linux/gfp.h>
  13 #include <linux/module.h>
  14 #include <linux/types.h>
  15 #include <linux/kernel.h>
  16 #include <linux/string.h>
  17 #include <linux/skbuff.h>
  18 #include <linux/tc_ematch/tc_em_ipt.h>
  19 #include <linux/netfilter.h>
  20 #include <linux/netfilter/x_tables.h>
  21 #include <linux/netfilter_ipv4/ip_tables.h>
  22 #include <linux/netfilter_ipv6/ip6_tables.h>
  23 #include <net/pkt_cls.h>
  24
  25 struct em_ipt_match {
  26         const struct xt_match *match;
  27         u32 hook;
  28         u8 match_data[0] __aligned(8);
  29 };
  30
  31 struct em_ipt_xt_match {
  32         char *match_name;
  33         int (*validate_match_data)(struct nlattr **tb, u8 mrev);
  34 };
  35
  36 static const struct nla_policy em_ipt_policy[TCA_EM_IPT_MAX + 1] = {
  37         [TCA_EM_IPT_MATCH_NAME]         = { .type = NLA_STRING,
  38                                             .len = XT_EXTENSION_MAXNAMELEN },
  39         [TCA_EM_IPT_MATCH_REVISION]     = { .type = NLA_U8 },
  40         [TCA_EM_IPT_HOOK]               = { .type = NLA_U32 },
  41         [TCA_EM_IPT_NFPROTO]            = { .type = NLA_U8 },
  42         [TCA_EM_IPT_MATCH_DATA]         = { .type = NLA_UNSPEC },
  43 };
  44
  45 static int check_match(struct net *net, struct em_ipt_match *im, int mdata_len)
  46 {
  47         struct xt_mtchk_param mtpar = {};
  48         union {
  49                 struct ipt_entry e4;
  50                 struct ip6t_entry e6;
  51         } e = {};
  52
  53         mtpar.net       = net;
  54         mtpar.table     = "filter";
  55         mtpar.hook_mask = 1 << im->hook;
  56         mtpar.family    = im->match->family;
  57         mtpar.match     = im->match;
  58         mtpar.entryinfo = &e;
  59         mtpar.matchinfo = (void *)im->match_data;
  60         return xt_check_match(&mtpar, mdata_len, 0, 0);
  61 }
  62
  63 static int policy_validate_match_data(struct nlattr **tb, u8 mrev)
  64 {
  65         if (mrev != 0) {
  66                 pr_err("only policy match revision 0 supported");
  67                 return -EINVAL;
  68         }
  69
  70         if (nla_get_u32(tb[TCA_EM_IPT_HOOK]) != NF_INET_PRE_ROUTING) {
  71                 pr_err("policy can only be matched on NF_INET_PRE_ROUTING");
  72                 return -EINVAL;
  73         }
  74
  75         return 0;
  76 }
  77
  78 static const struct em_ipt_xt_match em_ipt_xt_matches[] = {
  79         {
  80                 .match_name = "policy",
  81                 .validate_match_data = policy_validate_match_data
  82         },
  83         {}
  84 };
  85
  86 static struct xt_match *get_xt_match(struct nlattr **tb)
  87 {
  88         const struct em_ipt_xt_match *m;
  89         struct nlattr *mname_attr;
  90         u8 nfproto, mrev = 0;
  91         int ret;
  92
  93         mname_attr = tb[TCA_EM_IPT_MATCH_NAME];
  94         for (m = em_ipt_xt_matches; m->match_name; m++) {
  95                 if (!nla_strcmp(mname_attr, m->match_name))
  96                         break;
  97         }
  98
  99         if (!m->match_name) {
 100                 pr_err("Unsupported xt match");
 101                 return ERR_PTR(-EINVAL);
 102         }
 103
 104         if (tb[TCA_EM_IPT_MATCH_REVISION])
 105                 mrev = nla_get_u8(tb[TCA_EM_IPT_MATCH_REVISION]);
 106
 107         ret = m->validate_match_data(tb, mrev);
 108         if (ret < 0)
 109                 return ERR_PTR(ret);
 110
 111         nfproto = nla_get_u8(tb[TCA_EM_IPT_NFPROTO]);
 112         return xt_request_find_match(nfproto, m->match_name, mrev);
 113 }
 114
 115 static int em_ipt_change(struct net *net, void *data, int data_len,
 116                          struct tcf_ematch *em)
 117 {
 118         struct nlattr *tb[TCA_EM_IPT_MAX + 1];
 119         struct em_ipt_match *im = NULL;
 120         struct xt_match *match;
 121         int mdata_len, ret;
 122
 123         ret = nla_parse(tb, TCA_EM_IPT_MAX, data, data_len, em_ipt_policy,
 124                         NULL);
 125         if (ret < 0)
 126                 return ret;
 127
 128         if (!tb[TCA_EM_IPT_HOOK] || !tb[TCA_EM_IPT_MATCH_NAME] ||
 129             !tb[TCA_EM_IPT_MATCH_DATA] || !tb[TCA_EM_IPT_NFPROTO])
 130                 return -EINVAL;
 131
 132         match = get_xt_match(tb);
 133         if (IS_ERR(match)) {
 134                 pr_err("unable to load match\n");
 135                 return PTR_ERR(match);
 136         }
 137
 138         mdata_len = XT_ALIGN(nla_len(tb[TCA_EM_IPT_MATCH_DATA]));
 139         im = kzalloc(sizeof(*im) + mdata_len, GFP_KERNEL);
 140         if (!im) {
 141                 ret = -ENOMEM;
 142                 goto err;
 143         }
 144
 145         im->match = match;
 146         im->hook = nla_get_u32(tb[TCA_EM_IPT_HOOK]);
 147         nla_memcpy(im->match_data, tb[TCA_EM_IPT_MATCH_DATA], mdata_len);
 148
 149         ret = check_match(net, im, mdata_len);
 150         if (ret)
 151                 goto err;
 152
 153         em->datalen = sizeof(*im) + mdata_len;
 154         em->data = (unsigned long)im;
 155         return 0;
 156
 157 err:
 158         kfree(im);
 159         module_put(match->me);
 160         return ret;
 161 }
 162
 163 static void em_ipt_destroy(struct tcf_ematch *em)
 164 {
 165         struct em_ipt_match *im = (void *)em->data;
 166
 167         if (!im)
 168                 return;
 169
 170         if (im->match->destroy) {
 171                 struct xt_mtdtor_param par = {
 172                         .net = em->net,
 173                         .match = im->match,
 174                         .matchinfo = im->match_data,
 175                         .family = im->match->family
 176                 };
 177                 im->match->destroy(&par);
 178         }
 179         module_put(im->match->me);
 180         kfree((void *)im);
 181 }
 182
 183 static int em_ipt_match(struct sk_buff *skb, struct tcf_ematch *em,
 184                         struct tcf_pkt_info *info)
 185 {
 186         const struct em_ipt_match *im = (const void *)em->data;
 187         struct xt_action_param acpar = {};
 188         struct net_device *indev = NULL;
 189         struct nf_hook_state state;
 190         int ret;
 191
 192         rcu_read_lock();
 193
 194         if (skb->skb_iif)
 195                 indev = dev_get_by_index_rcu(em->net, skb->skb_iif);
 196
 197         nf_hook_state_init(&state, im->hook, im->match->family,
 198                            indev ?: skb->dev, skb->dev, NULL, em->net, NULL);
 199
 200         acpar.match = im->match;
 201         acpar.matchinfo = im->match_data;
 202         acpar.state = &state;
 203
 204         ret = im->match->match(skb, &acpar);
 205
 206         rcu_read_unlock();
 207         return ret;
 208 }
 209
 210 static int em_ipt_dump(struct sk_buff *skb, struct tcf_ematch *em)
 211 {
 212         struct em_ipt_match *im = (void *)em->data;
 213
 214         if (nla_put_string(skb, TCA_EM_IPT_MATCH_NAME, im->match->name) < 0)
 215                 return -EMSGSIZE;
 216         if (nla_put_u32(skb, TCA_EM_IPT_HOOK, im->hook) < 0)
 217                 return -EMSGSIZE;
 218         if (nla_put_u8(skb, TCA_EM_IPT_MATCH_REVISION, im->match->revision) < 0)
 219                 return -EMSGSIZE;
 220         if (nla_put_u8(skb, TCA_EM_IPT_NFPROTO, im->match->family) < 0)
 221                 return -EMSGSIZE;
 222         if (nla_put(skb, TCA_EM_IPT_MATCH_DATA,
 223                     im->match->usersize ?: im->match->matchsize,
 224                     im->match_data) < 0)
 225                 return -EMSGSIZE;
 226
 227         return 0;
 228 }
 229
 230 static struct tcf_ematch_ops em_ipt_ops = {
 231         .kind     = TCF_EM_IPT,
 232         .change   = em_ipt_change,
 233         .destroy  = em_ipt_destroy,
 234         .match    = em_ipt_match,
 235         .dump     = em_ipt_dump,
 236         .owner    = THIS_MODULE,
 237         .link     = LIST_HEAD_INIT(em_ipt_ops.link)
 238 };
 239
 240 static int __init init_em_ipt(void)
 241 {
 242         return tcf_em_register(&em_ipt_ops);
 243 }
 244
 245 static void __exit exit_em_ipt(void)
 246 {
 247         tcf_em_unregister(&em_ipt_ops);
 248 }
 249
 250 MODULE_LICENSE("GPL");
 251 MODULE_AUTHOR("Eyal Birger <eyal.birger@gmail.com>");
 252 MODULE_DESCRIPTION("TC extended match for IPtables matches");
 253
 254 module_init(init_em_ipt);
 255 module_exit(exit_em_ipt);
 256
 257 MODULE_ALIAS_TCF_EMATCH(TCF_EM_IPT);